Structural and chemical modifications of typical South African biomasses during torrefaction

MAFU, L.; NEOMAGUS, H.; EVERSON, R.; CARRIER, M.; STRYDOM, C.; BUNT, J.
Bioresource Technology  202 (2016) 192-197.

DOI: 10.1016/j.biortech.2015.12.007

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 ¹³C 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.