| dc.description.abstract | The aviation sector is difficult to de-fossilize, with few alternatives to fossil jet fuel. The two alternatives that show the highest potential are sustainable air fuel (SAF) produced from either biomass or from CO2 derived from direct air capture (DAC) and renewable hydrogen. However, bio-based SAF (bio-SAF) and electro-SAF (e-SAF) both require substantially more land compared to the production of conventional jet fuel, as fossil sources have higher energy densities than biomass or renewable electricity. The current body of literature on sustainable aviation is missing an extensive land use comparison between bio-SAF and e-SAF production routes, while land use is an important environmental indicator of the energy sector. This research aims to fill that gap, by constructing a model which includes all necessary chemical conversions and maps the required utilities such as hydrogen, electricity and heat. The included routes are hydro-processed esters and fatty acids (HEFA), alcohol to jet (AtJ), biomass to liquid (BtL), CO2 hydrogenation and methanol upgrading (e-MeOH) and CO2 upgrading to SAF through Fischer-Tropsch synthesis (e-FT). Land should be used as efficiently as possible, so hybrid solar & wind farms and combinations of bio-SAF and e-SAF production are examined in this research.
The results show that e-SAF production uses 10 – 20 times less land compared to bio-SAF for the same amount of fuel production. This is mainly due to biomass harvests only taking place once a year, while CO2 capture and electricity production can take place continuously. However, e-SAF production requires 5 – 30 times as much electricity due to the large hydrogen demand, energy consumption of DAC and heat supply. As electricity is also becoming a scarcer resource, the trade-off between land and electricity requirements needs to be made for the production of SAF. It is expected that bio-SAF routes are a viable alternative to fossil jet fuel the next few decades as they are further in development and have lower costs compared to e-SAF. E-SAF routes are expected to be the better option towards 2050 when DAC and electrolyzers are further developed, costs have decreased and renewable electricity is more abundantly available. Combined routes are also an alternative, as electricity requirements are lower compared to individual e-SAF routes in exchange for slightly higher land use. | |
