Submitted to: Industrial and Engineering Chemistry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2007
Publication Date: 12/1/2007
Citation: Cantrell, K.B., Ro, K.S., Mahajan, D., Anjom, M., Hunt, P.G. 2007. Role of thermochemical conversion in livestock waste-to-energy treatments: Obstacles and opportunities. Industrial and Engineering Chemistry Research 46(26):8918-8927. Interpretive Summary: Animal waste can be converted into alternative energy products such as gases and liquid fuels. We reviewed the technologies that can process both dry and wet animal wastes and turn them into gas or liquid fuels for either direct combustion or additional processing into alcohols. From this review, we present conceptual designs for combining the technologies with current animal waste treatment practices that use waste straight from the house, a liquid-solid separator, or anaerobic treatment system. Even though the energy required to run these systems is much greater than anaerobic digestion, there are numerous environmental benefits: these systems are smaller, faster, can destroy pathogens, and provide a more sanitary means of disposal.
Technical Abstract: Integrating thermochemical conversion (TCC) technologies with current animal waste treatment practices can treat and reduce quantities of manure from consolidated animal feeding operations. Additionally, TCC technologies can produce value-added, renewable energy products. These products can meet heating and power needs or be catalytically converted into liquid fuels. The primary objectives of this study were to assess opportunities and obstacles in the treatment and energy conversion using currently available TCC proceses. Both dry and wet livestock manures were assessed. Dry wastes like poultry litter and feedlot manures can be processed directly via pyrolysis and air/steam gasification technology. The solids in the aqueous waste streams from dairy and swine operations can undergo wet gasification or direct liquefaction processes. Alternatively, these solids can be separated and dried before conversion. Due to high ash and sulfur contents, pretreatment of manure is necessary to prevent catalyst poisoning and promote effective unit-operation. While the energy input requirements for a conceptual wet gasification manure treatment system of a model swine farm is larger than a traditional anaerobic digestion operation, there are many significant advantages in implementing TCC technology including: compact design; faster treatment times; reduction of odors, BOD, and pharmaceutically activated compounds; and elimination of sludge.