## 3 Results
### Detailed Analysis of the Economic Impact  
The following section investigates the economic impacts of fossil kerosene and SAFs in more detail. Analogous to the previous section, the total impacts are split into the shares associated with the fuel supply chain and flight operation (Figure 5), and the key drivers of the impacts are analyzed.  
With LC of around USD 2.59 per 100 pkm, fossil kerosene ranked best among the alternatives. The LC of all SAFs considered in this study were between 149% and 786% higher than the fossil variant. In general, the main contributor in the case of all fuels was the fuel supply chain. This was responsible for around 98-99% of the total impact, while flight operation was responsible for 1-2%. Due to the more mature and industrially implemented production processes, the LC of fossil kerosene were significantly lower than for SAFs. Although the fuel supply chain was mainly responsible for the LC with about 98% of the total impact, this corresponded to costs of just USD 2.53 per 100 pkm, significantly lower than the SAFs. The main driver of LC for fossil kerosene was the processing of crude oil into kerosene, which accounted for about 66% of LC. Only 2% of the total LC resulted from the distribution of fossil kerosene and its storage at the airport.  
The most promising SAFs concerning economic impacts were biokerosene and synthetic kerosene (SMR), with LC of USD 7.66 per 100 pkm and USD 6.34 per 100 pkm, respectively. This was due to the significantly higher costs of USD 7.56 for biokerosene and USD 6.34 for synthetic kerosene in the fuel supply chain. In the case of biokerosene, these resulted primarily from miscanthus cultivation, gasification to biogas, and the subsequent production of biomethane, which was used as feedstock for the SMR. In total, about 62% of the LC could be attributed to this. In the case of synthetic kerosene (SMR), a large part of the LC could be attributed to the upstream chain of natural gas, which was required as feedstock for the SMR and was responsible for 54% of the LC.  
From an economic perspective, SAFs based entirely on renewable sources performed the worst. Synthetic kerosene (PEM and SOEC) had the highest LC at USD 22.94 and USD 17.82 per 100 pkm, respectively. Here, hydrogen production was the main driver, accounting for 87% and 83% of the total LC, respectively. More precisely, most of the costs were related  
Figure 5: Comparison of the life cycle costs per 100 pkm for SAFs and fossil kerosene and breakdown of the impact scores regarding the fuel supply chain and flight operation.  
to energy demands, which were particularly high at 55 kWh and 38 kWh per kg hydrogen, respectively, and an electricity price in Germany of USD 0.21 per kWh. At the current market maturity of industrial hydrogen production based entirely on renewable sources, synthetic kerosene (PEM and SOEC) is not competitive from an economic perspective.  
Overall, the economic analysis shows that SAFs are not yet competitive with fossil kerosene. Without political measures (e.g., substitution, subsidy programs, or tax measures for non-SAFs), airlines will maintain their preference toward the less expensive fossil fuels.