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.