Comparison of methane production performance of vinegar residue under liquid- and solid-state conditions

Vinegar residue (VR), a major by-product in the vinegar brewing process, is generated at least three million tons annually in China. Currently major part of the disposal of VR is fulfilled by landfill and incineration, however, serious environment pollution along with such processes is a challenging issue. Anaerobic digestion (AD) can provide benefits of environment and renewable methane generation, which seems to be a reasonable alternative to traditional treatment. Noticeably, total solids (TS) is an important influential parameter to AD performance. Therefore, VR was evaluated for methane production and associated kinetic characteristics during the liquid-state AD (LS-AD) and solid-state AD (SS-AD) in this study. The results indicated that the highest specific methane yield of 194.8 mL gVS(-1) and volumetric methane yield of 9.4 L-methane L-reactor volume(-1) were achieved in LS-AD (TS = 10%) and SS-AD (TS = 20%), respectively. The kinetic analysis showed a higher specific methane production rate for LS-AD than SS-AD, while volumetric methane production rate presented a reverse trend. This study provides useful guidance for the sustainable utilization of VR while contributes to environmental protection and alleviates the dependence on fossil fuels.