How is methane emitted from coal mines?
There are three primary sources of CMM: • Degasification systems at active underground mines. Also commonly referred to as drainage systems, these systems employ vertical and/or horizontal wells to recover methane before mining takes place to help the ventilation system keep the in-mine methane concentrations sufficiently low (well below the explosive limit) to protect miners. • Ventilation air methane (VAM). This refers to the very dilute methane that is released from underground mine ventilation shafts. Although it is typically less than 1 percent methane, it is the single largest source of CMM emissions globally. • Abandoned mine methane. Closed mines produce emissions of low- to medium-quality gas from diffuse vents, ventilation pipes, boreholes, or fissures in the ground. Other, more minor sources of methane from coal mines include surface mines and post-mining activities (coal continues to emit methane as it is stored in piles and transported).
