Effect of steam explosion on the extraction of lignins from grass, residual cereal biomass and wood for the production of high-value products

Integration of lignin into multi-component materials has become a major biotechnological goal over the last 10 years. A major challenge is that lignin is difficult to isolate and generates very high amounts of solid residue compared to other components of lignocellulose. Therefore, investigating the effects of different pre-treatment processes is a prerequisite to optimize the extraction process.

A currently applied pre-treatment technology is steam explosion which achieves separation of biomass fibres by implementation of steam with sudden release of pressure, hence steam explosion.  In turn, methods for the chemical extraction of lignin include organosolv method. This technique can be applied to produce relatively pure, sulphur-free and highly hydrophobic lignin. It was postulated that combining these two processes would affect the chemical properties of lignins improving the efficiency of extraction and the quality of the product.

The main aim was to develop new methods for extraction of different lignin fractions, focusing on high extraction yields. In this study, lignin was extracted from grass (Miscanthus x giganteus),residual cereal biomass (wheat straw, corn stover) and wood (pine, willow) using the formic/acetic acid/water organosolv method with and without a steam explosion pretreatment in acid or alkaline conditions.  

The initial lignin content in starting material was measured using the Klason method and the final extraction yield was calculated. The amount of lignin extracted depended on the feedstock source and pretreatment. In the case of Miscanthus, a 94% yield was achieved when pre-treated with steam explosion with acid treatment. Results from these experiments will be presented.