ARS | Publication request: Catalytic wet gasification of municipal and animal wastes

Submitted to: Industrial and Engineering Chemistry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2006
Publication Date: December 1, 2007
Citation: Ro, K.S., Cantrell, K.B., Elliott, D., Hunt, P.G. 2007. Catalytic wet gasification of municipal and animal wastes. Industrial and Engineering Chemistry Research. 46:8839-8845.

Interpretive Summary: Wet gasification is a new technology developed by the U.S. Department of Energy Pacific Northwest National Laboratory. This technology could directly process liquid form of wet biomass slurry to produce energy-rich gases and relatively clean water. We investigated the applicability of this new technology to treat and harness energy from animal and municipal wastes based on theoretical considerations and limited experiments with dairy manure wet gasification. Some of wet wastes such as swine manure and sewage sludge could be fed directly into a wet-gasifier. This process would produce more energy than combusting the same amount of brown coal. However, other wastes such as unpaved feedlot manure and municipal solid wastes would not generate positive energy returns from wet gasification because of their high ash contents. All of the wastes must be pretreated to remove sulfur to prevent poisoning catalysts. The costs of a conceptual first generation wet gasification manure management system for a model swine farm were significantly higher than that of traditional anaerobic lagoon systems. However, there are many significant environmental advantages of the wet gasification: 1) removing oxygen demanding wastes, estrogens, odorous compounds; 2) achieving total pathogen kills; 3) recovering most of nitrogen as ammonia which could be used as a fertilizer; and 4) producing relatively clean water which, after minimal treatment, could be used as a livestock drinking water.

Technical Abstract: Currently, there is worldwide interest in deriving energy from bio-based materials via gasification. Our objective was to assess the feasibility of wet gasification for treatment/energy conversion of both animal and municipal wastes. Wet wastes such as swine manure and raw sewage sludge could be processed directly via current wet gasification technology. Furthermore, these wastes generated high amounts of net energy based on reaction and energy balances. Municipal solid wastes and unpaved feedlot manure would not generate positive energy returns from wet gasification. Due to high sulfur content of the wastes, pretreatment to prevent the poisoning of catalysts is essential. The costs of a conceptual first generation wet gasification manure management system for a model swine farm were significantly higher than that of the anaerobic lagoon system. However, there are many significant environmental advantages of the wet gasification; e.g., BOD removal, odor elimination, and pathogen kill.