Development of a surrogate model for the simulation of anaerobic co-digestion of pineapple peel waste and slaughterhouse wastewater: Appraisal of experimental and kinetic modeling

This work focused on the development of a surrogate model for the prediction of biogas production by anaerobic digestion of slaughterhouse wastewater (SWW) and pretreated pineapple peel waste (PPPW). The process was carried out under mesophilic conditions involving five batch reactors containing different compositions of SWW and PPPW. Physicochemical characterization of SWW indicated that the substrate has a biodegradability ratio (biochemical oxygen demand, BOD5 / chemical oxygen demand, COD) of 62.66%, while FTIR analysis of PPPW depicted the rupturing and flattening of functional groups associated with the presence of lignin following hydrogen peroxide (H2O2) pretreatment. The maximum daily biogas production of 79 ml/g volatile solids (VS) was recorded in the first reactor (R1) containing 100% SWW, while the maximum cumulative biogas yield of 579 ml/g VS was obtained in the fourth reactor (R4) consisting of 30% SWW and 70% PPPW. Results from conventional kinetic models indicated that mono-digestion processes (R1 and R5) were best fitted with the modified Gompertz model (R2 ≥ 0.9890), while the logistic model best described the co-digestion systems (R2: R2 = 0.9767; R3: R2 = 0.9854; R4: R2 = 0.9966). However, comparative analysis of empirical data with surrogate model predictions illustrated the stability and high accuracy of the surrogate model (0.9921 ≥ R2 ≥ 0.9789) over other kinetic models in simulating both mono and co-digestions of SWW and PPPW. Using the proposed model as objective function in numerical optimization, an optimum biogas yield of 580.55 mg/l VS was obtained in R4 operating for 25 days.