What will it cost to decarbonise aviation? A study on Irish SAF production

New EU regulations will require at least 230 kilotonnes (kt) of sustainable aviation fuel (SAF) in the Irish aviation sector by 2035. Research at University College Dublin has explored what it will cost to produce this within the country’s borders.

SAF, a type of e-fuel (synthetic fuel produced using captured carbon dioxide and renewable hydrogen), is critical for decarbonising the aviation sector.

A minimum of 5% of Europe’s jet fuel will need to be SAF by 2035, according to the ReFuel EU Aviation Initiative, which is part of the 'Fit for 55' package (European Commission, 2023a). For Ireland, which consumes 50% more jet kerosene than it does petrol (SEAI, 2024a), this will equate to 232kt of domestic SAF demand by 2035.

A project recently conducted at University College Dublin investigated what it would cost to produce all this within Ireland's borders. The study investigated the optimum SAF production route for production based in Ireland, at a scale sufficient to meet the projected 2035 domestic demand.

One-quarter the size of Whitegate refinery

The findings show that to process at least 230kt of SAF annually, a production facility equivalent to approximately one-quarter the size of Whitegate refinery will be required.

Furthermore, 1,100 to 1,600MW of electrolysers and a total of 1,000kt of Direct Air Carbon Capture (DAC) capacity will be needed. This will require 8.37TWh of renewable electricity, which amounts to 3GW of installed offshore wind dedicated exclusively to e-fuel production.

Leveraging Ireland’s biogas potential can help reduce reliance on the less proven DAC technology. However, in all cases the costs are substantial, with Irish SAF production costing 3.72-6.96 €/kg: six to twelvefold more than the current price of Jet Fuel A1 (Jet-A1, 2025).

While policies such as ReFuelEU are important for combatting climate change, studies such as this highlight the challenges in achieving decarbonisation targets. Key questions still must be answered on how this will affect the greater economy and society, and whether additional or alternative policies will be needed to enable a just energy transition.

Sustainable aviation fuel (SAF) is needed – and lots of it

The aviation sector represented 3.8%-4% of total EU greenhouse gas (GHG) emissions in 2023, the second largest source of GHG emissions after road transport in the transport sector (European Commission, 2023b).

This is a big cause of concern as air transport is a rapidly growing sector, with EU air passenger numbers increasing by 19.3% from 2022 to 2023 (Eurostat, 2024).

To address this issue, the ReFuelEU Aviation Initiative has been introduced as part of the 'Fit for 55' package (European Commission, 2023a). This policy mandates a proportion of all jet fuel used within the EU aviation sector to be sustainable aviation fuel (SAF), with the level increasing every five years.

Figure 1. Mandated proportion of synthetic and unspecified SAF in aviation fuel from ReFuelEU. Unspecified SAF can be comprised of biofuels or synthetic SAF.

SAF is a renewable substitute for fossil-fuel based jet fuel and can consist of either biofuels or synthetic fuels. Biofuels are fuels produced from biochemical, chemical, thermochemical, or mechanical refining of biological feedstocks such as oil crops, starch crops, sugar crops, wood, grasses, aquatic biomass, or organic residues (European Commission, 2021).

While they are currently the most common SAF used, there are concerns that a significant increase in the demand for biofuels will compete with food production (Subramaniam et al., 2020). Therefore, ReFuelEU limits the proportion of biofuels as SAF.

By 2035, 5% of all aviation fuel will need to be synthetic. For the Irish aviation sector, this amounts to an expected 232 kilotonnes of synthetic SAF (Avolon, 2023): enough to fill 116 Olympic-sized swimming pools¹.

Irish resources for SAF production – offshore wind and biogas

Synthetic fuels are commonly referred to as electro-fuels or e-fuels, as they are produced using renewable hydrogen produced with electrolysis, carbon dioxide (CO₂) captured from renewable sources, and chemical synthesis methods such as methanol-to-kerosene or Fischer-Tropsch processes (Bube et al., 2025).

Due to the energy-intensive nature of e-fuel production, access to reliable, low-cost renewable energy is an essential factor. Ireland has significant potential in this regard, due to the country's renewable resources – in particular, offshore wind. Ireland ranks as the leading market for offshore wind generation capacity, with an estimated potential of 85GW (KPMG, 2023).

While the current cost of electricity from Irish offshore wind is 86 €/MWh (Department of the Environment, Climate and Communications, 2024), costs are expected to fall with increasing deployment (SEAI, 2024b).

However, affordable electricity is not the only thing needed for e-fuel production; significant quantities of CO₂ are also needed. Given current decarbonisation efforts, future CO₂ supply will be limited to DAC or point sourcing from renewable sources such as biogas production.

While only 30 DAC plants are currently in operation worldwide, the global market for DAC plants is rapidly developing, with 84 DAC plants expected to be operational by the end of the year (Balaji, 2025). This includes the massive Stratos project in Texas, which when completed will be capable of capturing 500 kilotonnes of CO₂ per year (1PointFive, 2023). However, given Ireland’s current non-existent DAC operations, the construction of a mega-scale HT DAC plant by 2035 is unlikely.

On the other hand, with its large agricultural sector Ireland has a large potential for CO₂ capture via biogas production. The SEAI estimates biomass availability for anaerobic digestion of about 5PJ when considering only waste-based feedstocks and 11PJ when considering all feedstock types (SEAI, 2017).

If the maximum amount of CO₂ is captured from this resource, between 438 and 972 kilotonnes of CO₂ could be available. Furthermore, if the biogas is combusted in a combined heat and power plant, the produced electricity and thermal heat can be utilised later in the synthesis process.

Challenges and costs

To analyse the feasibility of using solely domestically produced synthetic SAF (e-kerosene) production to meet the domestic demand of 232kt, 11 different possible process routes were investigated (Table 1). These process routes comprised of three main stages:

Renewable water electrolysis, in which polymer electrolyte membrane electrolyzers (PEMEL) or alkaline electrolysers (AEL) can be used;
Carbon capture, in which high-temperature (HT) DAC, low-temperature (LT) DAC, or biogas point sources can be used; and
Chemical synthesis, in which methanol-to-kerosene (M-2-K) or Fischer-Tropsch synthesis (FT) can be used.

Each technology was sized and costed based on the current state-of-the-art as well as anticipated technology improvements by 2035, which have been investigated in several recent studies (Villarreal Vives et al., 2023; Park et al., 2025; Ali Khan et al., 2023; Reksten et al., 2022; Fasihi et al., 2019; Cabello et al, 2022; Atsonios et al., 2023; Bube et al., 2025; Perez-Uresti et al., 2019).

Transport of the hydrogen and CO₂ to the e-kerosene production plant is also considered with costs taken from literature (Ortiz-Cebolla et al., 2021; Stollaroff et al., 2021). The preparation and sale of by-products, including oxygen, e-Naphtha, and e-diesel, were also included (Assuncao et al., 2024; Mike, 2025; Ravi et al., 2023).

The findings show that depending on the technology pathway, the following is needed:

11 to 16 x 100MW electrolysers;
1 x 1,000kt HT DAC plant, 3 x 360kt LT DAC plants, or 72 x 5MW biogas plants; and
3 x 100 kt e-fuel synthesis plants.

The levelised cost of e-kerosene production ranges from 3.72 €/kg to 6.96 €/kg across the process routes investigated. While it only achieves a levelised cost of €4.04/kg, the optimum production route is identified as Route 11, which involves a combination of HT DAC at a scale of 550,000 tonnes and biogas plants that utilise all waste-based feedstocks.

Route 11 is investigated as a process route as it addresses the limitations related to the scale of the HT DAC plant required while avoiding competition with food resources by using only waste-derived feedstocks for biogas production. Furthermore, it addresses the need for a renewable thermal heat source, with the added benefit of producing electricity, which reduces the energy intensity of the process.

This route involves 11 x 100MW PEM electrolysers for hydrogen production, a 550kt HT DAC plant, 33 x 5MW biogas plants for CO₂ sourcing, and 3 x 100kt per year Fischer-Tropsch synthesis plants.

Furthermore, this route requires 8.37TWh of renewable electricity, 88.3% of which is consumed during the electrolysis stage. This energy demand poses a significant challenge, given the projected electricity supply by 2030.

It will require 2GW of offshore wind capacity solely for green hydrogen production, and a further 19.8% of the planned 5GW offshore wind target (Department of the Environment, Climate and Communications, 2024), which had originally been intended to boost the renewable share of the grid. This electrical energy requirement totals to 43% of the projected offshore wind energy production for 2030.

The total capital cost of process Route 11 is projected to be €2.35bn, with the capital cost of the electrolysers being the most significant capital cost, accounting for 52.8% of the total capital cost of the e-kerosene production project.

This substantial initial capital outlay makes the capital costs a key consideration in terms of economic viability of the e-kerosene production project. Furthermore, given that time discounting was not included in this study, it is likely the true costs will be even higher.

Social impacts: Paying for the privilege to fly?

Given the current price of 0.62 €/kg (Jet-A1, 2025), e-kerosene produced in Ireland is at a minimum of 6.5 times more expensive than Jet Fuel A1. Based on the blended rate and assuming e-kerosene demand is met through local sources, this means future aviation fuel could cost at least two times more in 2035. Aviation fuel price is a key component of airfares, meaning that flying may become much more expensive in the future.

Whether or not this is a good thing is up for debate. Research has shown that cost has a measurable impact on transport demand (Litman, 2024), where higher prices reduce elastic demand, which leads to emissions savings.

Indeed, according to a study carried out for the European Commission, taxing aviation fuel (and consequently increasing the cost of flying) would reduce passenger demand and aviation emissions by 11% (European Federation for Transport and Environment, 2019). However, some, such as the CEO of Ryanair, argue that policies which increase the cost of aviation disproportionately affect island nations and have knock-on effects for the economy (Irish Examiner, 2022).

While the European Commission report as well as a study conducted for the Irish case (de Bruin and Yakut, 2022) found that aviation taxes would have a negligible impact on jobs or the economy as a whole, this was largely due to the additional government revenue, which was found to offset the negative effects on employment and GDP.

Increases in aviation costs due to the integration of SAF would not produce such revenues; on the other hand, the introduction of SAF production in Ireland would create new jobs and revenues. Additional research is needed to better understand these trade-offs.

There is also the question of how consumers will react to the new cost and associated privilege to fly, particularly in Ireland, where alternative modes of transport are limited (de Bruin and Yakut, 2022).

A recent poll found that while there is some public support for taxing aviation fuel in Ireland, most people would prefer targeted policies taxing private jets, with few accepting the idea of flying less to achieve climate targets (O’Sullivan, 2023).

Even small changes which affect household spending can cause significant negative emotions, hindering trust in government and policy acceptance.

For example, the introduction of water charges in Ireland were eventually scrapped, as they were met with widespread anger and resistance (Rodriguez-Sanchez et al., 2018). Given the substantial increase to aviation costs expected, social impacts and acceptance should be examined in further detail.

Conclusion

Ultimately, the energy transition will require a combination of technologies and policies, with the ReFuelEU initiative being a welcome step towards decarbonisation of the aviation sector. However, this research shows that the cost of producing SAF within Ireland is substantial, requiring significant amounts of electricity and infrastructure.

The increased costs of integrating this fuel into the aviation sector will increase the cost of flying, which could have significant implications for the economy and society.

It is therefore critical to better understand trade-offs associated with this policy and consider whether there are additional or alternative strategies to ensure Ireland’s resources are being used to the utmost efficiency in achieving clean and affordable energy for all.

Authors: Ben Toole is a final year student in the school of Chemical & Bioprocess Engineering Student, University College Dublin. Charlene Vance is a postdoctoral researcher in the School of Chemical and Bioprocess Engineering, University College Dublin. Eoin Syron is an Associate Professor in the School of Chemical and Bioprocess Engineering, University College Dublin.

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