Cultivating conditions optimization of the anaerobic digestion of corn ethanol distillery residuals using response surface methodology.

This study investigated the individual and interactive effects of three factors - temperature, inoculum/substrate ratio (ISR) and inoculum typology - on the anaerobic digestion of corn ethanol distillery wastewater. Biochemical methane potential assays planned with factorial design with two independent quantitative variables on three levels (ISR: 1:1, 2:1 and 3:1; temperature: 30°C, 33.5°C, 37°C) and one independent qualitative variable (inoculum type: suspended, granular, mixed) have been performed. Response Surface Methodology has been used to study the effect of the factors with the aim of maximizing the specific methane yields (Y) obtainable with this substrate. The results show that all three investigated factors influence in a significant matter the Y, the ISR having the strongest effect on it. The temperature has significant influence on the Y only in combination with high ISR values. The optimal conditions for the maximum Y (551 mL CH g VS) have been found at 37°C operating temperature, ISR=3:1 and using granular inoculum. These conditions gave rise to a 4-fold increase of Y with respect to the worst combination of factors (Y=129 mL g VS for the suspended inoculum type, at 30°C and ISR=1:1). The results improve the knowledge on the digestion of this substrate, providing information for successful process up-scaling. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]