Sources of Coal Mine Methane
Coal mine methane (CMM) refers to methane released from the coal and surrounding rock strata due to mining activities. In underground mines, CMM can create an explosion hazard for miners so it is removed by ventilation systems. In some instances it is necessary to supplement the ventilation system with a degasification system consisting of a network of boreholes and gas pipelines. In abandoned and surface mines, methane can also escape to the atmosphere through natural fissures or other diffuse sources.
CMM is emitted from primary five sources:
- Degasification systems at underground coal mines (also commonly referred to as drainage systems). These systems may employ vertical and/or horizontal wells to recover methane in advance of mining activities (known as "pre-mine drainage") or after mining activities (in "gob" or "goaf" wells).
- Ventilation air from underground mines, which contains dilute concentrations of methane.
- Abandoned or closed mines from which methane may seep out through vent holes or through fissures or cracks in the ground.
- Surface mines from which methane in coal seams is directly exposed and released to the atmosphere.
- Fugitive emissions from post-mining operations, in which coal continues to emit methane as it is stored in piles and transported.
EPA's Greenhouse Gas Reporting Program (GHGRP) collects information from all underground coal mines that liberate 36,500,000 actual cubic feet of methane or more per year. Surface mines and abandoned mines do not report to the GHGRP. In 2021, GHGRP reporters reported 29,135,039 metric tons of carbon dioxide equivalent (CO2e). See GHGRP trends from the underground coal mines sector.
CMOP provides information and resources for reducing methane emission from various sources types. You can access this information here: