Biogas production from thermophilic codigestion of air-dried rice straw and animal manure

In order to evaluate the effects of organic loading rate (OLR) on thermophilic codigestion of air-dried rice straw (RS) with pig manure (PM), cow manure (CM), and chicken manure (CHM), continuous bench experiments (40 L) were carried out at OLRs of 3.0, 3.6, 4.2, 4.8, 6.0, 8.0, and 12.0 kg VS/(m(3). d). Stable biogas production without inhibition by volatile fatty acids (VFA) or ammonia and foaming was achieved at OLRs of 3-12, 3-6, and 3-4.8 for the codigestions of RS + PM, RS + CM, and RS + CHM, respectively. Maximum average volumetric biogas production rates of 4.98, 2.64, and 2.03m(3)/(m(3) . d) were obtained at OLRs of 12, 6, and 4.8 kg VS/(m(3) . d) for the codigestions of RS + PM, RS + CM, and RS + CHM. Foaming was occurred at OLRs of 8 kg VS/(m(3) . day) for the codigestions of RS + CM. The codigestion of RS + CHM was inhibited by the accumulation of ammonia instead of VFA when the OLR was >= 6 kg VS/(m(3) . d). This study provided references for the engineering application of codigestion of RS and animal manure. Copyright (C) 2016 John Wiley & Sons, Ltd.