Production of Sustainable Aviation Fuels by CO2Valorisationvia Combined Fermentation and Chemical Catalysis
Aviation stands out as one of the sectors with the highest impact in greenhouse gas (GHG) emissions due to their intensive reliance on fossil resources. This contribution is only expected to increase given the lack of foreseeable replacements for the fossil origin of its fuels, not easily attainable by other means due to the complex regulations and specifications they require. Therefore, increasing efforts are being made in order to obtain the same compounds present in traditional jet fuels albeit with a renewable origin. The present PhD Thesis aims at developing a four-step process combining biotechnology and chemistry for the production of Sustainable Aviation Fuels (SAF). First, CO2 is captured by bacteria and turned into acetate. Then, another type of engineered bacteria produces key chemicals like alcohols (ethanol, 1-butanol, isopropanol) and ketones (acetone, butanone) through fermentation. These chemicals are then upgraded through a series of chemical reactions to create hydrocarbons similar to those found in traditional jet fuels.
The biotechnology section focused on genetically modifying the bacterium Parageobacillus thermoglucosidasius to produce butanol. This involves metabolic engineering, where genes from other butanol-producing bacteria are introduced into the genome. Butanol titres after initial engineering reached 0.375 g/L of butanol, with further efforts made to improve this output by adjusting fermentation conditions, such as the dissolved oxygen levels, and optimizing specific enzymes involved in the process. The chemistry section dealt with upgrading the fermentation products into longer-chain hydrocarbons, suitable for jet fuel. Ketones are combined with alcohols using Pd/C catalysts with K3PO4, which after optimisation reached high selectivities towards the intermediate 6-undecanone. This longer ketone then had its oxygen content removed using palladium zeolite catalysts along with renewable hydrogen, finally obtaining long chain alkanes that are suitable for use as aviation fuels.
Principal Supervisor:
Professor Anders Riisager, DTU Chemistry
Co-supervisor:
Professor Alex Toftgaard Nielsen, DTU Biosustain
Examiners:
Professor Jochen Förster, DTU Biosustain
Senior Scientist Beatriz Galán, Spanish National Research Council, Spain
Lead Scientist Esben Taarning, Topsoe A/S
Chairperson:
Associate Professor Susanne Mossin, DTU Chemistry
Zoom: https://dtudk.zoom.us/j/63678539270