Methane Generation and Capture of U.S. Landfills

Prof. Nickolas J. Themelis and Prof. A.C. (Thanos) Bourtsalas

Earth Engineering Center, Columbia University, 500 West 120th St., NY, NY 10027, USA

Analysis of the U.S. EPA (Environmental Protection Agency) database of 2,549 MSW (Municipal Solid Waste) landfills showed that there were 1,164 operating landfills in which 348 million short tons (316 million metric tons) of waste were landfilled in 2017. In total, these landfills occupy about 370 million square meters of land so it is not possible to monitor the generation of LFG (Landfill Gas) generation accurately, or collect most of the LFG generated. This study was based on the hypothesis that, on the average, methane generation is proportional to the tonnage of wastes landfilled annually. The Landfill Methane Outreach Program of the EPA (EPA-LMOP) compiles annual operating data of all methane-capturing landfills. Our analysis of the 2018 data for 396 LMOP operating landfills showed that 210 million short tons of wastes were deposited and 5.06 million short tons of methane were captured, i.e., an average capture of 0.024-ton CH4/ton waste. On the basis of the anaerobic reaction of the DOC (Degradable Organic Carbon) in landfilled wastes, the average rate of methane generation from all operating U.S. landfills was estimated to be 0.05 ton of CH4 per ton of annual capacity; this number corresponds to bioreaction of about one half of the total organic carbon in MSW. On this basis, the average rate of CH4 emission from the 396 LMOP landfills was estimated to be 0.026-ton CH4 per annual ton of deposition and the average efficiency of LFG capture, 48%. Adding up all 1,164 operating landfills, their total emission of methane was estimated at 11.9 million metric tons of CH4. At CH4/CO2 equivalence of 25, this number corresponds to CO2-eq emissions of 270 million metric tons, i.e., 5.1% of the U.S. energy related carbon dioxide emissions.

download article