Way More Methane than EPA Thinks, Maybe

by Emil Morhardt

The amount of the powerful greenhouse gas, methane (natural gas) released into the atmosphere by farmers and gas and oil companies is substantially underestimated by the USEPA according to a team led by Scott Miller, a Harvard Ph.D. student, published late last year in the Proceedings of the National Academy of Sciences. The previously unaccounted sources are ruminants, manure, and fossil fuel extraction and processing in the South-Central US, traced back to their sources from fixed towers and aircraft-based methane sensors using the Stochastic Time-Inverted Lagrangian Transport model (STILT). On the other hand, Hristov et al.(2014), in response to the Miller et al. paper, calculated cattle methane releases from the ground up  based on the number of cattle in the US and thought that the EPA had it right in the first place. So we have a calculation based on numbers of cattle competing with empirical data from the methane sensors processed through an interesting atmospheric model. This type of atmospheric modeling–tracing airborne chemicals back to their source–is what NASA is about to use with the data from its newly launched (July 2, 2014) Orbiting Carbon Observatory, OCO-2, except that the observatory will detect CO2 rather than methane. No public data from it are available as yet, but since methane oxidizes to CO2 in the atmosphere, it is possible that the satellite will soon confirm the sources of the methane. You can find out about the OCO-2 instrument here. http://1.usa.gov/1qT3KDI

Miller, S.M., Wofsy, S.C., Michalak, A.M., Kort, E.A., Andrews, A.E., Biraud, S.C., Dlugokencky, E.J., Eluszkiewicz, J., Fischer, M.L., Janssens-Maenhout, G., 2013. Anthropogenic emissions of methane in the United States. Proceedings of the National Academy of Sciences 110, 20018-20022. http://bit.ly/1sjEC7m

Hristov, A.N., Johnson, K.A., Kebreab, E., 2014. Livestock methane emissions in the United States. Proceedings of the National Academy of Sciences 111, E1320-E1320.   http://bit.ly/1kwu9Ve

Please let me know if you are aware of new papers that should be written about by the Climate Vulture emorhardt@cmc.edu


One thought on “Way More Methane than EPA Thinks, Maybe

  1. From Alex Hristov via email: I can’t speak for my co-authors, but I’m not aware of the OCO-2 satellite process and can’t really comment on it. What I can state is that estimates based on our ‘bottom-up’ approach should be pretty accurate. We have a good idea of feed intake for the various categories of cattle and CH4 emissions per unit of feed plus USDA’s cattle inventories should also be accurate.


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