Anaerobic co-digestion of brewery wastewater and soybean processing industry sludge to enhance biogas production

Abstract

Global energy demand continues to rise, necessitating innovative and sustainable renewable energy solutions. Among these, converting industrial waste into bioenergy stands out as one of the most sustainable options. This study aimed to investigate the co-digestion of brewery wastewater (BWW) and soybean processing industrial sludge (SPW) for biogas production. Various substrate mixing ratios of both wastes (SPW:BWW) were tested at four different hydraulic retention times (HRTs), ranging from 10 to 25 days, under mesophilic conditions (37 ± 2 °C). The experimental design was developed using Response Surface Methodology (RSM) with the help of Design Expert software. Physicochemical parameters including pH, electrical conductivity, turbidity, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), and nutrient content were monitored before and after digestion. The results showed that co-digestion significantly enhanced biogas production compared to mono-digestion. The 50:50 mixing ratio yielded the highest biogas output of 277.3 ± 6.0 ml/day at the longest HRT of 25 days. The highest methane content (65.39 %) was observed with a 75 % SPW: 25 % BWW ratio at 20 days HRT. Statistical analysis confirmed that both substrate mixing ratio and HRT had a significant effect on biogas production and methane content (p < 0.05). The RSM optimization process achieved a desirability score of 0.914, indicating optimal conditions for maximizing biogas production and methane concentration. These findings highlight the potential of converting soybean processing industrial residue and brewery wastewater into renewable energy through anaerobic co-digestion, offering a promising sustainable solution for waste management, greenhouse gases emission reduction, and energy diversification.