Kinetic Study of Alkaline Treatment in the Production of Bio-gas from Cocoa Pod Husks Using a Batch Reactor

Abstract

Cocoa pod husk (CPH) is one of the potential plantation wastes used for biogas production. However, the presence of lignin inhibits the production process. Therefore, pretreatment is required to reduce the lignin content. This study investigates the effect of several pretreatment methods on lignin reduction and biogas production enhancement. The study also investigates the kinetic models for biogas production from treated and untreated CPH. The pretreatment exploitation NaOH (N), NaOH with the addition of H2O2 at the same time (NHS) and consecutively (NHC) were administered to cut back lignin content in CPH and enhance methane series yield. The N, NHS, and NHC pretreatments obtained the maximum delignification of 78.10%, 91.42%, and 88.68%. Biogas production from NHS pretreated with CPH led to a better methane yield (0.0389 m3CH4 / kgVS) than the various pretreatments corresponding to 175.59% for CPH without pretreatment and productivity is 0.0009 m3CH4 / kgVS.day. The biogas production kinetic model parameters have been evaluated by fitting experimental data for the treated and untreated cocoa waste. The kinetic models investigated are the one-step first-order kinetic model, two-step first-order kinetic models, Gompertz model, and Transfer Function model. Based on Root Mean Square Error (RMSE) value, the one-step first-order model is more accurate than the two-step first-order model. When compared with other models, the Gompertz model is the best version.