Process modelling of the hydrothermal liquefaction of oil-palm waste for biocrude and hydrochar production

Energy production from biomass has promising prospects in the domain of clean and sustainable sources. Hydrothermal Liquefaction (HTL) is an emerging process to convert biomass into energy products and is less energy intensive than other thermal conversion processes including gasification and pyrolysis, as HTL does not require pre-drying of biomass. In this study, a process simulation is developed using Aspen Plus® V10 to quantify the yield of liquefaction products including bio-crude, hydrochar and gas from various palm oil wastes; such as palm kernel shell (PKS), empty fruit bunches (EFB), palm oil fronds (POF) and their blends. The use of PKS as feedstock for HTL resulted in the highest biocrude yield of ~441 kg/tonne, whereas the EFB was linked to the lowest biocrude yield of ~293 kg/tonne. Meanwhile, the highest yield of hydrochar was achieved at ~193 kg/tonne for EFB. The gas production was also higher in the case of EFB, at about 317 kg/tonne. The blend of all three wastes yielded ~356 kg/tonne of biocrude, 102 kg/tonne of hydrochar and 387 kg/tonne of gas. In addition, the produced gas composition is dominated by CO2 followed by CH4. The blended feed yielded the lowest CO2 composition, which indicates the importance of feedstock blending in CO2 mitigation. POF is found to be a more economical feedstock which has shown the lowest cost of 0.331USD/kg and 0.045 USD/kg. The generated biocrude replicates several petroleum properties, granting it a high potential for conventional refining into clean transportation fuels. This study provides insights and technical knowledge on HTL technology and its possible upgradation from lab and pilot into commercial scales. © 2023 Elsevier B.V.