Optimization of Process Parameters Influencing Biogas Production from Rumen and municipal waste: Analytical Approach

Abstract

Rumen waste with high carbohydrate, protein, and lipid content is considered as a suitable substrate for fermentation for methane gas. In this study, direct substrate and co-digestion of rumen waste (RW) and municipal waste (MW) were used. Samples (fresh cow rumen and food waste) were dried, grinded, and blended with water into a semi-solid to facilitate digestion. Central composite design (CCD) was applied to optimize parameters of co-digestion of RW and MW at a different temperature (29 – 33oC), initial pH values, agitation time (AGT), and carbon-nitrogen ratio (C/N). A comparative analysis was done using RSM in a predictive model of the experimental data obtained in accordance with the CCD. The combined effects of temperature, pH, AGT, and C/N as methane production by fermentation of RW and MW were investigated. Optimization using RSM showed a good fit between the experimental and the predicted data as elucidated by the coefficient of determination with R2 values of 0.9214. Quadratic RSM predicted the maximum yield to be 7764 mL CH4/g volatile solid (VS) at optimal conditions of 31°C; pH 7.05; 6s and C/N ratio 20.33. The maximum methane yield was 8550 mL CH4/g VS, at the optimal conditions for the experimental response obtained. The verification experiment successfully produced 8550 mL CH4/g VS within 30 days of incubation. This experiment indicated that the developed model was successfully and can be used for methane production from animal and municipal waste.