Product and economic analysis of direct liquefaction of swine manure

Hydrothermal processing of biomass is a technology that has shown promising results in treating waste and producing oil. A batch hydrothermal processing system that was previously developed at the University of Illinois at Urbana-Champaign was used to treat swine manure and it successfully converted up to 70% of swine manure volatile solids into oil and reduced manure chemical oxygen demand by up to 75%. A continuous reactor was developed and it resulted in similar conversion rates to the batch process and it indicated the potential for the process to be scaled-up. These results were also documented previously. Following these results, a slurry pump was designed and built to enable longer test durations and lower repair costs, and it was used to conduct 24-hour continuous tests and produce quantities of oil suitable for more detailed analysis. The hydrothermal process utilizes manure containing around 25% solids content which is not available in typical swine confinement facilities so a preliminary investigation of dewatering methods was conducted to determine the best dewatering method in terms of the resultant oil yields and the effects on fertilizer values. The best dewatering method appears to be a coarse filtering process or the use of a low-cost additive. A coarse filtering process followed by the hydrothermal process results in an oil product as well as a fertilizer product that retains the majority of its nitrogen value with a reduced level of phosphorus as compared to the unprocessed swine manure. Energy and economic analyses of the dewatering and hydrothermal processes were conducted for swine manure as well as general analyses for other domestic biomass feedstocks. The feasibility of the conversion of swine manure was judged to be high, dependent mainly on the validity of the assumptions for the value of the oil product.