Dairy product manufacturers contend with large volumes of waste ice cream (WIC) that cannot be sold due to allergen contamination and/or failed product specifications. Simultaneously, there is significant need and opportunity to thermochemically upgrade bioproduct waste into higher-value products, such as sustainable aviation fuel and biochar. As a two-pronged solution to both issues, we studied the hydrothermal liquefaction (HTL) of WIC, where our goal was to optimize process conditions for producing value-added products, while separating proteinaceous nitrogen. Two types of melted WIC (standard; high-fat content) underwent HTL for 1 hr at varying temperatures (210 – 330 oC), catalysts and additives (Ru/C, Pt/C, Pd/C, Na2CO3), and gaseous environments (N2, H2). HTL at 210 oC without any additives produced the highest yields of hydrochar (~16 wt%). However, sodium carbonate doubled the yield of biocrude for both WIC types and increased the efficiency of nitrogen partitioning into the hydrochar. Catalytic hydrogenation tended to increase unwanted partitioning of the proteinaceous nitrogen into the biocrude. However, Ru/C at 210 oC under hydrogen produced the highest yields of paraffinic biocrude (36 wt%). HPLC analysis indicated that catalytic HTL at 300 oC and above produced paraffinic hydrocarbons and eliminated remaining glycerides. Catalytic hydrotreatment of biocrude product produced purified paraffins indicative of hydrodeoxygenation, as evidenced by GC-MS and produced gas products.
