Enhanced Biogas Production in Anaerobic Digestion of Cassava Wastewater Though Supplementation of Biodiesel Waste as Co-substrate

Abstract

Anaerobic co-digestion is an attempt to enhance biogas production and improve the economic efficiency of large scale plant operations. In this work, the biodiesel processing waste (BDW) at different portions of 0.5-3.0% (v/v) in feed was subsequently added to an anaerobic hybrid reactor (AHR) treating cassava wastewater (CSW). Enhanced gases production, optimum dosage, digester’s performance and stability of each co-digestion conditions were evaluated. The results obtained clearly demonstrated the possible co-digestion of these wastes which increased gases production if BDW did not exceed 2.0%. The supplementation of BDW at 0.5-2.0% can increase 19.4-96.2% and 13.4-56.7% for biogas and methane production, respectively. These daily productions of biogas and methane were 12.6, 13.8, 15.5, 20.7, 18.8, 16.4 L-biogas/d and 8.6, 9.4, 10.3, 13.2, 11.0, 7.7 L-CH4/d for 0.5-3.0% BDW addition, compared to 10.6 L-biogas/d and 7.2 L-CH4/d of single CSW digestion. Similar gases yields (0.45-0.51 L-biogas/gCODremoved and 0.30-0.33 L-CH4/gCODremoved) and stable performance of AHR were maintained at 0.5-2.0% additions. The optimal dosage which promoted the maximum production was suggested to be 2.0%. Higher BDW dosage was claimed as the limitation. An imbalance digestion was observed as depicted as drop of pH, lower methane composition, and acid accumulation at particularly 3.0% of BDW supplementation.