Publication Date

2009

Document Type

Thesis

Committee Members

Abinash Agrawal (Advisor), Charles Bleckmann (Committee Member), Chad Hammerschmidt (Committee Member)

Degree Name

Master of Science (MS)

Abstract

There is a growing concern about the effects of global warming that many believe is anthropogenically caused. As such, scientists are trying to uncover a viable alternative fuel source and establish a way to reduce atmospheric carbon dioxide levels. A potential solution that addresses both of these aspects would be to capture atmospheric carbon dioxide and convert it into a natural gas, in particular methane, which could be used as an energy source. A laboratory-scale experiment using 6 160 mL microcosms (3 with anaerobic wetland soil and 3 relatively soil free) and 2 7.2 L bioreactors was conducted to learn more about the efficiency of the naturally occurring process called methanogenesis. The 6 microcosms and 2 reactors were analyzed regularly for methane, hydrogen and carbon dioxide in gaseous samples and pH in aqueous samples. The microcosms with soil were more productive and therefore produced more methane than the soil-free microcosms, presumably because the soil offered a higher surface area for the microbes to attach to and obtain micronutrient from. It was found that hydrogen utilization was in stoichiometric proportion to methane production indicating, hydrogenotrophic methanogenesis was the dominant process occurring in the microcosms. This study proved that hydrogen utilizing methanogens can be grown in a microcosm setting relatively easily and that the kinetics of methanogenesis is pseudo-first order. However, the hydrogen utilization was not in stoichiometric proportion to the methane production in the larger volume bioreactors. The hydrogen uptake in the reactors was greater than expected if hydrogenotrophic methanogenesis was the sole process occurring. This study indicates that some other microbial pathway is occurring in addition to hydrogenotrophic methanogenesis. As such, the trends observed in the microcosms differed from the trends that evolved in the bioreactors. Further research is needed in order to determine if carbon dioxide conversion to methane could be feasible on an industrial scale.

Page Count

158

Department or Program

Department of Earth and Environmental Sciences

Year Degree Awarded

2009

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