Coal Mine Methane
Coal mine methane (CMM) is a gas released from coal during and after coal mining operations. It is considered a mining hazard and a source of greenhouse gas emissions, with CMM accounting for 8 percent of total global methane emissions. To reduce emissions, CMM can be flared, used for onsite heating, or for electricity generation. Colorado has encouraged the development of electricity generated from CMM by adding it as an “eligible energy resource” for Colorado’s Renewable Energy Standard (RES).
As of 2015, one electricity producing CMM project has been developed in Colorado. Oxbow Mining LLC, Vessels Coal Gas, Gunnison Energy LLC, Aspen Skiing Company and Holy Cross Energy partnered to develop the Elk Creek Mine near Somerset in Gunnison County. This project co-locates a 3 MW power plant and a thermal oxidizer that destroys the remaining methane emissions.
A recent study prepared for the Colorado Energy Office (CEO) by Ruby Canyon Engineering, identified a total of 89 MW of electricity potential based on current federal emissions reporting of Coal Mine Methane (CMM) vented from active coal mines, ventilation air methane (VAM) from active coal mines and abandoned mine methane (AMM) emissions. Of that total, the analysis suggests 34 MW technically is feasible to develop with 80 percent of the potential originating in the Somerset mining area. Above is a map of aggregated mine groupings that CEO's study identified as having the best potential for electricity production. For more information on CMM in Colorado, see the following resources.
Decomposition of municipal solid waste at landfills produces gases as a byproduct. Landfill gas (LFG) is comprised of roughly half methane and half carbon dioxide. According to the EPA, LFG accounts for 17.7 percent of all U.S. methane emissions. To reduce emissions, LFG can be flared, used for onsite heating, further refined into a transportation fuel, or used to generate electricity.
LFG is recovered from a series of interconnected wells drilled into a landfill. It must then be transported, compressed, and filtered before it can be combusted to generate electricity. On average, 1 million tons of MSW provides about 432,000 cubic feet of LFG per day and 0.78 MW of electricity.
There are two operational LFG electricity plants in Colorado -- the Town of Erie’s Landfill Gas-to-Energy Project and the City of Denver’s Denver Arapahoe Disposal Site (DADS). As of 2015, one electricity producing CMM project has been developed in Colorado. The EPA’s Landfill Methane Outreach Program (LMOP) has identified 12 other landfills in Colorado as potential candidates for energy projects based on their size and volume of gas and operational status.
The development of successful landfill gas-to-energy projects depends on the consistent delivery of methane. As organic decompotition takes place, a variety of factors can influence the amount of methane produced at a landfill. The U.S. Environmental Protection Agency's Landfill Methane Outreach Program has identified candidate landfills in Colorado, but the economic and technical feasibility of those projects remain contingent on factors such as the size of the landfills, whether there are gas collection systems in place, and the aridity of the climate.