Comparative study of lignins from grass, residual cereal biomass and wood for conversion to biopolymers

Fossil fuel depletion has increased interest in the topic of biorenewable materials. Lignin, which is one of the main components of lignocellulosic biomass, has been traditionally seen as a waste in paper and pulp production. However, its chemical properties make it an ideal candidate for the development of new bio-based materials. Current demand for polyurethanes amounts to approximately 3 million tonnes, what represents approximately 7% of the demand for plastics in Europe. In turn, the global demand for phenol-formaldehyde resins is more than 2.5 million tonnes per year, and is expected to increase till approximately 16 million tonnes by 2016.

The use of lignin as a raw material could create a good alternative for the production of biopolymers.  However, there is currently a lack of understanding of how lignin composition and feedstock source relate to physico-chemical properties of lignin which is essential to identify optimal raw materials for applications in the chemical industry. Therefore, investigating the fundamental properties of lignin generated by different pretreatment processes and feedstocks can be beneficial to make the lignin component economically valuable.

The main aim of this work was to characterize lignin fractions produced from various feedstocks using an organosolv process and multiple processing technologies in terms of composition and suitability for production of polyurethanes and phenolic resins. Lignin characteristics were assessed for their purity (Klason lignin), solubility, thermal stability (thermogravimetric analysis), molecular weight (size-exclusion chromatography) and analysis of functional groups (spectroscopy methods, including FTIR, ³¹P-NMR). Results from these experiments will be presented.