3 Timber as a Sustainable Material

7/28/2019 3 Timber as a Sustainable Material

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timber in environmentally sustainable development

Timber as a Sustainable Material

Timber as a Sustainable Building Material

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Timbers innate attractions

Timber is a light, strongmaterial, used in

building structures for

millennia because it is:

Renewable;

Simple to manufacture;

Easy to use; and

Stable and safe.

Importantly now, it is

also a store for carbon.

Woolmers pump house, Tasmania, 1841


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Ease of manufacture

Producing timber,poles, veneer and

engineered timber

products is a relatively

simple, low capitalprocess.

It uses few chemicals,

relatively little energy,

and produces few

pollutants.

Staff of a small veneer plant


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Transport

Logs weigh about 1tonne/m3.They are

transported from the

forest in trucks.

Most sawmills arepositioned near their

log supply, so

transport distances

are usually not long.

Logs on landing and being unloaded


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Producing sawn timber

Logs are deliveredto site, stored andthen sawn.

Because of the

character of logs,only about 35% ofhardwood and 45%of softwood logs are

converted to timber. The remainder issawdust or chipped.

Hardwood saw mills


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Timber drying (or seasoning)

The timber is then dried. This is either in the

open air or in a kiln.

Air drying is slow and

very low energy. Air dried material can be

finished in the kiln.

Kiln drying is faster.

Often, shaving andsawdust fires the boilers

that heat the kilns.

Timber in racks for drying


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Dry milling & sale

Dry timber is gradedand sorted.

It can then be

moulded to different

shapes or sold forfurther processing.

Often, no other

processes arenecessary before it

can be used.Quality control in a dry mill


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Veneer manufacture

Logs for structural ordecorative veneer

are delivered to site.

It may be sawn into

flitches and heatedin water before

peeling or slicing.

Unused section oflog are often sawn

into timber.Stacking veneer from a slicer


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Veneer drying and grading

Once sliced orpeeled, the veneer is

dried in a dryer,

before being graded.

After grading, theveneer is trimmed

and can be laid up

into sheets.

Grading veneer


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Engineered products

Plywood and LVLare layers of peeled

veneer glued and

pressed together in

industrial equipment. Nail plating of

trusses requires a

simple hydraulic

press and a work

space.

Pressing nail plates


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Glue lamination

Glue laminatedmaterial is sawn

timber, planned to

give a smooth edges

and adhered with awaterproof glue.

Transport is the only

effective limitation

on the size of glulam

members

Prefabricating glulam beams


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ti b i i t ll t i bl d l t


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Carbon storage in forests

During photosynthesis trees absorb CO2from the air, stores the carbon in woody

tissue and give off oxygen.

To produce 1 Kg of wood, a tree: absorb in 1.47 Kg of CO2; and

returns 1.07 Kg of oxygen to the

atmosphere



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Carbon stored in forests

In 2001, Australia'splantations and managed

forests stored a net 22.7

million tonnes of carbon

dioxide equivalent. So, they stored more than

half of the greenhouse

gases emitted by all the

passenger cars in Australiathat year.

50% of CO2



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Carbon stored in building

When logs areconverted to timber

and other wood

products, the carbon

from the tree is storedin the products.

Timber buildings are

carbon stores.

Bus stop, Kings Meadow, Tasmania



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Current greenhouse accounting method

The current greenhouse accounting methodcalculates decomposition of forest productsusing product service life pools: Pool 1 - service life 3 years - paper products

Pool 2 - service life 10 years - pallets, palings Pool 3 - service life 30 years - kitchen furniture

Pool 4 - service life 50 years - poles, constructionmaterials

At the end of each pool life, the carbon isassumed to return to the atmosphere.

This may overestimate emission considerably.

timber in en ironmentall s stainable de elopment


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Alternative method

Establish five service life pools of 3, 10, 30,50 and 90 years

Establish three age groups within eachservice life pool - Young , Mid, and Old

Wood products then progress through each

age group with one of five alternatives: Progress to next age pool

Leave pool and enter landfill pool

Leave pool and enter recycling pool

Leave pool and their carbon is emitted toatmosphere

Long-term storage beyond pool service life



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Carbon

from

forest

Recycle Landfill

Bioenergy

Atmosphere

AtmosphereDecomposition

Product topermanent

storage

Longer-term storage

Leaves

pool

Young age

group of

pool

Mid age

group of

pool

Old age

group of

pool

Leaves

pool

Leaves

pool

Alternative Method



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Alternative Method

The alternative method better reflectswhat happens to wood products.

The effect on calculated emissions is

shown on the following two slides.



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Fate of Carbon in Wo od Products - decomposition over

service life, no age groups wi thin pools

0

50000

100000

150000

200000

250000

300000

19

4

4

19

4

9

1

95

4

1

95

9

1

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64

1

96

9

1

97

4

1

9

79

1

9

84

1

9

8

9

1

9

94

19

9

9

2

0

0

4

Ye ar

Carb

on,

Carbon from forest

Carbon in p roduct pools



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F ate o f Carbon in W ood P rod ucts - Age G roups W ith in Pools , w i th

Land f i l, Recycling an d Bioene rgy include d

0

50000

100000

150000

200000

250000

300000

1

9

4

4

1

95

2

19

6

0

1

9

68

19

7

6

1

9

84

19

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2

2

0

00

Ye ar

Ca

rbon,

Carbon f rom fores t

Total s torage in wood p ro ducts andlandfi l l poo ls

Carbo n in land fi ll p oo l

Carbon in woo d product po ols

Carbon in bioenergy po ol



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Alternative Methods - Conclusion

A life cycle approach, includingconsideration of the use of residues,

storage in service, recycling and

disposal to landfill has the potential tosignificantly decrease the contribution

from wood products to Australias

estimates of greenhouse gas emissions.



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Timber impacts compared to other materials

Timber is only one ofa range of materialsavailable forconstruction.

All material have animpact and it ispossible to comparetheir use inmanufacture anduse using LCAtechniques.

Shear connector positions in a glulam beam



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Timber uses less fossil fuel to make

1.5 235

435

0

100

200

300

400

500

Fossil fuel energy (MJ/kg)

Rough sawn timber Concrete Steel Aluminium



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Timber store carbon. Others release it

15 120

5320

250 0 0

0

1000

2000

3000

4000

5000

6000

Carbon released (kg/m3) Carbon stored (kg/m3)

Rough sawn timber Concrete Steel



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Comparative Energy Use in an idealised structure where 4

materials have an equal contribution to the structurederived from Factor 4- Doubling Wealth - Halving the Resource Use:

Embodied Energy of Materials

0

2

4

68

10

12

14

16

18

Effect

Steel

Glass

Concrete

Wood



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Timber has lower embodied energy



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Timber has lower ecological profile



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Timber elements have lower impact

Embodied energy of differing window frames



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3 Timber as a Sustainable Material

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