Abstract
Abstract A remarkable volume of coconut wastewater with extremely high levels of total solids (TS) and biochemical oxygen demand (BOD) is released by coconut (Cocos nucifera) oil mills. The fermented coconut water is highly acidic with a pH value of less than 4.5. Conversion of energy from coconut wastewater to methane by anaerobic digestion has significant importance in the abatement of pollution and production of renewable energy. The motive of the study was to evaluate the energy conversion from coconut wastewater using a floating gas holder digester on a lab scale. The digester was operated at different Hydraulic Retention Times (HRTs), ranging from 25 to 35 days, with a liquid volume of 150 L for each HRT. The HRTs were shortened from 35 to 25 days, and the biogas productivity of coconut wastewater decreased. During the switch to HRTs, the methane content of biogas decreased from 62% to 49.33%. Coconut wastewater can be bio-methanated in floating anaerobic bioreactors to produce electricity and reduce pollution. For the floating gas holder digester, the modified Gompertz model has a goodness of fit between 0.973 and 0.995, whereas first-order kinetics has a goodness of fit between 0.937 and 0.995.