Two-phase anaerobic digestion of spent tea leaves for biogas and manure generation

Anaerobic digestion of spent tea leaves from an instant tea manufacturing f actory was studied in a two-phase digester. The hydrolysis and acidificatio n phase resulted in the formation of high organic strength liquid called le achate, with a chemical oxygen demand (COD) of 12,880 mg/l, within the rete ntion time of 10 days. The leachate was tested in a batch methanaogensis re actor for biogas production. An average biogas yield of 0.48 m(3)/kg of COD destroyed was obtained with an average COD reduction of 93%. The biogas wa s analyzed for 73% methane content. (C) 2001 Elsevier Science Ltd. All righ ts reserved.