New Conversion Strategies and Analytical Tools for Lignin Valorisation

Currently, lignin is an underutilised waste material in the paper and pulping industry, and represents a significant portion of plant biomass waste. This is primarily due to its severe structural complexity and diversity, which impart varied and ill-defined macromolecular properties on different lignin samples. Thus, lignin is typically burned to provide process energy for the biorefineries/pulp-mills which generate it as a side product. However, with the efficiency of modern refinery technology, more lignin is generated than is required for the energy needs, and it thus acts as a bottleneck to the refining process. In order to maintain economic viability, alternative valorisation pathways are required for the lignin. Due to the aforementioned complexity and variance in structure, it was therefore critical to establish structure-property relationships, to better understand the macromolecular behaviour of each sample. Additionally, this section aimed to show how the structure of the lignin also impacts the properties of any materials derived from it. Another major focus of the thesis was the development of advanced spectroscopic-chemometric methods assist in more rapidly characterising the lignins, providing rapid access to a host of macromolecular properties, which otherwise require a variety of expensive analytical equipment, and cost vast amounts of time to acquire. The final section of the thesis focuses on the products of modern biomass refining processes, which are effectively modified monomers of the lignin. These in turn, were then chemically modulated to form a handful of different compounds, which could be polymerised to produce polyesters and polycarbonates, to show proof of concept of novel materials derived from lignin.