# Assessing the Carbon Intensity of e-fuels Production in European Countries: A Temporal Analysis
## 4 Conclusions & Perspective  
The major contribution of this paper is the quantification of the impact of electricity production (at high time resolution) and the effect of electricity exchange between different countries (at the time it occurs) on the carbon intensity of electricity and e-fuels. This is the most relevant aspect in determining whether any e-fuels produced are indeed \"green\" and to what extent they really contribute to the decarbonisation goals for transport. The results highlight that e-fuels, either hydrogen or fuels derived from it, can be produced using low-carbon intensity. The condition is to use electricity only when its carbon intensity is low enough, which significantly affects the potential operational load factor of an electrolysis unit. A reduced load factor means a reduced number of hours when low-carbon fuels can be produced, reduced operation power, or a combination of both. Thus, with the per unit of power capacity of electrolysis installed, this limits both the amount of hydrogen that can be produced and makes reaching economic viability more challenging. From that perspective, additional sources of income other than the fuel production itself may help. For instance, e-fuels could play a role in balancing the grid as storage, which could provide potential income for the provision of ancillary services to the grid. Indeed, even though combining environmental and economic performance is challenging, this is a necessary step to ensure the sustainable production of e-fuels. Making use of ENTSO-E data, covering the largest network of national grid operators in the world, we showed that exchanges of electricity between countries have the potential to dramatically change the carbon intensity of the national electricity mix. Some countries may have a carbon intensity of their production mix low enough to produce low-carbon e-fuels under the European legislative framework, but they may depend at some moments on electricity imports with a higher carbon intensity, which would result in an increase in the carbon intensity of their consumption mix above the limit. Another key parameter for the carbon intensity of e-fuels, whether hydrogen or derived fuels, is the considered temporal resolution. When considering an annual or monthly average of the carbon intensity, the country might satisfy (or not) the criteria of having an electricity carbon intensity low enough to produce low-carbon e-fuel over that period. However, with a finer time resolution, within that period, the carbon intensity of electricity may be low enough to be used, even if, on average, over the whole period, it is not, or the opposite. The risk of  
Figure 12: Influence of the considered time step on potential load factor for low-carbon e-fuel production. having a time step that is not fine enough is using electricity when the production is not sourced from low-carbon sources. Regarding the limits of this study, it is important to mention that massive electrolytic hydrogen production would require a massive amount of electricity and would involve major changes to the electricity mix to produce the expected low-carbon e-fuels. It would then become necessary to apply the proposed methods to prospective scenarios. This represents an interesting perspective, but that would require prospective production and exchanging time series between the considered territories, data the authors never found published in the scientific literature. In addition, it is important to remember that emissions related to the manufacture of infrastructures are not considered in the scope of this work; we only cover combustion emissions and upstream emissions related to fuel production. The inclusion of those emissions will necessarily increase the e-hydrogen footprint and lower the load factor below the threshold. Considering the importance e-hydrogen is expected to play inside the EU or outside for its international trading partners [45], the same methodology might be needed for the calculation of its carbon intensity.