(513n) Molecular Fractionation and Description of Food Waste Hydrothermal Bio-Crudes

Current waste management techniques primarily include the process of land-filling 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 advanced analytical techniques. Oil and aqueous characterization techniques such as Fourier transform mass spectroscopy and infrared spectroscopy (FT-MS and FT-IR) were used to determine heteroatom classes present in samples. Figure 1 displays a single heteroatom class (N₃O₂) for oil and aqueous phases. This compound class is present in both, yet the average carbon number is much higher for the oil phase than the aqueous. The double bond equivalency (DBE) also has a greater average in the oil signifying an increased degree of aromaticity/ unsaturation in the oil. Examining the breakdown of different heteroatom classes results in the same trend, wherein both oil and aqueous phases contain the same classes with increased carbon number and DBE in the oil phase.

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.