Water free anaerobic co-digestion of vegetable processing waste with cattle slurry for methane production at high total solid content

The increase of vegetable planting area lead to the large amounts of VPW (vegetable processing wastes). Effects of V% (VPW proportion) and I% (inoculum proportion) on water free anaerobic co-digestion of VPW with CS (cattle slurry) for methane production was investigated. The results showed that the total methane production was increased from 141.2 L/kg VS (volatile solids) to 186.8 L/kg VS with V% increasing from 17% to 35%. When V%, I% and TS% (total solids content) were 35%, 40% and 7.9%, respectively, the maximal methane production of 186.8 L/kg VS was obtained. However, the optimal conditions were 35% of V% and 30% of I%, the methane production was 170.8 L/kg VS, the maximal methane production was only 9.4% higher than that of the optimal conditions, the TS% of the optimal condition was 8.6% and higher than that of the maximal methane production, the reductions of TS% and VS% for this condition were 29.5% and 49.2%, respectively, and the T80 for this condition was 42.9% shorter than that of the maximal methane production. The results indicate VPW can be co-digested with CS without water addition.