Response Surface Methodology Application for the Optimization of Biogas Yield from an Anaerobic Co-Digestion Process

Abstract

Abstract This study carried out Bg anaerobic Cd. RSM was employed to investigate the optimum experimental conditions for Bg yield. The input parameters were PD substrates combination, either with WH or GS. Using six different identical 25 L cylindrical digesters, 6 experimental setups of the substrate combinations were carried out, for an incubation time of 22 days, under ambient T of 33 °C, and pH of 6.7. The setups digesters were: 25% PD:75% WH (1); 50% PD:50% WH (2); 75% PD:25% WH (3); 25% PD:75% GS (4); 50% PD:50% GS (5); and 75% PD:25% GS (6). From experimental observations, Bg yield started on day 5, for setups 1, 2, 4 and 5, followed by setup 3 on day 6. Setup 6 was the last digester to produce Bg, on day 7. Setup 2 recorded the highest Bg yield (75 cm3/day), while setup 6 had the lowest value yield (48 cm3/day). Furthermore, additional setups (7 and 8) were carried out for determining Bg characteristics and evaluating the effect of a pre-activated active slurry in its yields. Optimum Bg yield (75 cm3/day) was attained by 50% PD:50% WH. This result validates Bg production through substrates Cd, and the employment of optimization tools, in order to obtain ideal process parameters. Furthermore, quadratic model developed by RSM was highly reliable and reproducible, while the predicted values were close to the experimental ones.