# Comprehensive LCA of Biobased Sustainable Aviation Fuels and JET A-1 Multiblend
## 3 Results
### LCA of SAF  
Figure 2 shows the comparative life cycle environmental results of the considered sustainable aviation fuels. The results include all stages of biofuel supply from biomass production to supply and conversion and up to transport processes. Figure 1: System boundaries for SAF and multiblend assessment. The figure shows case B supply chain. SIP is not included in case A. The results clearly show that under the assumptions made, the HEFA concept was associated with the lowest potential environmental impacts. The advantages compared to ATJ and SIP concepts were most evident in the categories of agricultural land occupation (ALOP) and water depletion (WDP). As can be seen from the figures for ATJ (Figure 3a) and SIP (Figure 3c), ALOP and WDP were, for example, dominated by the biomass supply process. For both ATJ and SIP, this was mainly due to the use of arable land for maize and sugar cane cultivation, respectively, and the water requirements associated with the cultivation of these crops. While ATJ and SIP were based on the processing of cultivated biomass, tallow oil, a raw material declared as waste, was used for the HEFA concept. This meant that the assessment of the supply chain began with the transport of the tallow oil to the conversion plant, and upstream processes were not included. The terrestrial acidification potential (TAP) of ATJ and SIP production were also driven by biomass cultivation processes. This was due to the ammonium and nitrogen dioxide air emissions associated with the cultivation processes. The use of fossil fuels was the main factor for the impact categories of fossil depletion potential (FDP) and marine ecotoxicity potential (MEP) (primarily due to heavy metal emissions from the combustion of fossil fuels). In both FDP and MEPTInf, the ATJ concept showed the highest impacts, with the conversion process having the highest contribution. The reason for this was the use of fossil fuels to meet the process-specific demand for hydrogen, heat, and electricity. The contribution of biomass production process to both impact categories was primarily due to the use of fossil fuels for fertilizer production and the use of fossil fuels in agricultural machinery. The phosphate and phosphorous emissions causing freshwater eutrophication (FEP) also originated from the conversion and the biomass supply processes. This was not only due to the use of fertilizers in the cultivation processes but also again due to combustion emissions from fossil fuels. This type of illustration seen in Figures 2 and 3 was selected, on the one hand, to show the differences between the sustainable aviation fuels investigated here and, on the other hand, to show the shifting of the main drivers within the life cycle assessment of a process chain. Figure 2: Relative environmental impacts of SAF production. Figure 4 depicts the breakdown of climate change impacts for the assessed SAF. As can be seen, total GHG emissions of the considered SAF were between 3.1 (HEFA) and 35.8 gCO\({}_{2}\)-eq./MJ (ATJ). These relatively large differences could be explained based on a number factors. The significant differences in assessment of emissions from biomass supply were due to, on the one hand, the raw materials used and, on the other hand, the selected system boundaries. While the ATJ concept is based on cultivated biomass, the HEFA concept uses tallow oil, a raw material considered as waste. This meant the assessment of the supply chain started with the transport of the tallow oil to the conversion plant. Upstream processes associated with the provision of tallow oil (for example, the availability in a rendering plant) were therefore not included as they were outside of the selected system boundaries. The specific emissions associated with tallow oil supply were thus  
Figure 3: Environmental impacts of SAF production: (**a**) ATJ, (**b**) HEFA, and (**c**) SIP.