Evaluation of methane production from the anaerobic co-digestion of manure of guinea pig with lignocellulosic Andean residues

The objective of this research was to evaluate the anaerobic co-digestion of guinea pig manure (CY) with Andean agricultural residues such as amaranth (AM), quinoa (QU) and wheat (TR) in batch biodigesters under mesophilic conditions (37⁰C) for 40 days. As microbial inoculum, sewage treatment sludge was used in two inoculum/substrate ratios (ISR of 1 and 2). In terms of methane production, the best results occurred in the treatments that contained AM and QU as co-substrate and an ISR of 2. Thus, the highest methane production occurred in the CY:AM biodigesters (25:75) and CY:QU (25:75) with 341.86 mlCH4/g VS and 341.05 mlCH4/g VS, respectively. On the other hand, the results showed that methane production with an ISR of 2 was more feasible for guinea pig waste, where the methane fraction of the biogas generated was in a range of 57 and 69%. The kinetics of methane production from these raw materials was studied using five kinetic models: modified Gompertz, logistic equation, transfer, cone, and Richards. The cone model was the one that best adjusted the experimental values ​​with those observed with an r2 of 0.999 and an RMSE of 1.16 mlCH4/g VS. Finally, the highest biodegradability was obtained in the CY-AM biodigesters (25:75) with 67.92%.