Novel anaerobic process for the recovery of methane and compost from food waste.

Multi-step sequential batch two-phase anaerobic composting (MUSTAC) process was used to recover methane and composted material from food waste. The MUSTAC process consists of five leaching beds for hydrolysis, acidification and post-treatment, and an upflow anaerobic sludge blanket (UASB) reactor for methane recovery. This process involves the combined methods of sequential batch operation and two-phase anaerobic digestion for simple operation and high efficiency. Rumen microorganisms are inoculated due to their enhanced cellulolytic activity. Each leaching bed is operated in a sequential batch mode. Five leaching beds are operated in a multi-step mode with a two-day interval between degradation stages. Acidified products in the leachate from the leaching beds are converted to methane in the UASB reactor. The MUSTAC process demonstrated that it was capable of removing 84.9% of volatile solids (VS) and converting 85.6% of biochemical methane potential (BMP) into methane at 10.9 kg VS/m3 x d in 10 days. Methane gas production rate was 2.31 m3/m3 x d. The output from the post-treatment of residues in the same leaching bed without troublesome moving met the Korean regulation on compost, indicating that it could be used for soil amendment.