Print this pageInjection of Biogenic Landfill Gas into Coal Seams for Enhanced Coalbed Natural Gas Recovery and Carbon Sequestration
Timothy R. Carr1, K. David Newell1, James G. Blencoe2, and Saibal Bhattacharya1
1 Kansas Geological Survey, University of Kansas, Lawrence, KS
2 Oak Ridge National Laboratory, Oak Ridge, TN
Landfills are the largest source of anthropogenic methane (CH4) emissions in the USA, annually totaling 8.14 Mt (0.38 trillion cubic feet). Landfill gas (LFG) is a low-BTU gas composed of approximately 50% methane CH4, 40% carbon dioxide (CO2), and 10% miscellaneous gases, including non-methane volatile organic compounds (NMVOCs). Most CH4 and CO2 generated in solid-waste landfills is flared and vented -- a practice that ignores environmental impacts and potential economic value.
A possibly profitable economic option involves injecting LFG, or a CO2 enriched residual LFG gas into subsurface coal seams. Because CO2 and NMVOCs are preferentially adsorbed on coal surfaces, the CH4 concentration of LFG could be increased as it flows through a coal seam from an injection well toward a nearby production well. In addition, adsorbed CH4 present in the coal prior to LFG injection could be released as sorption proceeds, allowing additional amounts of CH4 to be produced. In this way, both profitable CH4 production and cost-effective CO2 sequestration are realized.
This concept is being tested through field, laboratory, and simulation studies by injecting LFG derived from a large landfill in the Kansas City metropolitan area into underlying Middle Pennsylvanian coals. Sorption/desorption experiments provide data to model gas behavior during and after LFG injection into an underground coal seam. Gas flow-through experiments will help understand permeability changes due to swelling as LFG is adsorbed onto the coal and CH4 is desorbed from it. Widespread distribution of organic shale and coalbeds provide potential targets for such value-added sequestration.