BBGG Blackwater Tier3 Method OpenCuts(2)

Tier 3 Method for Estimating Fugitive Emissions from Open Cut Coal Mining

Abouna SaghafiECBM and Greenhouse Gas Research

Blackwater, 26 February 2009

CSIRO. Saghafi, 2009

Fugitive emissions from Australian coal mining

Total fugitive emissions from coal mining = 22 Mt CO2 (Year 2005)

55%34%

8% 3%

UndergroundOpencutAbandonned minePost mining

Fugitive emissions from coal mining (Mt/y)Underground 12.10Opencut 7.48Abandonned mine 1.76Post mining 0.66Toatla 22.00


Definition of Tiers for emissions calculation

• Tier 1 –Country/group of countries Specific

• Cheap but very inaccurate

• Tier 2 –Basin Specific • Cost depends on how many

mines results are averaged

• Tier 3 –Mine Specific• Cost depends on the number

of gas zones in the mine but very accurate

Acc

urac

y

Tier 2

Tier 3

Cost $

Emissions estimates are classified in Tiers (1, 2 and 3) based on their accuracy (see IPCC reports)

Tier 1


Project path to the Tier 3 Methodology

• Department of Environment, Sports and Territories 1990-93

Methane emissions from open-cut mines and post-mining emissions from underground coal

• IEA Greenhouse Gas R&D Programme, 1994-96 Methane emissions from coal mining

• ACARP C9063, 2001-03. Toward the Development of an Improved Methodology for Estimating Fugitive

Seam Gas Emissions from Open Cut Mining

• ACARP C12072, 2003-04. Development of an improved methodology for Estimation of Fugitive Seam Gas

Emissions from Open Cut Mining

• ACARP C15076 2005-07. Evaluating a Tier 3 method for estimating fugitive emissions from open cut coal

mining


Direct measurement of emissions from opencutmines

• Global emissions (gas plume measurement):

• Measure crosswind profile of CH4 concentration using an instrumented vehicle driving downstream along mine access roads around mine perimeter

vwhCHQ 4%=

..4321 ++++= qqqqQ

v % CH4 Q

Open cut

Access road

• Individual emissions (chamber method)

• Direct in pit measurement from highwall, uncovered coal seams, blasted coal seam and and spoil piles.


Results of 1990-93 study –Regional Emission Factor (Tier 2)

• Emission measurements from 17 mines were used to suggest EF values for Bowen Basin and Hunter Valley open cut mines.

• These numbers were then adopted by the Australian Greenhouse Office (AGO).

• Emission factor for Queensland: 1.2 m 3 per tonne of produced coal (m 3/t)

• Emission factor for NSW : 3.2 m 3/t

• These emission factors were intended to be indicative and could only be used in the absence of any mine specific data.


ACARP C9063: Direct emission measurements

• In the course of the ACARP C9063 surface emissions were measured in numerous coal mines of Hunter and Bowen coalfields.

• Flow rates were also measured from exploration boreholes.


ACARP 12072: Estimation of emission rate from the in situ gas content measurement

• In situ gas content is the source of fugitive emissions.

Therefore, the sum of all emissions should be equal to the volume of gas in place

...4321 ++++≥ qqqqQ


Development of the new Tier 3 methodology ACARP Project C15076

• Coal seam gas emissions rate from open cut at any time is the sum of,

= q1 + q2 + q4 + q4 +…

QQ

q1 q4

If the mine advances at a certain regular speed over the year then the sum of all emissions would be equal to the gas contained in a slice of strata corresponding to the average speed:

Q =q1 + q2 + q3 + q4 + …


New Methodology (Concepts of emissions)

• During open cut mining, coal seams, overburden and underburden strata are fractured.

• The fracturing of the strata produces a ‘gas release zone ’ from which the trapped seam gas is released into the atmosphere

δh

Pit base

A Seam

B Seam

C Seam

D Seam

Ground surface

h

Gas release zone


Gas release zone is partitioned in a number of layers corresponding to the local geological strata.

Emissions from each layer are calculated,

β is the emission coefficient (0< β<1). It is the ratio of the gas volume which can be emitted to the gas volume which is in place.

Total emissions is the sum of emissions from all layers,

Pit floor level

Coal seam

Rock

Floor emissions (δh)

Overburden emissions (h )

Water table level

Layer 1

Layer 2

Layer 3

Layer i

Layer n

Layer i-1

Layer i+1

Carbonaceous rock

Layer n-1

hi

z

New emissions model (Emission layers)

iiiii hcq ρβ=

∑=n

iqQ

1


New methodology (Emission Factor)

Emission Factor (EF) is the volume of gas emitted per tonne of coal produced

Ground surface

Pit floor Target seam

Rock layer

Qcs

∆h

h

Gas Release Zone

P

QEF =

α = 1, seam minedα = 0, seam not mined (spoiled or in underburden)

qs

qc∑=n

iii hP1

ρα

Coal produced


Position and thickness of the layer (m)

Layer Nature of the layer

Top Bottom Mid-

depth Thickness

1 Conglomerate and sandstone 0 35.15 17.58 35.15

2 Coal, A Seam 35.15 39.25 37.20 4.10 3 Tuff 39.25 42.62 40.94 3.37 4 Coal, B Seam 42.62 48.51 45.57 5.89

5 Carbonaceous mudstone 48.51 49.89 49.20 1.38 6 Coal, C Seam 49.89 50.93 50.41 1.04

Base of the pit

7 Siltstone, shale & stony coal bands 50.93 61.55 56.24 10.62

8 Coal, D Seam 61.55 62.08 61.82 0.53

9 Claystone and tuff 62.08 70.93 66.51 8.85

Application of the method: Generic case

• A hypothetic open cut virgin ground cross section showing coal seams and rock strata for EFcalculation


Generic case

• Input data for calculation of emissions for generic open cut

Gas composition (%) Layer attributes

Layer Mid-

depth (m)

Thickness (m)

Density (t/m3)

Gas content (m3/t) CH4 CO2

Production coeff, α

Emission coeff. β

1 17.58 35.15 2.50 0.00 0.00 0.00 0.00 1.00

2 37.20 4.10 1.50 0.10 19.86 80.14 1.00 1.00 3 40.94 3.37 2.50 0.00 0.00 0.00 0.00 1.00 4 45.57 5.89 1.60 0.40 2.78 97.22 1.00 1.00

5 49.2 1.38 2.30 0.01 14.30 85.70 0.00 1.00 6 50.41 1.04 1.45 0.60 3.64 96.36 1.00 1.00

Base of the pit

7 56.24 10.62 2.20 0.03 77.60 22.40 0.00 0.71 8 61.82 0.53 1.40 0.80 80.00 20.00 0.00 0.43

9 66.51 8.85 2.30 0.01 85.00 15.00 0.00 0.20

Note that β =1 for the seams and strata above the pit base and β<1 for the undrburdenstrata.

CSIRO. Saghafi, 2009Saghafi, 2007

Generic case

The spreadsheet to calculate the emission factor for the Generic Case

Emission Factor (CO2-e)

EF = Q/P = 15.50/17.08 = 0.91 m3/t

Q = 5.30+1.22x8.36 = 15.50 m3/m2

P = 17.08 t/m 2


Basic concepts of the new model: gas zones

• A mine lease could be imagined as an assembly of ‘g as zones’

• The gas content and reservoir properties of the coal seams and strata within each gas zone should be relatively constant.

• Gas emissions is quantified in terms of specific emissions from these gas zones.

How to delineate a gas zone?

A gas zone may be identified by similarity of the local geology and coal formation sequences in the area as well as similar coal layout and hydrology regimes.

The data from previous exploration drilling and piezometric studies should assist in delineating these zones.


ACARP 15076: Application of the new methodology, Case Studies

The new methodology was applied to 4 cases:

• Case 1: A relatively deep open cut mine (~200 m) with a moderate gas content (4 - 6 m3/t) and data obtained from borecores specifically drilled for this project.

• Case 2: A relatively deep open cut mine (~200 m) with a low gas content (<1 m3/t) and data obtained from borecores specifically drilled for this project.

• Case 3: A shallow open cut mine (~60 m) with a low gas content (< 1m3/t) and data obtained from previous exploration drilling as well as from one purpose-drilled borehole.

• Case 4: An open cut mine for which no direct gas content data are available.


Examples: Estimate of emissions for Case 1 and Case 2

Item Value Unit

Total coal production, Σp i 41.46 t/m2

Total CO2 emissions, (Σq i)CO2 82.68

Total CH4 emissions, (Σq i)CH4 65.21

CO2 Emissions factor, EF CO2 1.99

CH4 Emissions factor, EF CH4 1.57Total emission factor 3.57Total emission factor CO2-e 15.14

m3/t

m3/t

m3/m2

Item Value UnitTotal coal production, Σp i 31.31 t/m2

Total CO2 emissions, (Σq i)CO2 8.00

Total CH4 emissions, (Σq i)CH4 0.10

CO2 Emissions factor, EF CO2 0.26

CH4 Emissions factor, EF CH4 0.00Total emission factor 0.26Total emission factor CO2-e 0.26

m3/m2

m3/t

m3/t

Case 1

Case 2


Tier 3 method requirements

Model requires knowledge of the in-situ gas content of coal seams and carbonaceous rock in the overburden, and to some extent, into the underburden of the gas release zone. Also required is gas composition.

Because of large spatial variations in gas content at shallow depths the best way to obtain the gas content data required for the model is to drill and core surface boreholes for the purpose of measuring the in situ gas content.

Mine lease may be partitioned into a limited number of gas zones based on knowledge of coal strata layout and hydrology. Within the same gas zone gas content should be approximately constant.

For the case of mixed gas conditions the gas content should be determined by quick crush method, so to inhibit the dissolution of CO2in the measuring water and to reduce frequent gas composition measurements.

References

• Saghafi A, Williams D J (1992). Estimation of methane emission from Australian coal mines. Symposium on Coalbed Methane Research and Development in Australia, Townsville, Australia. Vol. 5, pp. 7-13.

• Williams, D. J., Saghafi, A., Lange, A. L. and Drummond, M. S., (1993). Methane emissions from open-cut mines and post-mining emissions from underground coal, Report to Department of Environment, Sports and Territories, CSIRO Investigation Report CET/IR173, 17 p.

• Williams D J and Saghafi A (1993). Methane emissions from coal mining - A prospective. The Coal Journal, number 41, pp. 37-40.

• Williams, D. J., Saghafi, A. and Lama, R., D., (1996). Methane emissions from coal mining, IEA Greenhouse Gas R&D Programme, Report Number PH2/5, June 1996, Paris, 180 p.

• Saghafi, A. and Williams, D., J. (1996). Methane emissions from underground coal mining in Australia: Current and future development, In the Proceeding of the 13th International Clean Air and Environment Conference, Published by The Clean Air Society of Australia and New Zealand Inc. Adelaide, Australia, pp. 345-350

• Creedy, D., P., Saghafi, A. and Lama, R., D. (1997). Gas Control in Underground Coal Mining, IEA Coal Research, IEA CR/91, London, UK, 120 p.

• Saghafi, A., Williams, D., J. and Lama R., D., (1997). Worldwide methane emissions from underground coal mining. In the Proceedings of the 6th International Mine Ventilation Congress, Pittsburgh, PA, USA, pp. 441-445

• Saghafi, A., Day, S., Williams, D., J., Roberts, D., B., Quintanar, A. and Carras, J. N. (2003), Toward the Development of an Improved Methodology for Estimating Fugitive Seam Gas Emissions from Open Cut Mining, ACARP Project C9063, 49p.

• Saghafi A., Day S. J., Fry R., Quintanar A., Roberts D., Williams D. J. and Carras J. N. (2004), Development of an improved methodology for Estimation of Fugitive Seam Gas Emissions from Open Cut Mining, ACARP Project C12072, 55 p.

• Saghafi, A., Roberts, D.B., Fry, R.F., Quintanar, A., Day, S.J., Lange, T., Hoarau, P. and Dokumcu, C. (2008). Evaluating a tier 3 method for estimating fugitive emissions from open cut coal mining, ET/IR 1011R, ACARP Project C15076, 120 p.

Contact UsPhone: 1300 363 400 or +61 3 9545 2176

Email: [email protected] Web: www.csiro.au

Thank you

Dr Abouna SaghafiCSIRO Energy TechnologyP.O. Box 330,Newcastle, NSW 2300

+61-2- 9490 [email protected]

BBGG Blackwater Tier3 Method OpenCuts(2)

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