Unlocking efficiency: Investigating optimal co-digestion mixtures for enhanced biogas production in small-scale rural settings

Biogas production is traditionally limited to large-scale industries due to economic and logistical limitations. This study evaluates the anaerobic co-digestion of swine manure, food waste and agricultural organic waste using both laboratory biochemical methane potential tests and pilot-scale low-cost digester ramp-up analysis. Optimization at laboratory scale identified an optimal mixture containing 100 g of fresh swine manure with 0.5 g (VS) of dried meadow grass, yielding a methane production of 135 ± 5 mL CH 4 /g VS. When transferring to pilot scale, the system produced biogas at with a methane content of 67%, whilst maintaining stability under ambient winter climate characteristics, thus confirming the feasibility of scaling up low-cost digesters for rural applications. Key scale-up insights to be mentioned are the requirement for pH control and monitoring, buffering capacity additions, and design considerations to improve thermal insulation and process stability for multiple feedstock mixtures. • Highest yields gave 135 ± 5 mL CH4/g VS with 100 g swine manure & 0.5 g meadow grass. • Pilot-scale ramp-up saw 67% methane content despite ambient winter conditions. • Fresh orange skin outperformed processed skin; glycerol caused tank acidification. • Energy Efficiency: heating requirements exceed the recovery of chemical methane.