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 anaerobic co-digestion of guinea pig manure (GP) with Andean agricultural residues such as amaranth (AM), quinoa (QU) and wheat (TR) in batch biodigesters under mesophilic conditions (37 C-0) 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 treatments containing AM and QU as co-substrate and an ISR of 2. Thus, the highest methane production yield in the GP:AM biodigesters (25:75) and GP:QU (25:75) with 341.86 mlCH(4)/g VS added and 341.05 mlCH(4)/g VS added, respectively. On the other hand, the results showed that methane production with an ISR of 2 generated higher yields for guinea pig waste and the methane fraction of the biogas generated was in a range from 57 to 69%. Methane production kinetics from these raw materials was studied using five kinetic models: modified Gompertz, logistic equation, transfer, cone and Richards. The cone model adjusted best to the experimental values with those observed with r(2) of 0.999 and RMSE of 1.16 mlCH(4)/g VS added. Finally, the highest biodegradability (experimental yield/theoretical yield) was obtained in the GP-AM biodigesters (25:75) with 67.92%.

Automated summary

This research evaluated the anaerobic co-digestion of guinea pig manure with Andean agricultural residues in batch biodigesters, finding that the best methane production occurred with amaranth and quinoa as co-substrates with an ISR of 2. Additionally, methane production with an ISR of 2 resulted in higher yields for guinea pig waste, with methane fraction ranging from 57% to 69%. The cone model was the most suitable for studying methane production kinetics from these raw materials, with high accuracy and efficiency.