| dc.description.abstract | Highlights
• Very high aqueous phase yields achieved (79.88%).
• Energy dense (38.85 MJ/kg) biocrude shows promise for further valorisation.
• While scientific work suggests that addition of a catalyst increases biocrude yields, this was not the case for a low temperature (240 ⁰C) reaction environment.
Increasing population, dwindling fossil fuel resources and the efforts towards reducing carbon emissions sets the stage for new energy sources to rise. Every major market in the worlds is moving towards greener and more sustainable solutions for their energy needs, aviation sector is one of them [1]. These problems and the scientific effort to solve them, caused an interest in abundant, renewable and carbon neutral energy sources such as biomass and the processes to valorise them. One such lignocellulosic biomass is brewers’ spent grains (BSG) [2]. Since BSG has already been treated in the brewery, it has a high moisture content. Also, a waste product, this makes BSG is a very good candidate as a feedstock for processes such as hydrothermal liquefaction (HTL) [3]. BSG and HTL products, such as biocrudes, have high potential as energy sources for sustainable fuel pathways [4]. New sustainable aviation fuels (SAFs), have numerous pathways in development and BSG and its HTL products have high potential to be further valorised in such way.
This thesis focuses on valorisation of BSG with HTL and characterisation of its products. Valorisation is aimed to be achieved with an optimisation model, since HTL can be a costly process, an optimised setting leads to lower costs. Parameters of the process will be optimised to obtain the maximum product yields possible in a low temperature environment.
Experiments were performed with temperature locked at 240 ⁰C with varying catalyst dosage (10 – 25% (w/w)), retention time (20 – 125 minute) and biomass to water ratio (1:4 to 1:10). Initial yield results were promising with 16.64% biocrude yield and 79.88% aqueous phase yield. High heating value (HHV) data shows maximum biocrude value of 38.85 MJ/kg. This shows that the products are more energy dense compared to the feedstock, with a value of 19.77 MJ/kg. FTIR analysis of the products indicates cellulose and hemicellulose degradations. Also, elemental analysis provides valuable compositional analysis, as Van Krevelen diagrams exhibit possible decarboxylation.
Keywords: Brewers’ spent grains (BSG), hydrothermal liquefaction (HTL), valorisation, biocrude, sustainable aviation fuels (SAFs) | |