Anaerobic co-digestion of energy crop and agricultural wastes to prepare uniform-format cellulosic feedstock for biorefining

Abstract This study investigated the effects of mixtures of agricultural wastes and energy crop on solid digestate quality and biogas production. The feedstock mixtures of dairy manure and switchgrass (DM:SG) had the similar lag phase with the control feedstock of dairy manure, while was shorter than the feedstock mixtures of dairy manure and corn stover (DM:CS). Under the stable digestion conditions, the mixture of DM:SG at the mixture ratio of 80:20 had the highest methane production of 138 mL/g total solids (TS) loading; the mixtures of DM:SG and DM:CS at the mixture ratio of 60:40 had the highest VS reduction of 25.8%; and the mixture of DM:SG at the mixture ratio of 60:40 had the highest cellulose and xylan reduction of 40.4 and 40.7%, respectively. Two bacterial phyla (Firmicultes and Bacteroidetes) and three archaeal genera (Methanosarcina, Methanobrevibacter, and Methanobacterium) were the abundant microbial communities in all tested digestions. The statistical analysis concludes that anaerobic digestion can homogenize the feedstocks to generate solid digestates with uniform-format carbohydrate composition and similar mono-sugar conversion. The mean cellulose and xylan contents of the solid digestates were 26.6% and 15.2%, respectively. The corresponding mean glucose and xylose conversions of the solid digestates were 82.3% and 98.7%.