Thermochemical co-liquefaction of fruit pomace's blends in a binary solvent system towards value-added bioproducts

Abstract

Poland belongs to the most meaningful producers of fresh food products in the European Union, e.g. apples, cherries, carrots, as well as currants. A significant part of these products are subjected to further processing, which results in the generation of an abundant amount of wet residues, such as pomace. The present paper aims to investigate the possibility of co-processing various industrial residues in the form of fruit pomaces through thermochemical liquefaction toward high-energy density biocrude and biochar. More specifically, industrial wastes received from commercial juice production, i.e. blackcurrant, apple, and cherry pomaces, were converted under subcritical conditions of the water-isopropyl alcohol solvent system under fixed conditions. Particular focus was put on testing binary and ternary mixture feedstock systems and the possibility of predicting the bioproduct yield. Furthermore, the quality of the resultant biocrudes was analyzed by means of FTIR, GC-MS, and elemental analysis. For all separately studied raw materials and their binary and ternary mixtures, the dominant group fraction was biocrude, with its yield ranging between 45.8 and 54.5 wt.%. Produced liquids exhibit high energy density (HHV between 30.2–32.4 MJ/kg) thus all of them pose perspective alternative fuels for generating heat and electricity. Also, the solid biochars presented a high-energy density (HHV around 25-26 MJ/kg) and can be considered as an alternative energy carrier. The postulated approach aims to increase the flexibility and profitability of future technology of processing useless waste toward value-added bioproducts for the chemical and energy sectors.