Co-hydrothermal carbonization of the main components in food wastes: products characteristics and synergistic effects

This study investigated the product characteristics of (co-)hydrothermal carbonization (HTC) of staple food wastes (SW), vegetable waste (VW), and bone waste (BW) in food wastes (FW) and the potential synergistic effects. The result demonstrate that co-HTC showed a synergistic effect on oil production and antagonistic effects on gas and hydrochar production. Co-HTC further promoted decarboxylation, increased the carbon structure orderliness, and changed the surface chemical properties of hydrochars. Acid compounds were the main components of bio-oil, accounting for more than 50 %, followed by N-containing compounds. For the co-HTC of SW and VW, the decarboxylation of lipids, deoxygenation of carbohydrates, and reformation of cellulose and lipids resulted in the largest synergistic effect on hydrocarbons (interaction parameter, IP = 17.67 %). Aromatic compounds exhibited the largest synergistic effect (IP = 19.65 %) in the co-HTC of SW and BW, and N-containing compounds exhibited the largest synergistic effect (IP = 6.07 %) in the co-HTC of VW and BW. Accordingly, the reaction pathways for synergistic effects during the co-HTC of major FW components were analyzed.