Predictive modelling of biogas generation from palm oil mill effuent for the wastewayer-energy nexus

Abstract

Palm oil mill effluent (POME) wastewater from crude palm oil production has seen to be a valuable waste resource for biogas recovery. Nonetheless, with only improvements on the wastewater treatment processes, there is lack of study on specifically identifying significant biogas-production parameters and its correlations that will further enhance biogas recovery. In addition, there is also absence of a study to further exploit these relations in predicting parametric inputs and outputs to be applied in an interwoven, closed-loop relation known as the wastewater-energy nexus. Thus, this study aims to establish the identification of significant physicochemical parameters of POME wastewater and determine its correlation strength towards biogas production. Regression relations are also established in predicting biogas generation based on the significant parameters of POME wastewater. In addition, predictive assessment on economic and environmental implications from the predicted biogas production is also carried out. Following the methodology of this study, a predictive modelling approach based on statistical analysis, specifically regression analysis, on study parameters are carried out to predict biogas yield. Validation of the regression models are carried out with comparison on modelled and observed data with deviations observed. The results demonstrated a high correlation between pH of anaerobic digestion, temperature, percentage of COD removal and FFA percentage in POME towards biogas production with correlation coefficients higher than 0.8.Furthermore, based on an illustrative scenario analysis carried out on the linear and multilinear regression models, with an input of FFA percentage at 3%, it was able to be predicted that as much as 909.76 m3 of POME is needed to generate 34,489.70 m3 of biogas. The energy generated is predicted to be 68,979.40 kWh. Possible mitigation of CO2eq emissions were predicted at a value of 579,426.96. A Sankey diagram is presented to further demonstrate the application of the model on the wastewater-energy nexus in summarizing the system as a whole. This study is intended to be of significant importance to predict parametric control of POME on energy which in hand will deliver economic as well as environmental benefits.