Structural and chemical modifications of typical South African biomasses during torrefaction Lihle D. Mafu a , Hein W.J.P. Neomagus a,b,⇑ , Raymond C. Everson a,b , Marion Carrier c , Christien A. Strydom a , John R. Bunt b a School of Physical and Chemical Sciences, North-West University, Potchefstroom Campus, Private Bag X6001 Potchefstroom 2520, South Africa b School of Chemical and Minerals Engineering, Private Bag X6001, North-West University, Potchefstroom Campus, Potchefstroom 2520, South Africa c Aston University, EBRI, Bioenergy Research Group, Birmingham B4 7ET, United Kingdom highlights  Different fibre composition between woods and sweet sorghum bagasse.  Higher surface area increases after torrefaction for bagasse than wood.  Torrefaction reduced significantly hemicelluloses than cellulose.  Formation of acid-resistant was observed with torrefaction of bagasse.  Torrefaction treatment increases average crystallite diameter of biomass. article info Article history: Received 13 October 2015 Received in revised form 1 December 2015 Accepted 9 December 2015 Available online 14 December 2015 Keywords: Biomass Torrefaction CP-MAS 13 C NMR XRD abstract Torrefaction experiments were carried out for three typical South African biomass samples (softwood chips, hardwood chips and sweet sorghum bagasse) to a weight loss of 30 wt.%. During torrefaction, moisture, non-structural carbohydrates and hemicelluloses were reduced, resulting in a structurally modified torrefaction product. There was a reduction in the average crystalline diameter (L a ) (XRD), an increase in the aromatic fraction and a reduction in aliphatics (substituted and unsubstituted) (CPMAS 13 C NMR). The decrease in the aliphatic components of the lignocellulosic material under the torrefaction conditions also resulted in a slight ordering of the carbon lattice. The degradation of hemicelluloses and non-structural carbohydrates increased the inclusive surface area of sweet sorghum bagasse, while it did not change significantly for the woody biomasses. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Biomass utilization, either as a precursor for electricity generation or biofuel production, has received a lot of attention in the last decade in the wake of increasing calls for renewable energy utilisation. Waste biomass is of great interest as it avoids the competition between energy and food crops, which may assist with food security in the world (Aboyade et al., 2013). South Africa, amongst other African countries, produces large amounts of waste biomass from the paper industry, sugar industry as well as munic- ipal wastes (Damm and Triebel, 2008). These biomasses include wood chips (softwood and hardwood), sugarcane bagasse, sweet sorghum bagasse, dried corn cobs and corn stover (Aboyade et al., 2013; Damm and Triebel, 2008), having a large lignocellu- losic content, offering potential in thermochemical applications. Pre-treatment methods are often used to beneficiate the bio- mass, e.g. to ensure a reduction in oxygen, moisture, and smoking propensity of the generated fuel (Yang et al., 2014). Many pre- treatment methods have been studied to provide this highly sought ‘new biomass’ and the specific application seems to deter- mine the preferred pre-treatment method (Tumuluru et al., 2011). Often referred to as mild pyrolysis, torrefaction is most suited for thermochemical applications and is reported to upgrade biomass by producing a more hydrophobic fuel with an increased fixed car- bon content (Chen et al., 2015; Tumuluru et al., 2011; Wannapeera and Worasuwannarak, 2012; Yang et al., 2014). Torrefaction does not only reduce bulk and oxygenated discharges but torrefied biomass also has a higher energy yield and mass energy density http://dx.doi.org/10.1016/j.biortech.2015.12.007 0960-8524/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: School of Chemical and Minerals Engineering, North-West University, Potchefstroom Campus, Private Bag X6001 Potchefstroom 2520, South Africa. E-mail address: Hein.Neomagus@nwu.ac.za (H.W.J.P. Neomagus). Bioresource Technology 202 (2016) 192–197 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech