An on-site prototype two-stage anaerobic digester for co-digestion of food waste and sewage sludge for biogas production from high-rise building

•A prototype two-stage anaerobic digester for co-digestion of food waste and sewage sludge was newly designed and built.•Effects of hydraulic retention time and mixing ratio of food waste and sewage sludge on biogas production were investigated.•Anaerobic co-digestion can achieve the highest methane yield by mixing food waste with sewage sludge at the ratio of 7:1.•The methane content of biogas significantly decreased with a decrease in HRT in operating the two-stage co-digestion system.•At present, the biogas has been utilized for cooking as a model case study for high-rise building application.

Up to now, there has been less results from on-site pilot-scale anaerobic co-digestion system, especially for high-rise building application. The objective of this study was to develop an on-site prototype two-stage anaerobic digester for co-digestion of food waste and sewage sludge from high-rise building for biogas production. The optimal mixing ratio of food waste to sewage sludge, obtained from laboratory-scale, was found to be 7:1. Then, the prototype two-stage anaerobic digester was further designed and constructed. The results showed that COD and total volatile solid (TVS) reduction could be achieved up to 89 and 74%, respectively with the applied hydraulic retention time (HRT) of 24 days. The methane content of biogas was 64 percent. Up to now, the biogas from on-site production has been utilized for cooking at Chulalongkorn University as a model case study for high-rise building application.