Metals and Other Elements in Biocrude from Fast and Isothermal Hydrothermal Liquefaction of Microalgae

We determined the effects of different hydrothermal liquefaction (HTL) process variables (temperature, holding time, algae loading, and water loading) on 13 different elements in biocrude and the aqueous phase co-product. Reaction conditions included both fast and isothermal HTL. The concentrations of P, Mg, Na, and Ca in the biocrude had their highest values at the mildest HTL conditions explored, and the concentrations decreased precipitously as even moderate HTL conditions were used. The concentrations of Zn, Cu, and Ni do not show much variation with HTL severity, whereas the concentration of Fe in the biocrude first increases and then decreases. P and Na were the most abundant elements in the biocrude from fast HTL, but Fe was the most abundant from isothermal HTL. These results show that the HTL conditions can influence the concentrations of different metals and inorganic species in algal biocrude from HTL.