Three-stage anaerobic digester for food waste

A novel compact three-stage anaerobic digester (TSAD) was developed for high-efficiency anaerobic digestion of food waste and methane production. Through structure optimization by having three separate chambers in a single-stage anaerobic digester, hydrolysis, acidogenesis and methanogenesis were independently optimized with concomitant improvement in anaerobic digestion performance. Compared to traditional one-stage and two-stage anaerobic digesters, TSAD had a 24–54% higher methane yield at a high organic loading rate of 10g VSFW/L. A higher volatile solid reduction rate of 83.5±1.3% was also achieved in TSAD. Even at high organic loading, TSAD still presented a high buffering ability when the one-stage and two-stage digesters had already soured and failed. Pyrosequencing analysis indicated that the bacterial community in TSAD is more diverse than the control digesters. Multi-function methanogens Methanosarcina and some dominant populations with the function of acetogenesis, amino-acid-utilization and symbiosis were found to selectively enrich in TSAD.