Microbial mechanisms driving enhanced short-chain fatty acid and alcohol production during food waste fermentation via biochar addition in the pilot-scale reactor.

Maximizing carbon resources derived from food waste (FW) has attracted substantial global attention. This study investigated the mechanism of two types of biochar (bamboo-biochar and coconut shell-biochar) on FW anaerobic fermentation in a pilot-scale reactor. The results showed that biochar addition increased the concentrations of acetate, propionate, ethanol, and n-propanol during the 10-day fermentation period. Among these carbon resource, acetate and n-propanol were the primary components. During the first 7-day fermentation, bamboo-biochar and coconut shell-biochar increased the concentration of acetic acid by 23.72 % and 28.62 %, and the concentration of propanol by 14.93 % and 14.79, respectively. Microbial analysis revealed that bamboo-biochar and coconut shell-biochar improved the relative abundance of the Actinobacteriota phylum, benefiting the acidification process. Biochar also improved microbial metabolic functions, such as carbohydrate and amino acid metabolisms, facilitating the hydrolysis of organic matter. Additionally, the abundance of key enzymes (e.g., pyruvate dehydrogenase) related to acid and alcohol production also increased with biochar addition. This study elucidated the mechanism by which biochar enhanced fermentative products from FW in the pilot-scale reactor, providing a solid theoretical foundation for practical applications.