Impact of corn stover hydrothermal liquefaction conditions on the chemical composition and aerobic fermentation of the aqueous phase

Aerobic fermentation is a simple and environmentally friendly method to treat and recover nutrients from hydrothermal liquefaction aqueous phase (HTLAP). This study evaluated the chemical composition and aerobic biodegradability of HTLAP derived from corn stover under different hydrothermal liquefaction (HTL) conditions. The compositions of HTLAP followed specific patterns corresponding to HTL reaction severity, with high severity leading to increased concentrations of certain phenolic compounds. The elevated phenolics contributed to stronger inhibition of HTLAP on Aspergillus niger and Rhodococcus jostii. The half-maximal inhibitory concentration (IC₅₀) of HTLAP for both microbes can be well predicted by linear regression models with HTL reaction temperature and time as the input variables, while corn stover solid loading showed no significant effect on IC₅₀ and was not included in the models. Furthermore, aerobic fermentation with A. niger followed by R. jostii was demonstrated to be a versatile treatment process for corn stover HTLAP derived from a broad range of HTL conditions, achieving 45-70 % of COD removal. This research provides a quantitative understanding of the relationships between HTL reaction conditions, HTLAP composition, and aerobic biodegradability via A. niger and R. jostii, laying the foundation for integrating HTLAP aerobic fermentation into the HTL system, potentially enhancing its overall cost-efficiency and sustainability.