Dual biogas/biochar production from anaerobic co-digestion of petrochemical and domestic wastewater: a techno-economic and sustainable approach

Abstract

This study investigates the utilization of petrochemical and domestic wastewater (PCW and DW) for dual biogas and biochar production, focusing on the economic and sustainable development criteria. Biogas yield by anaerobic co-digestion of a 0:1 (PCW:DW) feed was 306.4±11.8 mL per g chemical oxygen demand (COD) removed, which dropped by 12.7% with changing PCW:DW to 1:0. The results indicated that increasing the DW fraction in the feed encouraged the conversion of COD into more biogas and sludge amounts. The anaerobic sludge was subjected to pyrolysis to generate biochar with a yield of 0.6 g/g dry sludge. The delivered biochar showed appropriate surface morphology, elemental composition, physical properties, and surface functional groups, as demonstrated by SEM/EDX, XRD, and FTIR characterizations. The COD mass balance estimation of the anaerobic digestion system, with biochar yield, was used to determine the economic feasibility of treating 30 m3/day of wastewater. The 1:0 (PCW:DW) condition provided the most feasible scenario, with profits of 3340, 192, and 2819 USD/year for energy income, biochar selling, and pollution reduction, respectively. This economic benefit was equivalent to a payback period of 5.38 years. The fulfillment of multiple sustainable development goals (SDGs) related to clean and renewable energy production, human health protection, and economic growth was highlighted.Graphical abstract