Estimation of Life Cycle CO Emission and Energy Cost of ...

Estimation of Life Cycle CO2 Emission and Energy Cost of

Different Building Materials

By

SHOVONA KHUSRU

Roll Number: 0409042310

A thesis submitted to the Department of Civil Engineering of Bangladesh University of

Engineering and Technology, Dhaka, in partial fulfillment of the requirements for the

degree of

MASTER OF SCIENCE IN CIVIL AND STRUCTURAL ENGINEERING

JUNE, 2012

The thesis titled “Estimation of Life Cycle CO2 Emission and Energy Cost of Different Building Materials” submitted by Shovona Khusru, Student No. 0409042310 and Session: April 2009 has been accepted as satisfactory in partial fulfillment of the requirement for the degree of M.Sc. Engg. (Civil and Structural) on June 5, 2012.

BOARD OF EXAMINERS

______________________________________ Chairman

Dr. Munaz Ahmed Noor (Supervisor) Professor Department of Civil Engineering, BUET, Dhaka-1000 _______________________________________ Member

Dr. Md. Mujibur Rahman (Ex-officio) Professor and Head Department of Civil Engineering, BUET, Dhaka-1000 _______________________________________ Member Dr. Raquib Ahsan Professor Department of Civil Engineering, BUET, Dhaka-1000 _______________________________________ Member Dr. Sharmin Reza Chowdhury (External) Associate Professor Department of Civil Engineering Ahsanullah University of Science and Technology , Dhaka -1208

References 109

REFERENCES ______________________________________________________________________

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ne.html, 3 December, 2010.

http://www.beneficiationchina.com , 2 December, 2010.

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Tsukuba, Japan pp. 159-162.

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for Transport and the Environment.

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Report GHG Emissions.

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study. Proceedings of the 33rd Australian and New Zealand Solar Energy Society

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Emission factors

APPENDIX A Emission Factors __________________________________________________________ Table A1: Fuel combustion emission factors (fuels used for stationary combustion) - 2008

Emission Source User Unit

Emission factor Total CO2-e

Emission factor

total (kg CO2-e/unit)

(kg CO2/unit)

Stationary Combustion

Distributed Natural Gas

Commercial KWh 0.194 0.192

GJ 54 53.3 Coal – Bituminous Commercial Kg 2.59 2.57 Coal – Sub-bituminous

Commercial Kg 1.98 1.97

Coal – Lignite Commercial Kg 1.41 1.4 Coal – Default* Commercial Kg 1.98 1.97 Diesel Commercial Litre 2.64 2.64 LPG** Commercial Kg 2.97 2.96 Heavy Fuel Oil Commercial Litre 3.01 3.01 Light Fuel Oil Commercial Litre 2.94 2.93 Distributed Natural Gas

Industry KWh 0.192 0.192 GJ 53.4 53.3

Coal – Bituminous Industry Kg 2.58 2.57 Coal – Sub-bituminous

Industry Kg 1.98 1.97

Coal – Lignite Industry Kg 1.41 1.4 Coal – Default* Industry Kg 1.98 1.97 Diesel Industry Litre 2.64 2.64 LPG** Industry Kg 2.97 2.96 Heavy Fuel Oil Industry Litre 3.02 3.01 Light Fuel Oil Industry Litre 2.94 2.93 Wood Industry*** Kg 0.0178 1.26 Wood Fireplaces**** Kg 0.0865 1.26

* The default coal emission factor should be used if it is not possible to identify the specific type of coal. ** LPG-use data in litres can be converted to kilograms by multiplying by the specific gravity of 0.536 kg/l. *** It is not expected that many commercial or industrial users will burn wood in fireplaces but this

emission factor has been provided for completeness. It is the default residential emission factor. **** The Total CO2-e emission factor (for wood) only includes CH4 and N2O emissions. This is based on

ISO 14064-1 and the GHG Protocol reporting requirements for combustion of biomass as Scope 1 emissions. CO2 emissions, from the combustion of biologically sequestered carbon, are reported separately.

Emission factors 114

Source: Guidance for Voluntary, Corporate Greenhouse Gas Reporting, 2008 Table A2: CO2 - from the combustion of different fuels

Fuel

Carbon Content (kg C/kg fuel)

Energy Content(kWh/kg)

Emission of CO2 (kg CO2/kWh)

Coal (bituminous/anthracite) 0.75 7.5 0.37 Gasoline 0.9 12.5 0.27 Diesel 0.86 11.8 0.24 Light Oil 0.7 11.7 0.26 Natural Gas, Methane 0.75 12 0.23 LPG - Liquid Petroleum Gas 0.82 12.3 0.24 Bioenergy 0 - 0 Source:http://saferenvironment.wordpress.com

Table A3: CO2 - from the combustion of different fuels Fuel Units Carbon emissions CO2 Intensity

(t/unit) (tCO2/GJ)

Coking coal tonne 0.58 0.074 Non-coking coal (reductant) tonne 0.56 0.092 Boiler Coal tonne tonne 0.43 0.095 Coke tonne 0.75 0.094 Petroleum Products tonne 0.85 0.074 Natural Gas 1000 nm3 0.5 0.053 Electricity* 1000 kwh 0.27 0.271 *Assuming a conversion efficiency of 35% in a coal fired thermal power plant. Source: Das and kandpal, 1997. Table A4: Best Practice Weighting Factors for Various Products in Steel Manufacturing Process.

Process Fuel (GJ/ton)

Electricity (GJ/ton)

Final Energy Use

(GJ/ton)

Blast Furnace (total)1 15.19 0.26 15.45 Sinter Plant 1.37 0.23 1.6 Pellet Plant 0.51 0.11 0.62 Blast Furnace 13.31 -0.09 13.22 DRI2 10.5 0.4 10.9 BOF-slab3 0.57 0.12 -0.45 EAF-slab3 0.79 1.52 2.31 Hot Rolling3 1.82 0.37 2.19 Cold Rolling3 1.1 0.53 1.63 Assuming a conversion efficiency of 35% in a coal fired thermal power plant Source: Das and Kandpal (1997).

Emission factors 115

Table A5: Emissions statistics across different modes Mode CO2

(g/tonne-km) Boeing 747-400 552 Heavy truck 50 Rail-diesel 17 Rail-electric 18 S-type container vessel 8.35 PS-type container vessel (6,600 TEU) 7.48

Source : Maersk Line (2007), Brochure: “Constant Care for the Environment”. Swedish Network for Transport and the Environment.

116

APPENDIX B Product Specifications _____________________________________________________________ 1. Sand Dredger Description: 1200 m3/hr sand dredger Suction main engine 1400 HP Fuel tank volume 50T Fresh water tank volume 80T Suction capacity 1200M3/h Fuel consumption per hour 282kg/h Date of built Jan, 1990 Hull Total 49.94m Length of the ship 47.30m Full load line 47.30m Breadth 12.00m Depth 3.70m Light draft 1.750m Load draft 2.200m Load displacement 1013.000t Light displacement 782.600t Source: Pan Asia ship Engineering Company limited, www.ecplaza.net ,October 7, 2010

2. Rotary screen

Specifications ISO: 9001:2008, CE standard Style: Opening and closed. Capacity: 1-200 t/h __________________________________________________________________________________

Source:http://www.alibaba.com/productgs/444230098/Diameter_1500mm_rotary_screen_machine.html, 3 December, 2010.

Product specifications 117

3. Concrete Mixers

Model NO.: JZC350A Trademark: chuangneng Origin: China(Mainland) Product Description Feed Capacity 560L Discharge Capacity 350L Productivity 10-14M3/H Lifing Capacity 5.5kw Driving Speed(Max) 20Km/h Mixing Material Max. Dia 60mm Drum Rotation Speed 14r/min Model of the Water Pump 40DWB8-12A Water Pump Capacity 0.55kw Weight 1950kg Appearance Dimension(Length*Width*Hight) 2765*2140*3000mm

4. Vibrator Product Description Model No. TMV28 Vibrating Head Dimensions(mm) 28x470 Vibration(v.p.m) 10,000-12,000 Vibration Amplitude(mm) 0.9 Flexible Shaft Dia.(mm) 10 Rubber Hose Dia. & L.(mm) 30mmx4m - 6m Work capacity: 163CC Max. Output: 5.5HP/4000rpm Fuel tank capacity 4 Liter Continuous operating time: 5 hours

Source: Pan Asia ship Engineering Company limited, www.ecplaza.net, October 7, 2010

5. Tower crane

Hoisting

kW

m/min 32/16/4.5 64 32 915/15/4

t 2 4 1 2 Derricking

m/min 39/26 2.2/1.5

Slewing

r/min 0.62 3.7

Jacking

m/min 0.4 4

Power Supply 380V/50HZ Power Capacity 24.9 Source: http://www.cranescn.com/favicon.ico/tower-crane-qtz40315%2028%, 21 July, 2011.

APPENDIX C Design Detail Charts _____________________________________________________________________________ CONCRETE BUILDING Table C1: Detail chart of Beam design of concrete building

STIRRUP

Location Description Bar No of

Floor

Length of beam

(ft)

Total Length of bar (ft) L

volume of main

steel(cft)

total volume of

main steel(cft)

spacingtotal no of

stirrup

Area (sft)

length (ft)

(one closed

stirrup)

Volume of shear

reinforcement (cft)

total volume of steel cft

Area of concrete per floor sft

Gross Volume of concrete cft

Net Volume of concrete cft

BeamFRAME A

#7 1 82.17 295.00 1.23#6 1 82.17 349.17 1.07#7 5 82.17 541.50 2.26#6 5 82.17 102.67 0.31

GRADE BEAM GB1 (12"x24")

#6 1 82.17 328.67 1.00 1.00 #4@ 24" 42 0.001 5 0.21 1.21 2 164.33 163.12

FRAME B#7 1 82.17 328.67 1.37#6 1 82.17 493.89 1.51#6 5 82.17 196 0.60#7 5 82.17 332.00 1.01#8 5 82.17 53.33 0.16#9 5 82.17 246.50 0.75

GRADE BEAM GB2 (12"x24") #6 1 82.17 448.50 1.37 1.37 #4@ 24" 42 0.001 5 0.21 1.21 2 164.33 163.12

FRAME C#6 1 32.67 16.33 0.05#7 1 32.67 130.67 0.54#8 1 32.67 81.67 0.45#7 5 32.67 196.00 0.60

#8 5 32.67 130.67 0.72


#6 1 32.67 163.33 0.50 0.50 #4@24" 17 0.001 5 0.09 0.58 2.00 65.33 64.83

B2 (18"X27")

B3 (18"X27")

B3 (18"X27")

FLOOR

ROOF

FLOOR

ROOF

FLOOR

B1 (18"x27")

B1 (18"x27")

B2 (18"X27")

361.04

6.58

#4@11"

2.88

12.65

#4@11" and #4@ 24" 0.001 6.5 3.60 16.452 3.375

#4@11" and #4@ 24" 80 0.001 6.5 0.72 3.015 277.31 274.297

3.375 277.31 274.297#4@11" and #4@ 24"

3.60

ROOF 2.30

12.85 399

1386.56 1370.111

1386.56 1370.111

3.375

80 0.001 6.5 0.72 3.015

#4@11"

16.452 3.375#4@11" and #4@ 24" 399 0.001 6.5

1.17 7.75 3.375 551.25 544.67

0.001 6.5 0.23 1.28 3.375

MAIN STEEL CALCULATION

110.25 108.97

180 0.001 6.5

Design detail charts 119

FRAME E#6 1 49.50 199.43 0.61#7 1 49.50 285.79 1.19#6 5 49.50 87.12 0.27#7 5 49.50 383.69 1.60


#6 1 49.50 198.01 0.61 0.61 #4@24" 25 0.001 5 0.12 0.73 2 99.00 98.27

FRAME G#7 1 32.67 106.18 0.44#8 1 32.67 65.34 0.36#7 5 32.67 130.68 0.54#9 5 32.67 65.34 0.45


#7 1 32.67 130.68 0.54 0.54 #4 @ 24" 16 0.001 5 0.08 0.63 2 65.34 64.71

FRAME H#5 1 82.17 33.00 0.07#6 1 82.17 33.00 0.10#7 1 82.17 426.69 1.78#8 1 82.17 164.34 0.90#6 5 82.17 98.84 0.30#7 5 82.17 591.03 2.46


#7 1 82.17 328.68 1.37 1.37 #4 @ 11" 41 0.001 5 0.21 1.57 2 164.34 162.77

FRAME I#7 1 82.17 229.68 0.96#9 1 82.17 164.34 1.14#6 5 82.17 77.22 0.24#7 5 82.17 394.02 1.64


#7 1 82.17 328.68 1.37 1.37 #4@ 24" 41 0.001 5 0.21 1.58 2 164.34 162.76

FRAME 1

#6 1 64.00 265.68 0.81 3.75

#7 1 64.00 242.67 1.01

#6 1 46.83 97.99 0.30 2.25

#7 1 46.83 93.66 0.39#6 5 64.00 594.48 1.82

#7 5 64.00 347.72 1.45

B9 (12"X27") #6 5 46.83 240.32 0.73 #4 @ 24"c/c 115 0.001 5.5 0.63 2.25

#6 1 64.00 128.00 0.39

#7 1 64.00 128.00 0.53

#6 1 46.83 93.66 0.29

#7 1 46.83 93.66 0.39

B4 (18"X27")

B4 (18"X27")

B5 (18"X27")

B5 (18"X27")

B6 (18"X27")

B6 (18"X27")

B8 (20"X27")

FLOOR

6.15

#4 @ 24"c/c

#4@ 10.5"c/c & #4@24"c/c

#4@11"

#4@11"

3.37

2.91

FLOOR

ROOF

FLOOR

#4 @ 11"

#4 @ 11"

2.09ROOF

0.001 6.5

0.001

GB5 (12"X24")

GB6 (12"X18")

GRADE BEAM

ROOF

FLOOR

ROOF

FLOOR

ROOF

3.375 1386.62 1374.32

#4@11" and #4@ 24"

277.32 274.6490

448

0.001

0.001

6.5

6.5

3.3752.68

12.30

3.375

10.76 3.375

3.375

0.00180

399

36

178

13.82

#4@11" and #4@ 24"

4.99

2.85

2.10

9.39

B9 (12"X27")

B8 (20"X27")

2.51

B7 (18"X27")

B7 (18"X27")

0.80

20.00

1.60

9.32 #4@11" and #4@ 24" 220 0.001 6.5 1.43

1.80 #4@11" and #4@ 24" 44 0.001 6.5 0.29

277.32

0.58

#4@ 10.5"c/c & #4@24"c/c 3.01

167.07 164.99

835.31 824.56

6.5 1.16

273.95

0.001 6.5 2.59 16.41 3.375 1386.62 1370.21

6.5 0.52

3.375 551.31 545.16

0.23 1.03 3.375 110.26 109.23

0.001

0.001

6.83333

5.5

6.833

5

4

32

23

0.37

0.13

1.84

0.09

0.16

0.001

0.001

0.001

342.36345.37

1.5

2

3.75

#4 @ 24"c/c

#4 @ 24"c/c

23

54

270

1.85

22.48

196.39198.25

1704.361726.84


FRAME 2#6 1 119.58 393.16 1.20#7 1 119.58 137.68 0.57#8 1 119.58 76.83 0.42#9 1 119.58 307.33 2.13#7 5 119.58 457.08 1.90#8 5 119.58 109.47 0.60#9 5 119.58 411.49 2.86#6 1 119.58 239.16 0.73#7 1 119.58 239.16 1.00

FRAME 3#6 1 119.58 393.16 1.20#7 1 119.58 137.68 0.57#8 1 119.58 76.83 0.42#9 1 119.58 307.33 2.13#7 5 119.58 457.08 1.90#8 5 119.58 109.47 0.60#9 5 119.58 411.49 2.86#6 1 119.58 239.16 0.73#7 1 119.58 239.16 1.00

FRAME 4

#6 134.42

298.31 0.91

#7 1 34.42 68.84 0.29#6 1 70.41 261.64 0.80

#7 1 70.41 140.82 0.59

#6 5 34.42 68.84 0.21

#7 5 34.42 103.26 0.43

#8 5 34.42 22.95 0.13

#9 5 34.42 103.26 0.72B14

(15"X27") #7 5 70.41 356.47 1.49 7.43 #4 @ 24" c/c 176 0.001 6 1.06 2.8125

#6 1 104.83 209.66 0.64 #4 @ 24" c/c 0.001 5

#7 1 104.83 209.66 0.87

TOTAL 234.22 19452.81

FLOOR

GRADE BEAM

B11 (18"X27")

B11 (18"X27")

GB8 (12"X24")

4.33ROOF

60

523

105 0.001

0.001

0.001

3.40

0.30

5.01

30.21

2.03

26.81

1.73 #4 @ 24"c/c

#4@ 10"c/c &

#4@24"c/c

#4@ 10"c/c &

#4@24"c/c398.57

3.375 2017.91 2014.52

2 239.16 237.13

0.001 6.5 0.68 5.01

3.375 403.586.5

6.5

5

0.68

3.40 30.21 3.375 2017.91 2014.52

ROOF B11 (18"X27") 4.33

#4@ 10"c/c &

#4@24"c/c105 3.375 403.58 398.57

FLOOR B11 (18"X27") 26.81

#4@ 10"c/c &

#4@24"c/c523 0.001 6.5

34#4 @ 12" c/c

2.81250.216

GRADE BEAM GB8 (12"X24") 1.73 #4 @ 24"c/c 60 237.130.001 5 0.30 2.03

1.20

1.39

7.42

1.51

2 239.16

3.750.246.8330.001

FLOOR

GB9 (12"X24")GRADE BEAM

B14 (15"X27")

B13 (20"X27")

B13 (20"X27")

ROOF 3.03

17.31

327.10

1635.52

324.07

1618.20

207.88

0.00135#4 @ 24" c/c

3.751.416.8330.001207#4 @ 10" c/c

209.6621.780.2652


Table C2: Detail Chart of Column Design of Concrete Building

Story Point designation Height (ft) bar rebar % Tie volume of tie (cft) Total As (cft) Gross Volume of

concrete (cft)Net Volumeof concrete

(cft)

BASE TO GL 1-A C2(18"X18") 8 10# 9 3.09 0.56GL TO FLOOR 2 C2(18"X18") 24 10# 9 3.09 1.67

FLOOR 2 TO FLOOR 4 C2(18"X18") 24 10#9 3.09 1.67 5.22 1.96 7.18 180.00 172.82FLOOR 4 TO FLOOR 6 C2(18"X18") 24 8#9 2.47 1.33

BASE TO GL 2-I C2(18"X18") 8 10# 9 3.09 0.56GL TO FLOOR 2 C2(18"X18") 24 10# 9 3.09 1.67


BASE TO GL 3-I C2(18"X18") 8 10# 9 3.09 0.56GL TO FLOOR 2 C2(18"X18") 24 10# 9 3.09 1.67


BASE TO GL 4-A C2(18"X18") 8 10# 9 3.09 0.56GL TO FLOOR 2 C2(18"X18") 24 10# 9 3.09 1.67


BASE TO GL 4-C C2(18"X18") 8 10# 9 3.09 0.56GL TO FLOOR 2 C2(18"X18") 24 10# 9 3.09 1.67


BASE TO GL 2-A C3(22"X22") 8 12#10 3.15 0.85GL TO FLOOR 2 C3(22"X22") 24 12#10 3.15 2.54


BASE TO GL 3-A C3(22"X22") 8 12#10 3.15 0.85GL TO FLOOR 2 C3(22"X22") 24 12#10 3.15 2.54


BASE TO GL 4-B C3(22"X22") 8 12#10 3.15 0.85GL TO FLOOR 2 C3(22"X22") 24 12#10 3.15 2.54


BASE TO GL 1-G C1(15"X15") 8 16#6 3.13 0.39GL TO FLOOR 2 C1(15"X15") 24 16#7 3.13 1.17


BASE TO GL 1-I C1(15"X15") 8 16#6 3.13 0.39GL TO FLOOR 2 C1(15"X15") 24 16#7 3.13 1.17


BASE TO GL 4-I C1(15"X15") 8 16#6 3.13 0.39GL TO FLOOR 2 C1(15"X15") 24 16#7 3.13 1.17


#3@18"c/c

#3@18"c/c

#3@18"c/c

#3@18"c/c

#3@18"c/c

#3@18"c/c

#3@18"c/c

#3@18"c/c

#3@12"c/c

#3@12"c/c

#3@12"c/c

Main steel (cft)


BASE TO GL 4-H C4(18"X22") 8 12#9 3.03 0.67GL TO FLOOR 2 C4(18"X22") 24 12#9 3.03 2.00


BASE TO GL 4-E C4(18"X22") 8 12#9 3.03 0.67GL TO FLOOR 2 C4(18"X22") 24 12#9 3.03 2.00







FLOOR 2 TO FLOOR 4 C6(24"X24") 24 10 #11 2.71 2.60 8.84 4.36 13.20 320.00 306.80FLOOR 4 TO FLOOR 6 C6(24"X24") 24 8#11 2.17 2.08




FLOOR 2 TO FLOOR 4 C8(20"X32") 24 16 #9 2.5 2.67 9.44 3.26 12.70 355.56 342.85FLOOR 4 TO FLOOR 6 C8(20"X32") 24 14#9 2.19 2.33

BASE TO GL 3-C C9(15"X30") 8 14#9 3.11 0.78GL TO FLOOR 2 C9(15"X30") 24 14#9 3.11 2.33


BASE TO GL 2-G C10(18"X26") 8 18#8 3.04 0.79GL TO FLOOR 2 C10(18"X26") 24 18#8 3.04 2.37


BASE TO GL 2-D C10(18"X26") 8 18#8 3.04 0.79GL TO FLOOR 2 C10(18"X26") 24 18#8 3.04 2.37






BASE TO GL 1-H C12(18"x24") 8 22#7 3.06 0.73GL TO FLOOR 2 C12(18"x24") 24 22#7 3.06 2.20

FLOOR 2 TO FLOOR 4 C12(18"x24") 24 18#7 2.5 1.80 6.33 3.14 9.48 240.00 230.52FLOOR 4 TO FLOOR 6 C12(18"x24") 24 16#7 2.22 1.60

TOTAL 221.44 5547.45

#3@16"c/c

#3@18"c/c

#3@18"c/c

#3@16"c/c

#3@16"c/c

#4@ 22"c/c

#3@18"c/c

#3@16"c/c

#3@14"c/c

#3@18"c/c

#3@15"c/c

#3@16"c/c

#3@16"c/c


Table C3: Detail Chart of Slab Design of Concrete Building

Steel Measurement

Panel ID Bar No Length of strip Spacing Nos Length of

Bar Total Length No of Floor

Volume of steel

ft inch ft ft cft Main Steel

AB14 # 4 8.50 8 13 82.17 1047.67 6.00 9.60 # 4 17.00 5.5 37 82.17 3047.76 6.00 27.94 # 4 8.50 8 13 82.17 1047.67 6.00 9.60

BD14 # 4 7.25 9 10 72.17 697.64 6.00 6.40 # 4 14.50 6 29 72.17 2092.93 6.00 19.19 # 4 7.25 9 10 72.17 697.64 6.00 6.40

AD12 # 4 6.50 10 8 63.92 498.58 6.00 4.57 11.00 7 19 63.92 1205.35 6.00 11.05 6.50 10 8 63.92 498.58 6.00 4.57

AI34 # 4 6.50 10 8 120.83 942.47 6.00 8.64 11.00 7 19 120.83 2278.51 6.00 20.89 6.50 10 8 120.83 942.47 6.00 8.64

EG41 # 3 13.00 5 31 82.17 2563.70 6.00 11.75 HI41 # 3 5.00 9 7 82.17 547.80 6.00 2.51

# 3 10.00 6 20 82.17 1643.40 6.00 7.53 # 3 5.00 9 7 82.17 547.80 6.00 2.51

EI12 # 3 32.67 6.5 60 33.00 1990.15 6.00 9.12 AI23 # 3 16.83 10 20 120.83 2440.28 6.00 11.18 CE34 # 3 5.92 9 8 32.00 252.44 6.00 1.16

11.75 6 24 32.00 752.00 6.00 3.45 5.92 9 8 32.00 252.59 6.00 1.16


Steel

Measurement

Panel ID Bar No

Length of strip Spacing Nos Length of

Bar Total Length No of Floor

Volume of steel

ft inch ft ft cft

EXTRA TOP

AB12 #3 8.50 16 6 8.00 51.00 6.00 0.23 17.00 11 19 8.00 148.36 6.00 0.68 8.50 16 6 8.00 51.00 6.00 0.23

AB34 #3 8.50 16 6 8.00 51.00 6.00 0.23 17.00 11 19 8.00 148.36 6.00 0.68 8.50 16 6 8.00 51.00 6.00 0.23

AB23 #3 8.50 16 6 24.00 153.00 6.00 0.70 17.00 11 19 24.00 445.09 6.00 2.04 8.50 16 6 24.00 153.00 6.00 0.70

BC13 #3 7.25 18 5 12.37 59.81 6.00 0.27 14.50 12 15 12.37 179.43 6.00 0.82 7.25 18 5 12.37 59.81 6.00 0.27

EG13 #3 13.00 10 16 12.37 193.04 6.00 0.88 HI14 #3 5.00 18 3 24.75 82.50 6.00 0.38

10.00 12 10 24.75 247.50 6.00 1.13 5.00 18 3 24.75 82.50 6.00 0.38

AI23 #3 16.83 20 10 13.92 140.53 6.00 0.64 AB23 #4 34.42 16 26 16.83 434.42 6.00 3.98 EG13 #4 13.00 10 16 12.37 193.04 6.00 1.77 HI14 #4 5.00 18 3 12.38 41.25 6.00 0.38

10.00 12 10 12.38 123.75 6.00 1.13 5.00 18 3 12.38 41.25 6.00 0.38

AI12 #4 6.50 20 4 19.67 76.70 6.00 0.70 11.00 14 9 19.67 185.43 6.00 1.70 6.50 20 4 19.67 76.70 6.00 0.70

Total Volume of Steel 209.12 cft Gross Volume of Concrete 22929.16 cft

Net Volume Of Concrete 22720.04 cft


CORNER REINFORCEMENT

Panel ID Bar No Panel

Length Spacing Nos Length of Bar Total Length weight

of steel

Total Weight of Steel

(ft) ()inch (ft) (ft) (ton) (ton)

Total Corner 4 # 4

32.67 ft X 34 .42 ft panel.

5.50 4 9.19 36.76 0.012 5.50 8 8.54 68.32 0.023

5.50 8 7.89 63.12 0.021 5.50 8 7.24 57.92 0.019 5.50 8 6.59 52.72 0.018 5.50 8 5.94 47.52 0.016 5.50 8 5.29 42.32 0.014 1.041 5.50 8 4.64 37.12 0.012 ( in 6 floors) 5.50 8 3.99 31.92 0.011 5.50 8 3.34 26.72 0.009 5.50 8 2.69 21.52 0.007 5.50 8 2.04 16.32 0.005 5.50 8 1.39 11.12 0.004 5.50 8 0.74 5.92 0.002

considering weight of steel = 7850.00 kg/m3 [1 kg/m3 = 0.0624 lb/ft3 ] = 489.84 lb/cft = 0.24 ton /cft

so total weight of steel in slab = 52.26 ton


STEEL BUILDING Table C4: Detail chart of Beam design of Steel building

FRAME ID GRID ID SECTION LENGTH NO WEIGHT PER FEET WEIGHTft lb/ft tonne

FRAME 1A-B W30X99 34.42 6 99 10.22

W8X58 34.42 1 58 1.00B-D W30X90 29.58 6 90 7.99

W 8X40 29.58 1 40 0.59E-G W16X26 14.17 6 26 1.11

W8X40 14.17 1 40 0.28G-H W8X40 13.83 1 40 0.28H-I W16X31 20.00 6 31 1.86

W8X40 20.00 1 40 0.40FRAME 2

A-B W30X148 34.42 6 148 15.28W30X173 34.42 1 173 2.98W8X35 34.42 1 35 0.60

B-D W30X108 29.58 3 108 4.79W30X173 29.58 2 173 5.12W30X116 29.58 1 116 1.72W8X35 29.58 1 35 0.52

D-E W8X10 8.83 6 10 0.26W8X18 8.83 1 18 0.08

E-G W16X31 14.17 6 31 1.32W8X15 14.17 1 15 0.11

G-H W12X26 13.83 6 26 1.08W8X15 13.83 1 15 0.10

H-I W21X55 20.00 6 55 3.30W8X18 20.00 1 18 0.18

FRAME 3A-B W30X148 34.42 6 148 15.28

W8X35 34.42 1 35 0.60B-C W14X30 14.83 6 30 1.34

W8X15 14.83 1 15 0.11C-D W24X76 14.75 6 76 3.36

W8X24 14.75 1 24 0.18F-H W30X99 28.00 6 99 8.32

W8X31 28.00 1 31 0.43H-I W24X62 20.00 6 62 3.72

W8X18 20.00 1 18 0.18


FRAME 4A-B W30X108 34.42 6 108 11.15

W8X58 34.42 1 58 1.00B-C W8X28 14.83 1 28 0.21C-E W 8X40 23.58 7 40 3.30E-G W24X68 28.00 6 68 5.71

W8X31 28.00 1 31 0.43H-I W18X40 20.00 6 40 2.40

W8X28 20.00 1 28 0.28FRAME A

1-2 W27X84 32.67 6 84 8.23W8X40 32.67 1 40 0.65

2-3 W16X31 16.83 6 31 1.57W8X28 16.83 1 28 0.24

3-4 W30X90 32.67 6 90 8.82W8X40 32.67 1 40 0.65

FRAME B1-2 W36X182 32.67 1 182 2.97

W36X150 32.67 5 150 12.25W8X35 32.67 1 35 0.57

2-3 W8X21 16.83 1 21 0.18W8X18 16.83 5 18 0.76W8X35 16.83 1 35 0.29W14X90 32.67 5 90 7.35

W30X173 32.67 1 173 2.83W8X67 32.67 1 67 1.09

FRAME C3-4 W14X99 32.67 6 99 9.70

W8X58 32.67 1 58 0.95FRAME E

2-3 W18X50 16.83 6 50 2.52W8X40 16.83 1 40 0.34

3-4 W21X147 32.67 1 147 2.40W30X132 32.67 5 132 10.78

W8X40 32.67 1 40 0.65FRAME G

1-2 W30X90 32.67 6 90 8.82W8X58 32.67 1 58 0.95

FRAME H1-2 W12X50 32.67 6 50 4.90

W8X58 32.67 1 58 0.952-3 W8X21 16.83 6 21 1.06

W8X24 16.83 1 24 0.203-4 W27X129 32.67 6 129 12.64

W8X35 32.67 1 35 0.57FRAME I

1-2 W30X90 32.67 6 90 8.82W8X40 32.67 1 40 0.65

2-3 W18X35 16.83 6 35 1.77W8X24 16.83 1 24 0.20

3-4 W30X108 32.67 1 108 1.76W30X90 32.67 5 90 7.35


Table C5: Detailing chart of column in Steel building

FRAME ID GRID ID SECTION LENGTH NO WEIGHT PER FEET WEIGHTft lb/ft tonne

1-A W14X82 80.00 1 82 3.281-B W30X211 80.00 1 211 8.441G W14X109 80.00 1 109 4.361H W14X145 80.00 1 145 5.801I W14X43 80.00 1 43 1.722A W14X176 80.00 1 176 7.042B W30X292 80.00 1 292 11.682D W14X161 80.00 1 161 6.442E W14X22 80.00 1 22 0.882G W14X109 80.00 1 109 4.362H W14X120 80.00 1 120 4.802I W14X109 80.00 1 109 4.363A W14X176 80.00 1 176 7.043B W14X233 80.00 1 233 9.323C W14X145 80.00 1 145 5.803E W14X193 80.00 1 193 7.723H W14X193 80.00 1 193 7.723I W14X99 80.00 1 99 3.964A W14X74 80.00 1 74 2.964B W14X145 80.00 1 145 5.804C W14X176 80.00 1 176 7.044E W14X120 80.00 1 120 4.804H W14X120 80.00 1 120 4.804I W14X43 80.00 1 43 1.72

378.11 tonTotal weight of steel in all the columns and beams =


Table C6: Detailing chart of slab of Steel building with corner reinforcements

AB41 # 4 8.50 8 13 82.17 1047.67 2.10# 4 17.00 5.5 37 82.17 3047.76 6.11# 4 8.50 8 13 82.17 1047.67 2.10

BD41 # 4 7.25 9 10 72.17 697.64 1.40# 4 14.50 6 29 72.17 2092.93 4.19# 4 7.25 9 10 72.17 697.64 1.40

AD12 # 4 6.50 10 8 63.92 498.58 1.0011.00 7 19 63.92 1205.35 2.426.50 10 8 63.92 498.58 1.00

AI34 # 4 6.50 10 8 120.83 942.47 1.8911.00 7 19 120.83 2278.51 4.576.50 10 8 120.83 942.47 1.89

EG41 # 3 13.00 5 31 82.17 2563.70 2.89HI41 # 3 5.00 9 7 82.17 547.80 0.62

# 3 10.00 6 20 82.17 1643.40 1.85# 3 5.00 9 7 82.17 547.80 0.62

EI12 # 3 32.67 6.5 60 33.00 1990.15 2.24AI23 # 3 16.83 10 20 120.83 2440.28 2.75CE34 # 3 5.92 9 8 32.00 252.44 0.28

11.75 6 24 32.00 752.00 0.855.92 9 8 32.00 252.59 0.28

AB12 # 3 8.50 16 6 8.00 51.00 0.0617.00 11 19 8.00 148.36 0.178.50 16 6 8.00 51.00 0.06

AB34 # 3 8.50 16 6 8.00 51.00 0.0617.00 11 19 8.00 148.36 0.178.50 16 6 8.00 51.00 0.06

AB23 # 3 8.50 16 6 24.00 153.00 0.1717.00 11 19 24.00 445.09 0.508.50 16 6 24.00 153.00 0.17

BC13 # 3 7.25 18 5 12.37 59.81 0.0714.50 12 15 12.37 179.43 0.207.25 18 5 12.37 59.81 0.07

EG13 # 3 13.00 10 16 12.37 193.04 0.22HI14 # 3 5.00 18 3 24.75 82.50 0.09

10.00 12 10 24.75 247.50 0.285.00 18 3 24.75 82.50 0.09

Nos Length of Bar Total Length weight of steel

MAIN STEEL

EXTRA TOP

Bar No Panel Length SpacingPanel ID


Considering weight of steel as 7850 kg/m3= 0.24 lb/cft Total weight of reinforcement in slab = 48.43 ton

AI12 #4 6.50 20 4 19.67 76.70 6.00 0.70

11.00 14 9 19.67 185.43 6.00 1.70

6.50 20 4 19.67 76.70 6.00 0.70

209.12 cft

22929.16 cft

22720.04 cft

Total Volume of Steel

Net Volume Of Concrete

Gross Volume of Concrete

Panel ID

ft inch ft ft tonne#4 5.50 4 9.19 36.76 0.012

5.50 8 8.54 68.32 0.0235.50 8 7.89 63.12 0.0215.50 8 7.24 57.92 0.0195.50 8 6.59 52.72 0.0185.50 8 5.94 47.52 0.0165.50 8 5.29 42.32 0.0145.50 8 4.64 37.12 0.0125.50 8 3.99 31.92 0.0115.50 8 3.34 26.72 0.0095.50 8 2.69 21.52 0.0075.50 8 2.04 16.32 0.0055.50 8 1.39 11.12 0.0045.50 8 0.74 5.92 0.002

TOTAL CORNER 4

32.67 ft X 34 .42 ft panel.

Bar No Panel Length Spacing Nos Length of Bar Total Length weight of

steel


Table C7: Calculation Chart of Bracings for Elevation 1 and 4of steel building

SECTION LENGTH (FT)

X -AREA (in2)

VOLUME (ft3)

NOTOTAL

VOLUME (CFT)

HSS 5X0.25 16.6 3.49 0.40 12HSS 5x0.375 13.73 5.1 0.49 6HSS 4X0.237 16.6 2.61 0.30 24HSS 5X0.50 16.6 6.62 0.76 6

19.55


Table C8: Calculation Chart of Bracings for Elevation A and I of steel building

Total volume of steel in bracing = 38 cft

SECTION LENGTH (FT)

X -AREA (in2)

VOLUME (ft3)

NOTOTAL

VOLUME (CFT)

HSS 5X0.25 16.2 3.49 0.39 42HSS 4X0.25 16.2 2.76 0.31 6

18.35


Table C9: Sample Calculation Chart of Beam to Column One Side End Plate Connection

Beam and Column Data:

Beam Size = W30x99 Member Properties:

Column Size = W14x82 Beam:

Beam Yield Stress, Fyb = 40 Beam:

Column Yield Stress, Fyc = 40 d = 29.70 in.

tw = 0.52 in.

Connection Loadings: bf = 10.50 in.

Beam End Moment, M = 108.33 tf = 0.67 in.

Moment Includes Wind or Seismic? Yes k = 1.32 in.

Beam End Reaction (Shear), R = 10.00 Column:

d = 14.30 in.

Connection Data and Parameters: tw = 0.51 in.

End Plate Length, Lp = 21.750 bf = 10.10 in.

End Plate Width, Bp = 8.000 tf = 0.86 in.

End Plate Thickness, tp = 0.7500 k = 1.45 in.

End Plate Yield Stress, Fyp = 36 k1 = 1.06 in.

ASTM Bolt Desig. (A325 or A490) = A325

Bolt Type (N, X, or SC) = SC

Bolt Hole Type (in End Plate) = Standard

Diameter of Bolts, db = 0.875

Total Number of Bolts, Nb = 8

Top Flange to End Plate Welding:

Top Flange to End Plate Welding:

Lw = 21.820 in.

fw = 2.052 kips/in.

w = 2/16 in. (size)

w(min) = 4/16 in. End plate volume 0.08 CFT

Beam Web to End Plate Welding:

fw = 6.240 kips/in. Total length of weld 73.34 in

w = 7/16 in. (size) Weld size 0.42 in

w(min) = 4/16 in. Area of weld 0.21 sqft

SUMMERY:


Table C10: Sample Calculation Chart of Beam to Column Both Side End Plate Connection

Left Side Beam Size = W16x31 Member Properties:

Right Side Beam Size = W27x84 Left Beam:

Column Size = W14x176 d = 15.900 in.

Yield Stress of Beams, Fyb = 40 tw = 0.275 in.

Yield Stress of Column, Fyc = 40 bf = 5.530 in.

Connection Loadings: tf = 0.440 in.

Left Beam Lateral Moment, M1L = 8.33 k = 0.8420 in.

Left Beam Gravity Moment, M1G = 0.00 Right Beam:

Left Beam End Reaction, R1 = 4.18 d = 26.700 in.

Left Beam Axial Force, P1 = 0.00 tw = 0.460 in.

Right Beam Lateral Moment, M2L = 112.50 bf = 9.960 in.

Right Beam Gravity Moment, M2G = 0.00 tf = 0.640 in.

Right Beam End Reaction, R2 = 18.69 k = 1.2400 in.

Right Beam Axial Force, P2 = 0.00 Column:

d = 15.200 in.

Connection Data and Parameters: tw = 0.830 in.

Left Side End Plate Length, Lp1 = 23.750 bf = 15.700 in.

Left Side End Plate Width, Bp1 = 8.000 tf = 1.310 in.

Left Side End Plate Thk., tp1 = 1.0000 k = 1.9100 in.

Right Side End Plate Length, Lp2 = 21.750 k1 = 1.6250 in.

Right Side End Plate Width, Bp2 = 8.000

Right Side End Plate Thk., tp2 = 1.0000 RIGHT SIDE :

End Plate Yield Stress, Fyp = 36 Top Flange to End Plate Welding:

ASTM Bolt Desig. (A325 or A490) = A325 Lw = 20.740 in.

Bolt Type (N, X, or SC) = SC fw = 2.498 kips/in.

Bolt Hole Type (in End Plate) = Standard w = 3/16 in. (size)

Diameter of Bolts, db1 = 0.875 w(min) = 5/16 in.

LEFT SIDE: Beam Web to End Plate Welding:

Top Flange to End Plate Welding: fw = 5.520 kips/in.

Lw = 11.665 in. w = 6/16 in. (size)

fw = 0.555 kips/in. w(min) = 5/16 in.

w = 1/16 in. (size) SUMMERY:

w(min) = 5/16 in. End plate volume 0.21 cft

Beam Web to End Plate Welding:

fw = 3.300 kips/in. Total length of weld 107.41 in

w = 4/16 in. (size) Weld size 0.31 in

w(min) = 5/16 in. 0.23 sqftArea of weld


Table C11: Calculation Chart of Concrete and Reinforcement in Stair per Floor

Detailing of stair

#4 38 0.74#3 17 0.41

bottom beam+ landing beam 12"x10" 6 # 5 2 0.38

stirrup #3 @ 6" 59 0.121.65 97.34

net volume of concrete

(cft)

4.58

68.54

4.58

bar size

24.21

69.69

24.72

weist slab+landing slab

stair steps

item dimension

22

6"

No volume of steel(cft) volume of concrete (cft)

tread 10 " and rise 6 " 0.00


Table C12: Calculation Chart of Concrete and Reinforcement in Shear Wall

Detailing of shear wall

Wall name

Gross concrete (cft)

Reinforcement (cft)

Net volume of concrete (cft)

1-DE 74.64 0.63 74.01D-12 261.36 2.40 258.96E-12 261.36 2.40 258.96

5.43 591.93

Volume


Table C13: Detail Chart of brick and timber work of Concrete Building

ESTIMATION OF BRICK WORK

Description No of floor F

No of item N

Dimensions Area (sft)= [ FxNxLxB]

Volume (cft)

No of bricks required Length L

(ft) Width B

(ft) Height H

(ft) Brick wall( without opening) exterior wall 6 405.83 0.83 12.00 29220.00 24350 interior wall 6 424.33 0.42 12.00 30552.00 12730 Deduction for opening considering 40 % opening for door and window exterior wall 6 11688 9740 interior wall 6 12220.80 5092

Brick wall( excluding opening) exterior wall 14610 214746 interior wall 7638 112268

327014

ESTIMATION OF TIMBER WORK Considering frame as well as doors and windows are made of timber Also considering 40 % opening for door and window in the walls

No of floor , F exterior wall (sft) interior wall

(sft)

thickness of door and

frame total volume(cft)

Door and window 6 11688 12220.80 0.25 5977.20

i

DECLARATION

Declared that except where specified by reference to other works, the studies embodied in

thesis is the result of investigation carried out by the author. Neither the thesis nor any

part has been submitted to or is being submitted elsewhere for any other purposes.

Signature of the student

Shovona Khusru

ii

TABLE OF CONTENT

Page

No.

Declaration i

Table of contents ii

List of Symbols And Abbreviations vi

Acknowledgement vii

Abstract viii

Chapter 1 Introduction

1.1 General 1

1.2 Environmental Implications of Buildings 1

1.3 Building Materials and Construction Sector 3

1.4 Life-Cycle Assessment of Building Materials 6

1.5 Energy Cost 7

1.6 Scope 7

1.7 Objective 8

1.8 Research Overview 9

Chapter 2 Literature Review

2.1 Life Cycle Analysis 11

2.2 Carbon Dioxide (CO2) Emissions 12

2.3 CO2 Emissions Components of a Medium Size Building 13

2.3.1 Embodied Energy and Embodied CO2 Emissions 13

2.3.2 Construction Energy and Construction CO2 Emission 13

2.3.3 Energy in Use 13

2.3.4 Operating Energy and Operating CO2 Emission 14

2.3.5 Demolition Energy Consumption and Demolition CO2

Emissions

14

2.4 Life Cycle Energy Cost 15

2.5 Previous Researches 15

iii

2.6 Manufacturing Procedures of Building Materials 19

2.6.1 Brick 19

2.6.2 Cement 20

2.6.3 Sand 22

2.6.4 Aggregate 24

2.6.5 Steel 26

2.6.6 Timber 28

2.6.7 Concrete 28

Chapter 3 Methodology

3.1 General 31

3.2 Methodology of Developing Life Cycle CO2 Emission Equations of

Building Materials

31

3.2.1 Selection Criteria 31

3.2.2 Mode of Material Transport 33

3.2.3 Functional Unit 33

Chapter 4 Development of Life cycle CO2 Emission and Energy Cost

Equations

4.1 General 35

4.2 Life Cycle CO2 Emission Equations of Materials 35

4.2.1 Brick Profile 35

4.2.2 Cement Profile 37

4.2.3 Steel Profile 40

4.2.4 Sand Profile 44

4.2.5 Aggregate Profile 46

4.2.6 Timber Profile 47

4.2.7 Concrete Profile 49

4.3 Life Cycle Energy Cost Equations of Materials 51

4.3.1 Brick 52

4.3.2 Timber 53

iv

4.3.3 Steel 54

4.3.4 Aggregate 58

4.3.5 Sand 59

4.3.6 Cement 60

4.3.7 Concrete 61

Chapter 5 Comparative Study on Life Cycle CO2 Emission of

Concrete and Steel Building

5.1 General 63

5.2 Case study 63

5.2.1 Design of Building 63

5.2.2 Concrete building and Design Procedure 65

5.2.3 Steel Building and Design Procedure 66

5.3 Life Cycle CO2 Emission of Concrete Building 67

5.3.1 Cradle to Gate CO2 Emission of Concrete building 68

5.3.2 Emission of CO2 in Transportation Phase of Concrete building 71

5.3.3 Emission of CO2 in Construction Phase of Concrete building 73

5.3.4 Emission of CO2 in Demolition Phase of Concrete building 73

5.3.5 Total CO2 Emission of Concrete building 74

5.4 Life Cycle CO2 Emission From Steel Building 75

5.4.1 Cradle to Gate CO2 Emission of Materials in steel Building 76

5.4.2 Emission of CO2 in Transportation Phase of steel Building 79

5.4.3 Emission of CO2 in Construction Phase of steel Building 80

5.4.4 Emission of CO2 in Demolition Phase of steel Building 81

5.4.5 Total CO2 Emission of Steel Building 82

5.5 Comparison of Concrete and Steel Building Based on CO2 Emission 83

Chapter 6 Comparative Study on Life Cycle Energy Cost of Concrete

and Steel Building

6.1 General 85

6.2 Life Cycle Energy Cost Analysis of Concrete Building 85

v

6.2.1 Cradle to Gate Energy Cost of Materials Used in Concrete

building

85

6.2.2 Energy Cost in Transportation Phase of Concrete building 89

6.2.3 Energy Cost in Construction Phase of Concrete building 90

6.2.4 Energy Cost in Demolition Phase of Concrete building 91

6.2.5 Total Energy Cost from Concrete building 92

6.3 Life Cycle Energy Cost Analysis of Steel building 93

6.3.1 Cradle to Gate Energy Cost of Materials Used in Steel building 93

6.3.2 Energy Cost in Transportation Phase of Steel building 96

6.3.3 Energy Cost in Construction Phase of Steel building 98

6.3.4 Energy Cost in Demolition Phase of Steel building 99

6.3.5 Total Energy Cost from Steel building 99

6.4 Comparison Of Concrete and Steel building Based on Energy Cost 101

Chapter 7 Conclusions and Recommendations

7.1 General 105

7.2 Findings of the Research Work 106

7.3 Recommendations for Future Studies 107

References 109

Appendix A Emission Factors 113

Appendix B Product Specifications 116

Appendix C Design Detail Charts 118

vi

LIST OF SYMBOLS AND ABBREVIATIONS

AISC American Institute of Steel Construction

ASTM American Society for testing and Materials

ASD Allowable Stress Design

db1 Distance in kilometer from brick field to market.

db2 Distance in kilometer from construction site to brick chips processing site

c Distance in kilometer from cement factory to market

dst2 Distance in kilometer from market to construction site.

A Total area of weld in connection in square meter.

W Total weight of steel member and plates required to be weld in ton.

h Hoisting height of crane in meter for one ton of steel element transfer.

L Derricking length of crane in meter for one ton of steel element transfer

ds Total distance in km from sand processing unit to market

da Total distance in kilometer from aggregate processing unit to market

dad Distance in kilometer from construction site to disposal site.

t No of trees cut

dt1 Distance in kilometer from wood to saw mill and sawmill to market

dt2 distance in kilometer from market to construction site and construction

site to disposal site.

V Volume of timber cut in cubic feet.

Pd Price of 1 liter diesel in BDT

Pc Price of 1 kg coal in BDT

PLPG Price of 1 liter LPG in BDT

vii

ACKNOWLEDGEMENT

First, I would like to express my sincerest gratitude to the Almighty, the benevolent and

the kind, for His graciousness, unlimited kindness and divine blessings.

I would like to express my heartfelt gratitude and sincere thanks to my thesis supervisor,

Dr. Munaz Ahmed Noor, Professor, Department of Civil Engineering, BUET for his

adept guidance and enthusiastic support throughout the progress of this thesis. I am

greatly indebted to him for his affectionate assistance, spirited encouragement and

constructive criticism at every stage of this study. I consider myself very fortunate to

work under his sincere and supportive supervision. I would also like to take the

opportunity to specially thank him for his generous help and invaluable advice

throughout my master’s education.

I also wish to convey my honest gratefulness to the Head of the Department of Civil

Engineering, BUET and all members of the defense board for their time and patience.

I am immensely thankful to my employer, the authority of Ahsanullah University of

Science and Technology, Dhaka for giving me the permission to continue M.Sc.

Engineering in BUET.

At the end, I would like to thank all my teachers for their gracious toleration, endless

inspiration, support and of course all my family members especially my parents, friends

and colleagues for their treasured companionship and warm affection at all stages of my

life. I will be ever grateful to all of them for as long as I live.

viii

ABSTRACT

The construction sector of Bangladesh has seen massive boom in last few decades and is

responsible for greenhouse gases contribution. In this research, an investigation has been

made to develop empirical equations of life cycle CO2 emission and energy cost for seven

most widely used construction materials of Bangladesh namely brick, cement, sand, steel;

both from billet and scrap, stone chips, timber and concrete.

Based on overall study, an attempt has been made to present a guideline to estimate life

cycle energy cost and CO2 emission of different structural systems. To carry out the

investigation, this research modeled two similar medium sized buildings each designed by

finite element analysis using primarily Concrete and Steel. The models were based on a

914 m2 (9833 sq feet) floor area six-storey building. Both the superstructure of buildings

has been analyzed individually using the empirical equations developed in this study. The

major phases have been cradle to gate, transportation of component raw materials to site,

construction of the building and finally demolition. Operational CO2 emission of the

building has not been taken into consideration.

Analysis result of the said six storey mid rise building showed that steel produced from

ship breaking scrap consumes maximum energy in its entire life cycle and concrete emits

maximum CO2 in transportation phase among all the materials considered in this study.

This may be due to the fact that all the component materials are obtained from different

source locations. Although in cradle to gate phase, concrete building emits 73% of the

total life cycle CO2 and steel building emits 53.7% CO2, in construction phase emission of

CO2 of concrete building is less than one ton whereas that of steel building is 26.9% of

total emission. Considering total life cycle CO2 emission Steel building emits 1.7 times

CO2 per square feet as compared to concrete building. Considering total energy cost, Steel

building has 3.7 times energy cost per square feet than that of Concrete building. Based on

the results it can be concluded that concrete building is more sustainable than steel

building in perspective of Bangladesh.

CHAPTER 1

INTRODUCTION

______________________________________________________________________

1.1 GENERAL

The introductory chapter discusses the specific context in which this research project

was undertaken and latent implications of the results found, leading on to the problem

statement, including the objectives.

1.2 ENVIRONMENTAL IMPLICATIONS OF BUILDINGS The growing concentration of atmospheric carbon dioxide (CO2) contributing to global

climatic change is a long-term and large-scale problem (Bernstein et al., 2007).

Buildings have a significant impact on the environment, consuming world’s resources,

including water and energy. Buildings are also responsible for 40% of the waste which

ends up in the landfills and 40% of the greenhouse gas emissions (Cole et al., 1996). All

these impacts can be directly associated with each of the building’s life stages that occur

during its effective life – its construction, operation, maintenance, renovation, and so on.

Buildings are labeled according to the main material used for their sub- and super-

structures but the vast majority of buildings use a large number of materials. Hence it is

often not clear which materials or combinations of materials can achieve the best

environmental performance in terms of life-cycle cost and CO2 emissions. Nevertheless

this thesis will retain this labeling system while conscious of its limitations, as it is the

current practice.

As concern over the environmental impacts of building construction grows, many

researchers are beginning to use life cycle assessment as a means to quantify natural

resources consumption, and emissions of global greenhouse gases. Historically, focus

has been on understanding energy use during the operational period of the structure and

total life cycle emission in use phase. With this approach, an important factor has been

neglected; the embodied energy of construction materials. To understand overall

Introduction 2

environmental impacts of the building, all life cycle stages should be inventoried such as

material production, manufacturing, use and retirement. Assessing the environmental

impact of a complex system, such as a house, requires an understanding of the

environmental impacts of all of its parts.

More recently, it has been suggested that CO2 emissions may be a more meaningful

single indicator of overall global environmental impact. To assess the environmental

impact of global CO2 emission a lot of work had been done worldwide based on life

cycle CO2 emission, embodied energy and energy at use. Reduction in energy demand

through more efficient buildings brings benefits for the global environment as well as

lower costs and improved quality of life for the occupants. Oppenheim and Treloar

(Oppenheim et al.) discussed that in both Australia and overseas the field of embodied

energy and CO2 emission analysis is generally still only of academic interest. There is

little interest in the market place for undertaking of these calculations and the design

changes that would follow from the results produced. Additionally, no country yet has

embodied energy regulations. Accurate knowledge is hard to find, and it is rare to find

calculations done during the design process.

Scenario of Bangladesh

Carbon dioxide emissions in Bangladesh are those stemming from the burning of fossil

fuels and the manufacture of cement. Gas fuels has the largest contributionwhich is 62%

of the total emission (Carbon Dioxide Information Analysis Center). Other sources

include consumption of solid, liquid, and gas flaring. Bangladesh is considered as a

developing economy which has recorded GDP growth above 5% during the last few

years. CO2 emission in Bangladesh has been increasesd tremendously in the last few

decades. During the decade 1970-1980s, the emission was 5 to 8 thousand metric tons,

in 1981-1990s it was 9 to 12 thousand metric tons which increased rapidly in the decade

1991-2000, reaching 12-25 thousand metric tons and in 2007, it reached 40 thousand

metric tons (www.tradingeconomics.com). World Resource Institute reported in 2003

that the per capita CO2 emission in Bangladesh is 29874 thousand metric tons and

position of Bangladesh is sixty five in the whole world. This study in 2001 considered

Introduction 3

carbon dioxide emission from energy use and cement manufacturing (United Nations

Framework Convention on Climate Change (UNFCCC). Sector wise study of CO2

emission showed that 33% emission is from manufacturing and construction sector and

13% emission is from residences (International Energy Agency (IEA), 2001). All this

data emphasise on the importance of estimating CO2 emission from construction

materials and building construction process in Bangladesh.

In terms of energy consumption, much of the existing commercial building stock is

made up of multi-storey, highly-glazed, thermally-lightweight developments that are

totally dependent on non-renewable energy for heating, cooling and lighting. In terms of

materials, most commercial buildings tend to make extensive use of brick, steel, glass

and concrete, all of which can be energy-intensive to produce, via processes with the

potential to have adverse environmental impacts and using resources that are in

shortening supply.

In this regard, it is worth noting the commercial rivalries that can exist between the

purveyors of competing materials, each promoting the potential environmental

advantages of their respective products such as the thermal mass properties of concrete,

the recycle-ability of steel, the renew-ability of wood, and so on and the necessity for an

independent academic researcher to remain detached from these influences.

1.3 BUILDING MATERIALS AND CONSTRUCTION SECTOR

In developing countries, the share of fixed capital formation in construction is often

about 50% of the total but can be as high as 80% (UNCHS, 1986). Therefore, the

construction sector may be regarded as one of the backbones of the development process

mainly because of its multiplier effect in other sectors of the economy. In many

developing countries the annual growth rate in construction is often considerable higher

than the growth of population and the gross domestic product.

Building materials form the single largest input in construction, accounting for about 50

to 80 per cent of the total value of construction. Although part of the building materials

may be imported, there is considerable production of building materials at the local level

Introduction 4

in developing countries. For many types of building materials, developing countries

have improved their share of global production. For locally produced building materials,

notably those produced at the rural level, much less is known. Fired and unfired bricks,

clay roof tiles, lime, timber, bamboo, etc. are the building materials widely produced and

used within Bangladesh. Bricks in particular as well as bamboo, wood and natural fibers,

are important building materials in both urban and rural areas. For instance, in

Bangladesh out of about 14.8 million households, 3.7 million or about 25% used bricks

(fired and unfired) as wall material, while 9.4 million or about 63% used bamboo and

natural fibers such as straw, jute sticks, etc. (SDCSKAT,1991).

Building activities can be grouped into three main categories: Modern, Conventional and

Traditional. Each category makes its own pattern of demand for building materials. The

first category often requires sophisticated and costly building materials. For the other

two, the structure of the demand is somewhat different and diversified. The use and

choice of building materials by the traditional sector, generally associated with rural

areas, is largely influenced by the suitability and local availability of such materials and

may show regional variations due to climatic conditions, etc. The conventional sector,

often found in urban and semi-urban areas is based partly on traditional methods and

materials but mostly influenced by modern sector materials such as cement, reinforced

concrete, aluminum, gypsum, etc.

Many developing countries have geared their construction efforts towards the

establishment of the infrastructure needed for economic development in the form of

highways, major townships, irrigation works, bridges, office buildings, etc., for which

building materials often had to be imported. Subsequently, local production capacities

were developed in varying degrees, but, as the major construction activities were in the

modern sector, production capacities were mainly directed towards more sophisticated

capital and energy intensive products such as cement, steel and glass. These production

capacities, in general, are large scale, using imported components such as expertise,

equipment, and sometimes even raw materials and they are often owned by the

government sector. Much less development effort has been geared towards the

Introduction 5

traditional building materials sector which, again in general, is small scale,

locally/privately owned and uses local raw materials and equipment. This phenomenon

is also evident from the energy requirements for the production of building materials.

The use of local building material

The changes in the building materials industry have had a distinct influence on the way

buildings such as houses, etc. are built and the type of materials used, not only in Asia,

but in other parts of the world as well. Formerly, most housing and other buildings were

constructed out of locally available natural materials and/or materials manufactured

locally. These include wood, mud, brick, stone, lime, clay-tile, bamboo, thatch, etc.

Although still widely used in rural areas, many of these traditional materials, have been

gradually replaced by cement, steel, aluminum, asbestos cement, gypsum board, glass,

plastics, plywood, particle board, etc., especially in urban areas. However, there is still a

strong demand for more traditional building materials such as lime, fired clay bricks and

timber, although the growth rate in the use of these materials may be lower than cement

and iron roofing sheet. Unfortunately, little is known about the traditional construction

sector's use of locally-available building materials. In most countries, statistics on the

production or use of traditional building materials, as well as construction activities in

the traditional (rural) sector are almost non-existent and figures, which are available, are

often based on estimates.

Changes in the use of local building materials

Despite a lack of hard data, it appears that in wood scarce-areas people are moving away

from timber construction in favor of other construction materials. To some extent these

changes are a result of scarcity, higher prices, lower quality and/or irregular supply of

traditional materials and the availability of relatively cheap alternatives. But there may

be other reasons as well. First the use of concrete and metal structures increases the

status of the owner and is considered a sign of being modern. There are other less

obvious reasons for preferring one type of building material over others. For instance, in

Bangladesh, users of corrugated iron roofing sheets state that in times of economic

hardship, their corrugated iron roof sheets can be sold to raise money, unlike clay

Introduction 6

roofing tiles which appear to have no resale value. In addition, iron roofing sheets in

many cases can be recovered after storms, while other roofing materials may be

damaged beyond repair. One the other hand, the skills necessary for construction with

local building materials may have been partly or completely lost. For instance, earth is

frequently identified as a nondurable construction material. However, with proper roof

overhangs and/or an appropriate rendering of the walls, the lifetime of earth can be very

long. In Central and South America massive churches have been built using earth only.

Use of excessive amounts of cement to stabilize soils may turn a low-cost building

material into an "industrial" product – too expensive to be considered a real competitor

to other local building materials.

The use of fired clay bricks in structural masonry in place of reinforced concrete can be

a cost saving technique but unfortunately the use of bricks requires more skill during

construction. Brick walls without plaster are cheaper, not only during construction but

afterwards as well, as they do not require maintenance such as whitewashing, etc.

However skilled bricklayers are necessary to achieve a pleasing look and uniform bricks

(straight, no broken edges, etc.) are also needed. However, in all cases local conditions

such as the climate should be taken into account. Earth construction for example is less

suitable in areas which often become waterlogged. Bamboo should not be used in direct

contact with the soil unless it has been properly treated. Roof tiles may have to be

fastened to rafters and purlins in areas with strong wind. Much depends on local

conditions. Building materials which are appropriate and/or competitive in one country

may not be suitable in other countries. For instance "pozzolana" or hollow cement

blocks, widely used in Indonesia, India and Thailand, were a failure in Bangladesh

because the blocks apparently were too expensive and/or were considered inferior to

fired or unfired clay bricks and other building materials such as bamboo.

1.4 LIFE-CYCLE ASSESSMENT OF BUILDING MATERIALS

Buildings go through many stages throughout their useful life, none of which are

particularly simple to analyze from an environmental point of view. From the initial

conception to final recycling, re-use or demolition of a building, a whole range of

Introduction 7

processes must be taken into account. These include transportation to site, site erection

and construction, lifetime use of the building, repairs, maintenance and refurbishment,

demolition or dismantling it at the end of its life, transportation for reuse, and recycling or

disposal (Cole and Kernan, 1996; Eaton and Amato, 1998). In short, a full Life Cycle

Analysis (LCA) is required if one is to properly and thoroughly assess the environmental

impact of a building.

1.5 ENERGY COST

As far as the selection of appropriate indicators of environmental impact is concerned,

energy has long been the measurement of choice (Alcorn, 1998; Baird and Chan, 1983;

Baird and Newsam, 1986; Stein, Stein, Buckley and Green, 1980). Operational energy

use is relatively straightforward to assess. With international protocols (IFIAS, 1974) in

place for the assessment of the embodied energy of materials which tend to be country-

specific, embodied energy calculations have been the subject of considerable study,

particularly following the various ‘energy crises’ in the latter part of the twentieth

century. In many cases it is feasible to calculate CO2 emissions from energy data, though

again this tends to be country-specific, depending on the energy mix and industrial base

of the region and chemical releases of CO2. Hence, energy cost of the building materials

represent the expenditure in energy used in several phases of life cycle.

1.6 SCOPE

Life cycle assessment (LCA) is an analytical methodology that assesses the

environmental performance of a building by taking a system perspective over the whole

life-cycle, from cradle to grave (Nebel, 2007; Zsuzsa and Nebel, 2006). Normally an

LCA involves various environmental assessments such as emissions, wastes and

resources used from all of the buildings life stages from initial conception to final

recycling or disposal. In this study, the scope of the assessment is reduced to CO2

emissions and energy cost estimation, in the following main stages in the life of a

building:

− Extraction of raw building materials

Introduction 8

− Embodied CO2 emission calculation

− Transportation to site

− Construction process of the building

− Demolition and reuse of material

Other stages such as operation of the building and maintenance of the building materials

over the building’s effective life have not been considered because the focus of the study

is on life cycle CO2 emission of construction materials. Materials in their useful life do

not emit any CO2. Emission of CO2 in demolition and disposal has been considered

although previous studies agree that these contribute a relatively small amount to their

respective total life cycle energy consumption and life-cycle CO2 emissions (Cole &

Kernan, 1996; Suzuki & Oka, 1998).

Problem statement: The aim is to estimate life cycle carbon dioxide emission and

energy cost of different building materials. A secondary aim is to identify if the use of

different materials, such as steel and concrete for a building with same plan does

influence the outcome and how.

1.7 OBJECTIVE

The objectives of the thesis are to

- Develop CO2 emission equations from cradle to gate for different types of cement,

sand, timber and aggregate (stone chips) in context of Bangladesh.

- Develop CO2 emission equation from cradle to grave for brick in context of

Bangladesh.

- Develop total life cycle CO2 emission equation of steel from two different

sources i.e. billet and steel scrap.

- Develop CO2 emission equation of concrete using the equations of component

materials for different mix ratios.

- Identify most CO2 emitting material used in building construction in Bangladesh.

Introduction 9

- Estimate energy cost of the above stated building materials in perspective of

Bangladesh.

- Compare CO2 emission and energy cost for a realistic design of two buildings

with steel and concrete as the main construction materials used as the case

studies in the assessment.

Possible outcome:

This study will help to develop a simple carbon dioxide calculator. It will help local

Civil Engineers to assess the environmental impact and cost comparison of alternative

building materials of Bangladesh. It will be possible to identify sustainable materials

considering both CO2 emission and life cycle energy cost.

1.8 RESEARCH OVERVIEW

This thesis is divided into seven main chapters, with the current introduction section

providing the specific context in which this research project has been undertaken, leading

up to the problem statement and the objectives.

Chapter 2 reviews and discusses literature regarding the different life stages of building’s

life-cycle energy consumption and CO2 emissions. It presents the order of magnitudes

between the energy cost and CO2 emissions life stages that a medium size building

incurred during its effective life-cycle.

Chapter 3 describes the methodology employed in this research to determine the life-

cycle energy cost and CO2 emissions of the case study buildings. Chapter 4 represents the

life cycle CO2 emission and energy cost equations. To achieve this, this chapter will be

divided into two parts: one part of it involves developing equations of CO2 emission and

second part of this chapter involves development of energy cost equations and also

describes the different variables involved in the equations. Chapter 5 describes the case

study design with emphasis on the great care taken to ensure a realistic design of the two

buildings used as case studies in the assessment with concrete and steel used as main

construction materials. Chapter 3 will also provide the rationale and emphasis will be

placed on CO2 emissions, and especially, total life cycle CO2 emissions for steel as it has

Introduction 10

recycling potential.

Chapter 6 represents the results produced from the assessment of energy cost of steel and

concrete buildings separately, considering the individual construction materials and

building as a whole and also provides a discussion and comparison.

Conclusions related to each of the objectives are presented in Chapter 7. The chapter

concludes by suggesting future implications and research avenues.

The Appendices found in the rear of this document provide additional information to

support the rationale, assumptions and findings of this research project. Finally, the

schedules of materials and the spread sheet with the calculations of CO2 emissions and

energy cost are attached in the appendix.

CHAPTER 2

LITERATURE REVIEW

__________________________________________________________

This chapter introduces the different components of life-cycle CO2 emissions of different

building materials, energy cost and manufacturing procedures of construction materials. It

will also present the order of magnitudes between each of those life-cycle components.

Data from previous researches on the significance of CO2 emissions in the total life of the

building material for different building systems are also discussed in this chapter.

2.1 LIFE CYCLE ANALYSIS

Life cycle analysis (LCA) quantifies the environmental impacts caused by the energy and

material flows in all stages of a product’s life cycle. In LCA research, the product system

being investigated is structured into several stages. Conventionally, these are 1) raw

material acquisition, 2) parts fabrication, assembly, and construction, 3) use, and 4)

retirement or end-of-life. Life cycle assessment is commonly referred to as a cradle-to-

cradle analysis because it looks at all inputs and outflows in a product system over its

entire life history. In a full LCA, all inputs like material, energy, water and outflows such

as air and water emissions and solid wastes are accounted for. LCA examines the total

environmental impact of a material or product through every step of its life – from

obtaining raw materials, for example, through mining or logging, through manufacture,

transport, their use in the home, and ultimate disposal or recycling. There may be different

system boundaries for LCA studies. They are discussed below.

Cradle to gate: Cradle to gate is the life cycle of a material from the extraction of its raw

materials until it leaves the ‘gate’ of the manufacturing facility. It does not include the

transport to the construction site.

Cradle to site: Cradle to site indicates the life cycle of a material from extraction of raw

material to construction site. It is the extension of life cycle from cradle to gate where the

transportation distance from manufacturing facility to market and construction site is

considered.

Literature review 12

Cradle to grave: Cradle to grave measures the environmental impact of a product from the

extraction of its raw materials until the product is disposed to landfill. This does include

the transport to the construction site.

2.2 CARBON DIOXIDE (CO2) EMISSIONS

Total CO2 emissions represent the mass of CO2 produced during the combustion of solid,

liquid, and gaseous fuels, from gas flaring and the manufacture of cement. These estimates

do not include bunker fuels used in international transportation due to the difficulty of

apportioning these fuels among the countries benefiting from that transport. Carbon

dioxide emissions are often calculated and reported in terms of their content of elemental

carbon. For these data, their values were converted to the actual mass of CO2 by

multiplying the carbon mass by 3.664 (the ratio of the mass of CO2 to that of carbon). The

primary difference between Carbon Dioxide Information Analysis Center (CDIAC,

reported here) and International Energy Agency (IEA) CO2 emission estimates (also

available from Earth Trends) is that the CDIAC data include emissions from sources other

than fossil fuel combustion, primarily cement manufacture.

CO2 emissions from solid fuels represent the mass of carbon dioxide emitted primarily,

but not exclusively, from burning coal. Carbon dioxide emissions from liquid fuels are

primarily, but not exclusively, from burning of petroleum products. These estimates do not

include bunker fuels used in international transportation due to the difficulty of

apportioning these fuels among the countries benefiting from that transport. Carbon

dioxide emissions from gaseous fuels are primarily, but not exclusively, from burning of

natural gas. Carbon dioxide emissions from gas flaring result from the burning of gas

released in the process of petroleum extraction. CO2 emissions from cement

manufacturing are produced as cement is calcined to produce calcium oxide.

Approximately 0.5 metric tons of carbon is released for each metric ton of cement

production. Per capita CO2 emissions figures are obtained by dividing total emissions of

carbon dioxide by the population for a particular country and year. Total CO2 emissions

represent the mass of CO2 produced during the combustion of solid, liquid, and gaseous

fuels, from gas flaring and the manufacture of cement.


2.3 CO2 EMISSIONS COMPONENTS OF A MEDIUM SIZE BUILDING

Different terminologies are used to discuss the life cycle energy consumption and CO2

emission of a building. They are discussed below.

2.3.1 Embodied Energy and Embodied CO2 Emissions

Embodied energy is the energy consumed in all activities necessary to support a process,

and comprises of both direct and indirect components (Baird and Chan, 1983). In building

construction, direct energy includes building assembly and indirect energy includes the

energy embodied in building materials and products (Treloar et al., 2001). As it was said

in Cole and Kernan (1996), “Normally embodied energy typically describes only the

energy to initially produce a building and does not include the energy associated with

maintaining, repairing and replacing material and components over the life of a building,

hence the importance of using the designation initial”.

In addition to the embodied energy, some processes in the production of building

materials release CO2, mainly due to the use of fossil fuel in the electricity mix used as

energy in the production of the materials or in for the use of carbonaceous materials. There

is some research done that accounts for embodied CO2 building materials’, but this is

much more infrequent than research on embodied energy (Nebel, 2007; Page, 2006).

2.3.2 Construction Energy and Construction CO2 Emission

Construction energy is the energy consumed in the construction phase of a building.

Construction activities and construction equipments is a great source of CO2 emission.

Construction of building involved a number of operations namely crane operation, mixing

of materials, use vibrator, compactor, lifts, welding and so on. The emission from this

operations and equipments are termed as construction CO2 emission.

2.3.3 Energy in Use

Energy in use that is the energy required by the occupants of an existing or planned

building, primarily for space heating, water heating and lighting – and of the need to

reduce it. Reduction in energy demand through more efficient buildings brings benefits for

the global environment as well as lower costs and improved quality of life for the

occupants. Buildings in use are the biggest source of energy demand in the UK, with


homes accounting for approximately 30% (and offices 20%) of national energy

consumption (i.e. as much as the industrial and transport sectors put together). Homes and

offices accounted for the release of 579 million tons of carbon dioxide (MtCO2) in 1990. It

has been estimated that 20-30% of this energy demand could be saved through the

application of cost-effective energy efficiency measures (HMSO 1998).

2.3.4 Operating Energy and Operating CO2 Emissions

Operational CO2 emission of buildings is the CO2 emitted to condition (heat, cool and

ventilate) and light the interior spaces and to power equipment and other services. It varies

considerably with building use patterns, climate and season, and the efficiency of the

buildings and its systems (Cole and Kernan, 1996). It is by far the largest component of

the life-cycle CO2 emission. It is far larger than the construction, initial embodied, and

demolition emission all added together (Aye et al., 1999). Cole and Kernan (1996)

conclude that for a building designed following conventional energy performance

standards operational energy will be the largest component of the life-cycle energy

consumption. The study states that only as the energy efficiency of the buildings improve,

the amount of energy required to produce them – embodied energy – will represent an

increasing component of the life-cycle energy consumption (Cole and Kernan, 1996).

Page (2006) briefly ranked the energy use components of life-cycle energy use of the

buildings studied in that research. He said that in terms of energy consumption, the

operation of office buildings is ranked first and contributes to 82% of the life-cycle energy

consumption, while construction work contributes only 15%. For the single storey health

building studied in his study over a 50 year life period, if construction contributes 15% of

the energy consumption, embodied energy accounts for between 7% and 9% of the life-

cycle energy use (Page, 2006).

2.3.5 Demolition Energy Consumption and Demolition CO2 Emissions

Demolition energy is the energy used to demolish buildings and the subsequent transport

and disposal of the building’s waste materials at the end of its effective life. The amount

of CO2 emitted in demolition of a building is termed as demolition CO2 emission. There is

limited information published and it is a process difficult to assess both demolition energy

and CO2 emission based on the prediction of demolition practice some 50 years, or more,


in the future. It can also be difficult to assume an increase in efficiency of demolition and

reutilization of materials during this period of time (Cole and Kernan, 1996). Suzuki and

Oka (1998) suggest that energy consumption is 0.49 GJ/m and CO2 emissions are 36

kg/CO2 from the demolition of a reinforced concrete office building. Both studies in this

section agree that energy consumption and CO2 emissions from the demolition work

contributes a relatively small amount to their respective totals (Cole and Kernan, 1996;

Suzuki and Oka, 1998).

2.4 LIFE CYCLE ENERGY COST

Life cycle costing can be defined as an economic assessment of a building or building

component that considers all the significant costs of ownership over its economic life

expressed in terms of equivalent monetary unit. Energy cost of a building material can be

defined as the expenditure involved in fuel, electricity and other forms of energy used in a

life cycle of a material. Each fuel source has a quantity of CO2 emissions associated with

it. These are not always available in a form that is complete for the end-use of these

energy sources. Coal, gas, petrol, diesel, electricity etc can be considered as the sources of

energy and amount of these energy sources used in the life cycle of a product can be

converted in monetary terms to calculate life cycle energy cost.

2.5 PREVIOUS RESEARCHES

Historically, embodied energy was the prime focus of the research on the life cycle CO2

emission of building materials. Cole and Kernan (1996) suggest distinguishing between

the following four distinct categories of a building’s life-cycle energy consumption.

− The energy to initially produce the building (Initial embodied energy).

− The recurring embodied energy required to refurbish and maintain the building over its

effective life.

− The operational energy, which is the energy use in the operation of the building, for

example the energy use to condition the building (heating, cooling and ventilation), light

the interior space and to power the equipment and other services.

− Energy to demolish and dispose of the building at the end of its effective life.


Eaton and Amato (1998) suggest a slightly more detailed sequence of life stages:

− Transportation to site.

− Site erection and construction.

− Life-time of the building or structure.

− Repairs.

− Maintenance and refurbishment.

− Demolition or dismantling of the structure at the end of its life.

− Transportation for reuse.

− Recycling or disposal.

From all of the building’s life stages, energy and CO2 emissions of construction and

demolition phases are normally neglected and not accounted into the life-cycle energy use

and CO2 emissions of buildings (Aye et al., 1999). On the other hand from all different

environmental burdens, the researches commonly found are carried out for just a selection

of environmental impacts. These are typically energy use and in some cases CO2

emissions (Eaton & Amato, 1998).Blanchard et al. (1998) studied a 2,450 ft2 residential

home referred to as SH or Standard Home built in Ann Arbor, Michigan to determine total

life cycle energy consumption of materials fabrication, construction, use and demolition

over a 50 year period. Life cycle global warming potential (GWP) and life cycle cost were

also determined. The home was then modeled to reduce life cycle energy consumption by

employing various energy efficiency strategies and substitution of selected materials

having lower embodied energy. The total life cycle energy was found to be 15,455 GJ for

SH (equivalent to 2,525 barrels of crude oil1) of which 14,482 GJ (93.7%) occurred

during the use phase (space and water heating, lighting, plug loads and embodied energy

of maintenance and improvement materials). The purchase price of SH was $US 240,000

(actual market value) and determined to be $22,801 more for Energy Efficient Home or

EEH.

Suzuki et al. (1998) quantify the total amount of CO2 emission of office buildings in

Japan. In this study a method for estimating the life cycle energy consumption and the life


cycle CO2 emissions of office building was proposed by construction price index from

1985 input/output (I/O) tables of Japan. Results produced showed that these were

representative of national average cases but it was unreliable mainly due to assumptions

regarding tariffs. The study found that the total emission of CO2 by the construction of

office building varies from 650 to 1100 kg/m2 with an average value of 790 kg/m2.

Nicolas (2008) studied a medium size commercial building to determine the influence of

construction material on the life cycle energy consumption and CO2 emissions. The

analysis was based on an actual 4250 m2 building with mixed mode ventilation system

which was under construction during the study at the University of Lanterberg in Christ

church. To estimate the embodied CO2, Alcorn (2003) and GaBi coefficients were used.

The building was also compared for timber, steel and concrete and timber plus material as

alternative structural system. The CO2 results showed that when using Alcorn coefficients

total embodied CO2 emission averaged 7% and operating CO2 emission averaged 93% and

using GaBi coefficients total embodied CO2 emission averaged 16% and operating CO2

emission averaged 84% of the total life cycle CO2 emission of the four buildings. Using

Alcorn coefficients, the difference between the highest (steel building ) and the lowest

(timber plus)life cycle CO2 emission represents 27% increment of the highest over the

lowest, while using GaBi coefficients it was 9%.

According to Center for Building Performance Research by Victoria University (Alcorn,

A., 2003), the embodied CO2 releases are as followed.

Table 2.1: Emission statistics of different building material

Material CO2 released g CO2/kg

g CO2/m2

Aluminium ( extruded, powder coated)

9205 24855

Concrete (30 MPa) 159 376 Steel (virgin, structural ) 1242 9749 Timber (pine) -1662 -698 Glass(float) 1735 4372

Source: Embodied energy and CO2 coefficients for New Zealand building materials, Center for Building

Performance Research by Victoria University of Wellington, 2003.

Hammond and Craig Jones (2008) of sustainable energy research team (SERT) of

Department of Mechanical Energy of University of Bath developed Inventory of Carbon


and Energy (ICE). The aim of the work was to create an inventory of embodied energy

and carbon coefficients for building materials. The boundary of this study was cradle to

gate and the data was restricted for British Isles. The data was collected from secondary

resources in the public domain, including journal articles, Life Cycle Assessments

(LCA’s), books, conference papers etc. The report was structured into 34 main materials

groups namely Aggregates, Steel, Timber, Sand, Concrete, Aluminium etc. A material

profile was created for each main material. Table 2.2 below represents a summary of some

most used materials.

Table 2.2: Inventory of Carbon and Energy (ICE) of construction materials by University

of Bath, UK.

Material Embodied Energy and Carbon Data EE-MJ/kg EC- kg CO2/kg Aggregate 0.1 0.005 Aluminium 155 8.24 Brick (per single brick) 8.4 0.62 Cement (CEM I) 4.6 0.83 Concrete 1:2:4 1:1.5:3 1:3:6

0.95 1.11 0.77

0.129 0.159 0.096

Glass 15 0.85 Iron 25 1.91 Sand 0.10 0.005 Steel (average of all steels) Virgin Recycled

24.40 35.30 9.50

1.77 2.75 0.43

Timber 8.50 0.46

Many researchers have done several studies on the carbon footprint of individual

construction material. According to Winters-Downey (2010) based on the study of

reclaimed structural steel, the production process including scrap recovery for structural

steel from an electric arc furnace contributes approximately 0.73 tons of CO2 per ton of

steel, with transportation, fabrication and erection contributing roughly an additional 0.3

tons of CO2 per ton of steel.

The three cases in Canada are part of the research undertaken by Cole and Kernan (1995)

in which a 4,620 m2 three storey generic office building is redesigned utilizing either


timber, steel or concrete as the material used mainly in the structural systems (finishing

materials remain the same for all cases). The results of that research show that the total

initial embodied energy is 4.26 GJ/m2, 4.86 GJ/m2 and 4.52 GJ/m2 for the timber, steel and

concrete building respectively. Steel is 1.14 times greater than Concrete, and concrete is

1.06 times greater than the wood structure (Cole and Kernan, 1996).

A research conducted in New Zealand in 2006 on a recently constructed building was

selected and the structural systems were re-designed, to an extent that was ‘practical and

reasonable’, in timber, concrete and steel. The building chosen was a health building

(Outpatient) with a floor area of 1640 m2 in a single storey. The layout consists of over 35

consultation and service rooms and an educational area attached to the back of the

building (Page, 2006). When looking at total embodied CO2 emissions, the results of that

research were 369 kg/m2, 253 kg/m2 and 149 kg/m2 for the concrete, steel and timber

building respectively. Note that this is a small single storey building and that not all

materials and fittings have been included in the alternative designs.

2.6 MANUFACTURING PROCEDURES OF BUILDING MATERIALS

2.6.1 Brick

In aggregate starved Bangladesh, fired clay bricks form a significant portion of the

materials used in the construction industry. They are the major “building-blocks” in all

infrastructure, building, road and highway projects. The stages of brick production are -

Clay Extraction, Transport and Preparation - The clay is excavated by hydraulic

excavator or by hand from nearby riverbeds and transported to the plant-stacking yard by

trucks. The clay is then crushed by means of roller mills, followed by a double-shaft

mixer, where water is added in such a manner as to ensure moisture content of 15%.

Brick Shaping - The tempered material is fed into a vacuum extruder for continuous

column production. The column is then cut with a cutter column and a cutter green to the

required size. The green brick is then manually loaded on to a drying car for drying.

Brick Drying - The drying car is then transported into the drying tunnel by means of a

hydraulic pusher. Hot air for drying is funneled into the tunnel from the annular kiln. The

drying cycle lasts for about 26 hours.


Brick Firing - The dried green bricks are unloaded manually into the kiln. The speed of

the firing is 1.25m/h at a sintering temperature of about 950 oC–1050 oC. The fired bricks

are unloaded and conveyed manually in carts to the stacking yard.

2.6.2 Cement

A cement production plant consists of the following three processes: raw material process,

clinker burning process and finish grinding process. The raw material process and the

clinker burning process are each classified into the wet process and the dry process. These

processes are selected with consideration given to properties of raw materials, costs of

fuel, conditions of location and others. Cement manufacturing dry process description is

given below:

Quarrying- Two types of materials are necessary for the production of cement: one rich in

calcium or calcareous materials such as limestone, chalk, etc., and one that is rich in silica

or argillaceous materials such as clay. Extensive quarry drilling and analysis are being

undertaken to reduce the variability of the raw material quality. The quality check that

starts from the quarry ensures optimization in the utilization of the reserves. Limestone

and clay are either scraped or blasted from the quarry and then transported to the crusher.

Crushing- The crusher is responsible for the primary size reduction of the quarried

materials. Boulders as big as 1 meter are being crushed to material sizes less than 80 mm.

Pre-blending-The crushed materials pass through an on-line analyzer to determine the pile

composition. A stacker is then used to create different piles of materials and to reduce

variation in material beds.

Raw grinding and blending- A belt conveyor transports the pre-blended piles into

individual bins where a weighing feeder proportions it according to the type of clinker to

be produced. The materials are then ground into the desired fineness by the raw mill

equipment. The powdered raw meal is then transported into a continuous blending storage

silo where variations are further reduced by mixing using aeration.

Burning and clinker cooling - The homogenized raw mix is fed into the pre-heater, a heat

exchange equipment composed of a series of cyclones wherein heat transfer between the

raw mix feed and the counter current hot gases from the kiln take place. Calcination


partially takes place in the preheater. Raw meal is fed directly from the preheater to the

rotary kiln. The slight angle of inclination and rotation of the kiln causes the raw feed to

slowly make its way through the kiln counter current to the burner flame. The heat of the

kiln breaks the chemical components and brings the raw mix into a semi-molten state. At

this point, raw materials form compounds that produce the cementitous properties. After

the burning section of the kiln, the materials turn into solid nodules known as clinker and

discharge into the clinker cooler.

Figure 2.1: Cement manufacturing (dry) process (www.cemex.com)

Clinkerization occurs between 1350-1400 °C wherein fine coal, pulverized by coal

milling, is often used as heating fuel. The clinker cooler cools the hot granular mass of

clinker by quenching air into it bringing the temperature down to 100 °C. So air becomes

hot and clinker cold. This hot air is then utilized as combustion air for the firing system of

the kiln. Conveyors transport then the cooled clinker to the clinker storage silo.

Finish grinding- From the clinker silo, clinker is transferred to the clinker bin. It passes

through the weighing feeder, which regulates its flow in proportion with the additive

materials. At this stage, gypsum is added to the clinker and then fed to the finish grinding


mills. Gypsum serves as a retarder in the too rapid setting or hardening of cement. Either

the mixture of clinker and gypsum for Type-1 cement or the mixture of clinker, gypsum

and pozzolan material for Type-P cement is pulverized in a closed circuit system in the

finish mills to the desired fineness, usually about 87% minimum passing 325 mesh sieves.

Cement is now piped to cement silos.

Packing and distribution- The cement from the cement silos are packed into bags by

rotary packers or loaded as bulk and are distributed either by land using forwarder trucks

and bulk trucks or by sea using barges or bulk ships.

2.6.3 Sand

Sand is loose material formed of quartz grains such as that of the beaches or dunes. Sand

grains are mostly siliceous; sometimes calcareous or of volcanic origin. Bangladesh is

quite rich in terms of sand and silt deposits. Extraction of sand keeps the river channels

clear for the free flow of water. The following steps are commonly used to process sand

and gravel for construction purposes.

Natural decomposition - Solid rock is broken down into chunks by natural mechanical

forces such as the movement of glaciers, the expansion of water in cracks during freezing,

and the impacts of rocks falling on each other. The chunks of rock are further broken

down into grains by the chemical action of vegetation and rain combined with mechanical

impacts as the progressively smaller particles are carried and worn by wind and water. As

the grains of rock are carried into waterways, some are deposited along the bank, while

others eventually reach the sea, where they may join with fragments of coral or shells to

form beaches. Wind-borne sand may form dunes.

Extraction - Extraction of sand can be as simple as scooping it up from the riverbank with

a rubber-tired vehicle called a front loader. Some sand is excavated from under water

using floating dredges. These dredges have a long boom with a rotating cutter head to

loosen the sand deposits and a suction pipe to suck up the sand. If the sand is extracted

with a front loader, it is then dumped into a truck or train, or placed onto a conveyor belt

for transportation to the nearby processing plant. If the sand is extracted from underwater

with a dredge, the slurry of sand and water is pumped through a pipeline to the plant.


Figure 2.2: Sand Manufacturing Process (http://www.beneficiationchina.com)

Sorting - In the processing plant, the incoming material is first mixed with water, if it is

not already mixed as part of slurry, and is discharged through a large perforated screen in

the feeder to separate out rocks, lumps of clay, sticks, and other foreign material. If the

material is heavily bound together with clay or soil, it may then pass through a blade mill

which breaks it up into smaller chunks. The material then pass through several / perforated

screens or plates with different hole diameters or openings to separate the particles

according to size. The screens or plates measure up to 10 ft (3.1 m) wide by up to 28 ft

(8.5 m) long and are tilted at an angle of about 20-45 degrees from the horizontal. They

are vibrated to allow the trapped material on each level to work its way off the end of the

screen and onto separate conveyor belts. The coarsest screen, with the largest holes, is on

top, and the screens underneath have progressively smaller holes.

Washing - The material that comes off the coarsest screen is washed in a log washer

before it is further screened. The name for this piece of equipment comes from the early

practice of putting short lengths of wood logs inside a rotating drum filled with sand and

gravel to add to the scrubbing action. A modern log washer consists of a slightly inclined

horizontal trough with slowly rotating blades attached to a shaft that runs down the axis of


the trough. The blades churn through the material as it passes through the trough to strip

away any remaining clay or soft soil. The larger gravel particles are separated out and

screened into different sizes, while any smaller sand particles that had been attached to the

gravel may be carried back and added to the flow of incoming material. The material that

comes off the intermediate screen(s) may be stored and blended with either the coarser

gravel or the finer sand to make various aggregate mixes. The water and material that pass

through the finest screen is pumped into a horizontal sand classifying tank. As the mixture

flows from one end of the tank to the other, the sand sinks to the bottom where it is

trapped in a series of bins. The larger, heavier sand particles drop out first, followed by the

progressively smaller sand particles, while the lighter silt particles are carried off in the

flow of water. The water and silt are then pumped out of the classifying tank and through a

clarifier where the silt settles to the bottom and is removed. The clear water is recirculated

to the feeder to be used again. The sand is removed from the bins in the bottom of the

classifying tank with rotating dewatering screws that slowly move the sand up the inside

of an inclined cylinder. The differently sized sands are then washed again to remove any

remaining silt and are transported by conveyor belts to stockpiles for storage.

Crushing - Some sand is crushed to produce a specific size or shape that is not available

naturally. The crusher may be a rotating cone type in which the sand falls between an

upper rotating cone and a lower fixed cone that are separated by a very small distance.

Any particles larger than this separation distance are crushed between the heavy metal

cones, and the resulting particles fall out the bottom.

2.6.4 Aggregate

Sandstones and granites are the main two types of aggregates mainly used in Bangladesh.

Granite is an intrusive igneous rock which is widely distributed throughout Earth’s crust at

a range of depths up to 31 mi (50 km). Many variations of granite appear on the

commercial market with white, gray, pink, and red being the most common primary

colors. Sandstone is a very common rock in the geological group-formations of

Bangladesh. Sandstone is often used as building material as blocks in the construction of

large buildings. Very small percentage of aggregates is quarried in Bangladesh.


Quarrying- Most large commercial quarries produce aggregate as their primary product,

and any large-stone material is a subordinate by-product. The same is true for quarries

producing flux for iron ore reduction. This imbalance must be appreciated when

considering an aggregate or flux-stone quarry as a source of large stone. The production

and stockpiling of large stone usually is constrained rigidly by the production of the

primary product. Occasionally, a separate operation for large stone is established within

the quarry.

Figure 2.3: Secondary crushing plant

for gabbro with cone Crushers Plant

throughput:1000t/h.(www.sbmmp.at)

Figure 2.4: Four vertical shaft impact

crushers with vertical shafts for improving

aggregate shape after cone crushers, material

gabbro and through output 700 ton/h.

(www.sbm-mp.at)

Processing- Some processing is usually necessary to achieve the stone size distribution

required in the specifications. Processing usually involves the removal of oversize and

undersize material at the minimum but may also involve sophisticated means of

separating stone pieces into classes by size. When crushing hard stone, the selection of

the crushers to be used for the individual crushing steps is decisive for the productivity of

the equipment:

• Jaw crushers

• Cone crushers

• Horizontal shaft impact crushers (HSI)


• Vertical shaft impact crushers (VSI)

Scheduling - The limitations imposed by the scale, methods, and principal product from

blasting and processing frequently impact on the availability of material on schedule.

2.6.5 Steel

Bangladesh imports 70% billets and other raw materials from foreign countries as scrap

ship import had been decreased. Sources of steel products include Australia, Belgium,

Canada, China, France, Germany, Greece, Hongkong, India, Indonesia, Italy, Japan,

Malaysia, Mexico, Netherlands, North Korea, Poland, Russia, Saudi Arabia, Singapore,

South Korea, Turkey, UK and the USA. But the major sources are India and South

Korea. So considering both the sources emission equations are developed. The history of

ship breaking is as nearly old as ship building. Generally 95% of a ships body is made of

mild steel (M.S.), 2% of stainless steel and 3% of miscellaneous metals, such as brass,

aluminium, copper, gun metal and other alloys which are important factors of ship

breaking . No sound technical system is used to recover valuable stores, spares, metals

and other items from the ships.

The main raw material in Billet Manufacturing process is mild steel scrap which is

procured from local and international markets. The scrap is mixed in pre-determined

proportions in the scrap yard and fed to the furnaces in charging buckets and melted by

Electric Arc using Graphite Electrodes. The molten metal is processed to remove the

impurities like sulphur and phosphorous and is subjected to slag off and further refining

by adding Ferro alloys and other fluxes to bring it to the required standard specifications.

Liquid metal samples are analyzed at frequent intervals to ensure quality if the product as

per I.S. The molten steel is tapped at the required temperature to the pre-heated ladles.

Steel ladles are equipped with latest slide gate opening system. Temperature of the

molten metal in the ladle is measured to ensure correct temperature at the continuous

casting machine. Currently, there are two main routes for the production of steel:

production of primary steel using iron ores and scrap and production of secondary steel

using scrap as the main raw material. A wide variety of steel products are produced by

the industry, ranging from slabs and ingots to thin sheets, which are used in turn by a


large number of manufacturing industries. Steel production requires several steps that can

be accomplished with different processes.

Figure 2.5: Steel manufacturing process in rerolling mills (www.sussex.ac.uk)

Both the input material (Schumacher et al., 1998) of each step and the process

substantially affect the total energy consumed during production. The liquid metal is then

poured from ladle to the tundish and then to the water cooled copper mould on


continuous casting machine. There takes place the billet formation by solidification of the

molten steel due to water cooling. Billets of 100 mm square coming out of the continuous

casting machine are cut to the required length by gas cutting and are again subjected to

stringent quality inspection and stacked according to color codes specified by BIS. The

Billets are further rolled and converted into constructional steel of various sections at

Rolling Mills.

2.6.6 Timber

Timber denotes structural wood. A study showed that embodied CO2 emissions of timber

were two to three times lower than for the steel or concrete building. Timber is

considered as an important structural member with less carbon footprint. The main source

of timber in Bangladesh is Sundarban .Thus, the life cycle of timber can be considered as

following stages in the figure 2.6.

Figure 2.6: Schematic flow chart of wood materials during the building lifecycle.

2.6.7 Concrete

Concrete is an artificial material obtained by mixing together cementing material, coarse

aggregate, fine aggregate and water. Concrete is a friend of the environment in all stages

of its life span, from raw material production to demolition, making it a natural choice for

sustainable home construction. Concrete can be classified as mud concrete, cement

concrete and lime concrete. Cement concrete is prepared by mixing together cement, sand


and coarse aggregate. It is a very important structural material and should be carefully

designed, mixed, placed and cured.

Concrete production process:

The processes used vary dramatically, from hand tools to heavy industry, but result in the

concrete being placed where it cures into a final form. Wide range of technological

factors may occur during production of concrete elements and their influence to basic

characteristics may vary. When initially mixed together, Portland cement and water

rapidly form a gel, formed of tangled chains of interlocking crystals. These continue to

react over time, with the initially fluid gel often aiding in placement by improving

workability. As the concrete sets, the chains of crystals join and form a rigid structure,

gluing the aggregate particles in place. During curing, more of the cement reacts with the

residual water called hydration. This curing process develops physical and chemical

properties. Among these qualities are mechanical strength, low moisture permeability and

chemical and volumetric stability.

Mixing concrete- Thorough mixing is essential for the production of uniform, high

quality concrete. For this reason equipment and methods should be capable of

effectively mixing concrete materials containing the largest specified aggregate to

produce uniform mixtures of the lowest slump practical for the work. Separate paste

mixing has shown that the mixing of cement and water into a paste before combining

these materials with aggregates can increase the compressive strength of the resulting

concrete. The paste is generally mixed in a high-speed, shear-type mixer at a w/c (water

to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include

admixtures such as accelerators or retarders, super plasticizers, pigments, or silica fume.

The premixed paste is then blended with aggregates and any remaining batch water and

final mixing is completed in conventional concrete mixing equipment.

Workability- Workability is the ability of a fresh (plastic) concrete mix to fill the

form/mold properly with the desired work (vibration) and without reducing the

concrete's quality. Workability depends on water content, aggregate (shape and size

distribution), cementitious content and age (level of hydration) and can be modified by


adding chemical admixtures, like super plasticizer. Raising the water content or adding

chemical admixtures will increase concrete workability. Excessive water will lead to

increased bleeding (surface water) and/or segregation of aggregates (when the cement

and aggregates start to separate), with the resulting concrete having reduced quality. The

use of an aggregate with an undesirable gradation can result in a very harsh mix design

with a very low slump, which cannot be readily made more workable by addition of

reasonable amounts of water.

Curing-In all but the least critical applications, care needs to be taken to properly cure

concrete, to achieve best strength and hardness. This happens after the concrete has been

placed. Cement requires a moist, controlled environment to gain strength and harden

fully. The cement paste hardens over time, initially setting and becoming rigid though

very weak and gaining in strength in the weeks following.

Considering these phases of manufacturing procedures equations of life cycle CO2 and

energy cost has been developed in the next chapter.

31 Methodology

CHAPTER 3

METHODOLOGY

________________________________________________________________________

3.1 GENERAL

For this study, data has been collected from the secondary resources of public domain,

including journal articles, life cycle assessments, books, websites, conference papers, field

data etc. All the information has been used considering perspective of Bangladesh. Cradle

to gate has been the most common boundary condition although for some material, like

brick, timber etc study has been also continued for cradle to grave. For some recyclable

materials like steel; from both billet and scrap, total life cycle emission term has been used

other than the boundary condition cradle to grave. Uncertainty is unfortunately a part of

CO2 analysis and even the most reliable data carries a natural level of uncertainty.

3.2 METHODOLOGY OF DEVELOPING EQUATIONS OF LIFE CYCLE

CO2 EMISSION AND ENERGY COST OF BUILDING MATERIALS

The life cycle CO2 emission and energy cost equations have been developed for seven

most widely used construction materials of Bangladesh namely brick, cement, sand, steel;

both from billet and scrap, stone chips, timber and concrete. The total life cycle of the

materials has been considered from perspective of Bangladesh. For example; aggregates

are mainly processed in Bangladesh though very small amount can be quarried. Equations

have been developed for both cases. The carbon coefficients selected for the study has

been representative of typical materials employed in the Bangladeshi market. In order to

ensure that this data have been representative of typical products, taking timber as an

example; the consumption of most common types of timber was applied to estimate a

single ‘representative’ value that can be used in the absence of more detailed knowledge

of the specific type of timber.

3.2.1 Selection Criteria

The criteria needed to be flexible but maintain an ideal set of conditions due to the

difficulties that have been experienced in selecting emission values. Six criteria have been

Methodology 32

applied for the selection of CO2 emission values for individual materials. This ensures the

consistency of the data. They are given below.

• Compliance with approved methodologies

Preference has been given to data sources that complied with accepted methodologies and

manufacturing procedure. For example, about 90% of the brick fields use manual molding,

drying procedures. In this case, mechanical operations have not been considered.

• System boundaries

The system boundary has been adopted mainly as ‘cradle to gate’, but in case of some

materials ‘cradle to grave’ has been considered. Construction phase and demolition phase

have been taken into consideration. Steel is recycled as raw material after use in building.

In this case the term ‘total life cycle emission’ has been used other than cradle to get or

cradle to grave. For component materials like sand, aggregate and cement which will be

finally incorporated into concrete, cradle to gate emissions have been considered.

• Origin of data

Ideally the data used and the equations developed would have been restricted to that

emanating from Bangladesh. In case of some materials it has not been feasible due to lack

of available data and study. Data of CO2 emission from manufacturing process,

construction equipments etc from foreign sources have been considered only if the same

procedures are followed in Bangladesh. For energy cost calculations, life cycle of each of

the materials has been broken down in several phases in which energy has been consumed.

Each of the phases has been again broken down in to more specific forms for ease of

calculation. Primary fuel and input energy have only been considered. Loss of energy and

transfer of energy has not been considered. Coal, diesel, natural gas, electricity etc has

been considered as the sources of energy and conversion factors have been used to convert

the energy data in to cost.

• Age of data sources

Preference has been given to modern sources of data. Historical changes in fuel mix and

carbon coefficients associated with electricity generation give rise to greater uncertainty in

the carbon dioxide emission values.

Methodology 33

• Operating CO2 emission

In this study, operating CO2 emission of building material, thermal conductivity and

diffusivity has not been considered. No of times the material has been recycled do not

have any significant impact on CO2 emission calculation.

• Carbon dioxide emission factors

Petro chemicals as fuels have been considered for number of manufacturing process of

materials. In case of developing CO2 emission equations, the fuel consumption has been

converted to CO2 emission values by using CO2 emission factors. Emission factors have

been used from unit conversion fact sheet by MIT (2007) and Guidance for Voluntary,

Corporate Greenhouse Gas Reporting: Data by New Zealand (Fuel combustion emission

factors 2008). In addition to these selection criteria the data primarily focused on

construction materials.

In case of energy cost equation, several conversion methodologies have been adopted.

CO2 emission from fuel consumption has been calculated for several materials. In this

case CO2 emission has been converted to fuel consumption units by using CO2 emission

factors. Emission factors have been used from unit conversion fact sheet by MIT (2007)

and Guidance for Voluntary, Corporate Greenhouse Gas Reporting: Data by New

Zealand: Fuel combustion emission factors 2008 from table 1 of appendix A. In some

cases energy data has been converted to cost. Again due to lack of sufficient data energy

cost has been calculated using the fuel consumption of the particular machineries used in

production of the materials for the required unit.

3.2.2 Mode of Material Transport

In most of the previous researches of life cycle CO2 emission of construction materials the

boundary conditions were cradle to site. This was based on the assumption that in many

cases transport from the factory gate to construction site would be negligible (Cole et

al.1996). Whilst this may be true for many materials but this is not exclusively the case. In

the case of materials which have very low carbon dioxide emissions from their processing

such as sand and aggregate, emission from transportation is likely to be significant. For

these reasons the ideal boundaries have been modified to cradle to gate from the previous

Methodology 34

cradle to site. This decision will also encourage the user to be transport specific to their

case in hand. In these study two types of transportation has been considered. They are -

− Shipment of materials ( for steel billets)

− Transportation by road of raw materials and products within the country.

Emission from transportation has been used from the chart of Swedish Network for

Transport and the Environment (Maersk Line 2007) which gives emission of carbon

dioxide directly for mode of transportation. In case of shipment distance, nautical miles

(http://www.searates.com/reference/portdistance/) have been converted into miles to

calculate emission from shipment. Bangladesh imports raw materials from a number of

countries. In this case, maximum and minimum distances for raw material import have

been selected considering local market survey to give representative values.

3.2.3 Functional unit

Empirical equations have been developed which required input values in desired unit. It is

inappropriate to consider material solely on kilogram basis. Material must be represented

on their functional unit basis. For example, cement is represented in tons, sand in kilogram

(kg), bricks in single unit etc. The manufacture of 1 kg of product requires raw materials

more than 1 kg. The quantity of waste, volume decrease, shrinkage etc has been

considered in this study. The impacts of maintenance on life cycle emission of materials

have not been considered. Highly fabricated and intricate items require manufacturing

operations that are beyond the boundaries of the study. As the energy cost equations give

the cost of input energy in context of Bangladesh, Bangladeshi currency taka (BDT) has

been considered.

35 Methodology

CHAPTER 4

DEVELOPMENT OF LIFE CYCLE CO2 EMISSION AND ENERGY

COST EQUATIONS

________________________________________________________________________

4.1 GENERAL

In this chapter, empirical equations of life cycle CO2 emission and energy cost have been

developed considering the methodology adopted in chapter 3. The equations have been

developed for seven most widely used construction materials of construction industry of

Bangladesh and described in the following articles.

4.2 LIFE CYCLE CO2 EMISSION EQUATIONS OF MATERIALS

Life Cycle CO2 emission equations have been developed for brick, cement, steel from

billet and steel from scrap, aggregates, timber, sand and concrete. The materials are

categorized in two groups. First group comprises of brick, steel from scrap, locally

produced cement, aggregates, timber, sand and concrete which are produced within our

country. Second group consist of the materials for which raw materials are imported from

other countries such as cement clinker and steel billet.

4.2.1 Brick Profile

In aggregate starved Bangladesh, fired clay bricks form a significant portion of the

materials used in the construction industry. Brick making is considered to be the largest

contributor to green house gas emissions in Bangladesh in the order of 3.0 million tones of

CO2 emissions annually (World Green Building Council 2006). Currently, the brick

making sector in Bangladesh uses four types of technologies: Fixed Chimney Kilns

(FCK), Bull’s Trench Kilns (BTK), Zigzag Kilns and traditional Hoffman Kilns.

Prior to 2004, of the kilns in Bangladesh used the BTK design, a relatively primitive

design that is over 150 years old. After promulgation of the Brick Burning (Control) Act

in 2004, almost all of the BTKs have been converted to FCKs (UNFCC 2008). Stages

considered for brick have been - clay extraction, clay delivery to brick plant, mixing and

shaping, drying and burning, transportation, installation in site, recycling as brick chips

Development of life cycle CO2 emission and energy cost equations 36

and reuse. As fixed chimney kilns are majority according to table 4.1, for drying and

burning of bricks, emission data of FCK kiln has been used. In FCK kiln coal is mainly

considered as energy input (UNFCC 2008).

Table 4.1: Current market share of technologies in the brick making sector.

Source: Improving Kiln Efficiency for the Brick Making Industry - PDF B Phase (UNDP-GEF-

BGD/04/014)

Hence calculations can be summarized as

Stage: Drying and burning of bricks

Energy input: Coal

Emission of CO2 from FCK kiln: 760.49 ton per 20, 00,000 bricks

(Improving kiln efficiency, 2006).

Emission per brick: 380.25 gCO2/brick

Equations have been developed for a single brick as functional unit and both the boundary

conditions i.e. cradle to gate and cradle to grave. In all calculations, standard brick

dimension i.e. 9.5″x 4.5″x 2.75″ given by Public works department (PWD) Bangladesh

has been considered.

For transportation of brick heavy truck has been considered. From table A5 of appendix A

CO2 emission for this type of vehicle has been found as 50 g CO2/ton-km.

Hence, CO2 emission for heavy truck: 50 g CO2/ton-km (Maersk line, 2007)

Volume of one brick: 0.07 cft (considering PWD standard brick dimension)

Density of brick: 120 lb /cft or 0.06 ton /cft (common red brick)

1 brick = 0.07 x 0.06 = 0.0042 ton

Kiln type

Number Percentage of total

Annual brick production (billions)

Percentage of total production

FCK 3,138 76 6,276 75.9 BTK 797 19 1.59 19.3 Zigzag 198 5 0.40 4.79 Total 4,133 100 8.27 100


1 ton: 238 bricks

CO2 emission for one brick = 50238

= 0.21 g CO2/brick-km

Hence, CO2 emission per brick is 0.21 g CO2/brick-km.

Table 4.2: Summery of Emission of CO2 through different stages of life cycle of Brick

Stages Emission of CO2 Unit Drying and burning in FCK kiln 380.25 g CO2/Single Brick Transportation 0.21 g CO2/brick-km

Cradle to Gate Emission = 380.25+0.21 db1, (g CO2/Single Brick) 4.1a

Cradle to Grave Emission = 380.25+0.21 (db1 + db2), (g CO2/Single Brick) 4.1b

Here,

db1= distance in kilometer from brick field to market.

db2= distance in kilometer from market to construction site and then to brick chips

processing site.

Similar studies on life cycle CO2 emission from single brick done in Australia (Grant

2010) showed that the emission is 700 g CO2 and 620 g CO2 in the study done by

University of Bath. In both these studies the whole process was mechanized and in cradle

to gate emission calculation operation CO2 emission from the building was also

considered.

4.2.2 Cement Profile

For developing life cycle CO2 emission of cement three types of cement composition have

been considered namely CEM-I, CEM-IIA and CEM-IIB. CEM-IIA has been considered

with 80% Portland cement and CEM-IIB has been considered with 65% Portland cement.

Locally produced cement

Most of the cement mills in Bangladesh are grinding mills which use imported lime stone,

local material shell and clay to produce cement. For locally produced cement, stages

considered are import of lime stone, raw material transport, primary and secondary


crushing, raw grinding, kiln process and finally finish grinding. Diesel has been

considered as energy source for transportation. For other stages coal has been considered.

Limestone which is raw material used in cement production is a source of calcareous

matter in cement. Considering, limestone contains 80% of CaCO3 and Portland cement

contains 65% of CaCO3. Most of the lime stones are imported from India. India with 286

nautical miles or 530 km has been considered as import distance from Chittagong port

(www.searates.com/reference/portdistance). For sea freight emission factor ranges from

7.48 to 8.35 g CO2/ton-km as shown in table A5 of appendix A. Therefore considering

emission rate 8 g CO2/ton-km for emission due to shipment. Emission for one ton of lime

stone is 4.2 kg CO2/ton and factors 0.80 and 0.65 are used for CEM1. This gives 0.002 kg

CO2/kg.

According to Athena report, energy consumed in production of Portland cement for

extraction, crushing and grinding are 44.42 kJ/ kg, 17.79 kJ/ kg and 35.53 kJ/ kg

respectively. Total CO2 emission per kg of cement has been found for this stage as 0.02 kg

CO2 (Venta et al. 1999). Hence emissions for above mentioned cement types are 0.812 kg

CO2, 0.650 kg CO2 and 0.53 kg CO2 respectively (Hendriks, 2002). As the grinding and

kiln process are similar worldwide, the emission data of Tec Eco cement

(www.tececo.com) has been used for CEM-I, CEM-IIA and CEM-IIB. Grinding is a

mechanical process and same for all countries. Emission due to finish grinding for CEM-I,

CEM-IIA and CEM-IIB are 0.04 kg CO2, 0.03 kg CO2 and 0.03 kg CO2 respectively

(Venta et al. 1999).

Table 4.3: Summery of Emission of CO2 through different stages of life cycle of locally

produced cement.

Stages Emission kg CO2/kg of CEM-I

Emission kgCO2/kg of CEM-IIA

Emission kgCO2/kg of CEM-IIB

Import of lime stone 0.002 0.002 0.001 Crushing and grinding 0.008 0.006 0.005 Kiln process 0.812 0.65 0.53 Finish grinding 0.038 0.03 0.03 Total 0.86 0.69 0.57


For transportation diesel powered heavy truck has been considered. From table A5 of

Appendix A, for transporting 1 ton freight per kilometer distance, emission of CO2 is 50 g

(Maersk line, 2007) or 0.05 kg CO2 /ton-km.

Life cycle CO2 emission equations have been developed for one ton of cement with cradle

to gate boundary condition.

Cradle to Gate Emission

CEM- I = 860 + 0.05 dc, (kg CO2/ton) 4.2 a

CEM-IIA = 690 + 0.05 dc, (kg CO2/ton) 4.2 b

CEM-IIB = 570 + 0.05 dc, (kg CO2/ton) 4.2 c

Here,

c = total distance in kilometer from cement factory to market

Cement from imported clinker

Again most of the cement factories of Bangladesh are the grinding mills. In this imported

clinker is used. Energy required for finish grinding is 194.51kJ/kg. Emission is 0.018 kg

CO2/kg. Clinkers are considered to be imported from India. For sea freight emission factor

ranges from 7.48 to 8.35 g CO2/ton-km as shown in table A5 of appendix A. Therefore

considering emission rate 8 g CO2/ton-km for emission due to shipment. Emission for one

ton of clinker is 4.2 kg CO2/ton. CEM-IIA has been considered with 80% Portland cement

and CEM-IIB has been considered with 65% Portland cement.

Table 4.4: Summery of Emission of CO2 through different stages of life cycle of cement

from imported clinker.

Stages Emission rate CEM-I kg CO2/ton

CEM-IIA kgCO2/ton

CEM-IIB kgCO2/ton

Import of clinker 0.008 kgCO2/ton-km 4.2 3.36 2.73

Finish grinding 18 kgCO2/ton 18 14.3 11.7 transportation 50 g/ton-km



CEM- I = 22+ 0.05 dc, (kg CO2/ton) 4.2 c

CEM-IIA = 17.6 + 0.05 dc, (kg CO2/ton) 4.2 d

CEM-IIB = 14.3 + 0.05 dc, (kg CO2/ton) 4.2 e

According to University of bath, CO2 emission from Portland cement was found to be 830

kg CO2/ton; whereas CO2 emission from cement with 26% fly ash was 620 kg CO2/ton

and 50% fly ash was 420 kg CO2/ton (Hammond et al. 2008).

4.2.3 Steel Profile

Bangladesh imports 70% billets and other raw materials from foreign countries

(www.secbd.org/Prospectus_BSRMS.pdf) as scrap ship import had been decreased.

Sources of steel products include Australia, Belgium, Canada, China, France, Germany,

Greece, Hong Kong, India, Indonesia, Italy, Japan, Malaysia, Mexico, Netherlands, North

Korea, Poland, Russia, Saudi Arabia, Singapore, South Korea, Turkey, UK and the USA.

But the major sources are India and South Korea. So considering both the sources

emission equations have been developed.

From Billet

In developing life cycle CO2 emission equation for steel from billet, import of billet has

been considered as cradle, where the life cycle has been considered to be started. The

major stages considered are Shipment of billet, rerolling process (Das et al. 1997), erection

considering use of crane and welding, and transportation. As steel has recycling potential

the term total life cycle CO2 emission has been used along with the term cradle to gate. For

cradle to gate criteria stages considered have been shipment of billet, rerolling process and

transportation. Separate equations of minimum and maximum values of CO2 emission are

given for minimum and maximum shipment distance respectively. South Korea with a

distance of 3976 nautical miles or 7364 km has been considered as maximum import

distance and India with 286 nautical miles or 530 km has been considered as minimum

import distance from Chittagong port (www.searates.com/reference/portdistance). For sea

freight emission factor ranges from 7.48 to 8.35 g CO2/ton-km as shown in table A5 of


appendix A. therefore considering emission rate 8 g CO2/ton-km for emission due to

shipment.

Equations have been developed for one ton of steel billet. As billets are imported to

Bangladesh, manufacturing process starts from rerolling process to cast steel into desired

shapes. Steel is highly resistant to shaping while cold and whatever may be the product

hot rolling process is the same. Rolls are driven by powerful electric motors. For hot

rolling process Coal and electricity is used as input energy. It involves 1.82 GJ/ton for coal

and 0.37 GJ/ton for electricity. Conversion factor 0.074 tCO2/GJ and 0.271 tCO2/ GJ have

been taken from table A4 of Appendix A.

Table 4.5: Summery of Emission of CO2 through different stages of life cycle of Billet

Phases Emission rate Emission kg CO2/ton

Import of billet

• From south Korea, distance -7364 km 0.008 kgCO2 /ton-km 60

• From India, distance -530 km 0.008 kgCO2 /ton-km 4.2 Hot rolling process

• Emission (coal) - 1.82 GJ/ton 0.074 tCO2/GJ 130

• Emission (electricity) - 0.37 GJ/ton 0.271 tCO2/GJ 100

Transportation 50 g CO2/ton-km

Total Emission (max) = 60 + 230 = 290 kg CO2/ton

Total Emission (min) = 4.2 + 230 = 234 kg CO2/ton

CO2 emission by diesel powered heavy truck due to transportation is same as article 4.2.2.

Hence, emission equations are,

Cradle to gate (min) = 234+0. 05 dst1 (kg CO2/ton) 4.3 a

Cradle to gate (max) = 290+0.05 dst1 (kg CO2/ton) 4.3 b

Here,

dst1= total distance in kilometer from port to rerolling mills and rerolling mills to market.


As the steel elements such as bean, column etc are taken to the construction site emission

of CO2 occur during erection, crane operation and welding of the steel elements.

QTZ50 model tower crane has been considered for fuel consumption and operation

specification (http://www.cranescn.com/). According to the specification given in

Appendix B, this crane has jib length of 50 meter, height 37.5/33 meter ,tip load 0.9-1 ton

and max load of 4 ton. Considering hoisting capacity 9 meter per minute with capacity 2

ton and energy used is 4 kW, 9 meter of hoisting requires energy 120 kWh per ton.

Therefore, emission of CO2 for hoisting is calculated as 8.1 kg CO2 /ton-m.

(http://web.mit.edu/mit_energy). For derricking, with 2 ton capacity and 50 meter jib

length, one meter of derricking requires energy 1.69 kWh per ton-m. Therefore emission

for derricking is 1.03 kg CO2 /ton-m. Considering electric arc welding each square meter

of welding emits 0.04 kg CO2 (www.izumi-mfg.co.jp/english/outline.html).

Table 4.6: Emission of CO2 during construction with steel members made from Billet

Operation Emission rate Crane operation

• Hoisting 8.1 kgCO2/ton-m • Derricking 1.03 kgCO2/ton-m

Welding 0.04 kgCO2/m2

At the end of the operational period of the structure the steel elements are again taken to

the rerolling mill for recycling and the system continues. Hence, considering all the stages

starting from shipment of the billets and neglecting emission during the useful life of the

building life cycle CO2 emission has been calculated.

Total life cycle emission (min)

= 234+ 0.05 (dst1+dst2) + 8.1h + 1.03L + 0.04 AW

(kgCO2/ton) 4.3 c

Total life cycle emission (max) =

290 + 0.05 (dst1+dst2) + 8.1h + 1.03L + 0.04 (kgCO2/ton) 4.3 d

Here,

dst2= distance in kilometer from market to construction site.


A = total area of weld for connection in square meter.

W = total weight of steel member and plates required to be weld in ton.

h = hoisting height of the crane in meter for one ton of steel element transfer.

L = derricking length of the crane in meter for one ton of steel element transfer.

From Scrap

The history of ship breaking is as nearly old as ship building. At present ship-breaking is

conducted by 20 Ship breaking yards in an area of about 8 km2 starting from a point near

Baro Awlia under police station, Sitakundu of Chittagong (Rahman et al.1999). All the

yards are located on the beach of the Bay of Bengal. There are 20 Ship breaking yards at

present in Kattoly-Kumira ship breaking areas (Rahman et al.1999). Generally 95% of a

ships body is made of mild steel (M.S.), 2% of stainless steel and 3% of miscellaneous

metals, such as brass, aluminium, copper, gun metal and other alloys which are important

factors of ship breaking . No sound technical system is used to recover valuable stores,

spares, metals and other items from the ships.

Thus, the main stages considered for steel produced from scrap are cutting procedure of

ship in ship breaking, rerolling process i.e. scrap melting and rerolling , use of crane and

welding in erection of steel member in building and transportation of steel into rerolling

mill and construction site. As steel has recycling potential along with the term cradle to

gate, total life cycle CO2 emission has been used. For cradle to gate criteria stages

considered has been ship breaking and rerolling process.

According to Gratsos (2005), Emission of CO2 in ship breaking activities involves cutting

of steel plates, of weight equal to the lightship. Data from specialized Greek repair

companies (e.g. NAVEP Ltd) indicate that cutting one ton of steel uses some 60 kg of

liquid propane (C3H8). That produces exactly 3 times as much CO2 in weight; therefore

the CO2 factor for cutting can be estimated to be 0.18 per ton of steel cut (Kameyama et al,

2004). Emission factor 2.96 from table A1of Appendix A has been used to calculate CO2

emission. In this factor emissions due to remelting the recycled steel are not taken into

account. For scrap melting electric arc furnace has been considered (Das and Kandpal)

with fuel energy consumed as 0.79 GJ/ton and electric energy 1.52 GJ/ton. Using


conversion factors from table A3 of Appendix 1, CO2 emission has been calculated as

given in table 4.7.

Table 4.7: Emission of CO2 in different stages of life cycle of steel from scrap.

Stages Emission data Conversion factor Emission ton CO2/ton steel

Steel cut in ship breaking 60 kg LPG /ton of steel

2.96 kg CO2/kg of LPG 0.18

Scrap melting in electric arc furnace (EAF)

0.79 GJ/ton (coal)

0.074 ton CO2/GJ 0.06

1.52 GJ/ton (electricity)

0.271 ton CO2/GJ 0.41

Hot rolling 1.82 GJ/ton (coal)

0.095 ton CO2/GJ 0.17

0.37 GJ/ton (electricity)

0.271 ton CO2/GJ 0.10

Total 0.92

For transportation same considerations has been taken as article 4.4.2.

Cradle to gate = 920 + 0.05 dst1 (kgCO2/ton) 4.4a

Considering CO2 emission from crane operation and welding per ton of steel same as table

4.5.

Total life cycle emission =

920 + 0.05 (dst1+dst2) + 8.1h + 1.03L + 0.04 (kgCO2/ton) 4.4b

4.2.4 Sand Profile

Sand is loose material formed of quartz grains such as that of the beaches or dunes. Sand

grains are mostly siliceous; sometimes calcareous or of volcanic origin. Bangladesh is

quite rich in terms of sand and silt deposits. Extraction of sand keeps the river channels

clear for the free flow of water. Thus, the stages considered for life cycle CO2 emission of

sand are extraction by dredging, sand screening, transportation to construction site or

market. For calculation of CO2 emission form sand extraction and screening the

mechanical capacity of dredger and sand screening machine available in Bangladesh has

been considered. 1200 m3/hr capacity sand dredger and rotary screener with 1500 mm


diameter have been considered (www.ecplaza.net) specifications of the dredger and

screener have been given in appendix B.

For 1200 m3/hr dredger,

Fuel consumption = 282 kg diesel = 331.76 liter diesel

(Density of diesel =0.85 kg/l)

331 liter diesel have suction capacity = 1200 m3 sand = 2304 ton sand

(Considering wet density of the sand as 1920 kg/m3)

1 ton sand =0.14 liter diesel.

For sand screening,

Output of the screener is 10 m3/ hr with power 3 kW.

Hence, considering unit weight of dry sand = 1600 kg /m3

Screening rate =3.33 m3/kWh or 5.3 ton/kWh

Electricity consumption = 0.19 kWh per ton of sand.

The fuel consumption capacity of the dredger and the mechanical capacity of the screener

were converted into CO2 emission with the conversion factor 1.34 lb/kWh

(http://web.mit.edu/mit_energy) for screener and 2.64 kg CO2/liter for sand dredger from

table A1 Appendix A.

Table 4.8: Emission of CO2 in different stages of life cycle of sand.

Stages Available data from calculation

Conversion factor

Emission kg CO2/ton

Sand extraction 0.14 liter diesel /ton of sand

2.64 kg CO2/liter 0.379

Sand screening 0.19 kWh electricity /ton of sand

1.34 lb /kWh 0.12

total 0.50


The boundary condition for sand has been set to cradle to gate.


Cradle to gate emission = 0.50+0.05 ds (kg CO2/ ton) 4.5

Here, ds = total distance in km from sand processing unit to market

Aggregate Profile

Sandstones and granites are the main two types of aggregates mainly used in Bangladesh.

Granite is an intrusive igneous rock which is widely distributed throughout Earth’s crust at

a range of depths up to 31 miles (50 km). Many variations of granite appear on the

commercial market with white, gray, pink, and red being the most common primary

colors. Sandstone is a very common rock in the geological group-formations of

Bangladesh. Sandstone is often used as building material as blocks in the construction of

large buildings.

Very small percentage of aggregates is quarried in Bangladesh. Stages considered for this

study are mining and processing of aggregates, transport to market and construction site.

Most of aggregate manufacturing units are processing units. Equations have been

developed for two different life cycles, one starting from mining and the other starting

from processing for both sandstone and granite. Total life cycle emission of aggregates has

been calculated in two distinct phases. First phase starting from extraction or processing to

transportation to market, prior to use in building where the second phase starting from

the segregation of aggregates from concrete after their effective life used in building; also

considering reuse and disposal in landfill. As crushing is considered in life cycle of

concrete so it has not been included in life cycle of aggregates. Blasting is the common

procedure for mining. Hence the research data of SISTech (Crishna et al.2010) regarding

carbon emissions at each stage in the extraction, processing have been used in developing

equation.

Cradle to gate CO2 emission equations of aggregates have been developed considering

extraction and processing of granite and sandstone according to data provided by the

natural stone specialists (Crishna et al 2010). It is important to note that the estimates of

embodied carbon of imported stone presented in that study were conservative as they

assumed the simplest, shortest scenarios and routes from source to use. One of the


assumptions was that the stone was processed at the same place as it is quarried. The

largest component of each stone footprint is attributable to the processing stage of the life

cycle, mostly due to the different stages of processing namely primary processing,

secondary processing, finishing etc. Results of the study gave CO2 emission in extraction

phase is 20 gCO2/ kg of stone and for processing is 70 gCO2/ kg. For sand stone the

amount of CO2 released are 10 gCO2 /kg and 55 gCO2/ kg respectively.


Cradle to Gate:

Granite (only processing) = 70 + 0.05 da (gCO2/kg) 4.6a

Granite (mining + processing) = 90 + 0.05 da (g CO2/kg) 4.6b

Sandstone (only processing) = 55 + 0.05 da (g CO2/kg) 4.6c

Sandstone (mining + processing) = 65+ 0.05 da (g CO2/kg) 4.6d

Hence, considering transportation to disposal site the cradle to grave equations can be

developed.

Life Cycle CO2 Emission:

Granite (only processing) =70 + 0.05(da + dad) (g CO2/kg) 4.7a

Granite (mining + processing) = 90 + 0.05 (da+ dad) (g CO2/kg) 4.7b

Sandstone (only processing) = 55 + 0.05 (da + dad) (g CO2/kg) 4.7c

Sandstone (mining + processing) = 65+ 0.05 (da + dad) (g CO2/kg) 4.7d

Here,

da = total distance in kilometer from processing unit to market .

dad = distance in kilometer from construction site to disposal site.

4.2.5 Timber profile

Timber denotes structural wood. A study (Page 2006) showed that embodied CO2

emissions of timber were two to three times lower than for the steel or concrete building.

Timber is considered as an important structural member with less carbon footprint. The


main source of timber in Bangladesh is Sundarban. In developing equation of life cycle

CO2 emission of timber, stages considered are felling of tree with chain saw,

transportation from forest to wood processing unit, natural seasoning, wood processing in

saw mill, demolition and transportation.

Equations have been developed considering trees with log diameter 10-18 inch. Felling of

trees involves cutting of trees with chain saw. For this study, craftsman 4 horsepower

capacity and 18 inch blade size chain saw has been considered (www.sears.com).

According to available data this saw can cut about 15 trees in 4 hour of above mentioned

specification. Therefore energy required is 0.20 kWh /tree.

For transportation, diesel powered heavy truck has been considered with CO2 emission 50

g/ton –km from table A5 of Appendix A. Considering teak as the timber with density 880

kg /m3 for door and window. Therefore,

CO2 emission for transportation = 50 g/ton-km

Density of timber = 880 kg /m3

1 ton timber = 40 cft

CO2 emission = = 1.25 g/cft- km

For wood processing in Saw mill, field data has been considered which gives

approximately 70-80 cft of wood are sliced everyday considering eight working hours per

day and diesel consumption in saw mill is 1 liter per hour. Hence, approximately 0.106

liter of diesel is required for sawing 1 cft of timber. Therefore emission has been

calculated using conversion factor 2.64 kg CO2/ liter from table A1 of appendix A.

Table 4.9: Emission of CO2 in different stages of life cycle of timber

Stages Available data Conversion factor

Emission of CO2

Cutting of trees Electricity consumption 0.20 kWh/tree

1.34 lb/kWh 0.12 kgCO2/tree

Transportation of timber

1 ton timber = 40 cft 50 g/ton –km 0.0013 kg/cft-km

Wood processing Diesel used = 0.11 liter / cft 2.64 kg CO2/liter 0.28 kgCO2/cft Burning of wood Density of timber = 880 kg /m3

1.9 g CO2/g timber burnt

47.5 kgCO2/cft


As natural seasoning is considered for the study there has been no energy cost. Equations

have been developed considering trees with log diameter 10-18 inch. As timber has

recycling potential it can be used number of times. After the demolition of the building

where timber was incorporated for the first time it can be used for land filling or it may be

burnt for cooking depending on the condition of the timber. Considering burning of timber

as the demolition criteria cradle to grave equation has been developed. Carbon dioxide

released when burning wood is about 1900g CO2 for each 1000 g of wood burnt

(http://transitionculture.org/wp-content/uploads/wood-pile.jpg).

Cradle to Gate Emission = 0.12 + (0.280+0.0013 d t1); (kg CO2/cft) 3.8a

Cradle to Grave Emission = 0.12 + 47.5+0.0013(d t1+d t2); (kg CO2/cft) 3.8b

Here,

t = no of trees cut

dt1= distance in kilometer from wood to saw mill and market.

dt2= distance in kilometer from market to construction site and construction site to disposal

site.

V= volume of timber cut in cubic feet.

4.2.6 Concrete Profile

Concrete is an artificial material obtained by mixing together cementing material, coarse

aggregate, fine aggregate and water. In this study stone chips have been considered as

coarse aggregate, CEM-I,CEMII A and CEM II B has been considered as cement types

and CO2 emission equations has been developed for three different mixing ratios. The

ratios are 1:2:4 with water cement ratio (w/c) 0.5, 1:3:6 with water cement ratio 0.65 and

1:1.5:3 with water cement ratio 0.45. The concrete mixes have been designed by absolute

volume basis (Singh et al.2005) and emission equations have been developed for one

cubic feet of concrete. The cradle to gate CO2 emission equations of the component

materials such as cement, sand and stone chips have been considered to develop the

equations of concrete. Emission of CO2 in mixing of component materials and due to


casting of concrete has been considered. Concrete mixer of model JZC 350A

(www.ecplaza.net) driven by electricity has been considered for mixing. TMV28 model

vibrator (www.ecplaza.net) with rate of concrete placement 352.8 cft per hour has been

considered. Detail description of the product is given in appendix B.

For mixing of materials,

Rate of concrete placement =10 m3/hr

Concrete (less than 80 mm slump) = 352.8 cft /hr

= 0.0028 hr /cft

= 0.016 kWh /cft

= 0.0095 kg CO2/cft

Emission factor has been taken as 1.34 lb/ kWh (http://web.mit.edu/mit_energy).

For mixing ratio 1:2:4 and water- cement ratio 0.5 using CEMI, designing for 1 bag of

cement by absolute volume basis.

Cement = 0.02 m3 = 0.05 ton

Sand = 0.042 m3 = 67.2 kg

Aggregate = 0.075 m3 = 112.5 kg

Water = 0.025 m3

Volume of total mix = 0.162 m3 = 5.71 cft

For one cft concrete emission of CO2 from component material before mixing

Cement = 0.05(0.86+0.00005 dc) 1000

Sand = 67.2(0.00049+0.00005ds)

Aggregate = 112.5(0.07+0.00005da)

Total emission (5.71 cft) = 51.29+0.0025dc+0.00336ds+0.00563da

Total emission per cft = 8.98+0.00053dc+0.00059ds+0.00099da

Cradle to gate emission has been calculated considering emission of individual material

prior to mixing and the mixing procedure

Cradle to Gate Emission = 9+ 0.00053dc+0.00059ds+0.00099da kg CO2/cft


= 9000+0.53dc+0.59 ds+0.99 da, gCO2/cft

Similarly, for all the mix ratios and water content CO2 emission can be calculated for

different cement as given in the following equations.


• For cement type: CEM I

For ratio 1:2:4 and w/c 0.5 = 9000 + 0.53dc + 0.59ds+ 0.99da, gCO2/cft 4.9a

For ratio 1:1.5:3 and w/c 0.45 = 10710 + 0.54dc + 0.58ds + 0.92da, gCO2/cft 4.9b

For ratio 1:3:6 and w/c 0.65 = 6010 + 0.304dc + 0.61ds +0.51da, gCO2/cft 4.9c

• For cement type: CEM IIA

For ratio 1:2:4 and w/c 0.5 = 7520+ 0.53dc + 0.59ds+ 0.99da, gCO2/cft 4.10a



• For cement type: CEM IIB

For ratio 1:2:4 and w/c 0.5 = 6470 + 0.53dc + 0.59ds+ 0.99da, gCO2/cft 4.11a



Here,

dc = distance in kilometer from cement factory to market and market to construction site

ds= distance in kilometer from sand processing unit to market

da= distance in kilometer from aggregate processing unit to market

The use phase of concrete in the effective life of the building is not considered. After

demolition of the building, concrete aggregate collected from demolition site is put into a

crushing machine. After crushing they can be used in land filling. Hence, the demolition


of the concrete is considered and CO2 emission from the first stage to demolition can be

termed as cradle to grave CO2 emission.

4.3 LIFE CYCLE ENERGY COST EQUATIONS OF MATERIALS

Considering the same stages of life cycle, equations of life cycle energy cost construction

materials have been developed in the following articles.

4.3.1 Brick

Brick production in Bangladesh is labor intensive. Most of the bricks are still hand

molded. Almost all the operations are manual, ranging from bringing the clay to the pug

mill, to the molding and drying ground, to the kiln and from the kiln to the warehouse.

In manufacturing brick energy is primarily used in two stages. They are drying and

burning of bricks in kiln and transportation. For drying and burning of bricks, FCK (fixed

chimney kiln) has been considered because FCK kiln holds the largest market share. In

FCK kiln coal is mainly considered as energy input. Emission of CO2 from FCK kiln has

been found 760.49 ton per year whereas average 20,00,000 bricks are manufactured per

kiln per year (Improving kiln efficiency, 2006). Hence emission of CO2 is 0.380 kg CO2

per brick. The emission data has been used to convert the emission data into energy cost

data using the factor 1.97 kg CO2/ kg of coal from table A1 of appendix A.

For transportation diesel driven truck has been considered with CO2 emission 50 g/ton –

km from table A5 of appendix A.

Hence, CO2 emission for heavy truck: 50 gCO2/ ton-km (Maersk line, 2007)

1 ton: 238 bricks, calculated in article 4.2.2

CO2 emission for a brick = 50238

= 0.21 gCO2/brick-km = 0.00021 kgCO2/brick-km

Table 4.10: Energy cost in different stages of life cycle of brick

Stages Emission of CO2 Conversion factor Energy cost factor Drying and burning in FCK kiln

0.380 g CO2/Single Brick

1.97 kg CO2/ kg of coal

0.193 kg coal/brick

Transportation 0.00021 kg CO2 /brick-km

2.64 kg CO2/ liter

0.08 liter diesel /thousand brick-km


Therefore the equation of energy cost for brick is

Cradle to gate = 193 Pc + 0.08 Pddb1 (BDT/ thousand brick) 4.12 a

Cradle to grave = 193 Pc + 0.08Pd (db1+ db2) (BDT/ thousand brick) 4.12 b

Where, Pd = price of 1 liter diesel in BDT

Pc = price of 1 kg coal in BDT

db1 = distance in kilometer from brick field to construction site.

db2 = distance in kilometer from construction site to brick chips processing site.

4.3.2 Timber

In developing equation of life cycle energy cost of timber, stages considered are felling of

tree with chain saw, transportation from forest to wood processing unit, natural seasoning,

wood processing in saw mill, demolition.

Equations have been developed considering trees with log diameter 10-18 inch. Felling of

trees involves cutting of trees with chain saw. For this study, craftsman 4 horsepower

capacity and 18 inch blade size chain saw (www.sears.com), operated by electricity has

been considered. According to available data this saw can cut about 15 trees in one hour of

above mentioned specification, which gives energy use 0.20 kWh per tree. Converting this

data into energy data energy cost has been calculated per tree.

For transportation diesel powered heavy truck has been considered with CO2 emission 50

g/ton –km from table A5 of Appendix A. For converting emission data into fuel data using

table A1 of Appendix A, conversion factor 2.64 has been selected.

Table 4.11: Energy cost in different stages of life cycle of timber

Stages Available data Conversion factor

Energy cost factor

Cutting of trees Electricity consumption 0.20 kWh/tree

0.20 kWh/tree

Transportation of timber 1.25 gCO2/cft-km (diesel fuel)

2.64 kgCO2/ liter

0.0005 liter /cft

Wood processing in saw mill

Diesel used= 0.11 liter/cft 0.11 liter /cft


For wood processing in Saw mill, field data has been considered which gives saw mill

slices 70-80 cft wood per day (8-9 working hours) and diesel consumption of this mills are

1 liter per hour. Approximately 0.11 liter of diesel is required for sawing 1 cft of timber.

As natural seasoning is considered for the study there has been no energy cost.

Finally summing up all the stages, equation of energy cost for cradle to gate is given

below.

Cradle to gate energy cost = 0.20 e

+ 0.0005 Pd (220+dt1+dt2) (BDT/ cft) 4.13

Where,

Pe = Price of 1 kWh electricity in BDT

t = No of trees cut.

V= volume of timber cut in cft

Pd = price of 1 liter diesel in BDT

dt1 = distance in km from forest to timber processing unit.

dt2 = distance in km from timber market to construction site and construction site to

market.

As timber has recycling potential it can be used number of times. After the demolition of

the building where timber was incorporated for the first time it can be used for land filling

or it may be burnt for cooking depending on the condition of the timber. Burning of timber

does not involve any external energy input. So cradle to gate and cradle to grave equations

for energy cost will be same.

4.3.3 Steel

Steel is one of the most important building materials of our country and it has its

application in almost all spheres of engineering. In this study, two separate life cycle of

steel has been considered from imported billet and other from ship breaking scrap.

From Billet


Billets are produced by the primary producers of steel. Billets are imported from other

countries as stated in article 4.2.3. For the simplification of study, maximum and

minimum import distance has been considered. South Korea with a distance 3976 nautical

miles has been considered as maximum import distance and India with a distance 286

nautical miles has been considered as minimum distance from Chittagong port

(www.searates.com/reference/portdistance). For sea freight emission of CO2 has been

calculated in article 4.2.3. Using conversion factor 2.64 kgCO2/ liter from table A1 of

Appendix A, minimum and maximum energy consumption has been calculated. For

transportation diesel powered heavy truck has been considered with CO2 emission 50

g/ton –km from table A5 of Appendix A. Converting emission data into fuel data from

table A1 of Appendix A , energy cost for transportation of billet has been calculated.

For hot rolling process Coal and electricity is used as input energy. CO2 emission of table

4.4 has been converted to energy cost data for coal using conversion factor of table A1 of

appendix A and for electricity conversion factor 1.34 lb/kWh or 2.95 kg CO2/kWh

(http://web.mit.edu/mit_energy) has been used

Table 4.12: Energy cost in different stages of life cycle of Billet

Stages CO2 emission Conversion factor Energy cost factor Shipment of billet • From South Korea 60 kgCO2/ton 2.64 kgCO2 /liter 22.73 liter diesel/ton • From India 4.2 kgCO2/ton 2.64 kgCO2 /liter 1.60 liter diesel/ton

Transportation 50 g/ton-km 2.64 kgCO2 /liter 0.02 liter diesel/ton-kmHot rolling process • Emission (coal) 130 kgCO2/ton 1.97 kgCO2 /kg 66 kg coal /ton • Emission (electricity) 100 kgCO2/ton 2.95 kgCO2 /kWh 34 kWh/ton

Cradle to gate equations:

Min = 0.02 Pd (80+dst1) + 66 Pc + 34Pe BDT/ ton 4.14a

Max =0.02 Pd (1137 + dst1) + 66 Pc + 34Pe BDT/ ton 4.14b

Here,

Pc = Price of 1 kg coal in BDT.


dst1 = total distance in km from port to rerolling mills and rerolling mills to market.

To develop equations for total life cycle of steel additional phases required to be

considered is transportation from market to construction site, erection by crane operation,

welding etc. QTZ50 model tower crane (www.cranescn.com/products/tower-crane/tower-

crane-qtz50.html) has been considered for fuel consumption and tower crane operation

specification. According to the specification this crane has jib length of 50 meter , height

37.5/33 meter , tip load 0.9-1 ton and max load 4 ton. Considering hoisting capacity 9

meter per minute with capacity 2 ton and energy used is 4 kW. One meter of hoisting

requires 13.33 kWh/ ton-m. For derricking, with 2 ton capacity and 50 meter jib length

one meter of derricking requires energy 1.69 kWh /ton-m. Considering electric arc

welding, each square meter of welding requires 0.16 kWh of electricity (www.izumi-

mfg.co.jp/english/outline.html).

Table 4.13: energy cost in Crane operations and Welding

Operation Energy cost factor Crane operation

• Hoisting 13.33 kWh/ton • Derricking 1.69 kWh/ton-m Welding 0.16 kWh/m2

Therefore total life cycle energy cost of billet is given below

Total life cycle energy cost (minimum)

= 0.02 Pd (80+dst1+dst2) +66Pc+1.69Pe (20.12 +7.88 h+L+0.1 ) BDT/ton 4.15a

Total life cycle energy cost (maximum)

= 0.02 Pd (1135+dst1+dst2) +66 Pc+1.69Pe (20.12 +7.88 h+L+0.1 ) BDT/ ton 4.15b

Here,

Pd = price of 1 liter diesel in BDT

Pc = Price of 1 kg coal in BDT

Pe = Price of 1 kWh electricity in BDT


A= total area of weld for connection in square meter.

W= total weight of steel member and plates required to be weld in ton.

h= hoisting height of the crane in meter for one ton of steel element transfer.

L= derricking length of the crane in meter for one ton of steel element transfer.

From scrap

The main stages considered for steel produced from scrap are cutting procedure of ship in

ship breaking, rerolling process i.e. scrap melting and rerolling , use of crane and welding

in erection of steel member in building and transportation of steel into rerolling mill and

construction site. As steel has recycling potential along with the term cradle to gate, total

life cycle CO2 emission has been used. For cradle to gate criteria stages considered has

been ship breaking and rerolling process.

To calculate energy cost due to ship breaking activities cutting of plates has been

considered mainly. Emission due to liquid propane gas (LPG) used in gas cutter has been

found 0.18 ton/ ton of steel as in article 4.2.3. Using Table A1of Appendix A factor is

2.96. Fuel factor is 60.81 kg of propane or 113.45 liter per ton of steel cut. For

transportation same considerations has been taken as article 4.2.3.

Scrap melting and hot rolling is considered in the rerolling process. According to world

coal organization, 29% of steel is produced in Electric Arc Furnaces (EAF); much of the

electricity used in this process is generated from coal-fired power stations. Using the

emission calculated in table 4.6, energy has been calculated. For scrap melting in electric

arc furnace emission refers to fuel used as charge carbon and the amount of charge carbon

can vary depending on each shop’s practice. Charge carbon is added to the bottom of the

furnace. This can be done by dumping the Charge Carbon into the furnace or putting the

Charge Carbon in the Charging Bucket.

Using the conversion factors 1.97 kg CO2/kg for coal and 2.95 kg CO2/kWh for electricity

and energy cost factors have been found as 30.5 and 139 respectively. For hot rolling

similar calculation is done as for billet. Considering energy cost of crane operation and

welding per ton of steel same as considered for billet.

Table 4.14: Energy cost in different stages of life cycle of steel from scrap


Stages CO2 emission Conversion factor Energy cost factor Cutting of ship 60 kg propane

CO2/ton of steel cut

2.96 kgCO2 /kg 113.45 liter LPG/ ton of steel

Transportation 50 g/ton-km 2.64 kgCO2 /liter 0.02 liter diesel/ton-km Scrap melting

• Emission (coal) 60 kgCO2/ton 1.97 30.5 kg coal /ton • Emission

(electricity) 410 kgCO2/ton 2.95 139 kWh/ton

Hot rolling process • Emission (coal) 130 kgCO2/ton 1.97 kgCO2 /kg 66 kg coal /ton • Emission

(electricity) 100 kgCO2/ton 2.95 kgCO2 /kWh 34 kWh/ton

Cradle to gate energy cost

= 113. 5 PLPG+0.02Pd dst1+ 173Pe+96.5Pc (BDT/ton) 4.16

Total life cycle energy cost =

113. 5 PLPG + 0.02Pd (dst1+ dst2) + 96.5 Pc +1.69Pe (102+7.88 h+L+0.1

(BDT/ton) 4.17

Here,

PLPG = Price of 1 liter LPG in BDT

4.3.4 Aggregate

Cradle to gate CO2 emission equations of aggregates have been developed considering

extraction and processing of granite and sandstone according to data provided by the

natural stone specialists (Crishna et al 2010). It is important to note that the estimates of

embodied carbon of imported stone presented in that study were conservative as they

assumed the simplest, shortest scenarios and routes from source to use. One of the

assumptions was that the stone was processed at the same place as it is quarried. The

largest component of each stone footprint is attributable to the processing stage of the life

cycle, mostly due to the different stages of processing namely primary processing,

secondary processing, finishing etc. Results of the study gave CO2 emission in extraction

phase is 0.02 kg CO2 /kg of stone and for processing is 0.07 kg CO2 /kg. For sand stone


the amount of CO2 released are 0.01 kg CO2 /kg and 0.055 kg CO2 /kg respectively.

Varieties of machinery are associated with each of the stages. Example of some

machineries commonly used are Jaw crushers, Cone crushers, Horizontal shaft impact

crushers (HSI), Vertical shaft impact crushers (VSI) etc used to run stone preparation

machinery ,dust extraction devices and water pumping machinery. All of these equipments

are electricity driven (www.sbm-mp.at). For simplified analysis, considering electricity to

be the main source of CO2 emission energy cost can be found converting CO2 into

electricity cost considering coal to be the source of electricity and emission factor 0.37 kg

CO2/kWh . For transportation same considerations has been taken as article 4.3.2. Hence,

considering both extraction and processing

For granite = 243 Pe+0.02 Pd da (BDT/ton) 4.18a

For sandstone = 176 Pe+0.02 Pd da (BDT/ton) 4.18b

And considering only processing,

For granite = 190 Pe+0.02 Pd da (BDT/ton) 4.19a

For sandstone = 149 Pe+0.02 Pd da (BDT/ton) 4.19b

Here, da = total distance in km from processing unit to market

4.3.5 Sand

Sand is a naturally occurring granular material composed of finely divided rock and

mineral particles. The composition of sand is highly variable, depending on the local rock

sources and conditions, but the most common constituent of sand in inland continental

settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the

form of quartz.

For calculation of energy cost from sand extraction and screening the mechanical capacity

of dredger and sand screening machine available in Bangladesh has been considered,

specification of the machines considered are given in appendix B. Fuel consumption of the

sand dredger is 282 kg per hour and suction capacity is 1200 cubic meter per hour. Hence,

the extraction of sand with this sand dredger is 6.96 ton per liter of diesel. Therefore the

fuel consumption of the dredger is 0.14 liter of diesel for per ton of sand extraction. For

sand screening, rotary and screener with 1500 mm diameter has been considered,


specifications of the screener has been given in appendix B. Output of the screener is 10

cubic meter per hour with power 3 kW. Hence considering unit weight of sand as 1600 kg

per cubic meter electricity consumption is 0.19 kWh per ton of sand. For transportation

same considerations has been taken as article 4.2.3. Hence summing up all the

considerations energy cost equation for cradle to gate boundary condition is given below.

Table 4.15: Energy cost in different stages of life cycle of sand

Stages Energy cost factors Sand extraction 0.14 liter diesel/ton Sand screening 0.19 kWh / ton Transportation 0.02 liter diesel/ton -km

Hence, Cradle to gate energy cost = 0.14 Pd +0.19 Pe +0.02 Pd ds (BDT/ton) 4.20

Here, ds = total distance in km from processing unit to market.

4.3.6 Cement

For developing life cycle energy cost of cement, stages considered are extraction, raw

material transport, primary and secondary crushing, raw grinding, kiln process and finally

finish grinding for three types of cement namely CEM-I, CEM-IIA and CEM-IIB.

Diesel has been considered as energy source for extraction and transportation. For other

stages coal has been considered. According to Athena report (Venta et al. 1999), total CO2

emission per kg of cement have been found 0.002 kg CO2, 0.002 kg CO2 and 0.001 kg

CO2 for CEM-I, CEM-IIA and CEM-IIB respectively for raw material transport for

diesel as fuel. Using table 1 of appendix A, CO2 to diesel quantity conversion factor 2.64,

fuel consumption has been found as 3.4, 3 and 2.3 liter of diesel per ton of cement.

For crushing, raw grinding, kiln process coal has been considered as raw material. As

stated in section 4.2.3, Emission have been found, 0.858 kg CO2, 0.68 kg CO2 and 0.569

kg CO2 for CEM-I, CEM-IIA and CEM-IIB respectively and using 1.97 as conversion

factor for CO2 to coal used cost factor for above mentioned cement types are 440, 350

and 280 BDT per kg of coal respectively.


Table 4.16: Energy cost in different stages of life cycle of cement

Type of cement

CO2 emission (kg CO2/kg)

Fuel Conversion factor

Energy cost factor

CEM-I 0.002 Diesel 2.64 0.8 0.858 Coal 1.97 440

CEM-IIA 0.002 Diesel 2.64 0.8 0.688 Coal 1.97 350

CEM-IIB 0.001 Diesel 2.64 0.4 0.569 Coal 1.97 280

For transportation same considerations has been taken as article 4.2.2. Life cycle energy

cost equations have been developed for one ton of cement with cradle to gate boundary

condition.


CEM- I = 0.8 Pd + 440 Pc + 0.02 Pddc, (BDT/ton) 4.21a

CEM-IIA = 0.8 Pd + 350 Pc + 0.02 Pddc, (BDT/ton) 4.21b

CEM-IIB = 0.4Pd + 280 Pc + 0.02 Pddc, (BDT/ton) 4.21c

Here, dc = total distance in kilometer from cement factory to market.

4.3.7 Concrete

Equations of concrete have been derived considering the same conditions as article 4.2.7.

The concrete mixes have been designed by absolute volume basis (Singh et al.2005) and

emission equations have been developed for one hundred cubic feet of concrete. The

energy cost of component materials derived earlier in this chapter has been combined for

different cement types, mix ratio and water content. Concrete mixer used for derivation of

equations and symbols are same as in article 4.2.7. Hence the equations are given below

for cradle to gate phase.

• For cement type: CEM I

For ratio 1:2:4 and w/c 0.5 = Pd+385Pc+347Pe, BDT/100cft 4.22a

For ratio 1:1.5:3 and w/c 0.45 = 3Pd+477Pc+325Pe, BDT/100cft 4.22b

For ratio 1:3:6 and w/c 0.65 = 0.7Pd+268Pc+181Pe, BDT/100cft 4.22c


• For cement type: CEM II-A

For ratio 1:2:4 and w/c 0.5 = Pd+306Pc+347Pe, BDT/100cft 4.23a

For ratio 1:1.5:3 and w/c 0.45 = Pd+380Pc+325Pe, BDT/100cft 4.23b

For ratio 1:3:6 and w/c 0.65 = 0.7Pd+213Pc+181Pe, BDT/100cft 4.23c

• For cement type: CEM II-B

For ratio 1:2:4 and w/c 0.5 =0.5Pd+245Pc+347Pe, BDT/100cft 4.24a

For ratio 1:1.5:3 and w/c 0.45 =0.6Pd+304Pc+325Pe, BDT/100cft 4.24b

For ratio 1:3:6 and w/c 0.65 =0.4Pd+170Pc+181Pe, BDT/100cft 4.24c

Based on these equations total life cycle CO2 emission and energy cost will be determined

for different structural systems in the next chapter.

CHAPTER 5

COMPARATIVE STUDY ON LIFE CYCLE CO2 EMISSION OF

CONCRETE AND STEEL BUILDING

__________________________________________________________________

5.1 GENERAL

In this chapter, estimation of life cycle CO2 emission in different phases of concrete and

steel buildings have been done using the empirical equations and symbols derived from

article 4.2 of chapter 4 , for different materials commonly used in construction sector of

Bangladesh.

5.2 CASE STUDY

The study of life cycle CO2 emission has been done considering a project site in

Gulshan -1 and analyzing different phases of life cycle individually for both structural

systems namely ‘Concrete Building’ and ‘Steel Building’.

5.2.1 DESIGN OF BUILDING

This section introduces the development of the case studies on the buildings. Firstly it

will introduce the common architectural design of two buildings and then it will approach

on two buildings individual differences between two buildings.

For each of the two buildings this section discusses the structural configuration. The

concrete and steel buildings are used as model for comparison of life cycle CO2 emission

and energy cost. For simplification of study only superstructure has been considered.

The building plan considered for analysis in this research is a six-storey 9832 square feet

gross floor area per storey as shown in fig 5.1. It has been designed with reinforced

concrete as the main material for structure and also for steel. The buildings are considered

to be made for an educational institution with seven rooms, a corridor with two staircases

and a lift. The perspective views of both the buildings are given in fig. 5.2 and fig. 5.3.

Comparative study on life cycle CO2 emission of concrete and steel building 64

.

Figure 5.1 Plan of the Building for Both Concrete and Steel Structural Systems.

Figure 5.2: Perspective view of

Concrete building.

Figure 5.3: Perspective view of Steel

building.


5.2.2 Concrete Building and Design Procedure

The concrete building is a reinforced concrete column and beam structure with 12 feet

typical storey height. It is consist of concrete with compressive strength 4 ksi and yield

strength 60 ksi as the main structural material for beams, columns, floors and roof

slabs, brick partition walls, and timber door - windows. The building is raised floor by

floor with shear concrete walls for lift core. Rectangular columns and beams form the

frame. Internal beams are supported on one internal row of columns. Fig 5.2 shows a

beam and column layout of the concrete building.

Figure 5.4 Beam and Column Layout of Concrete Building

The floors are supported by the frame beams. The thickness of the slabs is 6 inch.

Brick walls are considered for both the interior and exterior walls. Exterior walls are of

10 inch and the interior walls are of 5 inch thickness. For ease of calculations, 40%


opening of the total volume of walls has been considered for doors and windows. All

the design procedures have been followed according to Bangladesh national building

code (BNBC) 1993 and the building has been designed with vertical and lateral loads

such as wind and earthquake considering the project site located in Gulshan1 in Dhaka.

Details calculations of the concrete building are given in appendix C.

5.2.3 Steel Building and Design Procedure

The steel building consists of a 6 inch concrete slab supported on steel beams and

columns. Both internal and external walls are brick walls as considered in concrete

building and stair and lift core are made of concrete. For ease of calculations, 40%

opening of the total volume of walls has been considered for doors and windows.

Figure 5.5 Beam and Column Layout of Steel Building


Structurally the steel building is a column and beam steel structure braced by

Eccentrically Braced Frames (EBFs). EBFs have been used as this have a well-

established reputation as high-ductility systems and have the potential to offer cost-

effective solutions in moderate seismic region. The structural layout is shown in fig

5.5; there are four frames of columns and beams running along the building

longitudinally. Transverse secondary beams connect the four longitudinal frames. The

external frames are braced by EBFs. Beams and columns have been designed with W

sections and bracings are designed with HSS pipes. For the entire steel members 40

grade steel has been used. Extended end plate bolted connection has been considered

for beam - column and column - beam joints.

Steel building has been designed with the same loading conditions and project site as

considered for concrete building. AISC-ASD method has been followed for member

design. Therefore table 5.1 represents a brief summary of quantity of the materials

required for both the buildings.

Table 5.1: Comparison of Material Quantity in Concrete and Steel Building

Detail member detailing charts and sample of connection design are enclosed in

appendix C.

5.3 LIFE CYCLE CO2 EMISSION FROM CONCRETE BUILDING

For calculation of life cycle CO2 emission from Concrete building four stages of life

cycle have been considered namely

• Cradle to gate

• Transportation of raw materials to construction site

Material name Unit of Material

Total Quantity of Materials in concrete building

Total Quantity of Materials in Steel building

Brick Nos 327014 327014 Concrete cft 51856 26856 Timber cft 5977 5977 Steel from Billet ton 164 462 Steel from Scrap ton 164 462


• Construction phase

• Demolition or reuse of materials.

5.3.1 Cradle to Gate CO2 Emission of Materials in Concrete Building

Three different types of cement has been considered for concrete namely CEM-I,

CEM-IIA and CEM-IIB. Also three different concrete mix ratios such as 1:2:4, 1:1.5:3

and 1:3:6 have been considered for each of the cement type.

Concrete with CEM-I

Table 5.2 shows CO2 emission calculations details for concrete building considering

CEM-I used in concrete.

Table 5.2: Emission of CO2 in Cradle to Gate Phase (Concrete With CEM-I)

Concrete with CEM-IIA

Table 5.3 shows CO2 emission calculations details for concrete building considering

CEM-IIA used in concrete.

Material Name Emission Rate

Emission Rate Unit

Total Quantity of Materials

Unit of Material Quantity

Emission of CO2 (kg)

Brick 380.25 gCO2/single brick 327014 Nos 124347

Concrete mix 1:2:4 9000 g CO2/ cft 51856 cft 466703 1:1.5:3 10710 g CO2/ cft 51856 cft 555377 1:3:6 6010 g CO2/ cft 51856 cft 311654 Timber 0.28 kg CO2/ cft 5977.2 cft 1674 From Billet 234 kg CO2/ ton 164 ton 38376

290 kg CO2/ ton 164 ton 47560 From Scrap 920 kg CO2/ ton 164 ton 150880


Table 5.3: Emission of CO2 in Cradle to Gate Phase (Concrete with CEM-IIA)

Concrete with CEM-IIB

In table 5.4, CO2 emission calculation for Cradle to gate phase for concrete building

where concrete is considered to be composed of cement type CEM-IIB, which is the

most commonly used in construction sector of Bangladesh.

Table 5.4: Emission of CO2 in Cradle to Gate Phase (Concrete with CEM-II B)

Material name Emission Rate

Emission Rate Unit


Unit of Material



Concrete Mix 1:2:4 7520 g CO2/ cft 51855.92 cft 389957 1:1.5:3 8880 g CO2/ cft 51855.92 cft 460481 1:3:6 4990 g CO2/ cft 51855.92 cft 258761 Timber 0.28 kg CO2/ cft 5977.2 cft 1674

From Billet 234 kg CO2/ ton 164 ton 38376

290 kg CO2/ ton 164 ton 47560

From Scrap 920 kg CO2/ ton 164 ton 150880

Material name Emission Rate

Emission Rate Unit


Unit of Material



Concrete Mix ratio 1:2:4 6470 g CO2/ cft 51855.92 cft 335508 1:1.5:3 7590 g CO2/ cft 51855.92 cft 393586 1:3:6 4260 g CO2/ cft 51855.92 cft 220906

Timber 0.28 kg CO2/ cft 5977.2 cft 1674

From Billet 234 kg CO2/ ton 164 ton 38376 290 kg CO2/ ton 164 ton 47560

From Scrap 920 kg CO2/ ton 164 ton 150880


Table 5.2, table 5.3 and table 5.4 shows emission of CO2 for different construction

materials used in a concrete building such as brick, timber, reinforcement and concrete

in cradle to gate phase.

According to tables, between two sources of steel, scrap gives maximum cradle to gate

emissions and concrete with 1:1.5:3 mix ratios gives maximum CO2 emission among

the three mix ratios considered in calculation of cradle to gate phase. Hence maximum

total emission have been found as 832 ton for CEM-I , 737 ton for CEM-IIA and 670

ton for CEM II-B considering steel from scrap, concrete mix 1:1.5:3 ,timber and brick

considering the core materials for the super structure of the building. Again,

considering billet, 1:3:6 as the concrete mix ratio, timber and brick minimum CO2

emission have been found as 476 ton for CEM-I, 423 ton for CEM-IIA and 385 ton for

CEM II-B.

Figure 5.6: Life cycle CO2 emission in cradle to gate phase of Concrete Building with

different cement type.

As shown in fig.5.6 maximum emission 832 ton in cradle to gate phase has been found

if CEM-I and have been used in concrete and minimum emission 476 ton has been

found if CEM IIB has been used in concrete.

832737

670

476423 385

0

200

400

600

800

1000

CEM-I CEM-IIA CEM-IIB

CO

2 em

issi

on (t

on)

Types of cement

Max CO2 Emission Min CO2 Emission

Max CO2 emission Min CO2 emission


Figure 5.7: Life cycle CO2 emission in cradle to gate phase of different materials from

Concrete Building.

Fig. 5.7 shows cradle to gate emission of all the building materials. Results show that

concrete with mix ratio 1:1.5:3 emits maximum CO2 and timber emits minimum CO2

amongst the materials in cradle to gate phase. This may be because concrete is a

composite materials which involves cement, sand and coarse aggregate and each of the

materials is individually source of large share of CO2.

5.3.2 Emission of CO2 in Transportation Phase of Concrete Building

CO2 emission calculation in transportation phase involves selecting a particular project

site for concrete building. As project location Gulshan 1 has been considered.

Table 5.5: Distance of Different Material Source from Site

Location Distance (km) Distance from cement factory to site (Savar to Gulshan 1) dc = 27.4 Distance from aggregate processing unit to site, (Sylhet to Gulshan 1 ) da = 251

Distance from sand processing unit to site (Narayanganj to Gulshan 1) ds = 29

Distance from brick field to site (Ashulia to Gulshan 1) db = 21.6

Distance from Sundarban to site (Sundarban to Gulshan 1) dt1= 190 Distance from Chittagong port to site , ( from port to Gulshan 1) dst1+dst2 = 252

Source: RHD road network gazette, planning commission, Bangladesh (www.rhd.gov.bd).

124

466390

336

555

460394

311259

221

3848

151

0

100

200

300

400

500

600

700

800

900

Brick Concrete with CEM IA

Concrete with CEM II-A

Concrete with CEM II-B

Steel

CO

2em

issi

on (t

on)

Materials

Brick Mix ratio 1:2:4Mix ratio 1:1.5:3 Mix ratio 1:3:6Billet (min) Billet (max)Steel (scrap)


Table 5.6: Emission of CO2 from Different Materials in Transportation Phase

Material name Emission Rate Emission

Rate Unit

Total Quantity Of Materials

Unit of Material Quantity

Emission of CO2(g)

Brick 0.21 db g CO2/ brick 327014 Nos 1483336

Concrete Mix 1:2:4 0.53 dc+0.59ds+0.99da g CO2/ cft 51856 cft 145259841:1.5:3 0.54 dc+0.58ds+0.92da g CO2/ cft 51856 cft 136140461:3:6 0.304dc+0.61ds+0.51da g CO2/ cft 51856 cft 7987347Timber 1.25dt1 g CO2/ cft 5977 cft 1419585Reinforcement Both from billet and scrap

50(dst1+dst2) g CO2/ ton-km 164 ton 2066400

From table 5.6, maximum total CO2 emission has been found as 18.58 ton and

minimum CO2 emission has been found as 12.96 ton.

Figure 5.8: Life cycle CO2 emission in transportation phase of different materials

from Concrete Building.

Figure 5.8 shows maximum emission of CO2 from transportation phase in life cycle

CO2 emission calculation of concrete building which indicates raw material

transportation for the construction of concrete building contributes significant amount

1.48

14.5313.61

7.98

1.42 2.07

02468

101214161820

Brick Concrete 1:2:4

Concrete 1:1.5:3

Concrete 1:3:6

Timber Steel

CO

2 em

issi

on (t

on)

Materials

Emission of CO2(ton) Emission of CO2


of CO2. Although maximum transportation distance has been considered for timber

and minimum transportation distance has been considered for brick both of these

materials have similar amount of CO2 emission due to transportation. As different mix

ratios have been used, result indicates the greater amount of CO2 emission is from

cement mix ratio 1: 2: 4. Equations of concrete mixes and results indicate source of

sand has the major impact than the other two materials in concrete mix.

5.3.3 Emission of CO2 in Construction Phase of Concrete Building

Construction of a building involves several individual operations. In this study most

common and energy consuming operations in construction practice has been

considered. In construction phase of life cycle of concrete building mixing of concrete

with JZC350A model concrete mixer and casting of concrete with TMV28 concrete

vibrator have been considered as in developing the equations.

Table 5.7: Emission of CO2 from Different Materials in Construction phase

Operation Emission rate Unit

Total Quantity of Concrete in Building

Unit Emission of CO2(g)

Mixing of concrete 9.48 g CO2/ cft 51855.9 cft 491594 Casting of concrete 5.7 g CO2/ cft 51855.9 cft 2955799

From Table 5.7, total emission in construction phase has been found 0.79 ton.

In construction phase of concrete building mixing of concrete emits 492 kg whereas

casting of concrete emits 296 kg which indicates mixing of concrete emits almost 1.7

times CO2 than casting of concrete.

5.3.4 Emission of CO2 in Demolition Phase of Concrete Building

In demolition phase brick is considered to be converted into brick chips by manually

which is a common practice in Bangladesh and timber is considered to be used in

cooking which gives maximum emission after its repetitive use in building. Concrete is

considered to be crushed for demolition of the building using concrete crusher and

reinforcement to be transported to the rerolling mills for use in production of steel. The

details of calculation are presented in table 5.8.


Table 5.8: Emission of CO2 from Different Materials in Demolition phase

Material Name

State of material after demolition of building

Emission rate Quantity Unit

Emission of CO2(kg)

Brick Brick chips by manual labor 0 327014 Nos 0

Concrete Crushing of concrete 0.04 kg/cft 51855.9 cft 2074

Timber After demolition used in cooking 47.5 kg/cft 5977.2 cft 283917

Steel Transportation to rerolling mill in Gazipur (dst2 = 47 km )

0.05dst2 (kg/ton-km) 164 ton 385

From table 5.8, total emission in demolition phase has been found 283.92 ton. Timber

contributes maximum 284 ton of CO2 in demolition phase. As manual procedure has

been considered for bricks, there is no emission of CO2 from brick in demolition

phase.

5.3.5 Total CO2 Emission from Concrete Building

Summary of total life cycle CO2 emission and individual emission in each of the

phases in life cycle of concrete building are presented in fig 4.8 and 4.9 respectively.

Figure 5.9: Maximum and minimum Total Life cycle CO2 emission from Concrete

Building using different cement type in concrete.

1,139 1,044977

783 730

385

0

200

400

600

800

1000

1200

1400


CO

2em

issi

on (t

on)

Type of cement in concrete building

Max CO2 Emission( ton)Min CO2 Emission( ton)Maximum CO2Minimum CO2


From Fig 5.9, maximum total emission has been found for mix ratio 1:1.5:3 and

reinforcement from scrap and minimum for mix ratio 1:3:6 and reinforcement from

billet in cradle to gate although in transportation phase maximum CO2 emission has

been for concrete with mix ratio 1:2:4.

Figure 5.10: Maximum and minimum Life cycle CO2 emission in several phases of

different materials from Concrete Building.

Fig 5.10 shows, maximum and minimum emission from different phases of life cycle

of concrete building. Maximum CO2 is emitted in cradle to gate phase ranging value

between 385 to 832 tons and negligible amount in construction phase. Cradle to gate

phase emits about 73% of the total life cycle CO2 emission. Demolition phase of

concrete building have significant impact in total life cycle CO2 emission of concrete

building.

5.4 LIFE CYCLE CO2 EMISSION FROM STEEL BUILDING

Four stages of life cycle have been considered for analysis of life cycle CO2 emission

from steel building namely cradle to gate, transportation of raw materials to

construction site, construction phase and demolition or reuse of materials. Calculations

have been done considering the similar project site in Gulshan 1 as same as concrete

832

19

286

385

13

286

0

100

200

300

400

500

600

700

800

900

cradle to gate transportation to site

construction demolition

CO

2em

issi

on (t

on)

Phases of life cycle

Maximum emission

Minimum emission


building. Detail calculations throughout several phases of life cycle of steel building

are presented and discussed in the following articles.

5.4.1 Emission of CO2 of Materials in Cradle to Gate Phase of Steel Building

For steel building, cradle to gate analysis have been done with similar conditions as

taken for concrete building.

Concrete with CEM-I in steel building

Table 5.9: Emission of CO2 from Different Building Materials in Cradle to Gate Phase

(Concrete With CEM-I)

Material Name

Emission Rate

Emission rate Unit

Total Material Quantity

Material Quantity unit

Emission of CO2

(kg)Steel Billet 234 kg CO2/ ton 462 ton 108155

290 kg CO2/ ton 462 ton 134038Scrap 920 kg CO2/ ton 462 ton 425224Concrete mix 1:2:4 9000 g CO2/ cft 26856 cft 2417001:1.5:3 10710 g CO2/ cft 26856 cft 287624

1:3:6 6010 g CO2/ cft 26856 cft 161402

Timber 0.28 kg CO2/ cft 5977 cft 1674Brick 380.25 g CO2/single brick 327014 Nos 124347


Table 5.10: Emission of CO2 from Different Building Materials in Cradle to Gate

Phase (Concrete with CEM-IIA)

Material name

Emission Rate

Emission rate Unit



Emission of CO2(kg)

Steel Billet 234 kg CO2/ ton 462 ton 108155 290 kg CO2/ ton 462 ton 134038Scrap 920 kg CO2/ ton 462 ton 425224Concrete 1:2:4 7520 g CO2/ cft 26856 cft 2019551:1.5:3 8880 g CO2/ cft 26856 cft 2384781:3:6 4990 g CO2/ cft 26856 cft 134010Timber 0.28 kg CO2/ cft 5977 cft 1674Brick 380.25 g CO2/ brick 327014 Nos 124347



Table 5.11: Emission of CO2 from Different Building Materials in Cradle to Gate

Phase (Concrete with CEM-IIB)

Material name

Emission Rate

Emission Rate Unit




Steel Billet 234 kg CO2/ ton 462 ton 108155 290 kg CO2/ ton 462 ton 134038 Scrap 920 kg CO2/ ton 462 ton 425224 Concrete 1:2:4 6470 g CO2/ cft 26856 cft 173756 1:1.5:3 7590 g CO2/ cft 26856 cft 203835 1:3:6 4260 g CO2/ cft 26856 cft 114405 Timber 0.28 kg CO2/ cft 5977.2 cft 1674 Brick 380.25 gCO2/ brick 327014 Nos 124347

According to table 5.9, 5.10 and 5.11, between two sources of steel, scrap gives

maximum cradle to gate emissions and concrete with 1:1.5: 3 mix ratios gives

maximum CO2 emission among the three mix ratios considered in calculation of cradle

to gate phase. Hence maximum total emission have been found as 838.86 ton for

CEM-I , 789.72 ton for CEM-IIA and 755.08 ton for CEM II-B considering steel from

scrap, concrete mix 1:1.5:3 ,timber and brick considering the core materials for the

super structure of the building. Again, considering billet, 1:3:6 as the concrete mix

ratio, timber and brick, minimum CO2 emission have been found as 395.58 ton for

CEM-I, 368.18 ton for CEM-IIA and 348.58 ton for CEM II-B.

Fig. 5.12 represents CO2 emission from individual construction materials in cradle to

gate phase. Results show that steel from scrap emits maximum CO2 in steel building

and timber has negligible contribution compared to other materials.


Figure 5.11: Life cycle CO2 emission in cradle to gate phase of Steel Building with


Figure 5.12: Life cycle CO2 emission in cradle to gate phase of different materials of

Steel Building.

839 790 755

395 368 349

0

200

400

600

800

1000

1200

1400


CO

2em

issi

on(to

n)

Type of cement in steel building

Max Emission

Min Emission

124

242202 174

288238

204161

134 114 108134

425

0

100

200

300

400

500

600

700

800

Brick Concrete with CEM IA



Steel

CO

2em

issi

on (t

on)

Materials

Brick Mix ratio 1:2:4 Mix ratio 1:1.5:3Mix ratio 1:3:6 Billet (min) Billet (max)Steel (scrap)


5.4.2 Emission of CO2 in Transportation of Material to Construction Site

Considering project location in Gulshan 1, transportation distances from several

sources of material used in superstructure of steel building is same as presented in

table 5.12.

Table 5.12: Emission of CO2 from Different Materials in Transportation Phase of

Steel Building

Material name

Emission Rate Emission rate Total Material Quantity

Unit Of Materials

Emission of CO2(g)

Steel 50(dst1+dst2) g CO2/ ton 462 ton 5823720 Brick 0.21 db g CO2/ brick 327014 Nos 1483336 Concrete 1:2:4 0.53 dc+0.59ds+0.99da g CO2/ cft 26856 cft 7522861

1:1.5:3 0.54 dc+0.58ds+0.92da g CO2/ cft 26856 cft 7050578 1:3:6 0.304 dc+0.61ds+0.51da g CO2/ cft 26856 cft 4136567

Timber 1.25dt1 g CO2/ cft 5977 cft 1419585

According to table 5.12, maximum total CO2 emission from transportation is 16.85 ton

whereas minimum total CO2 emission is 12.87 ton.

Figure 5.13: Life cycle CO2 emission in transportation phase of different materials of

Steel Building.

5.82

1.48

7.52 7.05

4.14

1.42

0

2

4

6

8

10

12

Steel Brick Concrete 1:2:4

Concrete 1:1.5:3

Concrete 1:3:6

Timber

CO

2em

issi

on (t

on)

Materials

Emission of CO2(ton) Emissionof CO2


Figure 5.13 shows maximum CO2 emission in transportation phase is due to concrete

with mix ratio 1:2:4 and lowest is for timber.

5.4.3 Emission of CO2 in Construction of the Steel Building

In construction phase of steel building CO2 emission has been calculated for mixing of

concrete, casting of concrete, crane operations such as hoisting and derricking and

welding the connections of steel members. A QTZ50 model tower crane

(http://www.cranescn.com/) has been considered for crane operations. A detail

specification of this crane is given in Appendix B. Center point of the plan area given

in figure 5.1has been considered as the location of the tower crane and distances of the

members have been calculated from crane location for both hoisting and derricking. As

the emission of CO2 is in terms of kg CO2 / ton –m total weight of the steel members

have been calculated. Details of calculations are presented in table 5.13.

Table 5.13: Emission of CO2 in Construction Phase for Steel Building

Operation Emission Rate Unit Total Material

Quantity Unit of Materials

Emission of CO2(kg)

Mixing of concrete 9.48 g CO2/ cft 26856 cft 255

Casting of concrete 5.7 g CO2/ cft 26856 cft 1535

Hoisting by Crane 8.1h kg/ton -meter h =76.83, total wt = 403.57 ton m, ton 251151

Derricking by Crane 1.03L kg/ton -meter L = 405.1,total

wt = 403.57 ton m, ton 168391

Welding connections 0.04A kg/m2 199.2 m2 8

From table 5.13, emission due to concrete in construction phase is very small as

compared to steel. This is because concrete has a very small volume (used in slab, stair

and lift core) in steel building as compared to steel members. Hence, total CO2

emissions in construction phase have been found as 419.96 ton. In construction of steel

building maximum CO2 emission is due to hoisting of steel members by crane and

minimum CO2 emission is due to welding of connections.


5.4.4 Emission of CO2 in Demolition of building

Table 5.14: Emission of CO2 in Demolition Phase for Steel Building

Material name


Emission rate Quantity Unit


Brick Brick chips by manual labor 0 327014 no 0

Concrete Crushing of concrete 0.04 kg/cft 26856 cft 1074

Timber After demolition used in cooking 47.5 kg/cft 5977 cft 283908

Steel Hoisting by Crane 8.1h kg/ton -m

h =76.83, total wt = 403.57 ton

m, ton 251151

Derricking by Crane 1.03L kg/ton -m

L =405.1, total wt = 403.57 ton

m, ton 168391

Transportation to rerolling mill in gazipur (dst2 = 47 km from Gulshan 1 to gazipur)

0.05dst2 (kg/ton) 462 ton 1086

Summing up the CO2 emission data presented in table 5.14, total CO2 emission due to

demolition of steel building is found as 705.61 ton.

Figure 5.14: Life cycle CO2 emission in demolition phase of different materials of

Steel Building.

284

421

0

100

200

300

400

500

600

Brick Concrete Timber Steel

CO

2em

issi

on (t

on)

Materials

Emission of CO2(ton)Emissionof CO2


Fig. 5.14 shows that maximum CO2 emission is from steel and mainly due to crane

operations.

5.4.5 Total CO2 Emission of Steel Building

Summary of total life cycle CO2 emission and individual emission in each of the

phases in life cycle of steel building are presented in figure 5.15 and 5.16 respectively

for three different types of cement. From fig 5.15, maximum total CO2 emission has

been found as 1981.27 ton for concrete mix ratio 1:1.5:3 with CEM-I and

reinforcement from scrap and minimum total CO2 emission has been found as 1457 ton

for mix ratio 1:3:6 and reinforcement from billet in cradle to gate although in

transportation phase maximum CO2 emission has been for concrete with mix ratio

1:2:4.

Figure 5.15: Maximum and minimum total life cycle CO2 emission from Steel

Building using different cement type in concrete.

According to Fig 5.16, maximum CO2 is emitted in cradle to gate phase ranging

between 395 ton to 838.86 ton and negligible amount in transportation phase

indicating 12.87 tons to 16.25 tons. Cradle to gate phase emits up to about 53.7% of

the total life cycle CO2 emission where as construction of steel building emits about

26.9% of the total emission.

1981 1933 1898

1533 1507 1457

0

500

1000

1500

2000

2500

3000

CEM I CEM IIA CEM IIB

CO

2em

issi

on (t

on)

Type of cement

Max CO2 EmissionMin CO2 Emission

Max CO2 emission Min CO2 emission


Figure 5.16: Maximum and Minimum life cycle CO2 emission in different phases of

Steel Building.

5.5 COMPARISON OF CO2 EMISSION OF CONCRETE AND STEEL

BUILDING

Comparison of both steel and concrete structural systems based on CO2 emission is

presented in fig. 5.17 and fig.5.18.

Figure 5.17: Comparison of Steel and Concrete building for maximum life cycle CO2

emission for Concrete mix.

839

16

420

706

395

13

420

706

0

200

400

600

800

1000

1200



CO

2em

issi

on (t

on)


Maximum emission Minimum emission

1981 1933 1898

1139 1044 977

0

500

1000

1500

2000

2500

3000


CO

2em

issi

on(to

n)

Type of cement in steel and concrete building

Steel building Concrete building


According to fig.5.17, there is significant difference in total CO2emission from steel

and concrete building. Steel building emits 842 ton to 921 ton more CO2 than concrete

building based on different cement types.

Fig 5.18 shows, except construction phase life cycle CO2 emission in all other phases

of both the building are very close. As construction of steel building involves a number

of machineries and mechanical support, emission in construction of steel building is

huge, almost 531 times as compared to concrete building.

Figure 5.18: Maximum Life cycle CO2 emission in different phase of Steel and

Concrete Building.

It may be concluded that for the six storey 914 square meter (9833 square feet)

building total life cycle CO2 emission of concrete buildings ranges between 178 to 207

kg per square meter whereas that for steel building ranges between 346 to 361 kg per

square meter.

839

16

420

706832

19

286

0

200

400

600

800

1000

1200

1400



CO

2em

issi

on (t

on)


Steel buildingConcrete building

CHAPTER 6

COMPARATIVE STUDY ON LIFE CYCLE ENERGY COST OF

CONCRETE AND STEEL BUILDING

__________________________________________________________________

6.1 GENERAL

In this chapter, life cycle energy cost in different phases of concrete and steel

buildings have been estimated using the equations developed in chapter 4 for different

materials commonly used in construction sector of Bangladesh.

Similar concrete and steel building described in article 5.1, 5.2 and 5.3 has been used

for the energy cost analysis. Both the building will be compared to determine more

energy intensive building between the two.

6.2 LIFE CYCLE ENERGY COST ANALYSIS OF CONCRETE BUILDING

For calculation of life cycle energy cost of Concrete building, four stages of life cycle

mentioned in article 5.3 have been considered. To determine the energy cost different

fuel cost has been considered as given in table 6.1.

Table 6.1: Price list of several fuels

Fuel Price Diesel BDT 61 per liter

Electricity BDT 5 per kWh unit

Coal BDT 80 per 60 kg bag

LPG Gas BDT 94 per cft

Source: Bangladesh Petroleum Corporation, March, 2012

A summary of material quantity required for both the buildings are given in table 5.1

6.2.1 Cradle to Gate Energy Cost of Materials Used in Concrete Building

Three different cement types have been considered for concrete namely CEM-I, CEM-

IIA and CEM-IIB. Comparison has been made for three different concrete mix ratios

Comparative study on life cycle Energy cost of Concrete and Steel Building 86

such as 1:2:4, 1:1.5:3 and 1:3:6 for each of the cement type. Aggregate (sandstones)

have been considered with its life cycle starting from processing unit Two different

sources of reinforcement have been studied; one from ship breaking scrap and other

from imported billet. All the empirical equations and symbols used for cradle to gate

energy cost calculations are derived from article 4.3 of chapter 4.

Concrete with CEM-I

Table 6.2 shows Energy cost calculations details for concrete building considering

CEM-I used in concrete.

Table 6.2: Energy Cost in Cradle to Gate Phase (Concrete With CEM-I)

Material Name Energy Cost Energy

Cost Unit


Unit of Material

Total Cost

(BDT)

Brick 193 Pc BDT/1000 brick 327014 Nos 83941

Concrete 1:2:4 Pd+385Pc+347Pe BDT/100cft 51856 cft 11968621:1.5:3 3Pd+477Pc+325Pe BDT/100cft 51856 cft 12665361:3:6 0.7Pd+268Pc+181Pe BDT/100cft 51856 cft 676275Timber 0.11Pd BDT/cft 5977 cft 40107Steel (Billet) 22.74Pd+66 Pc+34 Pe BDT/ton 164 ton 269767Steel (Scrap) 113.5PLPG+96.5Pc+173 Pe BDT/ton 164 ton 1279748

Table 6.2 shows, concrete ratio 1:1.5:3 is more energy intensive among the mix ratios

and scrap consumes more energy than billet. Hence, maximum energy cost has been

found for concrete with mix ratio 1:1.5:3 and steel from scrap as 26.70 lac BDT and

minimum for concrete ratio 1:3:6 and billet as BDT 10.70 lac BDT


Table 6.3 shows energy cost calculations details considering CEM-IIA used in

concrete.


Table 6.3: Energy Cost in Cradle to Gate Phase (Concrete with CEM-IIA)

Material Name Energy Cost Energy Cost

Unit


Unit of Materials

Total Cost

(BDT)


Concrete mix 1:2:4 Pd+306Pc+347Pe BDT/100cft 51856 cft 11423771:1.5:3 Pd+380Pc+325Pe BDT/100cft 51856 cft 11363721:3:6 0.7Pd+213Pc+181Pe BDT/100cft 51856 cft 638342Timber 0.11Pd BDT/cft 5977 cft 40107Steel (Billet) 22.74Pd+66 Pc+34 Pe BDT/ton 164 ton 269767Steel (Scrap ) 113.5PLPG+96.5Pc+173 Pe BDT/ton 164 ton 1279748

According to Table 6.3, maximum energy cost has been found for concrete with mix

ratio 1:1.5:3 and steel from scrap as 25.40 lac BDT and minimum for concrete ratio

1:3:6 and billet as 10.32 lac BDT.


Table 6.4 displays energy cost calculation results for cradle to gate phase of concrete

building where concrete is considered to be composed of cement type CEM-IIB, which

is the most commonly used in construction sector of Bangladesh.

Table 6.4: Energy Cost in Cradle to Gate Phase (Concrete with CEM-II B)

Material Name Energy Cost Energy Cost

Unit


Unit of Material

Total Cost

(BDT)


Concrete 1:2:4 0.5Pd+245Pc+347Pe BDT/100cft 51856 cft 10844901:1.5:3 0.6Pd+304Pc+325Pe BDT/100cft 51856 cft 10713031:3:6 0.4Pd+170Pc+181Pe BDT/100cft 51856 cft 599512Timber 0.11Pd BDT/cft 5977 cft 40107Steel (Billet) 22.74Pd+66 Pc+34 Pe BDT/ton 164 ton 269767Steel (Scrap ) 113.5PLPG+96.5Pc+173 Pe BDT/ton 164 ton 1279748


From Table 6.4, maximum energy cost has been found for concrete with mix ratio

1:1.5:3 and steel from scrap as 24.75 lac BDT and minimum for concrete ratio 1:3:6

and billet as 9.93 lac BDT.

Figure 6.1: Life cycle Energy cost in cradle to gate phase of Concrete Building with


Figure 6.2: Life cycle Energy cost of different materials in cradle to gate phase of

Concrete Building.

2,670 2,540 2,475

1,070 1,032 993

0500

1,0001,5002,0002,5003,0003,5004,0004,5005,000

CEM- I CEM- IIA CEM- IIB

Ener

gy c

ost (

Tho

usan

d B

DT)

Materials

Maximum Energy Cost

Minimum Energy Cost

84

1197 1142 1084

12671136 1071

676 638 600

40

270

1280

0

500

1,000

1,500

2,000

Brick Concrete with CEM I



Timber Steel

Ener

gy c

ost (

thou

sand

BD

T)

Materials

Brick Concrete 1:2:4 Concrete 1:1.5:3Concrete 1:3:6 Timber Steel from BilletSteel from Scrap


As shown in fig.6.1 maximum energy cost 26.70 lac BDT in cradle to gate phase has

been found if CEM-I have been used in concrete and minimum energy cost 9.93 lac

BDT has been found if CEM-IIB has been used in concrete.

Fig 6.2 shows, steel from scrap consumes maximum energy in cradle to gate phase

with energy cost worth BDT 1.3 lac among all the materials considered in this

analysis. Among the concrete mix ratios, cradle to gate energy cost of concrete with

1:2:4 and 1:1.5:3 are very close. However timber has the minimum energy cost worth

40 thousand BDT in cradle to gate phase.

6.2.2 Energy Cost in Transportation Phase of Concrete Building

Energy cost calculation in transportation phase involves selecting a particular project

site for concrete building. Gulshan 1 has been considered as project site and materials

required for the building have been considered to be transported to project site from

their common source location as shown in table 6.5.

Table 6.5: Energy Cost from Different Materials in Transportation Phase of Concrete

Building

Material Name

Equation of Energy Cost

Energy Cost Unit

Material Quantity

Unit of Material

Energy Cost (BDT)

Brick 0.08 Pddb BDT/1000 brick 327014 Nos 34470

Concrete 1:2:4 Pd(0.02dc+0.02ds+0.04da) BDT/100 cft cft 353267 1:1.5:3 Pd(0.02dc+0.02ds+0.03da) BDT/100 cft 51856 cft 273871 1:3:6 Pd(0.01dc+0.02ds+0.02da) BDT/100 cft 51856 cft 185807 Timber 0.0005Pd dt1 BDT/ cft 51856 cft 34638 Steel (billet ) 0.02Pddst1 BDT/ton 5977 ton 50420 Steel (scrap) 0.02Pddst1 BDT/ton 164 ton 50420

From table 6.5, maximum total energy cost has been found as 4.41 lac BDT and

minimum energy cost has been found as 2.74 lac BDT.

Figure 6.3 shows; maximum energy cost due to transportation phase of concrete

building is due to concrete and timber. Although maximum transportation distance has


been considered for timber, concrete with mix ratio 1:2:4 have maximum energy cost.

It may be due to the fact that concrete involves three component materials which have

been obtained from different source locations, the distances of which have direct

impact on energy cost.

Figure 6.3: Life cycle Energy cost in transportation phase of different materials of

Concrete Building.

The energy cost equations for concrete shows greater impact of distance of aggregate

source and distance considered for the said source is 251 km which is also quite high.

However timber showed minimum transportation cost.

6.2.3 Energy Cost in Construction Phase of Concrete Building

Construction of a building involves several individual operations. In this study most

common and energy consuming operations in construction practice has been

considered. In construction phase of life cycle energy cost analysis of concrete

building mixing of concrete and casting of concrete has been considered.

34

353

274

186

34 50 50

0

100

200

300

400

500

600

Brick Concrete 1:2:4

Concrete 1:1.5:3

Concrete 1:3:6

Timber Steel from Billet

Steel from Scrap

Ener

gy c

ost (

thou

sand

BD

T)

Materials

Energy Cost


Table 6.6: Energy Cost from Different operations in Construction Phase of Concrete

Building

Operations Energy Cost Equation

Energy Cost

Material Quantity

Unit of Material

Energy Cost (BDT)

Mixing of concrete 0.016Pe BDT/ cft 51856 cft 4148 Casting of concrete 0.002 Pg BDT/ cft 51856 cft 9749

From table 6.6, total energy cost in construction phase has been found as 14 thousand

BDT.

6.2.4 Energy Cost in Demolition Phase of Concrete Building

In demolition phase, brick and timber do not worth any energy cost because for

conversion of bricks into brick chips manual labor has been considered which a

common practice in Bangladesh is and timber is considered to be used in cooking

which do not require any external energy input. Concrete is considered to be crushed

for demolition of the building using concrete crusher and reinforcement to be

transported to the rerolling mills for use in production of steel. The details of

calculation are presented in table 6.7.

Table 6.7: Energy Cost from Different Materials in Demolition phase

Material name State of material after demolition of building

Energy Cost Equation

Material Quantity

Unit of Material

Energy Cost (BDT)

Concrete Crushing of concrete 0.014Pd BDT/ cft 51855.92 cft 44285

Reinforcement

Transportation to rerolling mill in gazipur (dst2=47 km from Gulshan 1 to Gazipur)

0.02 Pddst2 (BDT/ton-km)

164 ton 9404

From table 6.7 energy cost in demolition phase has been found 54 thousand BDT.

Concrete contributes maximum energy cost, 44.3 thousand BDT in demolition phase.


6.2.5 Total Energy Cost from Concrete Building

Summary of total life cycle energy cost and individual emission in each of the phases

in life cycle of concrete building are presented in figure 4.26 and 4.27 respectively for

three different types of cement.

Figure 6.4: Maximum and minimum total life cycle energy cost of Concrete Building

using different cement type used in concrete.

From fig 6.4, maximum total energy cost has been found for mix ratio 1:1.5:3 with

CEM-I and reinforcement from scrap worth 32 lac BDT and minimum for mix ratio

1:3:6 with CEM II-B and reinforcement from billet worth 13.4 lac BDT.

Fig.6.5 shows, maximum energy is consumed in cradle to gate phase. Both

construction and demolition phase of concrete building have less impact in total life

cycle energy cost of concrete building. Results shows negligible amount of energy cost

in construction phase indicating 14 thousand BDT. Energy cost in cradle to gate phase

is about 84% of the total life cycle energy cost.

3,049 2,984 2,475

1,412 1,374 1,335

0500

1,0001,5002,0002,5003,0003,5004,0004,5005,000

CEM- I CEM- IIA CEM- IIB

Ener

gy c

ost (

Tho

usan

d B

DT)

Materials

Maximum Energy Cost

Minimum Energy Cost


Figure 6.5: Maximum and minimum life cycle energy cost in several phases of

Concrete Building.

6.3 LIFE CYCLE ENERGY COST OF STEEL BUILDING

Detail calculations of energy cost throughout several phases of life cycle of steel

building are presented and discussed in the following sections. Detail calculation

charts for Building design are enclosed in Appendix C of this thesis.

6.3.1 Energy Cost of Materials in Cradle to Gate Phase of Steel Building

For steel building, steel members have been studied considering their source both from

billet and ship breaking scrap. For billet minimum value in cradle to gate phase has

been for minimum shipment distance and maximum value has been for maximum

shipment distance. Cradle to gate analysis have been done for concrete with three

different mix ratios as considered for concrete building by absolute volume basis and

three different cement type: CEM I, CEM-IIA and CEM-IIB. Aggregates (sandstones)

have been considered with its life cycle starting from processing unit.

Concrete with CEM-I in steel building

Detail calculations of energy cost for the materials used in steel building are presented

in the following table 6.8.

2,670

441 54

993

274 540

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

Cradle to gate Transportation Construction Demolition

Ener

gy c

ost (

Tho

usan

d B

DT)

Materials

Maximum Energy Cost

Minimum Energy Cost


Table 6.8: Energy Cost in Cradle to Gate Phase of Steel Building.

Material name Energy Cost Rate

Energy Cost rate Unit

Material Quantity

Unit of Material

Energy Cost BDT

Steel (Billet) 22.74Pd+66 Pc+34 Pe BDT/ton 462 ton 760273Steel (Scrap ) 113.5PLPG+96.5Pc+173 Pe BDT/ton 462 ton 3606706

Concrete 1:2:4 Pd+385Pc+347Pe BDT/100cft 26856 cft 619850

1:1.5:3 3Pd+477Pc+325Pe BDT/100cft 26856 cft 655934

1:3:6 0.7Pd+268Pc+181Pe BDT/100cft 26856 cft 350240Timber 0.11Pd BDT/cft 5977 cft 40107


According to table 6.8 , maximum energy cost is 43.87 lac BDT considering steel

from scrap, concrete mix ratio 1:1.5:3 with CEM-I and timber and brick and minimum

energy cost is 12.35 lac BDT considering steel from billet, concrete mix ratio 1:3:6

with CEM-I, timber and brick.



Material Name Energy Cost Equation Energy

Cost Unit Material Quantity

Unit of Material

Energy Cost

(BDT)Steel (Billet) 22.74Pd+66 Pc+34 Pe BDT/ton 462 ton 760273Steel (Scrap ) 113.5PLPG+96.5Pc+173 Pe BDT/ton 462 ton 3606706Concrete 1:2:4 Pd+306Pc+347Pe BDT/100cft 26856 cft 5916321:1.5:3 Pd+380Pc+325Pe BDT/100cft 26856 cft 5548231:3:6 0.7Pd+213Pc+181Pe BDT/100cft 26856 cft 310485Timber 0.11Pd BDT/cft 5977 cft 40107Brick 193 Pc BDT/1000

brick 327014 Nos 83941

Table 6.9 shows , maximum energy cost is 43.22 lac BDT considering steel from

scrap, concrete with CEM-IIA with mix ratio 1:1.5:3 and timber and brick and

minimum energy cost is 11.95 lac BDT considering steel from billet, concrete with

CEM- IIA with mix ratio 1:3:6 , timber and brick.




Material name Energy Cost Equation Energy Cost

Unit Material Quantity

Unit of Material

Energy Cost BDT

Steel (Billet) 22.74Pd+66 Pc+34 Pe BDT/ton 462 ton 760273Steel (Scrap ) 113.5PLPG+96.5Pc+173 Pe BDT/ton 462 ton 3606706Concrete 1:2:4 0.5Pd+245Pc+347Pe BDT/100cft 26856 cft 5616531:1.5:3 0.6Pd+304Pc+325Pe BDT/100cft 26856 cft 5548231:3:6 0.4Pd+170Pc+181Pe BDT/100cft 26856 cft 310485Timber 0.11Pd BDT/cft 5977 cft 40107


According to table 6.10, maximum energy cost is 42.92 lac BDT, considering steel

scrap, concrete mix ratio 1:1.5:3 with CEM-IIB, timber and brick. Minimum energy

cost is 11.95 lac BDT for steel from billet, concrete mix ratio 1:3:6 with CEM-IIB,

timber and brick.

Figure 6.6: Life cycle energy cost in cradle to gate phase of Steel Building with


4,387 4,322 4,292

1,235 1,195 1,195

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

CEM I CEM II-A CEM II-B

Ener

gy c

ost (

thou

sand

BD

T)

Cement type

Maximumcost Minimum cost


Fig.6.6 shows it will be most economical in terms of energy cost if CEM- IIB is used

in concrete.

Figure 6.7: Life cycle Energy cost in cradle to gate phase of Steel Building

As steel is the core material for the members and connection of steel building energy

cost steel is highest among all the materials used in steel building. Fig. 6.7 shows that

maximum energy cost is for steel from scrap as scrap melting and rerolling process

requires maximum fuel input amongst all the materials considered for superstructure of

steel building. Steel from scrap consumes maximum energy amongst all the materials.

Second highest is Billet which is mainly due to energy requirement in rerolling

process. Brick requires negligible amount of energy than other materials hence has the

lowest energy cost.

6.3.2 Transportation of Material to Construction Site

As the same project location in Gulshan 1 has been considered for steel building also,

transportation distances from several sources are same as table 6.11.

760

3,607

84 620 592561656 554 555

350 310 310

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

Steel Brick Concrete with CEM I



Timber

Ener

gy c

ost (

thou

sand

BD

T)

Cement type

Steel from Billet Steel from ScrapBrick Concrete 1:2:4Concrete 1:1.5:3 Concrete 1:3:6Timber


Table 6.11: Energy Cost in Transportation Phase of Steel Building.

Material name

Energy Cost Equation Energy Cost Unit

Material Quantity

Unit of Material

Energy Cost BDT

Steel 0.02Pddst1 BDT/ton 462.2 ton 142099

Brick 0.08 Pddb BDT/1000 brick 327014 Nos 34470

Concrete 1:2:4 Pd(0.02dc+0.02ds+0.04da) BDT/100 cft 26855.66 cft 182954 1:1.5:3 Pd(0.02dc+0.02ds+0.03da) BDT/100 cft 26855.66 cft 141835 1:3:6 Pd(0.01dc+0.02ds+0.02da) BDT/100 cft 26855.66 cft 96228 Timber 0.0005Pd dt1 BDT/ton 5977.2 cft 34638

According to table 6.11, maximum total energy cost from transportation is 3.7 lac BDT

considering, 1:2:4 mix ratio for concrete and other materials whereas minimum total

energy cost is 2.80 lac BDT considering 1:3:6 mix ratio for concrete and other

materials listed in table.

Figure 6.8: Life cycle energy cost in transportation phase of different materials of

Steel Building.

Figure 6.8 shows maximum energy cost in transportation phase is due to transportation

of concrete as concrete is a composite material, component materials are obtained from

several locations.

142

34

183

142

96

35

0

50

100

150

200

250

300

Steel Brick Concrete 1:2:4

Concrete 1:1.5:3

Concrete 1:3:6

Timber

Ener

gy c

ost (

thou

sand

BD

T)

Materials

Energy Cost


6.3.3 Construction phase of Steel Building

In this phase of steel building, energy cost has been calculated for mixing of concrete,

casting of concrete, crane operations such as hoisting and derricking and welding the

connections of steel members. Details of calculations are presented in table 4.24.

Table 6.12: Energy Cost in Construction Phase for Steel Building

Operation Energy Cost Equation

Energy Cost Unit

Material Quantity

Unit of Material

Energy Cost BDT

Mixing of concrete 0.016Pe BDT/ cft 26855.66 cft 2148Casting of concrete 0.002 Pg BDT/ cft 26855.66 cft 5049Hoisting steel members by crane 13.31Peh BDT/ ton h=76.83,total

wt=403.57 ton m,ton 2063468

Derricking steel members by crane 1.69PeL BDT/ ton L=405.1,total

wt=403.57 ton m,ton 1381458

Welding connections 0.17PeA BDT/m2 199.2 m2 169

From table 6.12, it can be said that construction phase of steel building has significant

energy consumption in construction phase. Concrete used in steel building has very

nominal quantity (used in slab, stair and lift core) as compared to steel members.

Hence, total energy costs in construction phase have been found as 34.5 lac BDT.

Figure 6.9: Life cycle energy cost in construction phase of Steel Building.

2,063,468

1,381,458

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

Mixing of concrete

Casting of concrete

Crane operation

Hoisting Derricking Welding connections

Ener

gy c

ost (

BD

T)

Materials

Energy Cost


Fig. 6.9 shows that in construction of steel building, maximum energy cost is due to

hoisting of steel members by crane and minimum energy cost is due to welding of

connections.

6.3.4 Demolition of Steel Building

Table 6.13: Energy Cost in Demolition Phase of Steel Building

Material name


Energy Cost Equation

Material Quantity Unit

Energy Cost BDT

Brick Brick chips by manual labor 0 327014 no 0

Concrete Crushing of concrete 0.014 Pd BDT/ cft 26855.66 cft 22935

Steel Hoisting steel members by crane

13.31Peh BDT/ ton

h=76.83,total wt=403.57 ton

m,ton 2063468

Derricking steel members by crane

1.69PeL BDT/ ton

L=405.1,total wt=403.57 ton

m,ton 1381458

Transportation to rerolling mill in gazipur (dst2=47 km from Gulshan 1 to Gazipur)

0.02 Pddst2 462 ton 26491

Summing up the energy cost data presented in table 6.13, total energy cost due to

demolition of steel building is found as 34.94 lac BDT. Brick has no energy cost due

to conversion as brick has been considered to be converted as brick chips by manual

labor.

6.3.5 Total Energy cost from Steel Building

Figure 6.10 and 6.11 present summary of total energy cost and individual energy cost

in each of the phases in life cycle of steel building respectively. From Fig 6.10,

maximum total energy cost has been found as 117 lac BDT for concrete mix ratio

1:1.5:3 with CEM-I and reinforcement from scrap and minimum total energy cost has

been found as 84 lac BDT for mix ratio 1:3:6 and reinforcement from billet in cradle

to gate .


Figure 6.10: Maximum and minimum total Life cycle Energy cost from Steel Building

using different cement type in concrete.

Figure 6.11: Maximum and Minimum Energy cost in different phases of Steel

Building.

According to Fig 6.10, difference in maximum total energy cost of steel building with

three cement types is not very significant. Fig.6.11 shows cradle to gate phase

11,701 11,636 11,606

8,459 8,419 8,419

02,0004,0006,0008,000

10,00012,00014,00016,00018,00020,000

CEM I CEM IIA CEM IIB

Ener

gy c

ost (

thou

sand

BD

T)

Type of cement

Maximum energy cost

Minimum energy cost

4,387

370

3,450 3,494

1,195

3,450 3,494

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000



Ener

gy c

ost (

thou

sand

BD

T)


Maximum energy costMinimum energy cost


consumes largest share of energy cost of the total life cycle indicating 44 lac BDT.

Construction phase is the second largest phase in terms of energy cost.

6.4 COMPARISON OF CONCRETE AND STEEL BUILDING BASED ON

ENERGY COST

In this section life cycle energy cost of steel and concrete building is compared.

According to fig. 6.12, there is significant difference in total energy cost of steel and

concrete building. Energy cost of steel building ranges from 84.19 lac BDT to 117.01

lac BDT where as total energy cost of concrete building ranges from 132.35 lac BDT

to 31.79 lac BDT. Hence, considering maximum energy cost for both the structural

system, steel building has energy cost 3.7 times that of concrete building.

Figure 6.12: Comparison of Steel and Concrete building for maximum life cycle

Energy cost for Concrete mix.

Energy cost of 914 square meter six storey concrete building ranges from 243 to 580

BDT per square meter and that for steel building ranges from minimum 1535 to 2134

BDT per square meter.

Comparison has been made in several phases of their life cycle namely cradle to gate ,

transportation, construction and demolition separately in fig 6.13, fig 6.14, fig 6.15,

fig 6.16.

3,217

1,462

8,267

4,993

0

2000

4000

6000

8000

10000

12000

Maximum cost Minimum cost

Ener

gy c

ost (

thou

sand

BD

T) Concrete building

Steel building


.

Figure 6.13: Life cycle Energy cost of materials in cradle to gate phase of Steel and

Concrete Building.

Figure 6.14: Life cycle Energy cost in transportation phase of Steel and

Concrete Building.

270

1280 1197 1267

676

40 84

760

3607

656 620350

40 840

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

steel(billet) steel (scrap) concrete 1:2:4

concrete 1:1.5:3

concrete 1:3:6

timber brick

Ener

gy c

ost (

thou

sand

BD

T)

Materials

Concrete buildingSteel building

50

353

274

186

34.6 34.5

142183

14296

34.6 34.5

0

100

200

300

400

500

600

steel(billet) concrete 1:2:4

concrete 1:1.5:3

concrete 1:3:6

timber brick

Ener

gy c

osat

(tho

usan

d B

DT)

Material

Concrete building

Steel building


Figure 6.15: Life cycle Energy cost in construction phase of Steel and Concrete

Building.

Figure 6.16: Life cycle Energy cost in several phases of Steel and Concrete Building.

9,749

2,063,468

1,381,458

0

500000

1000000

1500000

2000000

2500000

mixing of concrete

casting of concrete

hoisting by crane

derricking by crane

welding connections

Ener

gy c

osat

(BD

T)

Operations in construction

Concrete building

Steel building

4,398

370

3,450 3,4942,694

44114 54

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000



Ener

gy c

ost (

thou

sand

BD

T)


Steel BuildingConcrete Building


According to the figures it can be said that except demolition phase, difference in life

cycle energy cost in all other phases of both the building are very significant. The

largest difference has been found in cradle to gate phase and construction phase. This

is because; production of steel is very energy intensive which requires huge fuel input

as compared to concrete and construction of steel building involves a number of

machineries and mechanical support.

.

Conclusion 105

CHAPTER 7

CONCLUSION AND RECOMMENDATIONS

______________________________________________________________________

7.1 GENERAL

This research work emanated with an aim to develop empirical equations of the life

cycle CO2 emission and energy cost of selected building materials of the construction

industry of Bangladesh and also to make a comparative study of medium size buildings

with different structural systems.

Empirical equations have been developed for the materials steel, cement, sand,

aggregate, timber, brick and concrete. Four stages of life cycle have been considered;

they are cradle to gate, transportation, construction and demolition of the building.

Operation phase of the building has not been considered as the building materials do not

emit any significant amount of CO2 and also do not require any external energy after

incorporating into a building. Uncertainty is unfortunately a part of CO2 analysis and

even the most reliable data carries a natural level of uncertainty. When describing

buildings by materials, there is a tendency to label according to the main material used,

however, the vast majority of buildings use a large number of materials. Hence it is not

clear which materials or combinations of materials can achieve the best performance, in

terms of life–cycle carbon dioxide emissions and energy cost.

In order to develop a set of ‘benchmarks’, this research modeled the performance of two

similar medium sized buildings, located in Dhaka city of Bangladesh, each designed by

finite element analysis using primarily Concrete and Steel. The models were based on a

six-storey 9833 square feet or 914 square meter floor area building. The analysis of each

case study includes the calculation of life cycle energy cost and carbon dioxide

emission. After completing the analysis a good number of graphs have been drawn for

different phases of life cycle of each of the buildings with the previously derived

equations. One can easily obtain the total energy cost and life cycle CO2 emission by

putting values in these equations and assess the environmental implications of several

Conclusion and Recommendations 106

building projects of Bangladesh. Thus the objective of this research comes out

successfully.

7.2 FINDINGS OF THE RESEARCH WORK

The outcomes of the research work are summarized as follows.

Empirical equations of life cycle CO2 emission and energy cost have been

developed for brick, cement, sand, steel; both from billet and scrap, stone chips,

timber and concrete which are very usable equations for the engineers for

decision making in choosing materials.

Two similar buildings have been modeled separately for steel and concrete

structural systems and compared on the basis of empirical equations developed in

four phases of life cycle namely cradle to gate, transportation of raw materials,

construction and demolition.

On the basis of analysis of life cycle CO2 emission and energy cost on two

individual case studies of Steel and Concrete building it can be said that-

Steel produced from ship breaking scrap emits the maximum life cycle CO2

and consumes maximum energy in its life cycle as compared to other

materials considered in this study. Imported billets have less energy cost even

smaller than concrete in cradle to gate phase.

Among three different type of cement CEM-IIB emits less life cycle CO2 and

is more economical in terms of life cycle energy cost.

Concrete with mix ratio 1:1.5:3 emits maximum life cycle CO2 in cradle to

gate phase and concrete with mix ratio 1:2:4 emits maximum life cycle CO2

in transportation phase. However, concrete with mix ratio 1:3:6 have

minimum energy cost and emits minimum CO2 in both the phases.

Concrete emits maximum CO2 in transportation phase among all the

construction materials considered in this study. This may be due to the fact

that concrete is a composite material which has three core materials such as

cement, sand and coarse aggregate, all of these are obtained from different

source locations.


Energy cost of timber in transportation phase is highest among all the materials.

Comparing both the structural system of 914 square meter floor area six storey mid

rise building it can be concluded that-

In cradle to gate phase, concrete building emits 73 % of the total life cycle

CO2 where as steel building emits 53.7% CO2 in this phase.

In construction phase emission of CO2 of concrete building is very

negligible indicating a value less than one ton. On the other hand 26.9% of

total life cycle CO2 of steel building is due to construction phase. Although

cradle to gate emissions of both the buildings are almost same, construction

phase of steel building emits 531 times CO2 of that of concrete building.

Total life cycle CO2 emission of concrete buildings ranges between 178 to

207 kg per square meter whereas that for steel building ranges between 346

to 361 kg per square meter. Steel building emits 1.7 times CO2 per square

meter as compared to concrete buildings considering maximum total life

cycle CO2 emission.

Energy cost of concrete building ranges from 243 to 580 BDT per square

meter and that for steel building ranges from minimum 1535 to 2134 BDT

per square meter. Considering maximum total energy cost, steel building has

3.7 times energy cost per square feet of concrete building.

7.3 RECOMMENDATIONS FOR FUTURE STUDIES

The following recommendations for the future work may be suggested:

In this study empirical equations have been developed for seven most widely

used materials of Bangladesh namely brick, cement, sand, and aggregate, timber

steel and concrete. However, the study can be extended considering more

materials such as glass, plastic, aluminium and other finishing materials.


The present study considers only superstructure of both the buildings. Life cycle

CO2 emission and energy cost may be studied for buildings considering

foundation also.

Empirical equations may be developed for several materials to assess variations

of structural systems and further comprehensive investigation can be made.

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