Pyrolysis of hydrochars obtained from blackcurrant pomace in single and binary solvent systems

The two-stage conversion of blackcurrant pomace as an industrial wet-type waste is presented. Firstly, the pomace was hydrothermally processed in a single solvent (water) and a binary solvent system (water mixed with isopropanol) at low and moderate processing temperatures (225 and 275 °C, respectively). More specifically, the focus was put on investigating the effect of operating conditions on the change in the yield distribution of bioproducts, particularly solid hydrochar. Also, the composition, textural properties, and morphology of hydrochars were examined by DRIFT and XRD, low-temperature nitrogen adsorption, and SEM, respectively. In the subsequent step, the upgrading of resultant hydrochars via fast pyrolysis by using microscale techniques (pyrolysis coupled with gas chromatography and mass spectrometry) and thermogravimetric analysis was done. The studies proved that the proposed approach allows to obtain alternative products exhibiting high energy density (21.9–29.3 MJ kg−1) that could be useful for power and heat generation. It was found that conversion in the binary solvent system involves a noticeably deeper decomposition of the pristine biomass structure. Furthermore, through two-stage processing, it is possible to obtain value-added chemicals, such as hydrocarbons, with the potential to serve as advanced biocomponents or reagents for the chemical industry.