Energy utilization of takeaway waste: Components separation and fuel preparation employing hydrothermal carbonization and gasification

Takeaway waste, which mainly consists of waste plastics and food residues, has increased dramatically and needs effective disposal nowadays. Considering the high moisture of food residues and significant density difference between food and plastic, hydrothermal carbonization (HTC) was proposed to realize the separation of plastics while upgrading food residues into hydrochar. In this study, plastic tube and cooked rice were studied as typical representatives of takeaway waste. The high heating value (HHV) of hydrochar can reach up to 26.48 MJ/kg which can be used as alternative fuel and whose combustion process was more stable compared to raw material. Due to polymer property, plastic tube only underwent a physical melt-condensation process during HTC and turned into a lump carrying hydrochar inside and outside, which could be separated at the filtration stage. By co-gasification with corn straw, the separated plastic lump can be converted into syngas, optimally with HHV of 17.40 MJ/Nm3 and yield of 0.75 L/gfeedstock. The hydrochar carried by the plastic lump enhanced its co-gasification process with corn straw, leading to a synergistic effect. The energy utilization of takeaway waste was achieved successfully employing HTC and gasification which could provide a new idea for waste disposal and fuel preparation.