Mining & Minerals
Coal mine methane (CMM) refers to methane released from the coal and surrounding rock strata due to mining activities. In underground mines, it is an explosion hazard to coal miners, so it is removed through ventilation systems. In some instances, it is necessary to supplement the ventilation with a degasification system consisting of a network of boreholes and gas pipelines. In abandoned mines and surface mines, methane escapes to the atmosphere through natural fissures or other means of diffusion.
What are the main CH4 emission sources in the coal mine industry?
CH4 from degasification systems
- Pre-mining (vertical wells): Produce medium-to high-quality gas that is often suitable for direct use in the natural gas pipeline system.
- In-mine (boreholes): Produce medium-quality gas ranging from about 30% to 90% methane.
- Post-mine (gob wells): Produce low- to medium-quality gas.
CH4 from ventilation air methane (VAM)
- Ventilation fans produce large volumes of gas with dilute concentrations of methane (only about 1%). VAM constitutes nearly half of all CMM and is critical to global reduction of CMM emissions.
CH4 from abandoned and closed mines
- Closed mines produce emissions of low- to medium-quality gas from vents, boreholes, or via diffusion.
How can CH4 emissions in coal mining activities be reduced?
The following activities would reduce the CH4 emissions in coal mining:
- Use of medium-quality gas as feedstock for on-site boilers, thermal dryers, or heaters.
- Use of medium-quality gas as feedstock for on-site electric power generation.
- Use of medium- to high-quality gas for natural gas pipeline sales.
- Process medium- to high-quality gas to meet natural gas pipeline specification.
- Process medium- to high-quality gas to liquefied natural gas (LNG).
- Process medium- to high-quality gas to compressed natural gas (CNG) for use as fuel for vehicles.
- Direct sales of medium- to high-quality gas to local industry.
- Destruction of VAM to generate thermal energy for use with electricity power generation.
- Coal Mine Methane Utilization