Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 42, Issue 17, Pages 6723-6729Publisher
AMER CHEMICAL SOC
DOI: 10.1021/es800671a
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Funding
- Illinois Department of Commerce and Economic Opportunity [02-20701]
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U.S. production of fuel ethanol from corn grain has increased considerably over the last 10 years. Intense debate regarding the true environmental impact of the overall production process has been ongoing. The present study evaluated the utilization of thin stillage (a major byproduct of the dry-mill corn grain-to-ethanol process) in laboratory-scale thermophilic anaerobic sequencing batch reactors for conversion to methane. We found that augmentation of cobalt as a growth factor to the thermophilic anaerobic digestion process is required. After reaching sustainable operating performances, the methane potential in the reactors was 0.254 L CH4/g total chemical oxygen demand (TCOD) fed. Together with a reduction in the mass of solids that needs drying, methane generation translates to a 51% reduction of natural gas consumption at a conventional dry mill, which improves the net energy balance ratio from 1.26 to 1.70. At the design hydraulic retention time of 10 days, the digesters achieved TCOD, biodegradable COD, volatile solids, and total solids removal efficiencies of 90%, 75%, 89%, and 81%, respectively. We also found that struvite precipitation occurred in the thermophilic digesters during the course of the study, resulting in possibilities for nutrient recovery.
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