Microbial heat reinforcement through enzyme–thermal coupling: A low-carbon biodrying approach for decentralized food waste management

Conventional biodrying of food waste (FW) is often constrained by limited microbial heat generation and high external energy demand, limiting decentralized applications. We developed an enzyme-thermal coupling strategy to enhance microbial thermogenesis and drying efficiency. FW was pretreated with a carbohydrase-protease-lipase blend, then biodried in insulated reactors under intermittent heating (IH) or continuous heating (CH), with microbial activity, moisture removal, and microbial community composition monitored. Enzymatic hydrolysis released over 60 % more soluble organic matter (SCOD increase from 193.4 mg/L to 325.8 mg/L within the first hour), which was associated with a shorter microbial lag phase, as indicated by earlier temperature rise and elevated OUR in the enzyme-treated group. Compared to CH, the IH strategy reduced energy consumption by 69.4 % (1.29 kWh/kg H₂O removed) while achieving a comparable final moisture content of 31.2 %. Carbon intensity decreased from 1.04 to 0.32 kg CO₂/kg FW. Microbial community analysis indicated shifts in composition and functional potential under IH, with enrichment of stress response and degradation pathways. βNTI analysis suggested a greater contribution of stochastic processes, which may support community diversity maintenance. Overall, the enzyme-thermal coupling approach leveraged microbial metabolism as an internal heat source, offering a promising low-carbon and energy-efficient solution for urban household-level organic waste treatment, with potential contributions to circular bioeconomy development and sustainable waste management.