Evaluation of biogas yield from co-digestion of varying particle sizes of corncob with poultry manure and process parameters optimization study

Abstract

The need to improve renewable energy generation, advance sustainable waste management techniques, and uncover beneficial agriculture methods, necessitated anaerobic co-digestion of grounded corncob (GC) biologically pretreated with cattle rumen (inoculum) and poultry poos (PP) for biogas generation, as discussed in this study, Corncob biomass (CB) and PP (substrates) were obtained at the teaching and research laboratory in LAUTECH Ogbomoso. CB was pretreated using mechanical grinding and sieving methods and then divided into two portions labelled A and B, using sieve sets of 0.30mm and 0.45mm. The ratio of the combination of substrates: GC: PP: inoculum is 1:0.5:0.5. Standard procedures were used to assess the physicochemical parameters of the substrates and digestates. Central Composite Design (CCD) was used to batch the experimental design of pretreated samples A and B with PP and inoculum to produce biogas which was analysed for methane content using a gas chromatograph mass spectrometer. Response Surface Methodology (RSM) was used to optimize data generated for temperature, pH, retention time, total solids, and volatile solids (VS) using the 'Design-Expert Application' version 11.

The biogas yields for experiments A and B were 1.368 L/kg VS and 1.221 L/kg VS, while the Methane compositions were 60.44% and 57.58%, respectively. The optimized data for A and B were; temperature (40 ^o C, 40 ^o C); pH (8.0, 6.0); retention time (30, 30 days); total solids (12, 4 g/kg); and volatile solids (12, 12 g/kg) respectively. The model's coefficient of determination (R²) was high (0.9267) for A, indicating strong modelling and prediction accuracy, thus, recommending the usage of corncob for bioenergy generation.