One plant's waste, another industry's product
The 'New concepts for upgrading pulp mill waste streams to value-added chemicals' (Wacheup) project worked to identify means of upgrading residual products for producing bio-based chemicals from the manufacture of pulp and cork. The EU-funded team expected to uncover methods for exploiting pulp and cork mill low-value waste without affecting the primary quality of products. Good-quality lignin was successfully precipitated from black liquor, with three pre-treatment techniques successfully used for decreasing the filtration resistance of hardwood (HW) lignin. An abundant yet complex organic polymer, lignin is the main non-carbohydrate part of wood. It binds to cellulose fibres and strengthens cell walls. Results in this area pave the way for designing and optimising plants that extract and refine lignin from liquors in pulp mills. In the case of eucalyptus cooking, there is less xylan than there is lignin concentration. Compared to birch wood chips, eucalyptus wood chips contain only half as much xylan — about 15 % and 30 %, respectively. Researchers developed a combination filtration process for isolating and upgrading xylans from spent black liquors. The optimal point for xylan extraction was identified at about 80 minutes, at which time xylan concentration reaches a maximum. In work focusing on valorisation of bark/cork suberin, Wacheup results paved the way for new areas of research and development of renewable materials. Suberin is a fatty waterproof substance found in the cell walls of cork tissue in higher plants. Research revealed that suberin can be refined into reactive co-polyesters; this occurs without the use of organic solvents, but rather by employing 'green' enzyme catalysis. Overall, the successes of the Wacheup project open up new avenues of research in natural-based composites.
