Hydrothermal conversion of grape pomace: Detailed characterization of obtained hydrochar and liquid phase

Abstract

In this study, carbonization products of grape pomace (hydrochar and process water) have been thoroughly characterized in order to assess its fuel properties, physico-chemical composition and to optimize its production. The obtained detailed insight into transformations of the biomass during hydrothermal conversion between 180-220 degrees C revealed that the hydrochar obtained at 220 degrees C exhibits a considerable energetic potential, increased porosity and re-adsorption abbility. Hydrothermally induced structural changes in the obtained hydrochars were unveiled by thermal and morphology analysis, FTIR and NIR spectroscopy. Temperature increment caused a decrease in antioxidative capacity, anthocyanin and organic acid content in process water and simultaneous increase in total phenolic and individual organic components content. The overall effect of the reaction temperature on products characteristics was assessed by multivariate data analysis. Obtained results substantiated the suitability of hydrothermal conversion of grape pomace into highly valuable fuels and versatile products.