Towards an economical ionic liquid based biorefinery

Lignocellulosic biomass has the potential to be used as feedstock for the sustainable and carbon-neutral production of fuels, materials and chemicals. For the realisation of this potential, cost-effective fractionation of the biomass in different product streams is necessary. The work presented in this thesis focuses on the use of protic ionic liquids for the fractionation of various types of lignocellulosic biomass with the aim of achieving process improvements leading to a potential cost reduction at industrial scale. Firstly, the use of triethylammonium hydrogensulfate as a lower-cost alternative to more commonly used aprotic ionic liquids for the fractionation of the grass Miscanthus x giganteus has been shown. A cellulose enriched pulp giving high enzymatic saccharification yields was recovered after pretreatment under mild conditions. Subsequent process intensification showed that high saccharification yields can be obtained after as little as 15 min of pretreatment time. Secondly, the more easily grown yet more recalcitrant softwood pine was used as a feedstock. N,N-dimethylbutylammonium hydrogensulfate was found to be effective at producing a highly digestible cellulose pulp. Thirdly, waste wood from construction and demolition as well as pre-consumer construction wood containing various heavy metals (as preservatives and contaminants) were successfully fractionated. The biocide copper was quantitatively extracted from copper azole treated wood, allowing for the production of bioethanol via fermentation. The copper was shown to be recoverable via electrodeposition. The use of contaminated waste wood as a feedstock for the production of materials, fuels and chemicals not only eliminates an unresolved waste management problem but also increases the economic viability of the bioeconomy. The ionic liquid was shown to be recyclable at least six times without losing performance. Alongside the pulp, the obtained lignin was analysed using 31P and 2D HSQC NMR, gel permeation chromatography and elemental analysis in order to elucidate the lignin extraction mechanism. Open Access