Optimization of Nanoparticle Concentration in Anaerobic Digestion by Response Surface Method

Recently, it has been discovered that nanoparticles (NPs) have efficiency-enhancing effects on biogas production in anaerobic digestion (AS). In this study, the effects of Fe3O4, ZnO and SiO2 NPs on AS were investigated. High concentrations of some NPs are toxic. Therefore, the Box-Benkhen Design of the Response Surface Methodology (RSM) was used to find the best NP concentrations in AD of cattle manure used as a substrate. RSM is a valuable statistical tool that maximizes the response surface affected by operating variables based on several sets of experiments within a selected range. As a result, the best NP concentration values for the independent variables were found to be 150 mg/L for SiO2, 150 mg/L for Fe3O4 and 150 mg/L for ZnO. While the biogas yield before adding NP was 290 ml/g volatile solids (VS), it was estimated at 320 mL/g VS under the optimum conditions of the independent variables. The analysis of variance and the high regression coefficient (98%) confirm that the experimental values are well predicted by the polynomial regression model. Thus, it is recommended to examine the effects of different NPs together in AS in future studies.