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Anaerobic Biodegradation of Biofuels (Ethanol and Biodiesel) and Proposed Biofuels (n-Propanol, iso-Propanol, n-Butanol)
Citation:
ADAIR, C. J. AND J. T. WILSON. Anaerobic Biodegradation of Biofuels (Ethanol and Biodiesel) and Proposed Biofuels (n-Propanol, iso-Propanol, n-Butanol). Presented at Battelle Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, May 20 - 26, 2010.
Impact/Purpose:
to observe the yield of methane from during anaerobic biodegradation of biofuels.
Description:
Biofuels, such as ethanol and biodiesel, are a growing component of the nation’s fuel supply. Ethanol is the primary biofuel in the US market, distributed as a blend with petroleum gasoline, in concentrations ranging from 10% ethanol (E10) to 85% ethanol (E85). Biodiesel, made from soybean oil or other vegetable oils or from waste cooking fats, is also available in the US market. Other compounds including n-propanol, iso-propanol, and n-butanol have been proposed as biofuels, but at present have not achieved an important share of the US market. U.S. EPA/ORD/NRMRL has constructed a microcosm study to follow the anaerobic biodegradation of these biofuels in aquifer sediment from two sites: an old methanogenic fuels spill site in North Carolina, and a spill of biodiesel in Minnesota. In some of the microcosms, sulfate was supplied at an initial concentration near 1,300 mg/L. The study followed the consumption of the biofuels, and concomitant consumption of sulfate and production of fatty acids and methane during anaerobic biodegradation of the biofuels. In sediment from the old fuel spill at Elizabeth City, NC, initial concentrations of ethanol, n-propanol, n-butanol, and iso-butanol ranging from 60 to 120 mg/l were consumed to the analytical detection limit within three months of incubation. If sulfate was not available, the methane produced was reasonable agreement with the methane expected, based on stoichiometric degradation of these alcohols to methane and carbon dioxide. If sulfate was available, the yield of methane from n-propanol, n-butanol, and iso-butanol was reduced at least ten fold. Sulfate had much less effect on the yield of methane from degradation of ethanol. The yield of methane from biodiesel was similar to the yield from the alcohols. Availability of sulfate had little effect on the yield of methane from the biodiesel. In sediment from the B-100 spill at St. Paul MN, initial concentrations of ethanol, n-propanol, n-butanol, and iso-butanol ranging from 60 to 150 mg/l were consumed to the analytical detection limit within only one month of incubation. The sediment used to construct the microcosms produced methane in the absence of any supplement with additional biodiesel or alcohols. It was not possible to attribute methane production in this sediment to degradation of the biofuels. Ethanol and biodiesel was degraded to produce acetate, n-propanol was degraded to produce propionate, and n-butanol was degraded to produce butyrate. The biofuels were degraded at rates that were effectively equivalent. In the absence of sulfate, all the alcohols and biodiesel degraded to produce methane. There seems to be little difference in the environmental impact of biodiesel and the alcohols.
URLs/Downloads:
Anaerobic Biodegradation of Biofuels (Ethanol and Biodiesel) and Proposed Biofules (n (PDF, NA pp, 268 KB, about PDF)The Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (PDF, NA pp, 1611 KB, about PDF)