Enhanced Biogas Production through Anaerobic Co-Digestion of Agricultural Wastes and Wastewater: A Case Study in South Africa

Abstract

The sustainable management of agricultural wastes (AWs) and their valorization for biogas production offer promising alternatives to fossil fuels and contribute to environmentally responsible waste management strategies. This study examines the anaerobic co-digestion (Co-AD) of various AWs, including apples, bananas, carrots, butternuts, and potatoes, combined with wastewater (WW) from a local fruit and vegetable market, using activated sludge (AS) as the inoculum. The biomethane potential test (BMP) was performed in 1L capacity digesters with an 80% working volume and maintained at 40℃ over a 21-day period. A mixing ratio of 1:1 (% w/w) between WW and AWs and 1:2 between the cosubstrates and inoculum was utilized. Biogas production was monitored daily to evaluate the effectiveness of the Co-AD process. The control group yielded a total production of 450 mL/day, while the apple and banana substrates demonstrated the highest biogas output at 595 mL/day and 585 mL/day, respectively. The potato substrate generated 525 mL/day, mixed AWs produced 485 mL/day, and butternut and carrot substrates resulted in 485 mL/day and 475 mL/day, respectively. These findings suggest that the Co-AD of AWs and WW, in combination with AS, presents a viable and eco-friendly approach to enhanced biogas production.