A Simplified Biorefinery Concept for the Valorization of Sugar Beet Pulp: Ecofriendly Isolation of Pectin as a Step Preceding Torrefaction

The valorization of sugar beet pulp (SBP) from sugar industry as a source of valuable substances has been taken in consideration in this work. In particular, the eco-friendly extraction of pectins with citric acid has been adopted as a preliminary step in a simplified biorefinery concept where the pectin-free solid is subsequently subjected to a torrefaction treatment for its upgrading into a commodity solid biofuel. An extensive physicochemical characterization of the raw feedstock and the isolated pectins has also been performed, which may be useful to identify suitable application routes. Results show that the extraction conditions [1.5 pH, 90 °C, 4 h contact time and SBP-to-solvent ratio of 1:30 (g/mL)] selected in this work allow obtaining a relatively high yield (25% wt, db) of high methoxyl pectins (with some impurities), which exhibit the same colorimetric characteristics of commercial citrus pectins and are not conducive to microbial growth. A further purification step of isolated pectins is required to improve the emulsifying properties. Graphical Abstract: [Figure not available: see fulltext.].