Food waste valorization using a novel system integrated dry fermentation, fractionation and torrefaction

Conventional biological and thermochemical technologies for food waste (FW) valorization are constrained by the long-term operation, products recovery, low value-added products and unwanted byproducts. Here, an integration of magnetite promoted dry fermentation, fractionation and torrefaction (DFFT) was proposed for simultaneous production and recovery of VFAs, biohydrogen, and biochar from a typical FW, potato peel. The yield of VFAs and H₂ could reach to 22.8 g/L and 24.2 mL/g VS, respectively. Meanwhile, fractionation can effectively collect ethanol (82.04 %) and VFAs (above 90 %) from fermentation products. What’s more, the prepared biochar from solid residues was rich in nutrients and surface functional groups, with abundant pore structure, indicated that its potential as fertilizer and soil conditioner. Additionally, economic and greenhouse gas (GHG) emission analysis of the scale-up DFFT plant showed that profits could reach to 100.37 CNY/t FW, resulting in a GHG emission reduction of 305.87 kg CO₂ eq/t FW, with carbon sequestration and emission reduction achieved at the same time. In order to quantify the comprehensive effect of the system, a new index (economic-carbon index, ECI) was proposed to evaluate different FW treatment paths, and the results showed that DFFT was more effective, with a ECI value of 0.96. This study proves DFFT could be a promising system for FW valorization for sustainable chemicals, materials and energy production.