Study of the methanogenic potential of used grease and bleaching earth by conversion into biogas: The case of a wastewater treatment plant and a refinery

Abstract

The structure from which this study was carried out is a food processing company specializing in the transformation of crude palm oil into table oil. In order to comply with environmental standards when discharging the refinery's wastewater, it has its own wastewater treatment unit. The aim of this study is to contribute to environmental protection by recovering grease and bleaching earth through biogas production by anaerobic digestion. The characterization provided us with moisture, dry matter and volatile solids contents the values obtained are 32.31%, 67.69% and 97.57% respectively. In the same order, those for bleaching earth are 1.80%, 98.20% and 59.97%. The values obtained during the characterization of the bleaching earth are not conducive to good anaerobic digestion. To optimise biogas production from fat, we used inoculums such as cattle dung and broiler droppings. Biodegradability tests carried out with different proportions of substrates and inoculums led to the conclusion that the presence of a large quantity of microorganisms is necessary for optimum biogas production. In addition, the grease produced a good quantity of biogas when co-digested with the inoculums. The cumulative volume of biogas obtained over 30 days with the grease was 445 ml. The highest quantity of biogas obtained by optimising gas production is 780 ml.