Methane from Coal
The natural gas methane is a byproduct of coalification -- the process where plant materials were gradually buried, compressed, and heated, resulting in the various ranks of coal.
In Pennsylvania, natural gas is extracted from coal as coalbed methane and as coal mine methane. Coalbed methane comes from virgin (unmined) coal. It rivals conventional natural gas in methane content and heating value with minimal processing.
Coal mine methane is released from rocks associated with active or abandoned coal mines and is more variable in quality. Capture of this type of methane from coal grew out of the necessity to vent the gas from underground coal mines for safety purposes.
Large volumes of methane also may be emitted from vents, fissures, or boreholes associated with abandoned mines.
Methane Gas in Pennsylvania
Today, coal is recognized as a significant source of gas at both domestic and international levels. During 2004, the Pennsylvania General Assembly listed coal mine methane as an alternative energy resource in the Pennsylvania Alternative Energy Portfolio Standards Act.
Some of the major end uses for methane from coal are:
Supplement to natural gas pipelines
Gas turbine or microturbine fuel for electric power generation or cogeneration
Local or on-site industrial use
Vehicle fuel as liquefied or compressed natural gas
Industry uses methane from coal in southwestern Pennsylvania as a commercial energy source. The producing units typically are from 300 to 1800 feet below the surface, and they may include coal beds that are too thin or deep to be economically mined.
Beneficial side effects of using this energy source include improved mine safety and a substantial reduction in methane emissions to the atmosphere.
Interest in developing this unconventional natural gas resource exists in Pennsylvania because of:
Established or negotiated ownership of acreage
Better understanding of coal as a natural gas reservoir
The need to develop domestic energy sources while practicing environmental stewardship for future generations