Molecular footprint of co-solvents in hydrothermal liquefaction (HTL) of Fallopia Japonica

•Oxygenated water soluble aliphatics were the most common HTL products.•High-value carboxylic acids constituted the core resilient to process tailoring.•Tetralin promoted formation of aromatics through solubilization and scavenging.•Acetone promoted low molecular weight oxygenates through retro-aldol splitting.