From waste to food : optimising the breakdown of oil palm waste to provide substrate for insects farmed as animal feed

Waste biomass from the palm oil industry is currently burned as a means of disposal and solutions are required to reduce the environmental impact. Whilst some waste biomass can be recycled to provide green energy such as biogas, this investigation aimed to optimise experimental conditions for recycling palm waste into substrate for insects, farmed as a sustainable high-protein animal feed. NMR spectroscopy and LC-HRMS were used to analyse the composition of palm empty fruit bunches (EFB) under experimental conditions optimised to produce nutritious substrate rather than biogas. Statistical pattern recognition techniques were used to investigate differences in composition for various combinations of pre-processing and anaerobic digestion (AD) methods. Pre-processing methods included steaming, pressure cooking, composting, microwaving, and breaking down the EFB using ionic liquids. AD conditions which were modified in combination with pre-processing methods were ratios of EFB:digestate and pH. Results show that the selection of pre-processing method affects the breakdown of the palm waste and subsequently the substrate composition and biogas production. Although large-scale insect feeding trials will be required to determine nutritional content, we found that conditions can be optimised to recycle palm waste for the production of substrate for insect rearing. Pre-processing EFB using ionic liquid before AD at pH6 with a 2:1 digestate:EFB ratio were found to be the best combination of experimental conditions

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 Acces

Exploring the Effect of Water Content and Anion on the Pretreatment of Poplar with Three 1-Ethyl-3-methylimidazolium Ionic Liquids

We report on the pretreatment of poplar wood with three different 1-ethyl-3-methylimidazolium ionic liquids, [EMim][OAc], [EMim][MeSO3], and [EMim][HSO4], at varying water contents from 0–40 wt% at 100 °C. The performance was evaluated by observing the lignin and hemicellulose removal, as well as enzymatic saccharification and lignin yield. The mechanism of pretreatment varied between the ionic liquids studied, with the hydrogen sulfate ionic liquid performing delignification and hemicellulose hydrolysis more effectively than the other solvents across the investigated water content range. The acetate ionic liquid produced superior glucose yield at low water contents, while the hydrogen sulfate ionic liquid performed better at higher water contents and produced a recoverable lignin. The methanesulfonate ionic liquid did not introduce significant fractionation or enhancement of saccharification yield under the conditions used. These findings help distinguish the roles of anion hydrogen bonding, solvent acidity, and water content on ionic liquid pretreatment and can aid with anion and water content selections for different applications