Ionic liquid biorefining: lignocellulose deconstruction and bio-derived renewable polymers

This project will develop key aspects of an ionic liquid-based biorefinery, by developing optimal strategies for production of pure cellulose for biofuels and high-quality lignin for chemical upgrading. The focus will be on aspects of the deconstruction (pretreatment) process that control the quality and yield of biopolymers from both pure and mixed feedstocks.
Lignocellulosic biomass is the most viable, non-fossil feedstock for large-scale chemical and materials production in an integrated biorefinery, which can only be commercially viable if all components become value-added products. This project will develop efficient routes for the separation of biomass into lignin and carbohydrates, and convert those into renewable materials, demonstrating full pathways from raw material to useful products and biofuels.
A major challenge for biorefineries will be securing a sufficient and reliable supply of sustainably produced feedstock throughout the year. This presents problems for processing due to variation in lignocellulosic composition. While there are various fast-growing bioenergy crops (Miscanthus, switchgrass, willow) and agricultural wastes (wheat straw, corn stover, sugar cane bagasse) available, there are no coherent strategies for processing of mixed feedstocks in an integrated manner. In this project, we will compare IL deconstruction efficiency on several feedstocks of mixed composition, including native (virgin) bioenergy crops, agricultural wastes, and municipal wastes. The goal is to develop a robust, adjustable strategy for dealing with mixed feedstocks.
Our approach. We will separate lignin from carbohydrates as the first step of a biorefinery, building upon our recent success in biomass fractionation with low-cost mineral acid-based IL/water mixtures. To enable this we will determine the key variables controlling both biomass fractionation and recovery of ILs, evaluate their potential for manipulation and exploit these to design ILs for biomass fractionation.
We will use a range of 'protic' ILs, the family used in all IL industrial processes, because their simple acid-base chemistry makes them easy and cheap to prepare and recycle. We recently reported that [HSO4]- ILs with 20% water can quantitatively delignify biomass. The lignin is recovered as a separate fraction in a soluble form, creating a valuable feedstock solution.
We will also assess the impact of these ILs on lignin depolymerization, as this will be a major factor in selecting a suitable solvent system. The suitability of lignin for further valorisation will be an important part of this process - we have targetted several renewable polymers to replace fossil-derived products with lignin- or cellulose-derived alternatives. A project could also be directed in this area, depending on the interests of the researcher.
The quality of both the lignin and cellulose fractions will ultimately drive biorefinery applications. Suitable lignin for chemical catalytic valorisation and cellulose for biofuel production are the essential products of any renewable resource-driven bioeconomy.