Modelling and Optimization of Biogas Production from Anaerobic Digestion of Agricultural Waste: A Factorial Design Analysis

Abstract

The aim of this study was to investigate the optimal conditions for biogas production from anaerobic digestion of agricultural waste (namely cow dung, chicken waste and saw dust) using full factorial design of experiments to study the effect of four factors (concentration (A), feed type (B), seeding (C) and time (D) on biogas produced after 28 days of anaerobic digestion. Main effects and interaction effects of these factors were analyzed using statistical techniques. The experimental results showed that the linear model terms of concentration, feed type, seeding and time had significant effect on yield with (p < 0.05). However, there was interactive effect between these variables (p < 0.05), though, concentration and time show no interaction (p> 0.05). The full model equation developed for biogas production is: Y = K-11.5842A+19.9868D. The constant K for biogas production with seeding = 930.877 for cow dung, 1483.28 for chicken waste and 555.692 for sawdust respectively. While K for biogas production without seeding = 351.309 for cow dung, 903.717 for chicken waste and -23.8759 for sawdust respectively. The highest amount of biogas produced was 1973.33mL at optimum conditions of: 20% concentration, chicken waste, seeding and retention time of 28 days.