Co-digestion of chicken manure with goose manure and thermo-oxidative-treated wheat straw in CSTR: co-digestion synergistics and OLR optimization through kinetic modeling

Due to the application of unknown organic loading rate (OLR), many studies had reported ammonia inhibition if using chicken manure on commercial scale. Therefore, three different OLRs of (1.50, 3.00, and 4.50) g.VS/L-d were applied by the current study, which were labeled as Phase-I, Phase-II, and Phase-III in two semi-continuous stirring tank reactors (CSTR) termed as R-A and R-B. Wheat straw was pretreated with 7.5% H 2 O 2 for consequent co-digestion with chicken manure and goose manure in both reactors. Experimental results concluded that Phase-II of Reactor-B (C/N = 25) proved optimal with methane enhancement capability of 260.14 mL/g.VS, 63.90% VS removal, and 56.76% chemical oxygen demand (COD) removal efficiency. To truly understand the reaction kinetics, first order-kinetics, cone model, transfer function model, and modified Gompertz model were employed and synergistic effects of co-digestion of chicken manure, goose manure, and thermally oxidized wheat straw were evaluated. Modified Gompertz model has provided best suitability and reliability with further kinetic predictions and explanations. Kinetic analysis and synergistic effect evaluations had validated the role of co-digestion in enhancing methane production. Graphical abstract