(272e) Understanding Molecular Fractionation of Food Waste Hydrothermal Bio-Crude Products

Current waste management techniques primarily include the process of landfilling as well as inefficient thermal and biological processes. Wet waste products (municipal solid waste) account for 4.5 lbs per person per day. Current processes are inefficient to handle these wastes due to energy-intense drying of wet feeds, transportation to centralized facilities and extremely sensitive and long process times. Hydrothermal liquefaction (HTL) is a promising alternative for processing wet waste feeds, including food waste due to reduced energy cost for drying, localized waste management and energy production, and feedstock flexibility.

Food waste HTL remains a black box process. The reaction pathways and chemical properties of the resultant phases (gas, oil, aqueous, char) were explored using fourier transform mass spectroscopy as well as density functional theory (DFT). Techniques were used to determine chemical reaction pathways, product concentrations, and heteroatom class distributions. Figure 1 displays a single heteroatom class (N₃O₂) for oil and aqueous phases. Heteroatom classes were noted to be present in both phases, with an increased average carbon number and double bond equivalency (DBE) in the oil. Utilizing DFT calculations, a kinetic model of nitrogen reactions in HTL revealed the dominant pathways partition nitrogen to the oil and aqueous phases.

This provides insight into potential reaction mechanisms, leading to one pathway including the breakdown of food into water-soluble molecules before carbon polymerization reactions occur to produce heavy oil-soluble organics. We have begun to uncover the black box reaction of food waste HTL, providing deeper insight into fundamental chemical mechanisms to assist us in producing a commercially feasible process.