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Livestock Waste-to-Energy Concepts

Cantrell, K.B., Ro, K.S., Hunt, P.G.
animal manure management, livestock, gasification, energy conversion, poultry manure, feedlots, pig manure, dairy manure, methane, waste treatment, sulfur, animal pathogens, wastewater treatment
Currently there is interest in energy-value-added products from agriculture wastes, namely animal manures using thermochemical conversion (TCC) processes. Our objective was to review the application of gasification technology with regards to the treatment and energy conversion of both dry and wet animal manures. From the conceptual designs that incorporate under-developed gasification technologies presented, dry wastes like poultry litter and feedlot manures can be processed directly via dry or steam gasification technology; the swine and diary manure aqueous waste streams can undergo wet gasification processing. All these manures are converted into an energy dense mixture of char, bio-oil, and methane-rich gas. Even still, integration of gasification is possible with current waste treatment systems utilizing solid-liquid separation processes and anaerobic digestion. The major roadblocks for implementing these processes are: developing adequate heat recovery systems; perfecting continuous operation of modular units; and establishing efficient pretreatments to remove sulfur and other harmful minerals. Despite these processing issues, all of the gasification systems discussed provide an environmentally friendly method of manure disposal by destroying pathogens, eliminating nuisance compounds, and minimizing residual material. In addition to these environmental benefits and energy products, wet feedstock gasification techniques provide a means to treat and clean the waste water, thus, creating a clean water recycle.