Effect of pretreatment on acid fermentation of organic solid waste

The effect of various pretreatment methods on acidogenesis of food waste from a cafeteria was investigated. Thermal, enzymatic, and combined thermal-enzymatic batch pretreatment were conducted. Solubilization of food waste in thermal or enzymatic pretreatment increased with either increasing thermal duration or enzyme dosage, respectively. An optimal condition in thermal or enzymatic pretreatment was 60 min of thermal processing or 0.1% (v/v) of enzyme dosage level, respectively, based on volatile suspended solids (VSS) reduction. In the combined pretreatment, increased thermal duration also increased VSS reduction and the solubilization efficiency was higher than that in only enzymatic or thermal pretreatment. The maximum volatile fatty acids (VFAs) production and the highest VFAs fraction in soluble COD in the acid fermentation were achieved with the food waste after 60 min of thermal processing followed by 0.1% (v/v) enzymatic treatment. Increase in VFAs production of the fermenter was over 380% compared to the control fermenter without any pretreatment.