Microbial community assembly during aging of food waste-derived hydrochar: key bacterial guilds mediate nutrient dynamics

Hydrochar aging may mitigate the adverse effects of direct hydrochar application on plant growth. However, little is known about the strategies for accelerating aging process and the microbiological mechanisms involved. This study explored the effects of three aging strategies, including the addition of straw and efficient-degrading microorganisms, on the aging processes of food waste-derived hydrochar, and identified the key microbial drivers. The bacterial and fungal sequencing was performed to estimate the species composition in hydrochar at different aging periods (i.e., day 1, 7, 14 and 35). The results showed that the addition of straw and microbial inoculum improved the maximum reaction temperature by 13%, and shortened the aging time by ∼30%. Three bacterial guilds, mainly including Bacillus-like species, were identified that showed significant correlations with the nitrogen and phosphorus dynamics during aging. This study demonstrates the feasibility of manipulating key microbial guilds artificially to achieve efficient harmless-treatment of hydrochar.