Development of a process to valorise lignin

When fossil fuel reserves are exhausted, essential by-products of refining will no longer be available. Since these aromatic chemicals are used in many processes including the manufacture of plastics, detergents, fertilisers, pharmaceuticals and synthetic fibres it is vital that alternative sources become available. Lignin can be produced sustainably, it is renewable and a natural form of carbon storage. Importantly for this proposal, it is a complex polymer made of aromatic chemical building blocks, potential replacements for aromatic oil-refining by-products. However, to utilize lignin as a feedstock, the development of an efficient process that enables its specific depolymerization is necessary. The use of enzymes is generally considered the best approach to provide controlled lignin degradation1 and this project seeks to integrate previous enzymatic degradation work conducted by the Horsfall group with the pretreatments that allow cost effective manufacturing of aromatic feedstock chemicals from Sikta Spruce sawdust. Sitka spruce is the main productive conifer species grown in Scotland, it is a fast growing and high yielding conifer with a lignin content of 19.8 - 29.4% w/w. Annual production is currently ~6.3 million and is forecast to rise to 9.3 million by 2027.
This studentship seeks to test combinations of enzymes alongside established pretreatments to optimise lignin degradation. It will assess process efficacy through the use of assays and mass spectrometry, with iterative cycles of trial and improvement on the process. The disruption of lignocellulosic biomass to access cellulose and hemi-cellulose for biofuels has long been prioritised over the degradation of lignin to useful feedstock chemicals. As such, harsh pre-treatments with acids and alkalis or energy-intensive high-temperature and pressure conditions have produced recalcitrant lignin waste of little value. The development of a new process, which prioritises the valorisation of lignin, may also provide access to cellulose and hemi-cellulose without creating such waste and thus contribute to a more circular bioeconomy.