Interactions Between Carbohydrate and Protein During Hydrothermal Liquefaction of Food Waste

Hydrothermal liquefaction (HTL) is a promising route to convert food waste (FW) to value-added biocrude. Real FW collected from a university campus dining hall and three principal FW components, namely carbohydrate (starch), lipid (oil), and protein (tryptone), were chosen to study the HTL performance (320 degrees C, 20 min). Significant interactions between carbohydrate and protein were observed, which promoted the biocrude yield and decreased solid residue yield dramatically. A biocrude yield prediction method was proposed based on this interaction, which was more precise than linear calculation. The optimal content of protein in carbohydrate and protein blends for the biocrude yield was between 37.5% and 50.0%. The interactions promoted the migrations of C and N in feedstock to biocrude, while the migration of C to solid residue decreased. The amino acids derived from protein would react with the reducing sugars derived from carbohydrate to produce N-heterocyclic compounds. The interactions between carbohydrate and protein also resulted in a more dispersed biocrude with a larger polydispersity (1.828).