hard coal mine

Coal mine methane leaks worse than shipping & aviation

New findings in today's IEA World Energy Outlook show that coal mine methane leaks are worse for climate change than shipping and aviation combined.

Dave Jones

Global Programme Lead

13 November 2019 | 12 min read

What does the IEA research say?

The IEA estimates that 40MT of methane leaked from global operational coal mines in 2018. This compares to an estimate of 80MT emitted by the oil and gas sector. Methane is a potent greenhouse gas. According to the IEA analysis, 40MT of methane emitted by coal mines is equivalent to around 1,200 MT CO2-eq, broadly similar to the current level of total annual emissions from international aviation and shipping combined.

Accounting for the new estimates of methane emissions, on average, the production of coal results in just over 0.3 tonnes of CO2-eq indirect emissions for every tonne of coal equivalent (tce) produced. This compares to a global average of 2.9 tonnes of CO2 emitted when that coal is burnt. Therefore, average lifecycle emissions are 10% higher than the direct CO2 emissions from burning coal.

But the average hides a huge variation at the level of individual mines. For the worst 10% of mines, indirect emissions are 3 x higher than the average. For these mines, indirect emissions (including methane leaks) average 1 tonne of CO2 equivalent per tonne of coal equivalent. Lifecycle emissions could be up to 34%(!) higher than the direct CO2 emissions from burning the coal. Conversely, the best-performing 10% of mines have upstream emissions of “only” 3%.

Therefore, coal lifecycle emissions are 31% higher for coal sourced from the worst coal mines, than from the best-performing mines.

In fact, the methane leaks from the worst mines will cause almost as much warming as the direct CO2 emissions from burning coal, when measured over 20 years. The IEA calculates the CO2 equivalent impact of methane over a 100 years timescale, but they make explicit that the warming potency of methane increases from x30 to x85 vs. CO2 when measured over 20 years instead. So although upstream emissions from the worst coal mines add 34% to overall emissions over 100 years, this becomes 98% when measured over 20 years, relative to the CO2 from burning the coal directly.

Coal mines in Russia, Poland and China have the worst upstream emissions.

China’s enormous volume of coal mined and large share of deep mines (>100m) – means it is by far the largest source of upstream emissions in absolute terms of the coal producing nations.

Coal methane leakage has escaped scrutiny partly due to lack of data, so this research is very welcome. The IEA methodology uses reported coal mine methane data from the US EPA, and from research papers in China and India. The methane data is combined with other mine specific data at these sites to calibrate a formula which can estimate methane emissions intensities from mines for which there are no reliable direct estimates.

Key inputs are mine depth, coal quality, geological age of coal seam, and regulatory oversight of mine methane emissions. Overall the IEAs calcuations indicate that methane leakage accounts for 2/3rds of all indirect (upstream) emissions from coal mining. The IEA’s quantification only considers operational coal mines, and makes clear that including abandoned coal mines – which also still emit methane – would boost reported emissions even further.

The IEA shows the worst mines for methane leakage are the deep mines. Also important is the geological age of the seam (older seams contain more methane), and also the extent of methane capture and abatement at the mine.

Unlike oil and gas, there is no quick-win for reducing coal methane. The IEA says 45% of oil and gas methane emissions can be stopped at zero cost, because of the value of capturing the methane to burn or sell. However, the solution is much harder for coal. The IEA states that: “mitigating coal mine methane is problematic in that the methane concentration of emissions is often very low and can fluctuate in quality and quantity. The lower the concentration of methane, the more technically and economically difficult it is to abate”.  

And nothing is currently being done about it. The IEA forecast coal mine methane (CMM) emissions unchanged by 2040 in the Stated Policies Scenario saying “there are very few policies in place globally that aim to reduce the emissions intensity of coal production and so CMM emissions remain broadly constant to 2040”.

Having such high-profile global research from the IEA showing such a big impact should help shock policy-makers into addressing coal mine methane. Coal is even more polluting than we thought. Policy needs to begin accounting for upstream coal emissions, especially methane leakage, and must ensure that coal mining receives the same attention as shipping and aviation is currently receiving in efforts to reduce emissions.

Dave Jones Electricity Analyst, Ember

Should deep coal mines be phased out first?

  • The IEA analysis suggests that governments should assess the full lifecycle emissions of all mines (including methane emissions) and focus phase out efforts on the most climate-damaging mines. In many countries this may be the deepest mines, but this is not guaranteed.
  • The IEA makes clear that it is not easy to abate the emissions from deep mines, so it’s questionable to what extent policy could reduce emissions. Closure is the only viable option.
  • Deep coal mines are generally the least economic, because the high costs of developing them, as well as safety equipment needed to protect against the risk of methane explosions.

Governments, research organisations and companies should: 

  • Improve monitoring of mine-by-mine methane levels.
  • Agree appropriate standards to encourage abatement and shut the worst polluters.
  • Include upstream coal emissions in energy and climate plans, in power sector planning and all emissions reporting.
  • Make sure upstream coal emissions are included in national carbon pricing schemes.

Coal mining is a major problem for the climate.   

Policy action to cut these emissions – especially at deep mines – must follow



Read the Guardian article on this finding here