Select Committee on Environmental Audit Appendices to the Minutes of Evidence


Annex A

Environmental Benefits from CMM Emissions Capture

This briefing contains new information on coal mine methane emissions research by ACMMO

1.  FULL POTENTIAL OF CAPTURING CMM

  Since its formation in January 2001, ACMMO has continued to gather research data on methane emissions and now calculates that there are more than 1,000 closed deep coal mines in the UK from which an estimated minimum of 600,000 tonnes of CMM are seeping into the atmosphere every year. This is equivalent to 12.6 million tonnes of carbon dioxide.

  The increase to a minimum of 600,000 tonnes of CMM from the 300,000 tonnes in the original brief is a result of including emissions from unvented mines as well as those with vents. The estimates have been checked by International Mining Consultants who broadly agree with the base data input and the conclusions.

  One aspect of CMM emissions not explicitly allowed for in the original briefings is that the flow rate of CMM under pumping is greater than the natural flow rate by about 150 per cent as a result of requiring a controlled gas flow at a commercially viable rate. The natural flow rate is unreliable and varies with barometric pressure as does the wind, and therefore pumps are installed to produce a controlled methane flow rate and power output. This means that a potential 32 million tonnes of CO2 can be captured from disused mines as CMM emissions are accelerated by this process. All this gas would have come out eventually through natural venting, and ACMMO's estimates for emissions reductions stated below therefore relate to the captured gas not to the naturally emitted gas.

2.  THE EFFECT OF POSSIBLE INCENTIVES

  ACMMO estimates that 45 sites are, or may be, commercially viable without any incentives and these will produce 300 MW of generating capacity saving 7.9 million tonnes of CO2e including currently operating sites.

  The potential benefit derived from making CMM generated power exempt from CCL remains at an extra 35 sites becoming viable and generating 175 MW, but the resulting CO2 reduction falls from the 5.7 million tonnes estimated originally to 4.6 million tonnes on a basis consistent with ACMMO's revised baseline calculations and cross checks.

  If CMM were to receive an Alternative Energy Obligation (AEO) incentive equivalent to that offered under the RO in addition to CCL exemption, then the number of additional sites that would be viable would be 330. These would have a generating capacity of 743 MW and would prevent 19.5 million tonnes of CO2e from escaping to atmosphere.

  If CCL were removed and an AEO introduced, then the total number of extra sites that could be developed would be 365 generating 918 MW and saving 24.1 million tonnes of CO2e.

  If all the potential sites were to become operational, then as much as 1.2 GW of electricity would be generated from CMM, the equivalent of one nuclear power station. This is more than the 834 MW total of power produced under NFFO and its sister projects up to June 2000.

  With CO2 emissions apparently increasing, despite the Government's efforts, the potential removal of 32 million tonnes, including that from current sites, should be a welcomed contribution to the Government's CO2 reduction target before other renewable energy technologies are sufficiently developed to have a sizeable impact on the UK's energy production.

3.  FIGURES


Sites
MW
Average
MW per site
CO2e tonnes

Sites estimated to be viable1
45
298
6.6
7,836,208
Marginal sites2
65
333
5.1
8,756,568
Uneconomic sites3
300
585
2.0
15,383,160




410
1,216
3.0
31,975,936




Sites under CCL
35
175
5.0
4,601,800
Sites under RO or equivalent
330
743
2.3
19,537,928




Marginal + uneconomic sites
365
918
2.8
24,139,728





1 Estimated that currently economic
2 Post NETA not economic. Some would become economic with CCL exemption
3 Need RO or equivalent to become economic


Assumption:

  Each 1 MW of capacity mitigates 26,296 tonnes of CO2 equivalent, at 7,000 hours, 36 per cent efficiency (HHV).


 
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Prepared 22 July 2002