Effect of Process Variables on Food Waste Valorization via Hydrothermal Liquefaction

Bita Motavaf, Phillip E. Savage

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We examined hydrothermal liquefaction (HTL) of simulated food waste over a wide range of temperatures (200.600 °C), pressures ( MPa), biomass loadings (2.20 wt %), and times (1.33 min). These conditions included water as vapor, saturated liquid, compressed liquid, and supercritical fluid and explored both isothermal and fast HTL. The highest biocrude yields (∼30 wt %) were from HTL near the critical temperature. The most severe reaction conditions (600 °C, 35.3 MPa, 30 min) gave biocrude with the largest heating value (36.5 MJ/kg) and transfer of up to 50% of the nitrogen and 68% of the phosphorus in the food mixture into the aqueous phase. Energy recovery in the biocrude exceeded 65% under multiple reaction conditions. Saturated fatty acids were the most abundant compounds in the light biocrude fraction under all the reaction conditions. Isothermal HTL gave a higher fraction of heavy compounds than fast HTL. A kinetic model for HTL of microalgae predicted 2/3 of the experimental biocrude yields from HTL of food waste to within ±5 wt %, and nearly 90% to within ±10 wt %. This predictive ability supports the hypothesis that biochemical composition of the feedstock is important input for a predictive HTL model.

Original languageEnglish (US)
Pages (from-to)363-374
Number of pages12
JournalACS ES and T Engineering
Issue number3
StatePublished - Mar 12 2021

All Science Journal Classification (ASJC) codes

  • Chemical Engineering (miscellaneous)
  • Environmental Chemistry
  • Process Chemistry and Technology
  • Chemical Health and Safety

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