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Prospects for Anaerobic Biodegradation of Biofuels (Ethanol and Biodiesel) and Proposed Biofuels (n-Propanol, iso-Propanol, n-Butanol, and 2,5-Dimethylfuran) in Aquifer Sediments
Citation:
ADAIR, C. J. AND J. T. WILSON. Prospects for Anaerobic Biodegradation of Biofuels (Ethanol and Biodiesel) and Proposed Biofuels (n-Propanol, iso-Propanol, n-Butanol, and 2,5-Dimethylfuran) in Aquifer Sediments . Presented at The 10th International In Situ and On-Site Bioremediation Symposium, Baltimore, MD, May 05 - 08, 2009.
Impact/Purpose:
To understand the fate of ethanol, n-propanol, iso-propanol, n-butanol, and 2,5-dimethylfuran and other biofuels if they are released from underground storage tank systems.
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, n-butanol, and 2,5-dimethylfuran have been proposed as biofuels, but at present have not achieved an important share of the US market. With increasing use of biofuels, ethanol in particular, in the fuel supply nationwide, and increases in the number of stations that sell gasoline that contains more than 10% ethanol, U.S. EPA needs to understand the fate of these materials if they are released from underground storage tank systems. We constructed a microcosm study to follow the anaerobic biodegradation of these biofuels in aquifer sediment from an old methanogenic fuels spill site in North Carolina. The study followed the consumption of the biofuels, and concomitant production of methane during anaerobic biodegradation of the biofuels. The alcohols were amended at concentrations from 62 to 144 mg/L. Due to the limited solubility of 2, 5-dimethylfuran in water, the concentration of 2,5-dimethylfuran was only 1.7 mg/L. All these biofuels were effectively degraded (>90% removal) in 110 days of incubation. At ambient concentrations of sulfate (20 mg/l) there was at least 50% of the expected stoichiometric conversion of the biofuels to methane. When the sediment was amended with 1300 mg/l sulfate, the yield of methane from ethanol was not affected, but the yield of methane from the other alcohols was less than 5% of the expected yield. Production of methane in the microcosms amended with 2,5-Dimethylfuran was no greater than methane production in control microcosms without any biofuels. The removal of biodiesel was not monitored. However, 285 mg/L of soy based biodiesel produced 55 mg/L of methane at ambient concentrations, and 34 mg/L methane in the presence of 1300 mg/L sulfate. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.
