Improvement of anaerobic digestion of food waste by addition of synthesized allophane.

Anaerobic digestion (AD) of food waste (FW) always confronts the challenges of over-acidification in application. This work evaluated the effectiveness of synthesized allophane, a mineral with desirable physicochemical properties (e.g., high pH buffer and organic matter adsorption capacity, and high porosity and specific surface area), in increasing biogas yield during AD of FW as an additive. Results showed that allophane addition (0 to 10 g total solid (TS)) increased the cumulative biogas yield from 409.69 ± 20.77 mL/g TS to 624.06 ± 6.63 mL/g TS, and methane production from 224.12 ± 9.26 mL/g TS to 391.52 ± 0.87 mL/g TS. Improved AD performance was mainly attributed to mitigating over-acidification during the start-up period, and favoring microbial growth, particularly the acetotrophic methanogen of Methanosarcina, indicating an intensified acetoclastic methanogenic pathway. The findings provided a mechanistic insight into the improved AD performance with allophane addition, and offered a potential strategy to stabilize AD of FW in application.