ASABE Technical Library - Abstract

Abstract. Arkansas produces about 1.3 million metric tons of poultry litter annually, ranking the second in the States. The conventional treatment for this waste is land application, which has created a series of environmental issues, such as surface and underground water contaminations, and pathogen growth in soil and water. Poultry litter is a kind of good feedstock for biogas (mainly containing methane) production using anaerobic digestion. In this study, methane production in batch anaerobic co-digestion of poultry litter and wheat straw was investigated for two factors (total solid percentage, and wheat straw percentage in a mixture of poultry litter and wheat straw) at three levels (2%, 5%, and 10% total solid, and 0, 25, and 50% of wheat straw). The results showed that co-digestion of poultry litter and wheat straw enhanced methane volume, and decreased the inhibition of free ammonia compared to the digestion with the sole poultry litter. The maximum specific methane and gas volumes (197 and 314 mL (g initial VS)^-1, respectively) were achieved at 50% of VS wheat straw of 5% of TS. It was estimated that the inhibitory threshold of free ammonia concentration was about 289 mg L^‑1. After this concentration, a great reduction of methanogens activity occurred (at least 54%). A novel general Gompertz model could be used to describe the sharp change of free ammonia threshold.