Towery, K. 2012. Increasing methane consumption in agricultural soils by use of bacterial inocula. M.S. Thesis, Michigan State University, East Lansing, MI USA.

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Methane (CH4 ) is 25 times more effective than carbon dioxide at trapping infrared radiation over a 100 year period and is the second most significant source of radiative forcing in Earth’s atmosphere. The largest biological sink is through oxidation by aerobic soil microbes, termed methanotrophs, which can be impacted by land management such that both methanotroph diversity and CH 4 consumption decrease by 70% when forests are converted to row-crop agriculture. In this study, the potential of a methanotrophic soil inoculum to enhance methane consumption was investigated in both microcosm and pilot-scale field experiments.

Mixed methanotrophic enrichment cultures were obtained from native forest soil and consist primarily of Methylocystis and Methylosinus species. Application of mixed methanotrophic enrichments significantly increased rates of methane consumption in agricultural soil microcosms. In preliminary field trials, methanotroph-inoculated sites demonstrated a 4-fold increase in total methane consumed over a 7 day period, as compared to uninoculated sites. Subsequent studies will focus on optimization of cultivation and soil inoculation methods, with the aim of increasing the magnitude and duration of in situ methane flux. These experiments serve as a starting point for a bioengineering solution to the effects of agriculture on climate change and the global methane budget.

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