Quantitative Characterization of Aqueous Byproducts from Hydrothermal Liquefaction of Municipal Wastes, Food Industry Wastes, and Biomass Grown on Waste

Hydrothermal liquefaction (HTL) is a viable thermochemical process for converting wet solid wastes into biocrude that can be hydroprocessed to liquid transportation fuel blendstocks and specialty chemicals. The aqueous byproduct from HTL contains significant amounts (20–50%) of the biogenic feed carbon, which must be valorized to enhance economic sustainability of the process on an industrial scale. In this study, aqueous fractions produced from HTL of food industry wastes, municipal wastes, and biomass cultivated on wastewater were characterized using a wide variety of analytical approaches. Organic species present in these aqueous fractions were identified using two-dimensional gas chromatography equipped with time-of-flight mass spectrometry. Identified compounds include organic acids, nitrogen compounds, alcohols, aldehydes, and ketones. Conventional gas chromatography coupled with flame ionization detection and liquid chromatography utilizing refractive index detection were employed to quantify the identified compounds. Inorganic species in the aqueous streams were also were quantified using ion chromatography and inductively coupled plasma optical emission spectroscopy. The concentrations of organic compounds and inorganic species are reported, and the significance of these results are discussed in detail