Proper management of abandoned mine methane is vital for reducing greenhouse gas emissions

Coal mining represents one of the main sources of anthropogenic (man-made) methane emissions. Whilst methane is a potent greenhouse gas (GHG) there is much that can be done to mitigate its effect on the climate, which will be essential if countries are to attain the ambitious targets of the 2030 Agenda for Sustainable Development and the Paris Agreement.

Mining operations release the methane formed during coalification and trapped under pressure in the coal seam as well as in the surrounding rock strata. The extraction of coal reduces pressure in the coal bed, creating a void and allowing surrounding strata to relax, freeing methane to escape into open fractures and ultimately into the atmosphere.

Approximately 8% of global anthropogenic methane emissions come from coal mines. Consequently, capturing and utilizing methane that in any case needs to be removed from underground for security purposes, offers a great potential for a significant reduction of the greenhouse gas footprint of the industry. 

After mine closure, methane emissions decrease, but do not stop completely. In most cases, the remaining coal still contains considerable amounts of gas that is slowly released. While the gas flow initially declines, it can later stabilize and maintain a near-constant rate for an extended period of time. If not prevented by an adequate sealing, the liberated gas will migrate to the surface and escape to the atmosphere. Under certain conditions, it may also be vented to avoid build-up and possible leaks through cracks and fractures in the overlying strata.

The UNECE Group of Experts on Coal Mine Methane (CMM) works on development and dissemination of best practices on effective drainage of methane in coal mines, as well as for economically viable and socially responsible use or destruction of the captured gas. Although traditionally orientated towards emissions generated from active mines, which are by far the largest source of methane emissions in the mining sector, the Group of Experts recognizes that the problem persists throughout the whole coal-mining life cycle, and stands ready to contribute its experience and expertise on managing methane from closed coal mines, also known as abandoned mine methane (AMM).

Current CMM estimates tend to overlook methane emissions generated from abandoned or closed mines, focusing predominantly on their active counterparts. Similarly, AMM emissions are not typically accounted for in national GHG inventories.

Nevertheless, in many UNECE countries AMM attracts the attention of both the government and the private sector. Consequently, the necessary regulatory framework is in place and AMM projects are being developed.

In terms of the number of operational AMM installations, Germany ranks first with 40 projects, followed by the United States and the United Kingdom, with 20 each, and the Czech Republic that hosts 10 sites. Germany is also the leader for avoided methane emissions at 400 million m³, followed by the US at 185 million m³.

In order to examine various aspects of AMM management from the technical, financial, environmental, legal, and policymaking angles, UNECE recently organized a workshop on Coal Mine Methane and Abandoned Mine Methane in the context of Sustainable Energy, gathering experts from around the world.

Mr. Michael Coté, the newly appointed Chair of the UNECE Task Force on Best practices in AMM, highlighted, “the need to include methane reserves in the value chain of the coal mining industry”. He underlined that “the value chain approach is important not only to identify methane reserves from the quantitative standpoint, but also to understand the energy value of the natural resource.”

The Chair of the Group of Experts on CMM, Mr. Raymond Pilcher observed “until coal mining companies and the countries that host these mines can fully account for methane resources that are co-located with coal deposits, we cannot fully appreciate either the value accrued from using this gas or the threat that it poses to the local and global environment if it escapes to the atmosphere unused.”