Wet torrefaction of oil palm trunk with initial pressurisation of 1 and 6 MPa at 180 and 260 °C and residence times of 30, 60, and 180 min was carried out. The hydrochar's solid yield treated at 180 and 260 °C ranged from 45.97 to 49.94 and 13.84�20.16, respectively. The higher heating values of the hydrochar treated at 180 and 260 °C were 17.76�18.60 MJ kg�1 and 24.72�27.62 MJ kg�1, respectively. Increasing the initial pressure at 260 °C resulted in decreased solid yield and higher heating values. The reduced solid yield and higher heating values was postulated to come from the suppression of dehydration and decarboxylation reactions along with partial lignin decomposition. Repolymerisation of lignin likely occurred; however, the contributions to solid yield and higher heating values from repolymerised lignin were insignificant compared to its depolymerisation that came from increased temperature. Glucose formation was promoted at high initial pressure (6 MPa) and low temperature (180 °C) and vice versa (i.e. 1 MPa and 260 °C gave higher glucose yield). Furthermore, the rehydration of 5-hydroxymethylfurfural to levulinic acid was enhanced with the increase in initial pressure due to the increased water density. Increasing the initial pressure inhibited lactic acid formation from glucose 1,2-enediol. © 2023 Institution of Chemical Engineers