Anaerobic Co-Digestion of Agro-Industrial Waste Mixtures for Biogas Production: An Energetically Sustainable Solution

In a climate crisis, searching for renewable energy sources is urgent and mandatory to achieve a low-carbon society. The food industry is an attractive source for providing different organic waste with great potential for energy generation, avoiding the environmental impacts of its inadequate management at the disposal stage. This manuscript determines the feasibility of using three agro-industrial byproducts for biogas production with a mesophilic anaerobic digestion process. Three mixture samples such as tomato pulp with olive cake (TP-OC), apple pomace with olive cake (AP-OC), and tomato pulp with apple pomace (TP-AP) at a 1:1 w/w ratio were evaluated using bovine manure as inoculum. During 7 to 12 days of operation, results indicate that TP-OC achieved the highest biogas production yield with 1096 mL/L (with up to 70% methane), followed by AP-OC and TP-AP with 885 (62% methane) and 574 mL/L (69% methane), respectively. Experimentally, TP-OC consistently encompassed the highest biogas and methane production and fit the kinetic models, whereas the modified Gompertz model produced the best fit (R2 = 99.7%). This manuscript supports the preference for mixing byproducts from the agro-industrial sector rather than using them individually for biogas production.