Advanced treatment and valorization of food waste through staged fermentation and chain elongation

[Display omitted] •Moderate saccharification provides suitable substrates for both ethanol and VFA production.•Staged fermentation realizes the advanced treatment of food waste.•Staged fermentation provides suitable ethanol and VFAs for chain elongation.•n-Caproate production from food waste shows advantages in economy.•Microbiomes related to chain elongation are enriched. A novel valorization approach of food waste via staged fermentation and chain elongation was proposed. Food waste was moderately saccharified, saccharification effluent was fermented to produce ethanol and saccharification residue was hydrolyzed and acidified to produce VFAs. The yeast fermentation effluent and hydrolytic acidification effluent were sequentially performed for chain elongation. Ethanol and volatile fatty acids from staged fermentation were suitable for direct chain elongation and the n-caproate production was 184.69 mg COD/g VS when yeast fermentation effluent to hydrolytic acidification effluent ratio was 2:1. Food waste was deeply utilized with an organic conversion of 80%. The relative abundance of Clostridium sensu stricto increased during chain elongation, which might be responsible for the improvement of n-caproate production. A profit of 10.65 USD/t was estimated for chain elongation of food waste staged fermentation effluent. This study provided a new technology to achieve advanced treatment and high-valued utilization of food waste.