Co-digestion of cocoa pods and cocoa leaves: Effect of C/N ratio to biogas and energy potential

In Indonesia, energy needs are mostly fulfilled by non-renewable fuels. In the longer term, such practices may lead to an energy crisis due to problems of resource continuity and availability. Therefore, the development of renewable energy remains a priority for the Indonesian Government, one of which is from biomass sources. Indonesia has vast and abundant biomass sources available for further transformation to bioenergy. Waste from the cocoa plantation (e.g. cocoa pods and cocoa leaves), for instance, contain organic materials that are potential for biogas production. This research aimed to evaluate the effect of the C/N ratio on biogas production and energy potential from the co-digestion of cocoa husk with cocoa leaves. The Biochemical Methane Potential (BMP) test operated under batch and mesophilic condition for 28 days were carried out. The samples tested include blank control, positive control (a-cellulose), and co-digestion samples at different C/N ratio in the range of 22 to 25, prepared in triplicate. The results indicated that pH inhibition was not evident during the digestion process. The findings also confirmed that the co-digestion of cocoa pods with cocoa leaves at a much higher C/N ratio was able to enhance biogas production. Further estimation on the electricity potential showed a potential application of this co-digestion strategy for providing alternative renewable energy sources.