Optimization of distillery-sourced wastewater anaerobic digestion for biogas production
Mebrahtom Gebresemati Weldehans
Abstract
Ethiopia produces large volumes of high-strength, acidic, recalcitrant, and colored wastewater from sugarcane molasses-based alcohol distilleries. Interestingly, distillery wastes are high in organic nutrients that facilitate microbial growth and serve as substrates for renewable energy production. Conversely, energy insecurity is a major issue in Ethiopia, as access to modern energy services is limited in many parts of the country, particularly in rural areas. To address both challenges simultaneously, this study investigated the effects of temperature, pH, and retention time on distillery-sourced wastewater anaerobic digestion for biogas production. A Box-Behnken design confirmed that retention time influenced biogas production and biomethane yield largely. The numerical optimization of the process determined that the optimal conditions for specific biogas production (SBP) and biomethane yield were 31.21°C temperature, 7.35 pH, and 16.85 days retention time. At this optimal point, the predicted values of SBP and biomethane yield were 0.469 l/g-COD removed and 57.87, respectively. The error percentages between experimental and predicted values were 1.71% for SBP and 1.57% for biomethane yield, suggesting the accuracy and predictability of the models. The study findings imply that simultaneous distillery waste treatment and energy production could be a viable option for providing affordable and clean energy to rural communities and small businesses in Ethiopia.