Enhanced methane production by semi-continuous mesophilic co-digestion of potato waste and cabbage waste: Performance and microbial characteristics analysis

Anaerobic granular sludge was used as an inoculum for co-digestion of potato waste (PW) and cabbage waste (CW) in batch and semi-continuous modes at 37 ± 1 °C for enhanced methane generation. Batch test results indicated that an equal proportion (1:1) by volatile solid was the optimal mixing ratio for co-digestion of PW and CW. Semi-continuous co-digestion process results showed that the stepwise increasing of the organic loading rates from 1.0 to 5.0 kg VS/m3·d improved the methane yield from 224 to 360 mL/g-VS. And the highest value was respectively 18.4% and 24.1% higher as compared to the mon-digestion of PW and CW. Further investigation with high-throughput sequencing analysis revealed that the enhanced methane generation was attributed to the partial shift from archaeal Methanosaeta to Methanosarcina and Methanobacterium, and from bacterial Firmicutes to Bacteroidetes and Proteobacteria. The volatile fatty acids concentration accounted for the modification of microbial communities.