Methane production from the co-digestion of pig manure and corn stover with the addition of cucumber residue: Role of the total solids content and feedstock-to-inoculum ratio.

This study investigated performance and stability of increasing total solids (TS) content (10-30%) and feedstock-to-inoculum (F/I) ratios (1, 2) on anaerobic co-digestion of agricultural wastes. The cumulative methane yields generally decreased with the increasing TS content except for the TS content of 30% at F/I ratio of 1 and TS content of 10% at F/I ratio of 2. This was consistent with the maximum methane production rate (Rmax) and rate of the hydrolysis (Kh) stage in reactors. The pH, VFAs and NH4+-N content were positively correlated with increasing TS contents and F/I ratios. Economic analysis results indicated the net present value generally increased with increasing TS contents and TS content of 30% at F/I ratio of 1 had the highest net present value (5.7 million US$) and internal rate of return (41.9%). This indicated solid-state anaerobic digestion was financially attractive under analyzed conditions.