Solvothermal Liquefaction of Blackcurrant Pomace in the Water-Monohydroxy Alcohol Solvent System

Abstract

Wet organic wastes are especially troublesome in valorization. Therefore, innovative solutions are still in demand to make valorization feasible. In this study, we tested a new transformation route of a blackcurrant pomace as a high-moisture industrial waste through a series of high-temperature and pressure solvothermal liquefaction experiments. The feedstock was directly converted under near-critical conditions of the binary solvent system (water/2-propanol). The goal was to examine the effect of conversion parameters (temperature, biomass-to-solvent ratio) on the change in the yield of resultant bioproducts, as well as the quality thereof. The experiments were conducted in a batch autoclave at a temperature between 250 and 300 °C. The main product of the transformation was liquid biocrude, which was obtained with the highest yield (ca. 52 wt.%) at 275 °C. The quality of biocrude was examined by ATR-FTIR, GC-MS, and elemental analysis. The ultimate biocrude was a viscous heterogeneous mixture containing various groups of components and exhibiting evident energy densification (ca. 145–153%) compared to the value of the feedstock. The proposed processing method is suitable for further development toward efficient valorization technology. More specifically, the co-solvent additive for liquefaction is beneficial not only for the enhancement of the yield of the desired product, i.e., biocrude, but also in terms of technological aspects (reduction of operational pressure and temperature).