Examining the mechanisms of short-term solubilization of ground food waste for high-rate anaerobic digestion

• Assays were conducted to measure maximum solubilization of ground food waste.
• Assays measured the soluble COD from endogenous release and enzymatic hydrolysis.
• The entire complement of endogenous soluble COD (27% of TCOD) was released within 1 h.
• An additional 30% of ground food waste TCOD was enzymatically hydrolyzed by 4 h.
• Rapid solubilization enables high-rate anaerobic digestion of food waste.

Optimizing short-term solubilization is essential for high-rate anaerobic digestion of food waste. The purpose of this study was to measure the short-term kinetics of food waste solubilization and understand what mechanisms are responsible for driving food waste solubilization. Two solubilization assays were conducted to measure the solubilization of mechanically processed food waste. Three methods of mechanical grinding were utilized: an in-sink food disposer and a manual meat grinder with either small or medium size plate openings. A control assay was conducted to measure the release of endogenous soluble material into an aqueous medium. An enzyme assay was conducted to examine short-term food waste hydrolysis. The assays were diluted and buffered to prevent product and pH inhibition, respectively, and allow maximum solubilization to occur. Percent solubilization was calculated as the soluble chemical oxygen demand (COD) fraction of total COD. Data from the two assays were used to calculate the kinetics of endogenous solubilization and enzymatic hydrolysis. Regardless of grinding method, food waste was 27% solubilized within 1 h through endogenous solubilization. Enzymatic hydrolysis was responsible for an additional 29–31% solubilization by 4 h. This study showed that ground food waste was approximately 60% solubilized within 4 h under optimal conditions.