Liquefaction of Lignocellulose in Fractionated Light Bio-Oil: Proof of Concept and Techno-Economic Assessment

The direct thermal liquefaction of lignocellulose can provide a biocrude that could be used as a precursor for biofuels. However, earlier attempts to use the whole reactor effluent as a liquefaction medium, by recycling it to the liquefaction reactor, were hampered by the buildup of heavy products. This paper reports on the integration of the liquefaction reaction and the fractionation of the reactor effluent to recover and recycle the light oil fraction of it to be used as a liquefaction solvent. The fractionation is based on solvent extraction and temperature-swing regeneration. Here, we demonstrate steady-state liquefaction of pine wood with high and constant liquid yields (90 C %) and constant liquid qualities over several recycles. The liquefaction was done at a temperature of 320 °C and at a pressure of 7–10 MPa. Process simulation confirms a significant savings in energy demand by incorporating the extraction in the process, compared to an alternative liquefaction/distillation scheme. A techno-economic assessment further estimates that a biocrude could be produced at an energy-equivalent crude oil price of 54 $/barrel at a wood cost of 85 $/dry ton.