Towards sustainable valorization of blackcurrant pomace: Investigation of hot-water extraction combined with hydrothermal liquefaction

Blackcurrants are popular fruits dominantly used for processing, resulting in the abundant generation of blackcurrant pomace (BCP). BCP is a waste containing valuable compounds, but it is not effectively utilized. This study presents an approach integrating hot-water extraction (HWE) and hydrothermal liquefaction (HTL) for the sustainable valorization of industrial-origin BCP. The HWE stage aimed to isolate monosaccharides and bioactive compounds. Subsequently, the resultant solid extraction residue and raw material (for comparison purposes) were subjected to HTL at 225-325°C. The pretreatment allowed for the isolation of 22.2 wt.% of the BCP into the aqueous phase consisting of 37% of the reducing sugars. Conversion of extraction residue via HTL resulted in biocrude with the yield reaching 39 wt.% which was increased by ca. 5-6 wt.% compared to direct HTL. The pretreatment also affected its quality, which is characterized by higher carbon content and heating value, as well as lower oxygen content. Performed analyses (FT-IR, GC-MS, GPC) showed slight changes in the composition of the biocrude. Overall, the studied approach is double beneficial because it allows for the acquisition of an additional sugar-rich extract stream which could be used in multiple ways (biocomponents, platform chemicals) and increases the efficiency of HTL conversion.