Evaluation of thermal decomposition and antioxidant activity of crop residues and ionic liquid extracted lignin.

Effective use of crop residues as a source material for the production of energy and biochemicals requires a fundamental understanding of its thermal degradation properties and reaction kinetics. Furthermore, identification of applications for lignin and extractives is essential. Thermogravimetric analysis was used to determine the effect of extractives on the thermal decomposition behaviour of three crop residues, wheat straw, triticale straw and flax shives. Thermal decomposition behaviour and the kinetic parameters of lignin extracted with ionic liquid 1-ethyl-3-methylimidazolium acetate (IL [emin] Ac) were determined. For all samples, rate of thermal decomposition increased over 200-400°C. Above 400°C, the lignin samples displayed the highest thermal stability while the extractive-free biomass samples demonstrated the highest degree of thermal degradation. The apparent activation energy (Ea ) values for the IL [emin] Ac extracted lignin samples were a determined using the Kissenger method and the Coats-Redfern method. The range of Ea values for the lignin a extracted from wheat straw, triticale straw and flax shive were: 40-135, 40-165 and 40-131 kJ mol⁻¹, respectively. The antioxidant activity of the crop residues along with extractives and lignins were determined. These results can be used to determine processing conditions and for development of novel bioenergy and biochemical products.