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Global CMM and AMM Emissions: Implications of Mining Depth and Future

Coal Production

April 16, 2018, Toronto, Canada

Nazar Kholod1, Meredydd Evans1, Raymond C. Pilcher2, Michael Coté3, Ron Collings3

1 Pacific Northwest National Laboratory; 2 Raven Ridge Resources; 3 Ruby Canyon Engineering

Global Methane Forum

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Introduction: CMM Emissions and Coal Production

▪ Coal mines get deeper every year and methane

emissions grow with increasing mining depth

▪ Data show flat or declining coal production, while

CMM emissions continue to grow

▪ No studies on future AMM estimates

▪ Purpose: estimate global CMM and AMM emissions

from hard underground and surface coal with

increasing mining depth through 2100

▪ This study was born out of discussions on emissions

and mine depth during GMI Coal Subcommittee

meeting

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CMM Methodology

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▪ Use coal production data from the Socioeconomic Pathways (2010-2100)

▪ Split hard coal by underground and surface

▪ Estimate the rate of change in mining depth

▪ Establish emission factors at given depths and for different coal ranks using

measured data

Gas content depend on coal rank and mining depth. Raven Ridge developed the formula using data from over 250 coal samples from North America, South America, Asia and Europe

Estimates of future coal production under various scenarios

0

5

10

15

20

25

30

0 100 200 300 400 500 600 700 800 900 1000

AnthraciteBituminousSubbituminous

Mining depth, meters

m3/t

0

100

200

300

400

500

2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

SSP2-Baseline

SSP2-6.0

SSP2-2.6

EJ/year

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Trends in Global Coal Mining

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▪ The study uses data from key coal producing countries in 1990-2010

▪ The share of underground mining is shrinking because surface mining is more

economical

▪ Depth of underground mines is increasing

▪ Share of brown coal is decreasing

▪ Trends are extended by 2100

0%

10%

20%

30%

40%

50%

60%

70%

80%

2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

Share of underground coal in hard coal,%

0

200

400

600

800

1000

1200

2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

Depth of underground mines, meters

SSP2-Baseline; Preliminary data

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Ratio of Emissions to Formula-Derived Gas Content

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▪ Based on coal production, emissions and mining depth data from the United

States, the ratio of emissions to gas content is estimated at 1.8

Specific emissions = gas content

0

2

4

6

8

10

12

14

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

Mine numbers

Rat

io o

f sp

ecif

ic e

mis

sio

ns

to g

as c

on

ten

t, t

imes

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Global CMM: Reference Scenario

6SSP2-Baseline (average); Ratio 1.8; No utilization. Preliminary data

▪ Share of CMM emissions from underground hard coal in total CMM emissions is 92% in 2010 and 78% in 2100

0

50

100

150

200

250

300

350

400

450

500

2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

Met

han

e em

issi

on

s, b

cm

Underground

Surface

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AMM Methodology

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▪ Calculate initial emissions from abandoned mines based on the CMM

methodology

▪ Calculate the global average coal abandonment rate

▪ Make assumption on the decline rates in emissions over time in dry and flooded

mines

▪ Calculate the emissions from the coal mines abandoned in the past (1971-2010)

▪ Calculate future AMM emissions from dry and flooded mines

Coal abandonment rate = Abandoned coal production (capacity) / Total coal production (capacity)

Global abandonment rate = 5% of coal production (capacity) per year 0

20

40

60

80

100

0 5 10 15 20

% o

f in

itia

l em

issi

on

s

Year from abandonment

Dry mines

Flooded mines

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Global AMM Emissions: Reference Scenario

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▪ AMM’s share in total methane from coal is 17% in 2010

▪ This share is projected to increase to 24% in 2050 and 27% in 2100

0

100

200

300

400

500

600

700

2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

CMM

AMM

CM

M a

nd

AM

M e

mis

sio

ns,

bcm

SSP2-Baseline (average); Ratio 1.7; No utilization. Preliminary data

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Importance of AMM: Baseline and Policy Scenarios

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▪ AMM increase faster than underground coal production and CMM

▪ Underground coal by 2.6 times, CMM by 3.5, AMM by 7.8 times

▪ AMM’s share in total emissions increases in policy scenarios

▪ 34% in SSP2-6.0 and 44% in SSP2-2.6 in 2100

CMM emissions follow the trajectory of coal production

AMM emissions continue to grow even if coal production and CMM decline

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Uncertainty

▪ Three most important factors for CMM calculations in 2050

Variable Low High

Future coal production (SSP2 from different models)

-25% +31%

Ratio of emissions to gas content -37% +26%

Future share of underground coal in hard coal production

-15% +16%

Research needs:

▪ Ratio of emissions to gas content

▪ Depth of underground and surface mines

▪ Ratio of dry and flooded mines

▪ Percentage of sealed mines

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Improving Inventories and Emission Factors

▪ Methodology and data used in this study could help

improve future inventories and emission factors

▪ CMM emissions factors by depth and coal rank are

more detailed than current emission factors and may

▪ AMM methodology can help in capturing more

complete emissions, mitigation opportunities

▪ Methodology can also be used to cross-check more

detailed, bottom-up estimates

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Conclusions

▪ Estimates are double those of previous studies

because of the additional detail on mining depth and

AMM

▪ AMM emissions will remain significant by the end of

the century regardless of future coal production

▪ Methodologies used in this study may help improve

future emission factors and inventories, for example,

with underground CMM and more comprehensive

AMM emissions