Valorization of Sugar Beet Pulp via Torrefaction with a Focus on the Effect of the Preliminary Extraction of Pectins Paola Brachi,* ,§ Evelina Riianova, ⊥ Michele Miccio, † Francesco Miccio, ‡ Giovanna Ruoppolo, § and Riccardo Chirone § § Institute for Research on Combustion, National Research Council, P.le Tecchio 80, 80125 Napoli, Italy ⊥ Department of Production Safety and Industrial Ecology, Ufa State Aviation Technical University, K. Marks 12, 450077 Ufa, Russian Federation † Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy ‡ Institute of Science and Technology for Ceramics (ISTEC-CNR), via Granarolo 64, 48018 Faenza (RA), Italy ABSTRACT: An agro-industrial residue, i.e., sugar beet pulp, was taken into consideration in this work as a feedstock for valorization as a solid fuel and, potentially, as a source of valuable biochemicals obtainable from the torgas condensable fraction. To this end, an experimental program based on torrefaction of such a residue after pectin extraction (PE-SBP) was performed. The alternative scenario of raw sugar beet pulp (raw-SBP) torrefaction was also investigated for comparison. Raw biomasses and torrefaction products were analyzed by different techniques including thermogravimetric analysis and derivative thermogravimetry (TGA-DTG), Fourier transform infrared spectroscopy (FTIR), gas chromatrography coupled to mass spectrometry (GC/MS), and proximate and ultimate analyses. This allowed the comparative investigation of the role played by the pectin extraction method and the torrefaction temperature on the process performance and main properties of the resulting solid products. Outcomes showed that light torrefaction (200-240 °C) is a suitable and more energy-efficient process for production of high quality solid fuels from SBP. Moreover, it resulted that PE-SBP is better than raw-SBP as a feedstock due to its lower nitrogen and ash content. 1. INTRODUCTION Sugar beet is the second largest source of sugar across the world, after sugar cane. In 2009, approximately 20% of the world’s sugar production (153.4 million tons) was obtained from sugar beet. 1 Sugar beet pulp (SBP) is the main solid byproduct of the sugar beet industry. On a dry mass basis, about 130 kg of sugar and 50 kg of dried SBP can be obtained from 1 t. 2 Due to its high organic matter content (carbohydrates, protein, fat, oil, etc.), SBP represents a cheap (around 110 €/t dry matter) and abundant (e.g., the production in Europe is around 14 million t/y dry matter) source of valuable biomass and nutrients. 3 In detail, its carbohydrate (cellulose, hemicellulose, pectin, and others) content has been reported to be as high as 75-85% (w/w, dry basis) and its lignin content as low as 1-4% (w/w, dry basis). SBP contains approximately 25% wt pectin, 24% wt cellulose, and 36% wt hemicellulose. 4 At present SBP is mostly sold as animal feed at a relatively low price due to its relatively low protein content compared to the requirements of most ruminants, which entail the use of an extra protein source. 5 However, alternative uses of such valuable byproducts of the sugar industry are currently being investigated to enhance its valorization. These mostly include the use of SBP as a carbohydrate source for the production of (i) food fibers 5 to be incorporated into bread, cookies, spaghetti, and meat products and (ii) biofuels, especially liquid fuels such as bio-oil 6 and bioethanol. 7 Chen et al. 8 also investigated the use of SBP as a filler in poly(lactic acid) composites, whereas Pavier and Gandini 9 evaluated the possible use of SBP as a source of polyol for the production of urethanes and polyurethanes. Due to its high content of pectic polysaccharides, SBP could also be a potential source of pectins, which are substances currently used in industry mainly for their gelling and thickening properties. Pectins from SBP have poor gelling properties compared with commercial pectins from apple pomace or citrus peels under classical conditions. However, SBP pectins have already proved to have great potential for alternative applications that justify its extraction. In particular, these include the use of SBP pectins as (a) cloud stabilizers in drinks; 3 (b) water-absorbing agents in sanitary products; 3 and (c) substrates for the biosorption of copper, cadmium, and lead. 10 On the other side, pectin extraction from SBP leaves a solid residue, which has currently no known use and poses a disposal issue. In this context, the potential valorization of pectin-extracted sugar beet pulp (PE-SBP) as a solid fuel was taken into consideration in this work. The major challenge in using such a residue (PE-SBP) as an energy source lies in the operational and logistic limitations associated with its inherent chemical and physical properties. Pectin-free beet pulp, being of biological origin, has high oxygen content, low calorific value, low bulk density, high moisture content, pronounced hygroscopic behavior, and a strong tendency to biodegrade Received: June 21, 2017 Revised: August 5, 2017 Article pubs.acs.org/EF © XXXX American Chemical Society A DOI: 10.1021/acs.energyfuels.7b01766 Energy Fuels XXXX, XXX, XXX-XXX