be found in the coal itself or trapped in the strata surrounding the coal. For every ton of coal formed, as much as 5,000 cubic feet of ''coalbed methane" may be generated in situ (DOE, 1994b). Coalbed methane liberated into mine workings by underground coal mining can be a serious safety hazard, since methane is highly explosive in volume concentrations of 5 to 15 percent. Thus, underground mines in the United States are required to maintain methane concentrations below I percent of the concentration of the air in the mine (CFR, 1988).

Methane has attracted recent attention as a greenhouse gas that may contribute to global warming (see Chapter 3). The Clinton administration's Climate Change Action Plan (Clinton and Gore, 1993) identifies coal mines as one of the primary sources of methane emissions in the United States and requires the EPA (U.S. Environmental Protection Agency) and DOE to launch a coalbed methane outreach program to raise awareness of the potential for cost-effective emissions reductions with key coal companies and state agencies. In addition, the Climate Change Action Plan requires DOE to expand its research, development, and demonstration (RD&D) efforts to broaden the range of cost-effective technologies and practices for recovering methane associated with mining.

State of the Art

While all coal seams contain some methane, the highest levels of coalbed methane in the United States occur in seams in Virginia, West Virginia, Utah, and Colorado. To mine these gassy seams, mining companies have developed a number of techniques to eliminate or reduce the amount of methane liberated during mining. The primary technique is to design the mine ventilation system with enough capacity to keep the concentration at acceptable levels well below the lower explosive limit—generally less than 1 percent methane by volume. Other methods involve vertical drilling into the coal seam to vent methane before and after mining and drilling horizontally into the seam and venting the gas to the surface. There are instances where mining companies collect high-concentration methane and, after limited cleaning, sell the gas to a commercial pipeline. The economics of collection and sale to a user or distributor can either be based on a direct payback basis or justified by a reduction in mine ventilation costs.

Current Programs

Section 1306 of EPACT requires DOE to study barriers to coalbed methane recovery, to assess environmental and safety aspects of flaring coalbed methane liberated from coal mines, and to disseminate information on state-of-the-art coalbed methane recovery techniques to the public. DOE is further required to establish a coalbed methane recovery demonstration and commercial application program, with emphasis on gas enrichment technology. DOE requested $300,000 in the FY 1994 budget for coalbed methane activities, but that funding was not

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement