Multi-Step Sequential Batch Two-Phase Anaerobic Composting of Food Waste

Abstract

This study was conducted to evaluate the newly devised process, called MUlti-step Sequential batch Two-phase Anaerobic Composting (MUSTAC). The MUSTAC process consisted of several leaching beds for hydrolysis, acidification and posttreatment, and a UASB reactor for methane recovery. This process to treat food waste was developed with a high-rate anaerobic composting technique based on the rate-limiting step approach. Rumen microorganisms were inoculated to improve the low efficiency of acidogenic fermentation. Both two-phase anaerobic digestion and sequential batch operation were used to control environmental constraints in anaerobic degradation. The MUSTAC process demonstrated excellent performance as it resulted in a large reduction in volatile solids (VS) (84.7%) and high methane conversion efficiency (84.4%) at high organic loading rates (10.8 kg VS m−3 d−1) in a short SRT (10 days). Methane yield was 0.27 m3 kg−1 VS, while methane gas production rate was 2.27 m3 m−3 d−1. The output from the post-treatment could be used as a soil amendment, which was produced at the same acidogenic fermenter without troublesome moving. The main advantages of the MUSTAC process were simple operation and high efficiency. The MUSTAC process proved stable, reliable and effective in resource recovery as well as waste stabilization.