Hydrothermal liquefaction (HTL) is the thermochemical conversion of wet biomass into energy-dense biocrude that can undergo subsequent upgrading to distillate fuels. HTL performed isothermally for tens of minutes under subcritical temperatures has been established as a viable process for valorizing a variety of agricultural and food processing wastes. Fast HTL, a recent variant of this technology uses rapid heating conditions and very short reaction times (tens of seconds) to produce biocrude. We subjected potato starch, casein and sunflower oil, representative of polysaccharide, protein, and lipid components of food waste, to both isothermal and fast HTL, individually and as ternary mixtures in different proportions. Fast HTL of sunflower oil at 600 °C set-point temperature and holding time of 1 min produced the highest biocrude yield (91 wt %), followed by casein (23 wt %) and potato starch (19 wt %). Up to 21% of the phosphorus and 57% of the nitrogen in the casein feedstock partitioned to the aqueous phase coproduct following fast HTL, which could then be recovered and used as a fertilizer for cultivating other biomass.  Higher biocrude energy recoveries were observed after fast HTL (600 °C, 1 min) than isothermal HTL (350 °C, 60 min) for all three feedstocks but potato starch experienced the largest effect. Furthermore, biocrude with greatest higher heating value (42 MJ/kg) was observed after fast HTL of a ternary mixture enriched in potato starch.  These results suggest that it is especially advantageous to process polysaccharides via fast HTL. The biocrude yields from the ternary mixtures investigated were in general agreement with the mass-averaged yields from the individual biochemical components. However, GC-MS analysis of the biocrudes from mixtures provide evidence of chemical reactions between the different biomolecules during HTL.

Fast and isothermal hydrothermal liquefaction of model food waste biomolecules and their ternary mixtures

256th National Meeting (2018)

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