Synthetic fuels may be a cheaper way to achieve climate-neutral aviation

Synthetic fuels may be a cheaper way to achieve climate-neutral aviation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Analysis Synthetic fuels may be a cheaper way to achieve climate-neutral aviation Nicoletta Brazzola, Amir Meskaldji, Anthony Patt, Tim Tröndle, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3981416/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 11 Jan, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Mitigating the impact of aviation on climate change faces significant challenges due to growing demand and limited scalable mitigation options. As a result, direct air capture (DAC), a novel technology, may gain prominence due to its versatile applications as either an emissions offset (DACCS) or a synthetic fuel production technology (DACCU). Through a comprehensive analysis of cost-effectiveness, life-cycle emissions, energy consumption, and technology scale-up, we explore the conditions under which synthetic fuels from DACCU can become competitive with an emit-and-offset strategy. We find that DACCU is competitive with an emit-and-offset strategy once we explicitly include non-CO 2 climate impacts and under favorable conditions such as low electricity and high fossil fuel prices and emissions pricing. By highlighting strategic interventions that favor these conditions and thus enhance the competitiveness of DACCU in the aviation sector, our results provide valuable insights into how policymakers could move the aviation sector away from fossil fuels. Earth and environmental sciences/Environmental social sciences/Climate-change mitigation Earth and environmental sciences/Environmental sciences/Environmental impact Earth and environmental sciences/Environmental social sciences/Energy and society/Energy economics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Aviation has historically contributed to approximately 4% of anthropogenic climate warming 1 . About two-thirds of this is attributed to non-CO 2 effects, such as contrail cirrus cloud formation or indirect effects due to nitrous oxide emissions 2–5 . While aviation’s historical contribution to climate change may appear small, its role in the future could be significant due to the expected growth of the sector and the challenges of mitigating its emissions 6–9,9–11 . The effects of viable decarbonization options, such as operational improvements and efficiency gains, are currently jeopardized by rising demand 12–14 , and the switch to biofuels is constrained by biophysical limits, such as the availability of sustainable biomass, which is also in demand for other mitigation purposes 15–17 . While some mitigation technologies, such as hydrogen and electric aircraft, could theoretically curb all emissions, they are not yet technically feasible, especially for long-haul flights, and would require a complete renewal of the global aviation fleet 18–21 . This led to the emergence of two additional mitigation strategies: offsetting aviation emissions with carbon removals 22–26 and deploying renewable Fischer-Tropsch synthetic fuels from air-captured CO 2 and green hydrogen 12,27–29 . To ensure scalability, both solutions could rely on direct air capture (DAC), as this technology has relatively small land and water footprints and does not require biomass 17,30–33 . DAC can be used either in combination with CO 2 storage to offset aviation emissions (as direct air carbon capture and storage [DACCS]) or to produce synthetic fuels via Fischer-Tropsch synthesis (as direct air carbon capture and utilization [DACCU]). In addition to its potential for scalability, especially if deployed in remote areas 31,34 , the use of DAC to tackle aviation’s climate impacts could benefit climate mitigation in a larger sense; bearing the high initial costs of this technology can be seen as an equitable strategy 35 to overcome the steepest segment of its learning curve 36–39 and realize its economic viability for other applications. Financing improvements in DAC via increases in ticket prices would indeed fall most heavily on middle-to-high income consumers and households 40,41 but provide long-term benefits for the entire world by making the technology ready for large-scale carbon removal 37,38,42 , which will be necessary to remedy overshoots of a Paris-aligned carbon budget 43,44 . On this background, we explore the use of DAC for medium-term mitigation of the aviation sector’s climate impacts and investigate the conditions under which the use of DACCU-based synthetic fuels could be cost-effective than offsets via DACCS. Previous techno-economic assessments have concluded that DACCS is a more cost-effective option for achieving CO 2 -neutral aviation globally 22,45 . However, they also noted that these cost benefits may not materialize because they are based on uncertain assumptions 45 and that DACCS offers fewer co-benefits, such as potential mitigation of non-CO 2 impacts 2,46,47 and alignment with fossil fuel phase-outs 45 . The only study that compared the deployment of DACCS and DACCU to achieve climate neutrality concluded that it is unrealistic to rely entirely on DACCU-based fuels for European aviation fuel consumption if green hydrogen production is to take place only in Europe 26 . In this study, we aim to broaden the discussion by offering a global perspective on DAC deployment to achieve CO 2 and climate neutrality in aviation. The global focus is justified by emerging trends in countries such as Chile, Saudi Arabia, Australia, and Morocco, which are positioning themselves as producers of cheap renewable energy and exporters of green hydrogen thanks to their abundant land and renewable energy resources 48,49 . In addition, recognizing the imperative to emancipate aviation from fossil entanglements 50 and societal preferences for DACCU over DACCS 51 and, more generally, for direct emissions reductions over the offsets 52–54 , we set out to identify the conditions under which DACCU can become cost-competitive with DACCS and even with fossil fuels. By examining the drivers of future costs and policy implications, we present a comprehensive analysis that contributes to the knowledge base and provides decision-makers with actionable insights to enable DACCU to take off. Results Scenarios and framework Our study examines two key technology scenarios for achieving CO 2 and climate neutrality in the global aviation sector by 2050. In the DACCU scenario, synthetic fuels produced from green hydrogen and CO 2 captured by DAC lead to a gradual substitution of fossil fuels, eventually replacing conventional jet fuels entirely by 2050. This substitution follows an S-shaped curve, according to technology diffusion theories 55–59 . Conversely, the DACCS scenario focuses on the incremental DACCS-based offsetting of continued fossil jet fuel use. To ensure comparability, the share of emissions offsets follows the same S-shaped curve of DACCU deployment, reaching 100% by 2050. Our analysis includes two different 2050 goals for the aviation sector. The first is to achieve CO 2 neutrality, that is, to reduce CO 2 emissions to net-zero by 2050. In the DACCS pathway, this means offsetting CO 2 emissions only. In the DACCU pathway, fuel substitution is assumed to fully eliminate CO 2 emissions (except for indirect emissions, cf. Methods). Since DACCU-based fuels are expected to burn cleaner 46,47 , this pathway also achieves a partial mitigation of the non-CO 2 effects. Therefore, the climate benefits of the two pathways are not equal under a CO 2 neutrality target. The second target, climate neutrality, on the other hand, includes non-CO 2 effects and thus enables a more balanced comparison of the two technology pathways. In fact, to achieve climate neutrality both pathways must neutralize any residual non-CO 2 effect with the deployment of DACCS. A schematic of how the different pathways and a business-as-usual with fossil kerosene achieve different targets is shown in Fig. 1 . Our analysis combines these different technologies and climate target scenarios while assuming rising aviation demand (cf. Methods). This comprehensive framework enables a holistic comparison of DACCU, DACCS and conventional aviation based on fossil kerosene in terms of costs, energy use, and climate impacts. Emit-and-offset is cheaper under a CO neutrality target, but not under a climate neutrality target We first calculate the costs of the two technology pathways to achieve CO 2 and climate neutrality under our standard input assumptions (see Methods and Supplementary Tables 1–3). For CO 2 neutrality, the DACCS pathway is significantly less costly than the DACCU pathway, which it outperforms by about €200 billion in 2050 (Fig. 2 ) and €120 billion in 2060 (see Supplementary Fig. 4). This cost difference is mainly due to the high electricity and capital costs of electrolysis in the DACCU pathway, which is essential for synthetic fuel production. The cost comparison under CO 2 neutrality does not capture the full benefits of DACCU-based fuels because the reduction in non-CO 2 impacts due to cleaner synthetic fuels is not reflected in the cost (see Supplementary Fig. 1). Both the DACCS and DACCU pathways achieve substantially higher costs than a business-as-usual scenario with continued fossil jet fuels use, which is cheaper than the DACCU scenario by over €500 billion. Under climate neutrality, where the climate impacts of the two pathways are identical, the DACCU pathway has significant cost advantages over DACCS, which it outperforms by over €280 billion in 2050. The higher cost of the DACCS pathway is mainly attributable to the higher carbon removal rates required to offset non-CO 2 emissions, which are higher than in the DACCU pathway (see Supplementary Figs. 1–2). The large offset requirements are due to the sustained demand growth assumed in the analysis. However, assuming no growth of the sector still results in a competitive advantage of the DACCU pathway (see Fig. 5 b). Despite its economic advantage, the DACCU pathway results in higher electricity consumption due to energy-intensive electrolysis (cf. Supplementary Fig. 3). This limits its scaling potential to regions with abundant and affordable renewable energy. Finally, both DACCS and DACCU pathways are more expensive alternatives compared to the continued use of fossil kerosene, highlighting the role of policy interventions to propel these pathways forward. Emit-and-offset is more expensive than synthetic fuels on a cost-per-avoided-emissions basis, but is more efficient in scaling DAC Looking at the total costs for abated emissions relative to the business-as-usual (Fig. 3 a), the resulting picture is almost opposite than the one drawn when looking at absolute yearly costs (Fig. 2 ). Under the CO 2 neutrality target, the DACCS pathway has the highest costs per emissions abated, reaching abatement costs over €500/tCO 2 e compared to less than €200/tCO 2 e for the DACCU pathway. This difference arises because DACCS only includes costs associated with reducing CO 2 emissions. Conversely, in the DACCU pathway, the abatement extends to non-CO 2 emissions, thereby increasing the total volume of abated emissions over which the costs are distributed. Under the climate neutrality target, where both technology pathways abate the same level of emissions, DACCU again emerges as more cost-effective because of the smaller amounts of carbon removals required to offset the remaining non-CO 2 effects. Apart from mitigating the aviation sector, both options could also serve as a means of scaling up DAC. This rationale is rooted in the potential role that the aviation sector could play as a niche for the initial deployment of DAC, as the sector is bound to face significant costs in mitigating its emissions due to the lack of affordable alternatives. This perspective results in a picture opposite to that of cost-effective abatement. We find that as the volume of DAC installations increases, the DACCS pathway consistently offers a lower cost per DAC unit than the DACCU pathway (Fig. 3 b). DACCU incurs higher costs due to the production of green hydrogen. This has a significant impact on the cost per unit of DAC installed. The price difference for a CO 2 -neutral flight with DACCS and DACCU is small We further assess the increase in price per flight per passenger to achieve CO 2 and climate neutrality via the DACCS and DACCU pathways. In the context of CO 2 neutrality, offsetting aviation CO 2 emissions with DACCS proves to be more economical than fueling the same flight with DACCU-based synthetic fuels. However, the cost difference per passenger is modest, ranging from approximately €20–55 for long-haul flights (London-New York and London-Perth) to only €4 for a short-haul flight from London to Berlin. While the overall cost per passenger increases to achieve climate neutrality, DACCU becomes cheaper than DACCS, saving about €35–100 per passenger on long-haul flights and €6 on short-haul flights. We also assessed the impact on the cost of flying relative to the expected future cost of flying in a business-as-usual scenario with continued use of fossil fuels. The projected increase in ticket prices for flights in 2050 ranges between 15–30% for DACCU and 8–20% for DACCS to achieve CO 2 neutrality, rising to up to 40% (DACCU) and 60% (DACCS) to achieve climate neutrality. However, the increase in price is not the same for all flights, since the contribution of fuel costs to ticket prices varies for different routes, as the price is adjusted to demand and to endure competition. While the increases in price due to a complete neutralization of the climate effects of a flight may seem substantial, they lie well below the range of current variance in prices. Indeed, the difference in price between buying a ticket two weeks or two months in advance is, on average, 400% for the London-Berlin route, over 100% for the London-New York route, and 70% for the London-Perth route 60 . Cheaper electricity and high fossil jet fuel prices can make DACCU cheaper than DACCS (and even business-as-usual) even under CO 2 neutrality To understand the conditions under which DACCU-based fuels could be economically competitive in the less-advantageous CO 2 -neutrality scenario with an emit-and-offset strategy via DACCS and even with the business-as-usual with continued use of fossil jet fuel, we perform local sensitivity analyses on the most influential parameters (see Supplementary Table 1–3). Figure 5 a shows that DACCU can become more cost effective than DACCS when electricity prices fall below 0.015 €/kWh. This threshold is well below the 2023 price of the cheapest renewable energy sources, onshore wind 61 , but not unachievable in the future through technology learning, optimal siting, or in moments of excess production of renewable electricity, for example on sunny summer days in grids with a high share of solar PV 62,63 . In contrast, even when powered by free electricity, DACCU is still not competitive with the business-as-usual. Conversely, rising fossil fuel prices prove transformative: DACCU becomes cost-competitive with DACCS at a fossil fuel price of €0.9/L and with the business-as-usual scenario at €1.8/L. Such high costs would not only make DACCU a more economical option, but would also discourage demand. However, doubling the current price of fossil jet fuel would require dedicated political ambition. Accelerated technological learning and steeper learning curves benefit both DACCU and DACCS scenarios. Thus, even a learning rate of 50% - higher than has been observed historically for fast-learning technologies such as solar PV - cannot close the gap between the DACCU and DACCS pathways. In summary, extremely optimistic changes in fossil fuel or electricity prices are required to make DACCU cost-competitive with DACCS or business-as-usual by varying a single parameter. However, a synergy of lower electricity prices with either rising fossil fuel costs or higher technological learning could accelerate a scenario where DACCU outperforms DACCS or even fossil jet fuels under optimistic but possible conditions (see Supplementary Figs. 6–8). Pricing aviation climate impacts or limiting DACCU operation to times when excess electricity is available is sufficient to make DACCU cheaper than DACCS Given the observed sensitivity of DACCS and DACCU performance to highly uncertain input assumptions, we examine the potential impact of different policies that affect these assumptions. Figure 6 shows the cost difference of DACCU compared to DACCS (Fig. 6 a) and fossil jet fuel (6b) under different policies affecting some of the key input variables (see Supplementary Table 4). Pricing emissions internalizes the impact of continued fossil jet fuel emissions and thus acts similarly to increasing the price of fossil fuels, while also internalizing the environmental costs of life-cycle emissions for both DACCS and DACCU. Conversely, pricing CO 2 emissions alone cannot make DACCU cost-competitive with DACCS since, under CO 2 neutrality, it applies only to indirect emissions, which are higher in the DACCU pathway (see Supplementary Fig. 1). On the other hand, pricing all aviation-related climate impacts can significantly favor the DACCU pathway, which already becomes more cost-effective than the DACCS pathways at €30/tCO 2e* . Pricing emissions is also crucial to make DACCU economically competitive with fossil jet fuels. However, the prices on emissions need to be extremely high, starting at €500/tCO 2 for CO 2 emissions alone and at least €100/tCO 2e* for all aviation-related impacts. In contrast to direct subsidies based on synthetic fuel production, which are not sufficient to make DACCU competitive with DACCS even at €500/t fuel (which corresponds to about €1600/tCO 2 DACCU-based fuels), a strategic approach is to leverage cheap electricity (below €0.01/kWh). Policies, such as seasonal restrictions aligned with periods of electricity surplus, could achieve this by limiting DACCU-based synthetic fuel production to periods of significantly cheaper surplus electricity. However, this approach comes with the constraint of limiting the volume of DACCU-based synthetic fuels that can be produced. While limiting the number of operating hours could increase the weight of capital expenditures per DACCU output, and thus lead to potential cost increases not accounted for in our modelling 64 , it could also reduce the deterioration, and thus extend the lifetime, of costly components of the electrolyzers and DAC, namely the stack and adsorbent. Discussion In this study, we investigate the conditions under which aviation mitigation via DACCU-based synthetic fuels becomes cost-competitive with an emit-and-offset strategy via DACCS. We found that these conditions are realized by either ( 1 ) ambitious climate targets for the aviation sector that consider the non-CO 2 impacts of aviation, or ( 2 ) policies that internalize the cost of unabated emissions or limit DACCU to the use of excess, cheap electricity. In addition, our analysis highlights that achieving CO 2 neutrality through DACCU increases flight ticket prices only slightly relative to the DACCS pathway and even relative to a business-as-usual pathway. This small price difference for consumers sheds light on the attractiveness of DACCU, which has a lower cost per avoided emissions and is consistent with broader societal goals of climate mitigation and fossil fuels phase-out. These findings mark a departure from previous studies 22,26 , which favored DACCS due to conservative assumptions about future electricity prices (which exceed current wind and solar PV prices) and carbon-intensive energy mixes, resulting in higher lifecycle emissions of DACCU. Furthermore, due to their regional focus on Europe, where land availability is scarce, Sacchi et al. concluded that the land use of the energy-intensive DACCU pathway is a bottleneck under a scenario of continued demand growth for the aviation sector. While their regional land availability constraint does not apply to our global analysis, spatial considerations may indeed affect the cost at which the DACCU pathway could be realized due to the spatial distribution of electricity costs and the potential need for additional transportation infrastructure from remote locations. The efforts needed to enable CO 2 neutral and, especially, climate neutral flying may not be feasible. In fact, more than 2 GtCO 2 of DAC would need to be installed by 2050 to achieve CO 2 neutrality, rising to 7 GtCO 2 if the goal is to offset fossil jet fuel emissions to achieve climate neutrality. These amounts of DAC far exceed the projections of novel CDR methods by 2050 in Integrated Assessment Models simulations consistent with < 2°C targets 31,42,43,65 . However, the assumed growth rate up to 2050 (roughly 50 to 60% annually) is in line with that assumed by Integrated Assessment Models for the years between 2040–2080 31 and with that observed historically for solar PV 66 . On the other hand, by 2050, the DACCU pathway will require over 15 PWh of electricity to produce the amount of synthetic fuels necessary to fully meet global aviation demand if this continues to grow. Given that in 2021 the global renewable energy produced amounted to 8 PWh 67 , this energy demand would require a massive scale-up of renewable energy. However, DACCU’s renewable energy requirements are compatible with estimates of the total technical renewable energy potential (170–270 PWh according to Angliviel de La Beaumelle et al., 2023) . The superiority of DACCU in our results also hinges on uncertain variables, particularly the effectiveness of DACCU-based synthetic fuels in mitigating non-CO 2 impacts. While early empirical evidence is consistent with this trend 46,47,69 , the limited number of studies evaluating the impacts of synthetic fuels, coupled with the inherent uncertainty surrounding aviation’s non-CO 2 effects, introduces a degree of uncertainty. Notably, our analysis explicitly accounts for these uncertainties, and while they could significantly alter the absolute costs of DACCS and DACCU, their relative merit mostly remains unchanged. By shedding light on the conditions that make DACCU cost-competitive, our analysis can guide policymakers in designing strategies to facilitate the competitiveness of DACCU with both a emit-and-offset pathway relying on DACCS and a business-as-usual scenario. These strategic policy interventions could be justified based on the drawbacks of the DACCS pathway associated with its reliance on fossil jet fuels and the climate mitigation benefits of DACCU fuels. Methods In this study, we combined techno-economic modelling with life cycle assessment to compare the costs of mitigating the aviation sector by either compensating aviation emissions with DACCS or by replacing the whole volume of jet fuel with DACCU-based synthetic fuels, as shown in Fig. 7 . Demand and fuel scenarios All scenarios are based on the same demand for jet fuel, which is derived from a combination of historical data 5 from 1990 to 2018 with estimates of future demand until 2060. These are based on the assumptions of full recovery to pre-covid levels by 2024–2025 and on a 2% growth from 2024 to 2060, which are consistent with projections from various studies 10,70–75 . In addition to the total fuel demand, we also project the total annual distance flown by applying a 2% increase in efficiency, consistent with the International Civil Aviation Organization’s target 76 , to the historical relationship between distance flown and amount of fuel burned 5 . While this relationship may change in the future due to an increase in long-haul flights 9,77 that burn more fuel per kilometer 78 , its effect would not significantly alter the results of our analysis, as shown in our sensitivity analysis (see Fig. 5 a and Supplementary Fig. 9). As detailed in the “Scenarios and Framework” section, we consider two different mitigation pathways for aviation, one based on continued reliance on fossil jet fuel and offsetting through DACCS, and the other based on the gradual substitution of fossil fuels with DACCU-based synthetic fuels. Although the American Society for Testing Material D7566 standard 79 currently allows only up to 50% synthetic fuels blends, we assume that aircraft will operate on 100% DACCU-based synthetic fuels by 2050, being expected that blends up to 100% will be certified in due course, so that planes can fully run on synthetic fuel. Similarly, we model an upscaling of DACCS that enables full offsetting of aviation emissions by 2050, simplistically assuming no constraints on the rate of adoption of this technology. Emissions and offsets To calculate the amount of direct emissions from fossil jet fuel combustion, we apply the relationships between fossil jet fuel and CO 2 , water vapor, sulfur dioxide, soot, and NO x emissions reported by Lee et al. 5 . Contrail cirrus formation was calculated using the relationship between the distance flown contrail length, also reported in Lee et al. 5 . To calculate the emissions and contrail clouds formation of DACCU-based fuels, we follow the approach described in Brazzola et al. 25 (see their Supplementary Table 2) and propagate their uncertainty ranges throughout the analysis. The direct flight emissions then drive the demand for carbon removals via DACCS to offset their climate impact. The amount of removals is further determined by ( 1 ) the specific climate target chosen (i.e., CO 2 or climate neutrality, see Fig. 1 ), and ( 2 ) the lifecycle emissions of each technology pathway. First, to achieve CO 2 neutrality, we simplistically assume that we can fully compensate the climate impact of one ton of CO 2 by removing an equivalent amount via DACCS, neglecting the uncertainties of this relationship 80,81 . To achieve climate neutrality, we compensate for the non-CO 2 effects with DACCS based on the GWP* metric following the approach of Brazzola et al. 25 and using their ‘Gold’ definition of climate neutrality 25 . Thereby, we use and propagate throughout the analysis the uncertainties in the relationship between non-CO 2 emissions and their effective radiative forcing reported in Lee et al. 5 . Finally, we also offset through DACCS the lifecycle emissions due to the material and energy footprint of the two pathways. We calculate lifecycle emissions for both fossil fuels, DACCU-based fuels and DACCS. For fossil jet fuels, we considered the well-to-tank emissions from Moretti et al. 82 , which reflect European averages. Future reductions in oil refining emissions are based on the oil industry decarbonization prospects 83 , leading to a progressive decrease in well-to-tank emissions for fossil jet fuels. Material footprints are based on values for the production of required adsorbents and DAC modules by Deutz and Bardow 84 ; values for electrolysers by Delpierre et al. 85 ; values for CO electrolysis production units from Adnad and Kibria 86 . In addition, we calculated the energy requirements of all technologies involved and applied an electricity carbon footprint for an average global electricity grid 84 , assuming high decarbonization efforts over time leading to near net-zero emissions in 2060. As the synthesis of DACCU-based fuels is a multi-functional unit process with by-products, notably diesel, we assume the production of 0.82 tons of diesel per ton of jet fuel 22 . The lifecycle inventory of the unit processes up to the Fischer-Tropsch unit was then allocated to jet fuel by means of mass allocation (resulting in a 54.5% share for jet fuel). Techno-economic assessment of DACCS and DACCU pathways Finally, we calculate the energy consumption and capital costs of each technology and fuel included in the DACCS and DACCU pathways from 2020 to 2060. This includes the cost of fossil jet fuel, electricity and heat consumption, CO 2 transport and storage, and the capital costs of DAC, CO 2 reduction, electrolysis, and Fischer-Tropsch synthesis. For both pathways, we consider a low-heat solid-sorbent DAC system. While high-temperature liquid-solvent DAC may be more energy-efficient for the production of DACCU-based fuels, there are currently no plants that operate completely without burning natural gas 87 . As a result, using liquid-solvent DAC to produce jet fuel may result in net CO 2 emissions. We moreover assume a fixed cost of 20 €/tCO 2 for CO 2 transport and storage as in Becattini et al. 22 , based on the assumption that DACCS would be optimally located next to storage sites. For the production of DACCU-based synthetic fuels, we introduce some variance by considering four different combinations of two water electrolysers (either polymer membrane or alkaline electrolysers) and two CO 2 reduction methods (electrochemical CO 2 reduction and reverse-water-gas-shift). While we also calculate total costs for each technology configuration (cf. Supplementary Fig. 9), in the main results we use an average of the costs of all four possible configurations since we cannot predict which technology will ultimately prevail more established due to the low technological maturity, uncertain future development, and trade-offs in terms of cost and energy intensity of different technologies involved in DACCU-based synthetic fuel production. We first derive the installed capacities of each technology from the amounts of synthetic jet fuel required and from calculations of DACCS-based offset, as explained in the previous sections. To calculate their costs and energy consumption, we apply the parameters and assumptions summarized in Supplementary Tables 1–3. To calculate changes in energy efficiency, we polynomially interpolate between current values and future estimates (see Supplementary Table 2). In the case of CAPEX, we apply a learning rate following Eq. 1: $$CAPEX\left(t\right)=CAPEX\left({t}_{0}\right)*{\left(\frac{{Q}_{t}}{{Q}_{{t}_{0}}}\right)}^{-b}$$ ( 1 ) Where Q is the quantity of installed capacity of a technology and b equals \({log}_{2}\left(1-LR\right)\) , and LR is the learning rate. To calculate the increase in ticket price per passenger for three representative flights, we first calculate the cost of achieving CO 2 or carbon neutrality per kilometer flown each year. We then assume that the non-fuel cost of tickets will remain constant in the future, while replacing the cost of fuel with the cost of achieving either CO 2 or climate neutrality, including the cost of DACCS and DACCU. The relevant parameters for these calculations are shown in Supplementary Table 4. Finally, we conduct a local sensitivity analysis on key parameters highlighted in Supplementary Table 1–3, including those associated with alternative policy scenarios outlined in in Supplementary Table 5. To ensure comparability, we systematically vary uncertain input parameters by fixed percentages, which are right-skewed towards increases in the input assumption to accommodate the constraint that many parameters cannot be reduced below − 100% due to the impracticality of negative values. References Klöwer, M. et al. Quantifying aviation’s contribution to global warming. Environ. Res. Lett. 16 , 104027 (2021). Burkhardt, U., Bock, L. & Bier, A. Mitigating the contrail cirrus climate impact by reducing aircraft soot number emissions. Npj Clim. Atmospheric Sci. 1 , 1–7 (2018). Kärcher, B. Formation and radiative forcing of contrail cirrus. Nat. Commun. 9 , 1824 (2018). Lee, D. S. et al. Aviation and global climate change in the 21st century. Atmos. Environ. 43 , 3520–3537 (2009). Lee, D. S. et al. The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018. Atmos. Environ. 244 , 117834 (2021). Airbus. Global Market Forecast 2018-2037, Global Networks, Global Citizens . (2018). Boeing. Commercial Market Outlook 2021-2040. https://www.boeing.com/commercial/market/commercial-market-outlook/ (2021). Dray, L. et al. Cost and emissions pathways towards net-zero climate impacts in aviation. Nat. Clim. Change 12 , 956–962 (2022). Gössling, S. & Humpe, A. The global scale, distribution and growth of aviation: Implications for climate change. Glob. Environ. Change 65 , 102194 (2020). Grewe, V. et al. Evaluating the climate impact of aviation emission scenarios towards the Paris agreement including COVID-19 effects. Nat. Commun. 12 , 3841 (2021). Terrenoire, E., Hauglustaine, D. A., Gasser, T. & Penanhoat, O. The contribution of carbon dioxide emissions from the aviation sector to future climate change. Environ. Res. Lett. 14 , 084019 (2019). Gössling, S. & Humpe, A. Net-zero aviation: Time for a new business model? J. Air Transp. Manag. 107 , 102353 (2023). Larsson, J., Elofsson, A., Sterner, T. & Åkerman, J. International and national climate policies for aviation: a review. Clim. Policy 19 , 787–799 (2019). Scheelhaase, J., Maertens, S., Grimme, W. & Jung, M. EU ETS versus CORSIA–A critical assessment of two approaches to limit air transport’s CO2 emissions by market-based measures. J. Air Transp. Manag. 67 , 55–62 (2018). Committee on Climate Chnage. Biomass in a Low-Carbon Economy . https://www.theccc.org.uk/publication/biomass-in-a-low-carbon-economy/ (2018). Dooley, K., Christoff, P. & Nicholas, K. A. Co-producing climate policy and negative emissions: trade-offs for sustainable land-use. Glob. Sustain. 1 , (2018). Smith, P. et al. Biophysical and economic limits to negative CO2 emissions. Nat. Clim. Change 6 , 42–50 (2016). Gnadt, A. R., Speth, R. L., Sabnis, J. S. & Barrett, S. R. H. Technical and environmental assessment of all-electric 180-passenger commercial aircraft. Prog. Aerosp. Sci. 105 , 1–30 (2019). Noland, J. K. Hydrogen Electric Airplanes: A Disruptive Technological Path to Clean Up the Aviation Sector. IEEE Electrification Mag. 9 , 92–102 (2021). Peeters, P., Higham, J., Kutzner, D., Cohen, S. & Gössling, S. Are technology myths stalling aviation climate policy? Transp. Res. Part Transp. Environ. 44 , 30–42 (2016). Schäfer, A. W. et al. Technological, economic and environmental prospects of all-electric aircraft. Nat. Energy 4 , 160–166 (2019). Becattini, V., Gabrielli, P. & Mazzotti, M. Role of Carbon Capture, Storage, and Utilization to Enable a Net-Zero-CO2-Emissions Aviation Sector. Ind. Eng. Chem. Res. 60 , 6848–6862 (2021). Becken, S. & Mackey, B. What role for offsetting aviation greenhouse gas emissions in a deep-cut carbon world? J. Air Transp. Manag. 63 , 71–83 (2017). Bergero, C. et al. Pathways to net-zero emissions from aviation. Nat. Sustain. 6 , 404–414 (2023). Brazzola, N., Patt, A. & Wohland, J. Definitions and implications of climate-neutral aviation. Nat. Clim. Change 12 , 761–767 (2022). Sacchi, R. et al. How to make climate-neutral aviation fly. Nat. Commun. 14 , 3989 (2023). Scheelhaase, J., Maertens, S. & Grimme, W. Synthetic fuels in aviation – Current barriers and potential political measures. Transp. Res. Procedia 43 , 21–30 (2019). Terwel, R. & Kerkhoven, J. Carbon Neutral Aviation with Current Enginge Technology: The Take-off of Synthetic Kerosene Production in the Netherlands . 62 . https://kalavasta.com/assets/ reports/Kalavasta_Carbon_Neutral_Aviation.pdf (2018). Timmons, D. & Terwel, R. Economics of aviation fuel decarbonization: A preliminary assessment. J. Clean. Prod. 369 , 133097 (2022). Fuhrman, J. et al. Food–energy–water implications of negative emissions technologies in a +1.5 °C future. Nat. Clim. Change 10 , 920–927 (2020). Fuhrman, J. et al. The role of direct air capture and negative emissions technologies in the shared socioeconomic pathways towards $\mathplus$1.5 °C and $\mathplus$2 °C futures. Environ. Res. Lett. 16 , 114012 (2021). Terlouw, T., Treyer, K., Bauer, C. & Mazzotti, M. Life Cycle Assessment of Direct Air Carbon Capture and Storage with Low-Carbon Energy Sources. Environ. Sci. Technol. 55 , 11397–11411 (2021). The Royal Society. Net Zero Aviation Fuels: Resource Requirements and Environmental Impacts . (London, UK, 2023). Ali, M. et al. Recent advances in carbon dioxide geological storage, experimental procedures, influencing parameters, and future outlook. Earth-Sci. Rev. 225 , 103895 (2022). Andreoni, P., Emmerling, J. & Tavoni, M. Inequality repercussions of financing negative emissions. Nat. Clim. Change 1–7 (2023) doi:10.1038/s41558-023-01870-7. Küng, L. et al. A roadmap for achieving scalable, safe, and low-cost direct air carbon capture and storage. Energy Environ. Sci. (2023) doi:10.1039/D3EE01008B. Meckling, J. & Biber, E. A policy roadmap for negative emissions using direct air capture. Nat. Commun. 12 , 2051 (2021). Nemet, G. F. How Solar Energy Became Cheap: A Model for Low-Carbon Innovation . (Routledge, 2019). Young, J. et al. The cost of direct air capture and storage can be reduced via strategic deployment but is unlikely to fall below stated cost targets. One Earth 0 , (2023). Owen, A., Burke, J. & Serin, E. Who pays for BECCS and DACCS in the UK: designing equitable climate policy. Clim. Policy 22 , 1050–1068 (2022). Addepalli, S., Pagalday, G., Salonitis, K. & Roy, R. Socio-economic and demographic factors that contribute to the growth of the civil aviation industry. Procedia Manuf. 19 , 2–9 (2018). Nemet, G. F. et al. Near-term deployment of novel carbon removal to facilitate longer-term deployment. Joule 0 , (2023). IPCC. Global Warming of 1.5°C.An IPCC Special Report on the Impacts of Global Warming of 1.5°C above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change, Sustainable Development, and Efforts to Eradicate Poverty . https://www.ipcc.ch/site/assets/uploads/sites/2/2019/06/SR15_Full_Report_High_Res.pdf (2018). IPCC. Summary for Policymakers. in Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge University Press, Cambridge, UK and New York, NY, USA, 2022). Cames, M., Chaudry, S., Göckeler, K., Kasten, P. & Kurth, S. E-Fuels versus DACCS . https://www.transportenvironment.org/wp-content/uploads/2021/08/2021_08_TE_study_efuels_DACCS.pdf (2021). Braun-Unkhoff, M., Riedel, U. & Wahl, C. About the emissions of alternative jet fuels. CEAS Aeronaut. J. 8 , 167–180 (2017). Voigt, C. et al. Cleaner burning aviation fuels can reduce contrail cloudiness. Commun. Earth Environ. 2 , 1–10 (2021). PwC. Green hydrogen economy - predicted development of tomorrow. PwC https://www.pwc.com/gx/en/industries/energy-utilities-resources/future-energy/green-hydrogen-cost.html (2023). World Energy Council. World Energy Insights: Executive Summary Regional Insights Into Low-Carbon Hydrogen Scale-Up . https://www.worldenergy.org/assets/downloads/World_Energy_Insights_Executive_Summary_Regional_insights_into_low-carbon_hydrogen_scale_up_April_2022.pdf?v=1680701563 (2022). Malm, A. & Carton, W. Seize the Means of Carbon Removal: The Political Economy of Direct Air Capture. Hist. Mater. 29 , 3–48 (2021). Arning, K. et al. Same or different? Insights on public perception and acceptance of carbon capture and storage or utilization in Germany. Energy Policy 125 , 235–249 (2019). Arning, K., Linzenich, A., Engelmann, L. & Ziefle, M. More green or less black ? How benefit perceptions of CO2 reductions vs. fossil resource savings shape the acceptance of CO2-based fuels and their conversion technology. Energy Clim. Change 2 , 100025 (2021). Markusson, N., McLaren, D. & Tyfield, D. Towards a cultural political economy of mitigation deterrence by negative emissions technologies (NETs). Glob. Sustain. 1 , e10 (2018). Satterfield, T., Nawaz, S. & St-Laurent, G. P. Exploring public acceptability of direct air carbon capture with storage: climate urgency, moral hazards and perceptions of the ‘whole versus the parts’. Clim. Change 176 , 14 (2023). Geels, F. W. Technological transitions as evolutionary reconfiguration processes: a multi-level perspective and a case-study. Res. Policy 31 , 1257–1274 (2002). Kemp, R., Schot, J. & Hoogma, R. Regime shifts to sustainability through processes of niche formation: The approach of strategic niche management. Technol. Anal. Strateg. Manag. 10 , 175–198 (1998). Kemp, R. & Volpi, M. The diffusion of clean technologies: a review with suggestions for future diffusion analysis. J. Clean. Prod. 16 , S14–S21 (2008). Roberts, C. et al. The politics of accelerating low-carbon transitions: Towards a new research agenda. Energy Res. Soc. Sci. 44 , 304–311 (2018). Rogers, E. M. Diffusion of Innovations. J. Pharm. Sci. 52 , 612 (1963). Kayak. Search Flights, Hotels & Rental Cars | KAYAK. https://www.kayak.com/ (2023). IRENA. Renewable Power Generation Costs in 2022. https://www.irena.org/Publications/2023/Aug/Renewable-Power-Generation-Costs-in-2022 (2023). Kost, C. et al. Levelized Cost of Electricity - Renewable Energy Technologies . https://www.ise.fraunhofer.de/en/publications/studies/cost-of-electricity.html (2021). Grahn, M. et al. Review of electrofuel feasibility—cost and environmental impact. Prog. Energy 4 , 032010 (2022). IRENA. Green Hydrogen Cost Reduction: Scaling up Electrolysers to Meet the 1.5C Climate Goal . (2020). Fuhrman, J. et al. Diverse carbon dioxide removal approaches could reduce impacts on the energy–water–land system. Nat. Clim. Change 1–10 (2023) doi:10.1038/s41558-023-01604-9. Odenweller, A., Ueckerdt, F., Nemet, G. F., Jensterle, M. & Luderer, G. Probabilistic feasibility space of scaling up green hydrogen supply. Nat. Energy 7 , 854–865 (2022). IEA. Renewable Electricity – Analysis . https://www.iea.org/reports/renewable-electricity (2022). Angliviel de La Beaumelle, N. et al. The Global Technical, Economic, and Feasible Potential of Renewable Electricity. Annu. Rev. Environ. Resour. 48 , 419–449 (2023). Riebl, S., Braun-Unkhoff, M. & Riedel, U. A Study on the Emissions of Alternative Aviation Fuels. J. Eng. Gas Turbines Power 139 , (2017). Chen, C.-C. & Gettelman, A. Simulated 2050 aviation radiative forcing from contrails and aerosols. Atmospheric Chem. Phys. 16 , 7317–7333 (2016). Dray, L. et al. Cost and emissions pathways towards net-zero climate impacts in aviation. Nat. Clim. Change 12 , 956–962 (2022). IATA. Passenger Demand Recovery Continued in 2021 but Omicron Having Impact. https://www.iata.org/en/pressroom/2022-releases/2022-01-25-02/ (2021). IEA. World Energy Outlook 2021 . 386 https://www.iea.org/reports/world-energy-outlook-2021 (2021). Klöwer, M. et al. Quantifying aviation’s contribution to global warming. Environ. Res. Lett. 16 , 104027 (2021). U.S. Energy Information Administration. International Energy Outlook - U.S. Energy Information Administration (EIA). https://www.eia.gov/outlooks/ieo/tables_side_xls.php (2021). International Civil Aviation Organisation. Long term global aspirational goal (LTAG) for international aviation. https://www.icao.int/environmental-protection/Pages/LTAG.aspx (2022). Bain & Company. Air Travel Forecast to 2030: The Recovery and the Carbon Challenge. Bain https://www.bain.com/insights/air-travel-forecast-interactive/ (2023). Filippone, A. Advanced Aircraft Flight Performance . (Cambridge University Press, 2012). Anuar, A., Undavalli, V. K., Khandelwal, B. & Blakey, S. Effect of fuels, aromatics and preparation methods on seal swell. Aeronaut. J. 125 , 1542–1565 (2021). Zickfeld, K., Azevedo, D., Mathesius, S. & Matthews, H. D. Asymmetry in the climate–carbon cycle response to positive and negative CO2 emissions. Nat. Clim. Change 11 , 613–617 (2021). Zickfeld, K. et al. Net-zero approaches must consider Earth system impacts to achieve climate goals. Nat. Clim. Change 13 , 1298–1305 (2023). Moretti, C., Moro, A., Edwards, R., Rocco, M. V. & Colombo, E. Analysis of standard and innovative methods for allocating upstream and refinery GHG emissions to oil products. Appl. Energy 206 , 372–381 (2017). Griffiths, S., Sovacool, B. K., Kim, J., Bazilian, M. & Uratani, J. M. Decarbonizing the oil refining industry: A systematic review of sociotechnical systems, technological innovations, and policy options. Energy Res. Soc. Sci. 89 , 102542 (2022). Deutz, S. & Bardow, A. Life-cycle assessment of an industrial direct air capture process based on temperature–vacuum swing adsorption. Nat. Energy 6 , 203–213 (2021). Delpierre, M., Quist, J., Mertens, J., Prieur-Vernat, A. & Cucurachi, S. Assessing the environmental impacts of wind-based hydrogen production in the Netherlands using ex-ante LCA and scenarios analysis. J. Clean. Prod. 299 , 126866 (2021). Adnan, M. A. & Kibria, M. G. Comparative techno-economic and life-cycle assessment of power-to-methanol synthesis pathways. Appl. Energy 278 , 115614 (2020). McQueen, N. et al. Cost Analysis of Direct Air Capture and Sequestration Coupled to Low-Carbon Thermal Energy in the United States. Environ. Sci. Technol. 54 , 7542–7551 (2020). Smith, S. M. et al. The State of Carbon Dioxide Removal - 1st Edition . http://dx.doi.org/10.17605/OSF.IO/W3B4Z (2023) doi:10.17605/OSF.IO/W3B4Z. IRENA. Making the Breakthrough: Green Hydrogen Policies and Technology Costs . https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2020/Nov/IRENA_Green_Hydrogen_breakthrough_2021.pdf?la=en&hash=40FA5B8AD7AB1666EECBDE30EF458C45EE5A0AA6 (2021). Christensen, A. Assessment of Hydrogen Production Costs from Electrolysis: United States and Europe . https://theicct.org/publication/assessment-of-hydrogen-production-costs-from-electrolysis-united-states-and-europe/ (2020). Zang, G. et al. Synthetic Methanol/Fischer–Tropsch Fuel Production Capacity, Cost, and Carbon Intensity Utilizing CO2 from Industrial and Power Plants in the United States. Environ. Sci. Technol. 55 , 7595–7604 (2021). Jouny, M., Luc, W. & Jiao, F. General Techno-Economic Analysis of CO2 Electrolysis Systems. Ind. Eng. Chem. Res. 57 , 2165–2177 (2018). Shin, H., Hansen, K. U. & Jiao, F. Techno-economic assessment of low-temperature carbon dioxide electrolysis. Nat. Sustain. 4 , 911–919 (2021). Moretti, C. Reflecting on the environmental impact of the captured carbon feedstock. Sci. Total Environ. 854 , 158694 (2023). Gabrielli, P., Gazzani, M. & Mazzotti, M. The Role of Carbon Capture and Utilization, Carbon Capture and Storage, and Biomass to Enable a Net-Zero-CO2 Emissions Chemical Industry. Ind. Eng. Chem. Res. 59 , 7033–7045 (2020). Schmidt, P., Weindorf, W., Roth, A., Batteiger, V. & Riegel, F. Power-to-Liquids: Potentials and Perspectives . (2016). Sutter, D., van der Spek, M. & Mazzotti, M. 110th Anniversary: Evaluation of CO2-Based and CO2-Free Synthetic Fuel Systems Using a Net-Zero-CO2-Emission Framework. Ind. Eng. Chem. Res. 58 , 19958–19972 (2019). Yates, J. et al. Techno-economic Analysis of Hydrogen Electrolysis from Off-Grid Stand-Alone Photovoltaics Incorporating Uncertainty Analysis. Cell Rep. Phys. Sci. 1 , 100209 (2020). Kopp, M. et al. Energiepark Mainz: Technical and economic analysis of the worldwide largest Power-to-Gas plant with PEM electrolysis. Int. J. Hydrog. Energy 42 , 13311–13320 (2017). Alfian, M. & Purwanto, W. W. Multi-objective optimization of green urea production. Energy Sci. Eng. 7 , 292–304 (2019). Schmidt, P., Batteiger, V., Roth, A., Weindorf, W. & Raksha, T. Power-to-Liquids as Renewable Fuel Option for Aviation: A Review. Chem. Ing. Tech. 90 , 127–140 (2018). Nosherwani, S. A. & Neto, R. C. Techno-economic assessment of commercial ammonia synthesis methods in coastal areas of Germany. J. Energy Storage 34 , 102201 (2021). Schmidt, O. et al. Future cost and performance of water electrolysis: An expert elicitation study. Int. J. Hydrog. Energy 42 , 30470–30492 (2017). Treyer, K., Sacchi, R. & Bauer, C. Life Cycle Assessment of Synthetic Hydrocarbons for Use as Jet Fuel: ‘Power-to-Liquid’ and ‘Sun-to-Liquid’ Processes. (2022). Liu, C. M., Sandhu, N. K., McCoy, S. T. & Bergerson, J. A. A life cycle assessment of greenhouse gas emissions from direct air capture and Fischer–Tropsch fuel production. Sustain. Energy Fuels 4 , 3129–3142 (2020). Rosental, M., Fröhlich, T. & Liebich, A. Life Cycle Assessment of Carbon Capture and Utilization for the Production of Large Volume Organic Chemicals. Front. Clim. 2 , (2020). Doty, F. D., Doty, G. N., Staab, J. P. & Holte, L. L. Toward Efficient Reduction of CO2 to CO for Renewable Fuels. in 775–784 (American Society of Mechanical Engineers Digital Collection, 2010). doi:10.1115/ES2010-90362. Matute, G., Yusta, J. M. & Correas, L. C. Techno-economic modelling of water electrolysers in the range of several MW to provide grid services while generating hydrogen for different applications: A case study in Spain applied to mobility with FCEVs. Int. J. Hydrog. Energy 44 , 17431–17442 (2019). Reksten, A. H., Thomassen, M. S., Møller-Holst, S. & Sundseth, K. Projecting the future cost of PEM and alkaline water electrolysers; a CAPEX model including electrolyser plant size and technology development. Int. J. Hydrog. Energy 47 , 38106–38113 (2022). Terlouw, T., Bauer, C., McKenna, R. & Mazzotti, M. Large-scale hydrogen production via water electrolysis: a techno-economic and environmental assessment. Energy Environ. Sci. (2022) doi:10.1039/D2EE01023B. Elsernagawy, O. Y. H. et al. Thermo-economic analysis of reverse water-gas shift process with different temperatures for green methanol production as a hydrogen carrier. J. CO2 Util. 41 , 101280 (2020). Footnotes With Boeing 787-9 Dreamliner Average of Boeing 787-9 Dreamliner, Boeing 777-200LR, Boeing 777-3000LR, and Boeing 767 − 300 With Boeing 737–900 Additional Declarations There is NO Competing Interest. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3981416","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Analysis","associatedPublications":[],"authors":[{"id":278781600,"identity":"46db6174-fda4-4823-b692-ffdd52542dff","order_by":0,"name":"Nicoletta Brazzola","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-5041-9972","institution":"ETH Zurich (Swiss Federal Institute of Technology)","correspondingAuthor":true,"prefix":"","firstName":"Nicoletta","middleName":"","lastName":"Brazzola","suffix":""},{"id":278781601,"identity":"a7ce61f3-bfb9-42d1-8c8f-be21a664d8a6","order_by":1,"name":"Amir Meskaldji","email":"","orcid":"","institution":"ETH Zürich","correspondingAuthor":false,"prefix":"","firstName":"Amir","middleName":"","lastName":"Meskaldji","suffix":""},{"id":278781602,"identity":"fbbac206-0ec8-4329-9c5c-5e8b969839f7","order_by":2,"name":"Anthony Patt","email":"","orcid":"https://orcid.org/0000-0001-8428-8707","institution":"ETH Zurich","correspondingAuthor":false,"prefix":"","firstName":"Anthony","middleName":"","lastName":"Patt","suffix":""},{"id":278781603,"identity":"d657beb5-2d0b-4bd6-bea5-973130e022e7","order_by":3,"name":"Tim Tröndle","email":"","orcid":"https://orcid.org/0000-0002-3734-8284","institution":"ETH Zurich","correspondingAuthor":false,"prefix":"","firstName":"Tim","middleName":"","lastName":"Tröndle","suffix":""},{"id":278781604,"identity":"d2685b3d-4df8-41fd-bd4b-4cb4037253e3","order_by":4,"name":"Christian Moretti","email":"","orcid":"","institution":"ETH Zurich and Paul Scherrer Institute","correspondingAuthor":false,"prefix":"","firstName":"Christian","middleName":"","lastName":"Moretti","suffix":""}],"badges":[],"createdAt":"2024-02-23 10:01:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3981416/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3981416/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-024-55482-6","type":"published","date":"2025-01-11T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":54292733,"identity":"e4f39924-7d62-4398-8622-560b3f814c87","added_by":"auto","created_at":"2024-04-08 12:09:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":59500,"visible":true,"origin":"","legend":"\u003cp\u003eOverview of the technology scenarios and climate policy targets that our analysis spans. Colored bars show the direct aviation emissions under different technology pathways, while gray bars show emissions that are either directly mitigated or offset through DACCS.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/e1cf5d82df89c19a911d254e.png"},{"id":54293330,"identity":"ed5529a6-e5b7-431d-9445-b64c7b1cb815","added_by":"auto","created_at":"2024-04-08 12:17:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":46561,"visible":true,"origin":"","legend":"\u003cp\u003eCost to achieve CO\u003csub\u003e2\u003c/sub\u003e and climate neutrality in the year 2050 under a scenario where synthetic fuels replace 100% of kerosene by 2050 (\"DACCU\") and under a scenario where fossil kerosene is used continuously, and emissions are offset through DACCS (\"DACCS\").\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/287ef4ef8c70b2c8531db5e3.png"},{"id":54293740,"identity":"4ec60188-cde8-443d-b54c-3959bf382c81","added_by":"auto","created_at":"2024-04-08 12:25:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":42628,"visible":true,"origin":"","legend":"\u003cp\u003eCost of achieving CO\u003csub\u003e2\u003c/sub\u003e and climate neutrality by 2050 a) divided by abated emissions and b) divided by the installed units of DAC. Costs are shown for a scenario where synthetic fuels replace 100% of kerosene by 2050 (\"DACCU\") and for a scenario where fossil kerosene continues to be used and emissions are offset by DACCS (\"DACCS\").\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/189da74357cb8f5b93ceff9c.png"},{"id":54293332,"identity":"00361a25-5b00-4b74-a71e-35fe7f7768dd","added_by":"auto","created_at":"2024-04-08 12:17:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":31350,"visible":true,"origin":"","legend":"\u003cp\u003ea) Total costs per flight per passenger and b) change in cost per flight per passenger relative to business as usual to achieve either CO\u003csub\u003e2\u003c/sub\u003e or climate neutrality in 2050 for representative short-, medium-, and long-haul flights under the DACCU and DACCS pathways.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/89a5560f39d55222dfee1458.png"},{"id":54292737,"identity":"edc7d1d0-28bd-4be6-8b8a-6491db4f52db","added_by":"auto","created_at":"2024-04-08 12:09:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":193266,"visible":true,"origin":"","legend":"\u003cp\u003eImpacts of the local variation in important input parameters on the 2050 difference between a) DACCU and DACCS pathway to achieve CO\u003csub\u003e2\u003c/sub\u003e neutrality and b) DACCU and fossil jet fuels assuming a 100% dominance of the respective fuel types by 2050. Blue cells indicate when DACCU becomes cheaper than fossil kerosene, while red cells are the opposite.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/d1f238251f66f3d74e7ae71b.png"},{"id":54292739,"identity":"fb632f3a-4ca0-4c3d-8904-584fd6e6bed2","added_by":"auto","created_at":"2024-04-08 12:09:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":207844,"visible":true,"origin":"","legend":"\u003cp\u003eImpact of varying assumptions on different policies on the difference in cost by 2050 of a) DACCS and DACCU pathways to reach CO\u003csub\u003e2\u003c/sub\u003e neutrality and b) DACCU and fossil jet fuels assuming a 100% dominance of each fuel type by 2050. The row with 0% represents the standard assumption about how the policy is implemented, namely a price on CO\u003csub\u003e2\u003c/sub\u003e emissions by 100€/tCO\u003csub\u003e2\u003c/sub\u003e, a price on aviation climate impacts by 100 €/tCO\u003csub\u003e2eq\u003c/sub\u003e, a subsidy to DACCS by 100€/tCO\u003csub\u003e2\u003c/sub\u003e, a subsidy to DACCU by 33 €/t synthetic fuel, or a restricted use of excess electricity of a price by 0.003€/kWh. The other rows represent variation of this input assumptions on the policy value (e.g., by -70% the price on CO\u003csub\u003e2\u003c/sub\u003e emissions will be 30€/tCO\u003csub\u003e2\u003c/sub\u003e, while by +400% it will be 500€/tCO\u003csub\u003e2\u003c/sub\u003e).\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/b8a6ced52a00b3dcad24cdfb.png"},{"id":73588014,"identity":"0f49ac6e-f972-4fe8-9203-f5a5709adf64","added_by":"auto","created_at":"2025-01-12 08:05:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1525165,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/bd98e887-55cc-48a5-b17c-b9047d66a080.pdf"},{"id":54292736,"identity":"b8fffa47-866a-4599-944b-09010e1dbac2","added_by":"auto","created_at":"2024-04-08 12:09:46","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1149625,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-3981416/v1/1311b53361c2a443334c8658.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Synthetic fuels may be a cheaper way to achieve climate-neutral aviation","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAviation has historically contributed to approximately 4% of anthropogenic climate warming\u003csup\u003e1\u003c/sup\u003e. About two-thirds of this is attributed to non-CO\u003csub\u003e2\u003c/sub\u003e effects, such as contrail cirrus cloud formation or indirect effects due to nitrous oxide emissions \u003csup\u003e2\u0026ndash;5\u003c/sup\u003e. While aviation\u0026rsquo;s historical contribution to climate change may appear small, its role in the future could be significant due to the expected growth of the sector and the challenges of mitigating its emissions \u003csup\u003e6\u0026ndash;9,9\u0026ndash;11\u003c/sup\u003e. The effects of viable decarbonization options, such as operational improvements and efficiency gains, are currently jeopardized by rising demand \u003csup\u003e12\u0026ndash;14\u003c/sup\u003e, and the switch to biofuels is constrained by biophysical limits, such as the availability of sustainable biomass, which is also in demand for other mitigation purposes \u003csup\u003e15\u0026ndash;17\u003c/sup\u003e. While some mitigation technologies, such as hydrogen and electric aircraft, could theoretically curb all emissions, they are not yet technically feasible, especially for long-haul flights, and would require a complete renewal of the global aviation fleet \u003csup\u003e18\u0026ndash;21\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis led to the emergence of two additional mitigation strategies: offsetting aviation emissions with carbon removals \u003csup\u003e22\u0026ndash;26\u003c/sup\u003e and deploying renewable Fischer-Tropsch synthetic fuels from air-captured CO\u003csub\u003e2\u003c/sub\u003e and green hydrogen \u003csup\u003e12,27\u0026ndash;29\u003c/sup\u003e. To ensure scalability, both solutions could rely on direct air capture (DAC), as this technology has relatively small land and water footprints and does not require biomass\u003csup\u003e17,30\u0026ndash;33\u003c/sup\u003e. DAC can be used either in combination with CO\u003csub\u003e2\u003c/sub\u003e storage to offset aviation emissions (as direct air carbon capture and storage [DACCS]) or to produce synthetic fuels via Fischer-Tropsch synthesis (as direct air carbon capture and utilization [DACCU]). In addition to its potential for scalability, especially if deployed in remote areas \u003csup\u003e31,34\u003c/sup\u003e, the use of DAC to tackle aviation\u0026rsquo;s climate impacts could benefit climate mitigation in a larger sense; bearing the high initial costs of this technology can be seen as an equitable strategy\u003csup\u003e35\u003c/sup\u003e to overcome the steepest segment of its learning curve\u003csup\u003e36\u0026ndash;39\u003c/sup\u003e and realize its economic viability for other applications. Financing improvements in DAC via increases in ticket prices would indeed fall most heavily on middle-to-high income consumers and households\u003csup\u003e40,41\u003c/sup\u003e but provide long-term benefits for the entire world by making the technology ready for large-scale carbon removal \u003csup\u003e37,38,42\u003c/sup\u003e, which will be necessary to remedy overshoots of a Paris-aligned carbon budget \u003csup\u003e43,44\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOn this background, we explore the use of DAC for medium-term mitigation of the aviation sector\u0026rsquo;s climate impacts and investigate the conditions under which the use of DACCU-based synthetic fuels could be cost-effective than offsets via DACCS. Previous techno-economic assessments have concluded that DACCS is a more cost-effective option for achieving CO\u003csub\u003e2\u003c/sub\u003e-neutral aviation globally \u003csup\u003e22,45\u003c/sup\u003e. However, they also noted that these cost benefits may not materialize because they are based on uncertain assumptions\u003csup\u003e45\u003c/sup\u003e and that DACCS offers fewer co-benefits, such as potential mitigation of non-CO\u003csub\u003e2\u003c/sub\u003e impacts \u003csup\u003e2,46,47\u003c/sup\u003e and alignment with fossil fuel phase-outs \u003csup\u003e45\u003c/sup\u003e. The only study that compared the deployment of DACCS and DACCU to achieve climate neutrality concluded that it is unrealistic to rely entirely on DACCU-based fuels for European aviation fuel consumption if green hydrogen production is to take place only in Europe \u003csup\u003e26\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn this study, we aim to broaden the discussion by offering a global perspective on DAC deployment to achieve CO\u003csub\u003e2\u003c/sub\u003e and climate neutrality in aviation. The global focus is justified by emerging trends in countries such as Chile, Saudi Arabia, Australia, and Morocco, which are positioning themselves as producers of cheap renewable energy and exporters of green hydrogen thanks to their abundant land and renewable energy resources \u003csup\u003e48,49\u003c/sup\u003e. In addition, recognizing the imperative to emancipate aviation from fossil entanglements \u003csup\u003e50\u003c/sup\u003e and societal preferences for DACCU over DACCS \u003csup\u003e51\u003c/sup\u003e and, more generally, for direct emissions reductions over the offsets \u003csup\u003e52\u0026ndash;54\u003c/sup\u003e, we set out to identify the conditions under which DACCU can become cost-competitive with DACCS and even with fossil fuels. By examining the drivers of future costs and policy implications, we present a comprehensive analysis that contributes to the knowledge base and provides decision-makers with actionable insights to enable DACCU to take off.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eScenarios and framework\u003c/h2\u003e \u003cp\u003eOur study examines two key technology scenarios for achieving CO\u003csub\u003e2\u003c/sub\u003e and climate neutrality in the global aviation sector by 2050. In the DACCU scenario, synthetic fuels produced from green hydrogen and CO\u003csub\u003e2\u003c/sub\u003e captured by DAC lead to a gradual substitution of fossil fuels, eventually replacing conventional jet fuels entirely by 2050. This substitution follows an S-shaped curve, according to technology diffusion theories \u003csup\u003e55\u0026ndash;59\u003c/sup\u003e. Conversely, the DACCS scenario focuses on the incremental DACCS-based offsetting of continued fossil jet fuel use. To ensure comparability, the share of emissions offsets follows the same S-shaped curve of DACCU deployment, reaching 100% by 2050.\u003c/p\u003e \u003cp\u003eOur analysis includes two different 2050 goals for the aviation sector. The first is to achieve CO\u003csub\u003e2\u003c/sub\u003e neutrality, that is, to reduce CO\u003csub\u003e2\u003c/sub\u003e emissions to net-zero by 2050. In the DACCS pathway, this means offsetting CO\u003csub\u003e2\u003c/sub\u003e emissions only. In the DACCU pathway, fuel substitution is assumed to fully eliminate CO\u003csub\u003e2\u003c/sub\u003e emissions (except for indirect emissions, cf. Methods). Since DACCU-based fuels are expected to burn cleaner \u003csup\u003e46,47\u003c/sup\u003e, this pathway also achieves a partial mitigation of the non-CO\u003csub\u003e2\u003c/sub\u003e effects. Therefore, the climate benefits of the two pathways are not equal under a CO\u003csub\u003e2\u003c/sub\u003e neutrality target. The second target, climate neutrality, on the other hand, includes non-CO\u003csub\u003e2\u003c/sub\u003e effects and thus enables a more balanced comparison of the two technology pathways. In fact, to achieve climate neutrality both pathways must neutralize any residual non-CO\u003csub\u003e2\u003c/sub\u003e effect with the deployment of DACCS. A schematic of how the different pathways and a business-as-usual with fossil kerosene achieve different targets is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOur analysis combines these different technologies and climate target scenarios while assuming rising aviation demand (cf. Methods). This comprehensive framework enables a holistic comparison of DACCU, DACCS and conventional aviation based on fossil kerosene in terms of costs, energy use, and climate impacts.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eEmit-and-offset is cheaper under a CO neutrality target, but not under a climate neutrality target\u003c/h3\u003e\n\u003cp\u003eWe first calculate the costs of the two technology pathways to achieve CO\u003csub\u003e2\u003c/sub\u003e and climate neutrality under our standard input assumptions (see Methods and Supplementary Tables\u0026nbsp;1\u0026ndash;3). For CO\u003csub\u003e2\u003c/sub\u003e neutrality, the DACCS pathway is significantly less costly than the DACCU pathway, which it outperforms by about \u0026euro;200\u0026nbsp;billion in 2050 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) and \u0026euro;120\u0026nbsp;billion in 2060 (see Supplementary Fig.\u0026nbsp;4). This cost difference is mainly due to the high electricity and capital costs of electrolysis in the DACCU pathway, which is essential for synthetic fuel production. The cost comparison under CO\u003csub\u003e2\u003c/sub\u003e neutrality does not capture the full benefits of DACCU-based fuels because the reduction in non-CO\u003csub\u003e2\u003c/sub\u003e impacts due to cleaner synthetic fuels is not reflected in the cost (see Supplementary Fig.\u0026nbsp;1). Both the DACCS and DACCU pathways achieve substantially higher costs than a business-as-usual scenario with continued fossil jet fuels use, which is cheaper than the DACCU scenario by over \u0026euro;500\u0026nbsp;billion.\u003c/p\u003e \u003cp\u003eUnder climate neutrality, where the climate impacts of the two pathways are identical, the DACCU pathway has significant cost advantages over DACCS, which it outperforms by over \u0026euro;280\u0026nbsp;billion in 2050. The higher cost of the DACCS pathway is mainly attributable to the higher carbon removal rates required to offset non-CO\u003csub\u003e2\u003c/sub\u003e emissions, which are higher than in the DACCU pathway (see Supplementary Figs.\u0026nbsp;1\u0026ndash;2). The large offset requirements are due to the sustained demand growth assumed in the analysis. However, assuming no growth of the sector still results in a competitive advantage of the DACCU pathway (see Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). Despite its economic advantage, the DACCU pathway results in higher electricity consumption due to energy-intensive electrolysis (cf. Supplementary Fig.\u0026nbsp;3). This limits its scaling potential to regions with abundant and affordable renewable energy. Finally, both DACCS and DACCU pathways are more expensive alternatives compared to the continued use of fossil kerosene, highlighting the role of policy interventions to propel these pathways forward.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eEmit-and-offset is more expensive than synthetic fuels on a cost-per-avoided-emissions basis, but is more efficient in scaling DAC\u003c/b\u003e \u003c/p\u003e \u003cp\u003eLooking at the total costs for abated emissions relative to the business-as-usual (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea), the resulting picture is almost opposite than the one drawn when looking at absolute yearly costs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Under the CO\u003csub\u003e2\u003c/sub\u003e neutrality target, the DACCS pathway has the highest costs per emissions abated, reaching abatement costs over \u0026euro;500/tCO\u003csub\u003e2\u003c/sub\u003ee compared to less than \u0026euro;200/tCO\u003csub\u003e2\u003c/sub\u003ee for the DACCU pathway. This difference arises because DACCS only includes costs associated with reducing CO\u003csub\u003e2\u003c/sub\u003e emissions. Conversely, in the DACCU pathway, the abatement extends to non-CO\u003csub\u003e2\u003c/sub\u003e emissions, thereby increasing the total volume of abated emissions over which the costs are distributed. Under the climate neutrality target, where both technology pathways abate the same level of emissions, DACCU again emerges as more cost-effective because of the smaller amounts of carbon removals required to offset the remaining non-CO\u003csub\u003e2\u003c/sub\u003e effects.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eApart from mitigating the aviation sector, both options could also serve as a means of scaling up DAC. This rationale is rooted in the potential role that the aviation sector could play as a niche for the initial deployment of DAC, as the sector is bound to face significant costs in mitigating its emissions due to the lack of affordable alternatives. This perspective results in a picture opposite to that of cost-effective abatement. We find that as the volume of DAC installations increases, the DACCS pathway consistently offers a lower cost per DAC unit than the DACCU pathway (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). DACCU incurs higher costs due to the production of green hydrogen. This has a significant impact on the cost per unit of DAC installed.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eThe price difference for a CO\u003csub\u003e2\u003c/sub\u003e-neutral flight with DACCS and DACCU is small\u003c/h2\u003e \u003cp\u003eWe further assess the increase in price per flight per passenger to achieve CO\u003csub\u003e2\u003c/sub\u003e and climate neutrality via the DACCS and DACCU pathways. In the context of CO\u003csub\u003e2\u003c/sub\u003e neutrality, offsetting aviation CO\u003csub\u003e2\u003c/sub\u003e emissions with DACCS proves to be more economical than fueling the same flight with DACCU-based synthetic fuels. However, the cost difference per passenger is modest, ranging from approximately \u0026euro;20\u0026ndash;55 for long-haul flights (London-New York and London-Perth) to only \u0026euro;4 for a short-haul flight from London to Berlin. While the overall cost per passenger increases to achieve climate neutrality, DACCU becomes cheaper than DACCS, saving about \u0026euro;35\u0026ndash;100 per passenger on long-haul flights and \u0026euro;6 on short-haul flights.\u003c/p\u003e \u003cp\u003eWe also assessed the impact on the cost of flying relative to the expected future cost of flying in a business-as-usual scenario with continued use of fossil fuels. The projected increase in ticket prices for flights in 2050 ranges between 15\u0026ndash;30% for DACCU and 8\u0026ndash;20% for DACCS to achieve CO\u003csub\u003e2\u003c/sub\u003e neutrality, rising to up to 40% (DACCU) and 60% (DACCS) to achieve climate neutrality. However, the increase in price is not the same for all flights, since the contribution of fuel costs to ticket prices varies for different routes, as the price is adjusted to demand and to endure competition. While the increases in price due to a complete neutralization of the climate effects of a flight may seem substantial, they lie well below the range of current variance in prices. Indeed, the difference in price between buying a ticket two weeks or two months in advance is, on average, 400% for the London-Berlin route, over 100% for the London-New York route, and 70% for the London-Perth route \u003csup\u003e60\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eCheaper electricity and high fossil jet fuel prices can make DACCU cheaper than DACCS (and even business-as-usual) even under CO\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003eneutrality\u003c/b\u003e\u003c/p\u003e \u003cp\u003eTo understand the conditions under which DACCU-based fuels could be economically competitive in the less-advantageous CO\u003csub\u003e2\u003c/sub\u003e-neutrality scenario with an emit-and-offset strategy via DACCS and even with the business-as-usual with continued use of fossil jet fuel, we perform local sensitivity analyses on the most influential parameters (see Supplementary Table\u0026nbsp;1\u0026ndash;3).\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows that DACCU can become more cost effective than DACCS when electricity prices fall below 0.015 \u0026euro;/kWh. This threshold is well below the 2023 price of the cheapest renewable energy sources, onshore wind \u003csup\u003e61\u003c/sup\u003e, but not unachievable in the future through technology learning, optimal siting, or in moments of excess production of renewable electricity, for example on sunny summer days in grids with a high share of solar PV\u003csup\u003e62,63\u003c/sup\u003e. In contrast, even when powered by free electricity, DACCU is still not competitive with the business-as-usual.\u003c/p\u003e \u003cp\u003eConversely, rising fossil fuel prices prove transformative: DACCU becomes cost-competitive with DACCS at a fossil fuel price of \u0026euro;0.9/L and with the business-as-usual scenario at \u0026euro;1.8/L. Such high costs would not only make DACCU a more economical option, but would also discourage demand. However, doubling the current price of fossil jet fuel would require dedicated political ambition.\u003c/p\u003e \u003cp\u003eAccelerated technological learning and steeper learning curves benefit both DACCU and DACCS scenarios. Thus, even a learning rate of 50% - higher than has been observed historically for fast-learning technologies such as solar PV - cannot close the gap between the DACCU and DACCS pathways.\u003c/p\u003e \u003cp\u003eIn summary, extremely optimistic changes in fossil fuel or electricity prices are required to make DACCU cost-competitive with DACCS or business-as-usual by varying a single parameter. However, a synergy of lower electricity prices with either rising fossil fuel costs or higher technological learning could accelerate a scenario where DACCU outperforms DACCS or even fossil jet fuels under optimistic but possible conditions (see Supplementary Figs.\u0026nbsp;6\u0026ndash;8).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003ePricing aviation climate impacts or limiting DACCU operation to times when excess electricity is available is sufficient to make DACCU cheaper than DACCS\u003c/b\u003e \u003c/p\u003e \u003cp\u003eGiven the observed sensitivity of DACCS and DACCU performance to highly uncertain input assumptions, we examine the potential impact of different policies that affect these assumptions. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the cost difference of DACCU compared to DACCS (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea) and fossil jet fuel (6b) under different policies affecting some of the key input variables (see Supplementary Table\u0026nbsp;4).\u003c/p\u003e \u003cp\u003ePricing emissions internalizes the impact of continued fossil jet fuel emissions and thus acts similarly to increasing the price of fossil fuels, while also internalizing the environmental costs of life-cycle emissions for both DACCS and DACCU. Conversely, pricing CO\u003csub\u003e2\u003c/sub\u003e emissions alone cannot make DACCU cost-competitive with DACCS since, under CO\u003csub\u003e2\u003c/sub\u003e neutrality, it applies only to indirect emissions, which are higher in the DACCU pathway (see Supplementary Fig.\u0026nbsp;1). On the other hand, pricing all aviation-related climate impacts can significantly favor the DACCU pathway, which already becomes more cost-effective than the DACCS pathways at \u0026euro;30/tCO\u003csub\u003e2e*\u003c/sub\u003e. Pricing emissions is also crucial to make DACCU economically competitive with fossil jet fuels. However, the prices on emissions need to be extremely high, starting at \u0026euro;500/tCO\u003csub\u003e2\u003c/sub\u003e for CO\u003csub\u003e2\u003c/sub\u003e emissions alone and at least \u0026euro;100/tCO\u003csub\u003e2e*\u003c/sub\u003e for all aviation-related impacts.\u003c/p\u003e \u003cp\u003eIn contrast to direct subsidies based on synthetic fuel production, which are not sufficient to make DACCU competitive with DACCS even at \u0026euro;500/t\u003csub\u003efuel\u003c/sub\u003e (which corresponds to about \u0026euro;1600/tCO\u003csub\u003e2\u003c/sub\u003e DACCU-based fuels), a strategic approach is to leverage cheap electricity (below \u0026euro;0.01/kWh). Policies, such as seasonal restrictions aligned with periods of electricity surplus, could achieve this by limiting DACCU-based synthetic fuel production to periods of significantly cheaper surplus electricity. However, this approach comes with the constraint of limiting the volume of DACCU-based synthetic fuels that can be produced. While limiting the number of operating hours could increase the weight of capital expenditures per DACCU output, and thus lead to potential cost increases not accounted for in our modelling\u003csup\u003e64\u003c/sup\u003e, it could also reduce the deterioration, and thus extend the lifetime, of costly components of the electrolyzers and DAC, namely the stack and adsorbent.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, we investigate the conditions under which aviation mitigation via DACCU-based synthetic fuels becomes cost-competitive with an emit-and-offset strategy via DACCS. We found that these conditions are realized by either (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) ambitious climate targets for the aviation sector that consider the non-CO\u003csub\u003e2\u003c/sub\u003e impacts of aviation, or (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) policies that internalize the cost of unabated emissions or limit DACCU to the use of excess, cheap electricity. In addition, our analysis highlights that achieving CO\u003csub\u003e2\u003c/sub\u003e neutrality through DACCU increases flight ticket prices only slightly relative to the DACCS pathway and even relative to a business-as-usual pathway. This small price difference for consumers sheds light on the attractiveness of DACCU, which has a lower cost per avoided emissions and is consistent with broader societal goals of climate mitigation and fossil fuels phase-out.\u003c/p\u003e \u003cp\u003eThese findings mark a departure from previous studies \u003csup\u003e22,26\u003c/sup\u003e, which favored DACCS due to conservative assumptions about future electricity prices (which exceed current wind and solar PV prices) and carbon-intensive energy mixes, resulting in higher lifecycle emissions of DACCU. Furthermore, due to their regional focus on Europe, where land availability is scarce, Sacchi et al. concluded that the land use of the energy-intensive DACCU pathway is a bottleneck under a scenario of continued demand growth for the aviation sector. While their regional land availability constraint does not apply to our global analysis, spatial considerations may indeed affect the cost at which the DACCU pathway could be realized due to the spatial distribution of electricity costs and the potential need for additional transportation infrastructure from remote locations.\u003c/p\u003e \u003cp\u003eThe efforts needed to enable CO\u003csub\u003e2\u003c/sub\u003e neutral and, especially, climate neutral flying may not be feasible. In fact, more than 2 GtCO\u003csub\u003e2\u003c/sub\u003e of DAC would need to be installed by 2050 to achieve CO\u003csub\u003e2\u003c/sub\u003e neutrality, rising to 7 GtCO\u003csub\u003e2\u003c/sub\u003e if the goal is to offset fossil jet fuel emissions to achieve climate neutrality. These amounts of DAC far exceed the projections of novel CDR methods by 2050 in Integrated Assessment Models simulations consistent with \u0026lt;\u0026thinsp;2\u0026deg;C targets \u003csup\u003e31,42,43,65\u003c/sup\u003e. However, the assumed growth rate up to 2050 (roughly 50 to 60% annually) is in line with that assumed by Integrated Assessment Models for the years between 2040\u0026ndash;2080 \u003csup\u003e31\u003c/sup\u003e and with that observed historically for solar PV \u003csup\u003e66\u003c/sup\u003e. On the other hand, by 2050, the DACCU pathway will require over 15 PWh of electricity to produce the amount of synthetic fuels necessary to fully meet global aviation demand if this continues to grow. Given that in 2021 the global renewable energy produced amounted to 8 PWh\u003csup\u003e67\u003c/sup\u003e, this energy demand would require a massive scale-up of renewable energy. However, DACCU\u0026rsquo;s renewable energy requirements are compatible with estimates of the total technical renewable energy potential (170\u0026ndash;270 PWh according \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eto Angliviel de La Beaumelle et al., 2023)\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eThe superiority of DACCU in our results also hinges on uncertain variables, particularly the effectiveness of DACCU-based synthetic fuels in mitigating non-CO\u003csub\u003e2\u003c/sub\u003e impacts. While early empirical evidence is consistent with this trend \u003csup\u003e46,47,69\u003c/sup\u003e, the limited number of studies evaluating the impacts of synthetic fuels, coupled with the inherent uncertainty surrounding aviation\u0026rsquo;s non-CO\u003csub\u003e2\u003c/sub\u003e effects, introduces a degree of uncertainty. Notably, our analysis explicitly accounts for these uncertainties, and while they could significantly alter the absolute costs of DACCS and DACCU, their relative merit mostly remains unchanged.\u003c/p\u003e \u003cp\u003eBy shedding light on the conditions that make DACCU cost-competitive, our analysis can guide policymakers in designing strategies to facilitate the competitiveness of DACCU with both a emit-and-offset pathway relying on DACCS and a business-as-usual scenario. These strategic policy interventions could be justified based on the drawbacks of the DACCS pathway associated with its reliance on fossil jet fuels and the climate mitigation benefits of DACCU fuels.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eIn this study, we combined techno-economic modelling with life cycle assessment to compare the costs of mitigating the aviation sector by either compensating aviation emissions with DACCS or by replacing the whole volume of jet fuel with DACCU-based synthetic fuels, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eDemand and fuel scenarios\u003c/h3\u003e\n\u003cp\u003eAll scenarios are based on the same demand for jet fuel, which is derived from a combination of historical data\u003csup\u003e5\u003c/sup\u003e from 1990 to 2018 with estimates of future demand until 2060. These are based on the assumptions of full recovery to pre-covid levels by 2024\u0026ndash;2025 and on a 2% growth from 2024 to 2060, which are consistent with projections from various studies\u003csup\u003e10,70\u0026ndash;75\u003c/sup\u003e. In addition to the total fuel demand, we also project the total annual distance flown by applying a 2% increase in efficiency, consistent with the International Civil Aviation Organization\u0026rsquo;s target\u003csup\u003e76\u003c/sup\u003e, to the historical relationship between distance flown and amount of fuel burned\u003csup\u003e5\u003c/sup\u003e. While this relationship may change in the future due to an increase in long-haul flights\u003csup\u003e9,77\u003c/sup\u003e that burn more fuel per kilometer\u003csup\u003e78\u003c/sup\u003e, its effect would not significantly alter the results of our analysis, as shown in our sensitivity analysis (see Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and Supplementary Fig.\u0026nbsp;9).\u003c/p\u003e \u003cp\u003eAs detailed in the \u0026ldquo;Scenarios and Framework\u0026rdquo; section, we consider two different mitigation pathways for aviation, one based on continued reliance on fossil jet fuel and offsetting through DACCS, and the other based on the gradual substitution of fossil fuels with DACCU-based synthetic fuels. Although the American Society for Testing Material D7566 standard\u003csup\u003e79\u003c/sup\u003e currently allows only up to 50% synthetic fuels blends, we assume that aircraft will operate on 100% DACCU-based synthetic fuels by 2050, being expected that blends up to 100% will be certified in due course, so that planes can fully run on synthetic fuel. Similarly, we model an upscaling of DACCS that enables full offsetting of aviation emissions by 2050, simplistically assuming no constraints on the rate of adoption of this technology.\u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eEmissions and offsets\u003c/h2\u003e \u003cp\u003eTo calculate the amount of direct emissions from fossil jet fuel combustion, we apply the relationships between fossil jet fuel and CO\u003csub\u003e2\u003c/sub\u003e, water vapor, sulfur dioxide, soot, and NO\u003csub\u003ex\u003c/sub\u003e emissions reported by Lee et al.\u003csup\u003e5\u003c/sup\u003e. Contrail cirrus formation was calculated using the relationship between the distance flown contrail length, also reported in Lee et al.\u003csup\u003e5\u003c/sup\u003e. To calculate the emissions and contrail clouds formation of DACCU-based fuels, we follow the approach described in Brazzola et al.\u003csup\u003e25\u003c/sup\u003e (see their Supplementary Table\u0026nbsp;2) and propagate their uncertainty ranges throughout the analysis.\u003c/p\u003e \u003cp\u003eThe direct flight emissions then drive the demand for carbon removals via DACCS to offset their climate impact. The amount of removals is further determined by (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) the specific climate target chosen (i.e., CO\u003csub\u003e2\u003c/sub\u003e or climate neutrality, see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), and (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) the lifecycle emissions of each technology pathway. First, to achieve CO\u003csub\u003e2\u003c/sub\u003e neutrality, we simplistically assume that we can fully compensate the climate impact of one ton of CO\u003csub\u003e2\u003c/sub\u003e by removing an equivalent amount via DACCS, neglecting the uncertainties of this relationship\u003csup\u003e80,81\u003c/sup\u003e. To achieve climate neutrality, we compensate for the non-CO\u003csub\u003e2\u003c/sub\u003e effects with DACCS based on the GWP* metric following the approach of Brazzola et al.\u003csup\u003e25\u003c/sup\u003e and using their \u0026lsquo;Gold\u0026rsquo; definition of climate neutrality\u003csup\u003e25\u003c/sup\u003e. Thereby, we use and propagate throughout the analysis the uncertainties in the relationship between non-CO\u003csub\u003e2\u003c/sub\u003e emissions and their effective radiative forcing reported in Lee et al.\u003csup\u003e5\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFinally, we also offset through DACCS the lifecycle emissions due to the material and energy footprint of the two pathways. We calculate lifecycle emissions for both fossil fuels, DACCU-based fuels and DACCS. For fossil jet fuels, we considered the well-to-tank emissions from Moretti et al. \u003csup\u003e82\u003c/sup\u003e, which reflect European averages. Future reductions in oil refining emissions are based on the oil industry decarbonization prospects \u003csup\u003e83\u003c/sup\u003e, leading to a progressive decrease in well-to-tank emissions for fossil jet fuels. Material footprints are based on values for the production of required adsorbents and DAC modules by Deutz and Bardow\u003csup\u003e84\u003c/sup\u003e; values for electrolysers by Delpierre et al.\u003csup\u003e85\u003c/sup\u003e; values for CO electrolysis production units from Adnad and Kibria\u003csup\u003e86\u003c/sup\u003e. In addition, we calculated the energy requirements of all technologies involved and applied an electricity carbon footprint for an average global electricity grid\u003csup\u003e84\u003c/sup\u003e, assuming high decarbonization efforts over time leading to near net-zero emissions in 2060. As the synthesis of DACCU-based fuels is a multi-functional unit process with by-products, notably diesel, we assume the production of 0.82 tons of diesel per ton of jet fuel\u003csup\u003e22\u003c/sup\u003e. The lifecycle inventory of the unit processes up to the Fischer-Tropsch unit was then allocated to jet fuel by means of mass allocation (resulting in a 54.5% share for jet fuel).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eTechno-economic assessment of DACCS and DACCU pathways\u003c/h2\u003e \u003cp\u003eFinally, we calculate the energy consumption and capital costs of each technology and fuel included in the DACCS and DACCU pathways from 2020 to 2060. This includes the cost of fossil jet fuel, electricity and heat consumption, CO\u003csub\u003e2\u003c/sub\u003e transport and storage, and the capital costs of DAC, CO\u003csub\u003e2\u003c/sub\u003e reduction, electrolysis, and Fischer-Tropsch synthesis.\u003c/p\u003e \u003cp\u003eFor both pathways, we consider a low-heat solid-sorbent DAC system. While high-temperature liquid-solvent DAC may be more energy-efficient for the production of DACCU-based fuels, there are currently no plants that operate completely without burning natural gas\u003csup\u003e87\u003c/sup\u003e. As a result, using liquid-solvent DAC to produce jet fuel may result in net CO\u003csub\u003e2\u003c/sub\u003e emissions. We moreover assume a fixed cost of 20 \u0026euro;/tCO\u003csub\u003e2\u003c/sub\u003e for CO\u003csub\u003e2\u003c/sub\u003e transport and storage as in Becattini et al.\u003csup\u003e22\u003c/sup\u003e, based on the assumption that DACCS would be optimally located next to storage sites.\u003c/p\u003e \u003cp\u003eFor the production of DACCU-based synthetic fuels, we introduce some variance by considering four different combinations of two water electrolysers (either polymer membrane or alkaline electrolysers) and two CO\u003csub\u003e2\u003c/sub\u003e reduction methods (electrochemical CO\u003csub\u003e2\u003c/sub\u003e reduction and reverse-water-gas-shift). While we also calculate total costs for each technology configuration (cf. Supplementary Fig.\u0026nbsp;9), in the main results we use an average of the costs of all four possible configurations since we cannot predict which technology will ultimately prevail more established due to the low technological maturity, uncertain future development, and trade-offs in terms of cost and energy intensity of different technologies involved in DACCU-based synthetic fuel production.\u003c/p\u003e \u003cp\u003eWe first derive the installed capacities of each technology from the amounts of synthetic jet fuel required and from calculations of DACCS-based offset, as explained in the previous sections. To calculate their costs and energy consumption, we apply the parameters and assumptions summarized in Supplementary Tables\u0026nbsp;1\u0026ndash;3. To calculate changes in energy efficiency, we polynomially interpolate between current values and future estimates (see Supplementary Table\u0026nbsp;2). In the case of CAPEX, we apply a learning rate following Eq.\u0026nbsp;1:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$CAPEX\\left(t\\right)=CAPEX\\left({t}_{0}\\right)*{\\left(\\frac{{Q}_{t}}{{Q}_{{t}_{0}}}\\right)}^{-b}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/h2\u003e \u003cp\u003eWhere \u003cem\u003eQ\u003c/em\u003e is the quantity of installed capacity of a technology and \u003cem\u003eb\u003c/em\u003e equals \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({log}_{2}\\left(1-LR\\right)\\)\u003c/span\u003e\u003c/span\u003e, and \u003cem\u003eLR\u003c/em\u003e is the learning rate.\u003c/p\u003e \u003cp\u003eTo calculate the increase in ticket price per passenger for three representative flights, we first calculate the cost of achieving CO\u003csub\u003e2\u003c/sub\u003e or carbon neutrality per kilometer flown each year. We then assume that the non-fuel cost of tickets will remain constant in the future, while replacing the cost of fuel with the cost of achieving either CO\u003csub\u003e2\u003c/sub\u003e or climate neutrality, including the cost of DACCS and DACCU. The relevant parameters for these calculations are shown in Supplementary Table\u0026nbsp;4.\u003c/p\u003e \u003cp\u003eFinally, we conduct a local sensitivity analysis on key parameters highlighted in Supplementary Table\u0026nbsp;1\u0026ndash;3, including those associated with alternative policy scenarios outlined in in Supplementary Table\u0026nbsp;5. To ensure comparability, we systematically vary uncertain input parameters by fixed percentages, which are right-skewed towards increases in the input assumption to accommodate the constraint that many parameters cannot be reduced below \u0026minus;\u0026thinsp;100% due to the impracticality of negative values.\u003c/p\u003e \u003c/div\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eKl\u0026ouml;wer, M. \u003cem\u003eet al.\u003c/em\u003e Quantifying aviation\u0026rsquo;s contribution to global warming. \u003cem\u003eEnviron. Res. Lett.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 104027 (2021).\u003c/li\u003e\n \u003cli\u003eBurkhardt, U., Bock, L. \u0026amp; Bier, A. Mitigating the contrail cirrus climate impact by reducing aircraft soot number emissions. \u003cem\u003eNpj Clim. Atmospheric Sci.\u003c/em\u003e \u003cstrong\u003e1\u003c/strong\u003e, 1\u0026ndash;7 (2018).\u003c/li\u003e\n \u003cli\u003eK\u0026auml;rcher, B. Formation and radiative forcing of contrail cirrus. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 1824 (2018).\u003c/li\u003e\n \u003cli\u003eLee, D. S. \u003cem\u003eet al.\u003c/em\u003e Aviation and global climate change in the 21st century. \u003cem\u003eAtmos. Environ.\u003c/em\u003e \u003cstrong\u003e43\u003c/strong\u003e, 3520\u0026ndash;3537 (2009).\u003c/li\u003e\n \u003cli\u003eLee, D. S. \u003cem\u003eet al.\u003c/em\u003e The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018. \u003cem\u003eAtmos. Environ.\u003c/em\u003e \u003cstrong\u003e244\u003c/strong\u003e, 117834 (2021).\u003c/li\u003e\n \u003cli\u003eAirbus. \u003cem\u003eGlobal Market Forecast 2018-2037, Global Networks, Global Citizens\u003c/em\u003e. (2018).\u003c/li\u003e\n \u003cli\u003eBoeing. Commercial Market Outlook 2021-2040. https://www.boeing.com/commercial/market/commercial-market-outlook/ (2021).\u003c/li\u003e\n \u003cli\u003eDray, L. \u003cem\u003eet al.\u003c/em\u003e Cost and emissions pathways towards net-zero climate impacts in aviation. \u003cem\u003eNat. Clim. Change\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 956\u0026ndash;962 (2022).\u003c/li\u003e\n \u003cli\u003eG\u0026ouml;ssling, S. \u0026amp; Humpe, A. The global scale, distribution and growth of aviation: Implications for climate change. \u003cem\u003eGlob. Environ. Change\u003c/em\u003e \u003cstrong\u003e65\u003c/strong\u003e, 102194 (2020).\u003c/li\u003e\n \u003cli\u003eGrewe, V. \u003cem\u003eet al.\u003c/em\u003e Evaluating the climate impact of aviation emission scenarios towards the Paris agreement including COVID-19 effects. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 3841 (2021).\u003c/li\u003e\n \u003cli\u003eTerrenoire, E., Hauglustaine, D. A., Gasser, T. \u0026amp; Penanhoat, O. The contribution of carbon dioxide emissions from the aviation sector to future climate change. \u003cem\u003eEnviron. Res. Lett.\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, 084019 (2019).\u003c/li\u003e\n \u003cli\u003eG\u0026ouml;ssling, S. \u0026amp; Humpe, A. Net-zero aviation: Time for a new business model? \u003cem\u003eJ. Air Transp. Manag.\u003c/em\u003e \u003cstrong\u003e107\u003c/strong\u003e, 102353 (2023).\u003c/li\u003e\n \u003cli\u003eLarsson, J., Elofsson, A., Sterner, T. \u0026amp; \u0026Aring;kerman, J. International and national climate policies for aviation: a review. \u003cem\u003eClim. Policy\u003c/em\u003e \u003cstrong\u003e19\u003c/strong\u003e, 787\u0026ndash;799 (2019).\u003c/li\u003e\n \u003cli\u003eScheelhaase, J., Maertens, S., Grimme, W. \u0026amp; Jung, M. EU ETS versus CORSIA\u0026ndash;A critical assessment of two approaches to limit air transport\u0026rsquo;s CO2 emissions by market-based measures. \u003cem\u003eJ. Air Transp. Manag.\u003c/em\u003e \u003cstrong\u003e67\u003c/strong\u003e, 55\u0026ndash;62 (2018).\u003c/li\u003e\n \u003cli\u003eCommittee on Climate Chnage. \u003cem\u003eBiomass in a Low-Carbon Economy\u003c/em\u003e. https://www.theccc.org.uk/publication/biomass-in-a-low-carbon-economy/ (2018).\u003c/li\u003e\n \u003cli\u003eDooley, K., Christoff, P. \u0026amp; Nicholas, K. A. Co-producing climate policy and negative emissions: trade-offs for sustainable land-use. \u003cem\u003eGlob. Sustain.\u003c/em\u003e \u003cstrong\u003e1\u003c/strong\u003e, (2018).\u003c/li\u003e\n \u003cli\u003eSmith, P. \u003cem\u003eet al.\u003c/em\u003e Biophysical and economic limits to negative CO2 emissions. \u003cem\u003eNat. Clim. Change\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 42\u0026ndash;50 (2016).\u003c/li\u003e\n \u003cli\u003eGnadt, A. R., Speth, R. L., Sabnis, J. S. \u0026amp; Barrett, S. R. H. Technical and environmental assessment of all-electric 180-passenger commercial aircraft. \u003cem\u003eProg. Aerosp. Sci.\u003c/em\u003e \u003cstrong\u003e105\u003c/strong\u003e, 1\u0026ndash;30 (2019).\u003c/li\u003e\n \u003cli\u003eNoland, J. K. Hydrogen Electric Airplanes: A Disruptive Technological Path to Clean Up the Aviation Sector. \u003cem\u003eIEEE Electrification Mag.\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 92\u0026ndash;102 (2021).\u003c/li\u003e\n \u003cli\u003ePeeters, P., Higham, J., Kutzner, D., Cohen, S. \u0026amp; G\u0026ouml;ssling, S. Are technology myths stalling aviation climate policy? \u003cem\u003eTransp. Res. Part Transp. Environ.\u003c/em\u003e \u003cstrong\u003e44\u003c/strong\u003e, 30\u0026ndash;42 (2016).\u003c/li\u003e\n \u003cli\u003eSch\u0026auml;fer, A. W. \u003cem\u003eet al.\u003c/em\u003e Technological, economic and environmental prospects of all-electric aircraft. \u003cem\u003eNat. Energy\u003c/em\u003e \u003cstrong\u003e4\u003c/strong\u003e, 160\u0026ndash;166 (2019).\u003c/li\u003e\n \u003cli\u003eBecattini, V., Gabrielli, P. \u0026amp; Mazzotti, M. Role of Carbon Capture, Storage, and Utilization to Enable a Net-Zero-CO2-Emissions Aviation Sector. \u003cem\u003eInd. Eng. Chem. Res.\u003c/em\u003e \u003cstrong\u003e60\u003c/strong\u003e, 6848\u0026ndash;6862 (2021).\u003c/li\u003e\n \u003cli\u003eBecken, S. \u0026amp; Mackey, B. What role for offsetting aviation greenhouse gas emissions in a deep-cut carbon world? \u003cem\u003eJ. Air Transp. Manag.\u003c/em\u003e \u003cstrong\u003e63\u003c/strong\u003e, 71\u0026ndash;83 (2017).\u003c/li\u003e\n \u003cli\u003eBergero, C. \u003cem\u003eet al.\u003c/em\u003e Pathways to net-zero emissions from aviation. \u003cem\u003eNat. Sustain.\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 404\u0026ndash;414 (2023).\u003c/li\u003e\n \u003cli\u003eBrazzola, N., Patt, A. \u0026amp; Wohland, J. Definitions and implications of climate-neutral aviation. \u003cem\u003eNat. Clim. Change\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 761\u0026ndash;767 (2022).\u003c/li\u003e\n \u003cli\u003eSacchi, R. \u003cem\u003eet al.\u003c/em\u003e How to make climate-neutral aviation fly. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, 3989 (2023).\u003c/li\u003e\n \u003cli\u003eScheelhaase, J., Maertens, S. \u0026amp; Grimme, W. Synthetic fuels in aviation \u0026ndash; Current barriers and potential political measures. \u003cem\u003eTransp. Res. Procedia\u003c/em\u003e \u003cstrong\u003e43\u003c/strong\u003e, 21\u0026ndash;30 (2019).\u003c/li\u003e\n \u003cli\u003eTerwel, R. \u0026amp; Kerkhoven, J. \u003cem\u003eCarbon Neutral Aviation with Current Enginge Technology: The Take-off of Synthetic Kerosene Production in the Netherlands\u003c/em\u003e. 62 . https://kalavasta.com/assets/ reports/Kalavasta_Carbon_Neutral_Aviation.pdf (2018).\u003c/li\u003e\n \u003cli\u003eTimmons, D. \u0026amp; Terwel, R. Economics of aviation fuel decarbonization: A preliminary assessment. \u003cem\u003eJ. Clean. Prod.\u003c/em\u003e \u003cstrong\u003e369\u003c/strong\u003e, 133097 (2022).\u003c/li\u003e\n \u003cli\u003eFuhrman, J. \u003cem\u003eet al.\u003c/em\u003e Food\u0026ndash;energy\u0026ndash;water implications of negative emissions technologies in a +1.5 \u0026deg;C future. \u003cem\u003eNat. Clim. Change\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 920\u0026ndash;927 (2020).\u003c/li\u003e\n \u003cli\u003eFuhrman, J. \u003cem\u003eet al.\u003c/em\u003e The role of direct air capture and negative emissions technologies in the shared socioeconomic pathways towards $\\mathplus$1.5 \u0026deg;C and $\\mathplus$2 \u0026deg;C futures. \u003cem\u003eEnviron. Res. Lett.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 114012 (2021).\u003c/li\u003e\n \u003cli\u003eTerlouw, T., Treyer, K., Bauer, C. \u0026amp; Mazzotti, M. Life Cycle Assessment of Direct Air Carbon Capture and Storage with Low-Carbon Energy Sources. \u003cem\u003eEnviron. Sci. Technol.\u003c/em\u003e \u003cstrong\u003e55\u003c/strong\u003e, 11397\u0026ndash;11411 (2021).\u003c/li\u003e\n \u003cli\u003eThe Royal Society. \u003cem\u003eNet Zero Aviation Fuels: Resource Requirements and Environmental Impacts\u003c/em\u003e. (London, UK, 2023).\u003c/li\u003e\n \u003cli\u003eAli, M. \u003cem\u003eet al.\u003c/em\u003e Recent advances in carbon dioxide geological storage, experimental procedures, influencing parameters, and future outlook. \u003cem\u003eEarth-Sci. Rev.\u003c/em\u003e \u003cstrong\u003e225\u003c/strong\u003e, 103895 (2022).\u003c/li\u003e\n \u003cli\u003eAndreoni, P., Emmerling, J. \u0026amp; Tavoni, M. Inequality repercussions of financing negative emissions. \u003cem\u003eNat. Clim. Change\u003c/em\u003e 1\u0026ndash;7 (2023) doi:10.1038/s41558-023-01870-7.\u003c/li\u003e\n \u003cli\u003eK\u0026uuml;ng, L. \u003cem\u003eet al.\u003c/em\u003e A roadmap for achieving scalable, safe, and low-cost direct air carbon capture and storage. \u003cem\u003eEnergy Environ. Sci.\u003c/em\u003e (2023) doi:10.1039/D3EE01008B.\u003c/li\u003e\n \u003cli\u003eMeckling, J. \u0026amp; Biber, E. A policy roadmap for negative emissions using direct air capture. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 2051 (2021).\u003c/li\u003e\n \u003cli\u003eNemet, G. F. \u003cem\u003eHow Solar Energy Became Cheap: A Model for Low-Carbon Innovation\u003c/em\u003e. (Routledge, 2019).\u003c/li\u003e\n \u003cli\u003eYoung, J. \u003cem\u003eet al.\u003c/em\u003e The cost of direct air capture and storage can be reduced via strategic deployment but is unlikely to fall below stated cost targets. \u003cem\u003eOne Earth\u003c/em\u003e \u003cstrong\u003e0\u003c/strong\u003e, (2023).\u003c/li\u003e\n \u003cli\u003eOwen, A., Burke, J. \u0026amp; Serin, E. Who pays for BECCS and DACCS in the UK: designing equitable climate policy. \u003cem\u003eClim. Policy\u003c/em\u003e \u003cstrong\u003e22\u003c/strong\u003e, 1050\u0026ndash;1068 (2022).\u003c/li\u003e\n \u003cli\u003eAddepalli, S., Pagalday, G., Salonitis, K. \u0026amp; Roy, R. Socio-economic and demographic factors that contribute to the growth of the civil aviation industry. \u003cem\u003eProcedia Manuf.\u003c/em\u003e \u003cstrong\u003e19\u003c/strong\u003e, 2\u0026ndash;9 (2018).\u003c/li\u003e\n \u003cli\u003eNemet, G. F. \u003cem\u003eet al.\u003c/em\u003e Near-term deployment of novel carbon removal to facilitate longer-term deployment. \u003cem\u003eJoule\u003c/em\u003e \u003cstrong\u003e0\u003c/strong\u003e, (2023).\u003c/li\u003e\n \u003cli\u003eIPCC. \u003cem\u003eGlobal Warming of 1.5\u0026deg;C.An IPCC Special Report on the Impacts of Global Warming of 1.5\u0026deg;C above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change, Sustainable Development, and Efforts to Eradicate Poverty\u003c/em\u003e. https://www.ipcc.ch/site/assets/uploads/sites/2/2019/06/SR15_Full_Report_High_Res.pdf (2018).\u003c/li\u003e\n \u003cli\u003eIPCC. Summary for Policymakers. in \u003cem\u003eClimate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change\u003c/em\u003e (Cambridge University Press, Cambridge, UK and New York, NY, USA, 2022).\u003c/li\u003e\n \u003cli\u003eCames, M., Chaudry, S., G\u0026ouml;ckeler, K., Kasten, P. \u0026amp; Kurth, S. \u003cem\u003eE-Fuels versus DACCS\u003c/em\u003e. https://www.transportenvironment.org/wp-content/uploads/2021/08/2021_08_TE_study_efuels_DACCS.pdf (2021).\u003c/li\u003e\n \u003cli\u003eBraun-Unkhoff, M., Riedel, U. \u0026amp; Wahl, C. About the emissions of alternative jet fuels. \u003cem\u003eCEAS Aeronaut. J.\u003c/em\u003e \u003cstrong\u003e8\u003c/strong\u003e, 167\u0026ndash;180 (2017).\u003c/li\u003e\n \u003cli\u003eVoigt, C. \u003cem\u003eet al.\u003c/em\u003e Cleaner burning aviation fuels can reduce contrail cloudiness. \u003cem\u003eCommun. Earth Environ.\u003c/em\u003e \u003cstrong\u003e2\u003c/strong\u003e, 1\u0026ndash;10 (2021).\u003c/li\u003e\n \u003cli\u003ePwC. Green hydrogen economy - predicted development of tomorrow. \u003cem\u003ePwC\u003c/em\u003e https://www.pwc.com/gx/en/industries/energy-utilities-resources/future-energy/green-hydrogen-cost.html (2023).\u003c/li\u003e\n \u003cli\u003eWorld Energy Council. \u003cem\u003eWorld Energy Insights: Executive Summary Regional Insights Into Low-Carbon Hydrogen Scale-Up\u003c/em\u003e. https://www.worldenergy.org/assets/downloads/World_Energy_Insights_Executive_Summary_Regional_insights_into_low-carbon_hydrogen_scale_up_April_2022.pdf?v=1680701563 (2022).\u003c/li\u003e\n \u003cli\u003eMalm, A. \u0026amp; Carton, W. Seize the Means of Carbon Removal: The Political Economy of Direct Air Capture. \u003cem\u003eHist. Mater.\u003c/em\u003e \u003cstrong\u003e29\u003c/strong\u003e, 3\u0026ndash;48 (2021).\u003c/li\u003e\n \u003cli\u003eArning, K. \u003cem\u003eet al.\u003c/em\u003e Same or different? Insights on public perception and acceptance of carbon capture and storage or utilization in Germany. \u003cem\u003eEnergy Policy\u003c/em\u003e \u003cstrong\u003e125\u003c/strong\u003e, 235\u0026ndash;249 (2019).\u003c/li\u003e\n \u003cli\u003eArning, K., Linzenich, A., Engelmann, L. \u0026amp; Ziefle, M. More green or less black ? How benefit perceptions of CO2 reductions vs. fossil resource savings shape the acceptance of CO2-based fuels and their conversion technology. \u003cem\u003eEnergy Clim. Change\u003c/em\u003e \u003cstrong\u003e2\u003c/strong\u003e, 100025 (2021).\u003c/li\u003e\n \u003cli\u003eMarkusson, N., McLaren, D. \u0026amp; Tyfield, D. Towards a cultural political economy of mitigation deterrence by negative emissions technologies (NETs). \u003cem\u003eGlob. Sustain.\u003c/em\u003e \u003cstrong\u003e1\u003c/strong\u003e, e10 (2018).\u003c/li\u003e\n \u003cli\u003eSatterfield, T., Nawaz, S. \u0026amp; St-Laurent, G. P. Exploring public acceptability of direct air carbon capture with storage: climate urgency, moral hazards and perceptions of the \u0026lsquo;whole versus the parts\u0026rsquo;. \u003cem\u003eClim. Change\u003c/em\u003e \u003cstrong\u003e176\u003c/strong\u003e, 14 (2023).\u003c/li\u003e\n \u003cli\u003eGeels, F. W. Technological transitions as evolutionary reconfiguration processes: a multi-level perspective and a case-study. \u003cem\u003eRes. Policy\u003c/em\u003e \u003cstrong\u003e31\u003c/strong\u003e, 1257\u0026ndash;1274 (2002).\u003c/li\u003e\n \u003cli\u003eKemp, R., Schot, J. \u0026amp; Hoogma, R. Regime shifts to sustainability through processes of niche formation: The approach of strategic niche management. \u003cem\u003eTechnol. Anal. Strateg. Manag.\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 175\u0026ndash;198 (1998).\u003c/li\u003e\n \u003cli\u003eKemp, R. \u0026amp; Volpi, M. The diffusion of clean technologies: a review with suggestions for future diffusion analysis. \u003cem\u003eJ. Clean. Prod.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, S14\u0026ndash;S21 (2008).\u003c/li\u003e\n \u003cli\u003eRoberts, C. \u003cem\u003eet al.\u003c/em\u003e The politics of accelerating low-carbon transitions: Towards a new research agenda. \u003cem\u003eEnergy Res. Soc. Sci.\u003c/em\u003e \u003cstrong\u003e44\u003c/strong\u003e, 304\u0026ndash;311 (2018).\u003c/li\u003e\n \u003cli\u003eRogers, E. M. Diffusion of Innovations. \u003cem\u003eJ. Pharm. Sci.\u003c/em\u003e \u003cstrong\u003e52\u003c/strong\u003e, 612 (1963).\u003c/li\u003e\n \u003cli\u003eKayak. Search Flights, Hotels \u0026amp; Rental Cars | KAYAK. https://www.kayak.com/ (2023).\u003c/li\u003e\n \u003cli\u003eIRENA. Renewable Power Generation Costs in 2022. https://www.irena.org/Publications/2023/Aug/Renewable-Power-Generation-Costs-in-2022 (2023).\u003c/li\u003e\n \u003cli\u003eKost, C. \u003cem\u003eet al.\u003c/em\u003e \u003cem\u003eLevelized Cost of Electricity - Renewable Energy Technologies\u003c/em\u003e. https://www.ise.fraunhofer.de/en/publications/studies/cost-of-electricity.html (2021).\u003c/li\u003e\n \u003cli\u003eGrahn, M. \u003cem\u003eet al.\u003c/em\u003e Review of electrofuel feasibility\u0026mdash;cost and environmental impact. \u003cem\u003eProg. Energy\u003c/em\u003e \u003cstrong\u003e4\u003c/strong\u003e, 032010 (2022).\u003c/li\u003e\n \u003cli\u003eIRENA. \u003cem\u003eGreen Hydrogen Cost Reduction: Scaling up Electrolysers to Meet the 1.5C Climate Goal\u003c/em\u003e. (2020).\u003c/li\u003e\n \u003cli\u003eFuhrman, J. \u003cem\u003eet al.\u003c/em\u003e Diverse carbon dioxide removal approaches could reduce impacts on the energy\u0026ndash;water\u0026ndash;land system. \u003cem\u003eNat. Clim. Change\u003c/em\u003e 1\u0026ndash;10 (2023) doi:10.1038/s41558-023-01604-9.\u003c/li\u003e\n \u003cli\u003eOdenweller, A., Ueckerdt, F., Nemet, G. F., Jensterle, M. \u0026amp; Luderer, G. Probabilistic feasibility space of scaling up green hydrogen supply. \u003cem\u003eNat. Energy\u003c/em\u003e \u003cstrong\u003e7\u003c/strong\u003e, 854\u0026ndash;865 (2022).\u003c/li\u003e\n \u003cli\u003eIEA. \u003cem\u003eRenewable Electricity \u0026ndash; Analysis\u003c/em\u003e. https://www.iea.org/reports/renewable-electricity (2022).\u003c/li\u003e\n \u003cli\u003eAngliviel de La Beaumelle, N. \u003cem\u003eet al.\u003c/em\u003e The Global Technical, Economic, and Feasible Potential of Renewable Electricity. \u003cem\u003eAnnu. Rev. Environ. Resour.\u003c/em\u003e \u003cstrong\u003e48\u003c/strong\u003e, 419\u0026ndash;449 (2023).\u003c/li\u003e\n \u003cli\u003eRiebl, S., Braun-Unkhoff, M. \u0026amp; Riedel, U. A Study on the Emissions of Alternative Aviation Fuels. \u003cem\u003eJ. Eng. Gas Turbines Power\u003c/em\u003e \u003cstrong\u003e139\u003c/strong\u003e, (2017).\u003c/li\u003e\n \u003cli\u003eChen, C.-C. \u0026amp; Gettelman, A. Simulated 2050 aviation radiative forcing from contrails and aerosols. \u003cem\u003eAtmospheric Chem. Phys.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 7317\u0026ndash;7333 (2016).\u003c/li\u003e\n \u003cli\u003eDray, L. \u003cem\u003eet al.\u003c/em\u003e Cost and emissions pathways towards net-zero climate impacts in aviation. \u003cem\u003eNat. Clim. Change\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 956\u0026ndash;962 (2022).\u003c/li\u003e\n \u003cli\u003eIATA. Passenger Demand Recovery Continued in 2021 but Omicron Having Impact. https://www.iata.org/en/pressroom/2022-releases/2022-01-25-02/ (2021).\u003c/li\u003e\n \u003cli\u003eIEA. \u003cem\u003eWorld Energy Outlook 2021\u003c/em\u003e. 386 https://www.iea.org/reports/world-energy-outlook-2021 (2021).\u003c/li\u003e\n \u003cli\u003eKl\u0026ouml;wer, M. \u003cem\u003eet al.\u003c/em\u003e Quantifying aviation\u0026rsquo;s contribution to global warming. \u003cem\u003eEnviron. Res. Lett.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 104027 (2021).\u003c/li\u003e\n \u003cli\u003eU.S. Energy Information Administration. International Energy Outlook - U.S. Energy Information Administration (EIA). https://www.eia.gov/outlooks/ieo/tables_side_xls.php (2021).\u003c/li\u003e\n \u003cli\u003eInternational Civil Aviation Organisation. Long term global aspirational goal (LTAG) for international aviation. https://www.icao.int/environmental-protection/Pages/LTAG.aspx (2022).\u003c/li\u003e\n \u003cli\u003eBain \u0026amp; Company. Air Travel Forecast to 2030: The Recovery and the Carbon Challenge. \u003cem\u003eBain\u003c/em\u003e https://www.bain.com/insights/air-travel-forecast-interactive/ (2023).\u003c/li\u003e\n \u003cli\u003eFilippone, A. \u003cem\u003eAdvanced Aircraft Flight Performance\u003c/em\u003e. (Cambridge University Press, 2012).\u003c/li\u003e\n \u003cli\u003eAnuar, A., Undavalli, V. K., Khandelwal, B. \u0026amp; Blakey, S. Effect of fuels, aromatics and preparation methods on seal swell. \u003cem\u003eAeronaut. J.\u003c/em\u003e \u003cstrong\u003e125\u003c/strong\u003e, 1542\u0026ndash;1565 (2021).\u003c/li\u003e\n \u003cli\u003eZickfeld, K., Azevedo, D., Mathesius, S. \u0026amp; Matthews, H. D. Asymmetry in the climate\u0026ndash;carbon cycle response to positive and negative CO2 emissions. \u003cem\u003eNat. Clim. Change\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, 613\u0026ndash;617 (2021).\u003c/li\u003e\n \u003cli\u003eZickfeld, K. \u003cem\u003eet al.\u003c/em\u003e Net-zero approaches must consider Earth system impacts to achieve climate goals. \u003cem\u003eNat. Clim. Change\u003c/em\u003e \u003cstrong\u003e13\u003c/strong\u003e, 1298\u0026ndash;1305 (2023).\u003c/li\u003e\n \u003cli\u003eMoretti, C., Moro, A., Edwards, R., Rocco, M. V. \u0026amp; Colombo, E. Analysis of standard and innovative methods for allocating upstream and refinery GHG emissions to oil products. \u003cem\u003eAppl. Energy\u003c/em\u003e \u003cstrong\u003e206\u003c/strong\u003e, 372\u0026ndash;381 (2017).\u003c/li\u003e\n \u003cli\u003eGriffiths, S., Sovacool, B. K., Kim, J., Bazilian, M. \u0026amp; Uratani, J. M. Decarbonizing the oil refining industry: A systematic review of sociotechnical systems, technological innovations, and policy options. \u003cem\u003eEnergy Res. Soc. Sci.\u003c/em\u003e \u003cstrong\u003e89\u003c/strong\u003e, 102542 (2022).\u003c/li\u003e\n \u003cli\u003eDeutz, S. \u0026amp; Bardow, A. Life-cycle assessment of an industrial direct air capture process based on temperature\u0026ndash;vacuum swing adsorption. \u003cem\u003eNat. Energy\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 203\u0026ndash;213 (2021).\u003c/li\u003e\n \u003cli\u003eDelpierre, M., Quist, J., Mertens, J., Prieur-Vernat, A. \u0026amp; Cucurachi, S. Assessing the environmental impacts of wind-based hydrogen production in the Netherlands using ex-ante LCA and scenarios analysis. \u003cem\u003eJ. Clean. Prod.\u003c/em\u003e \u003cstrong\u003e299\u003c/strong\u003e, 126866 (2021).\u003c/li\u003e\n \u003cli\u003eAdnan, M. A. \u0026amp; Kibria, M. G. Comparative techno-economic and life-cycle assessment of power-to-methanol synthesis pathways. \u003cem\u003eAppl. Energy\u003c/em\u003e \u003cstrong\u003e278\u003c/strong\u003e, 115614 (2020).\u003c/li\u003e\n \u003cli\u003eMcQueen, N. \u003cem\u003eet al.\u003c/em\u003e Cost Analysis of Direct Air Capture and Sequestration Coupled to Low-Carbon Thermal Energy in the United States. \u003cem\u003eEnviron. Sci. Technol.\u003c/em\u003e \u003cstrong\u003e54\u003c/strong\u003e, 7542\u0026ndash;7551 (2020).\u003c/li\u003e\n \u003cli\u003eSmith, S. M. \u003cem\u003eet al.\u003c/em\u003e \u003cem\u003eThe State of Carbon Dioxide Removal - 1st Edition\u003c/em\u003e. http://dx.doi.org/10.17605/OSF.IO/W3B4Z (2023) doi:10.17605/OSF.IO/W3B4Z.\u003c/li\u003e\n \u003cli\u003eIRENA. \u003cem\u003eMaking the Breakthrough: Green Hydrogen Policies and Technology Costs\u003c/em\u003e. https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2020/Nov/IRENA_Green_Hydrogen_breakthrough_2021.pdf?la=en\u0026amp;hash=40FA5B8AD7AB1666EECBDE30EF458C45EE5A0AA6 (2021).\u003c/li\u003e\n \u003cli\u003eChristensen, A. \u003cem\u003eAssessment of Hydrogen Production Costs from Electrolysis: United States and Europe\u003c/em\u003e. https://theicct.org/publication/assessment-of-hydrogen-production-costs-from-electrolysis-united-states-and-europe/ (2020).\u003c/li\u003e\n \u003cli\u003eZang, G. \u003cem\u003eet al.\u003c/em\u003e Synthetic Methanol/Fischer\u0026ndash;Tropsch Fuel Production Capacity, Cost, and Carbon Intensity Utilizing CO2 from Industrial and Power Plants in the United States. \u003cem\u003eEnviron. Sci. Technol.\u003c/em\u003e \u003cstrong\u003e55\u003c/strong\u003e, 7595\u0026ndash;7604 (2021).\u003c/li\u003e\n \u003cli\u003eJouny, M., Luc, W. \u0026amp; Jiao, F. General Techno-Economic Analysis of CO2 Electrolysis Systems. \u003cem\u003eInd. Eng. Chem. Res.\u003c/em\u003e \u003cstrong\u003e57\u003c/strong\u003e, 2165\u0026ndash;2177 (2018).\u003c/li\u003e\n \u003cli\u003eShin, H., Hansen, K. U. \u0026amp; Jiao, F. Techno-economic assessment of low-temperature carbon dioxide electrolysis. \u003cem\u003eNat. Sustain.\u003c/em\u003e \u003cstrong\u003e4\u003c/strong\u003e, 911\u0026ndash;919 (2021).\u003c/li\u003e\n \u003cli\u003eMoretti, C. Reflecting on the environmental impact of the captured carbon feedstock. \u003cem\u003eSci. Total Environ.\u003c/em\u003e \u003cstrong\u003e854\u003c/strong\u003e, 158694 (2023).\u003c/li\u003e\n \u003cli\u003eGabrielli, P., Gazzani, M. \u0026amp; Mazzotti, M. The Role of Carbon Capture and Utilization, Carbon Capture and Storage, and Biomass to Enable a Net-Zero-CO2 Emissions Chemical Industry. \u003cem\u003eInd. Eng. Chem. Res.\u003c/em\u003e \u003cstrong\u003e59\u003c/strong\u003e, 7033\u0026ndash;7045 (2020).\u003c/li\u003e\n \u003cli\u003eSchmidt, P., Weindorf, W., Roth, A., Batteiger, V. \u0026amp; Riegel, F. \u003cem\u003ePower-to-Liquids: Potentials and Perspectives\u003c/em\u003e. (2016).\u003c/li\u003e\n \u003cli\u003eSutter, D., van der Spek, M. \u0026amp; Mazzotti, M. 110th Anniversary: Evaluation of CO2-Based and CO2-Free Synthetic Fuel Systems Using a Net-Zero-CO2-Emission Framework. \u003cem\u003eInd. Eng. Chem. Res.\u003c/em\u003e \u003cstrong\u003e58\u003c/strong\u003e, 19958\u0026ndash;19972 (2019).\u003c/li\u003e\n \u003cli\u003eYates, J. \u003cem\u003eet al.\u003c/em\u003e Techno-economic Analysis of Hydrogen Electrolysis from Off-Grid Stand-Alone Photovoltaics Incorporating Uncertainty Analysis. \u003cem\u003eCell Rep. Phys. Sci.\u003c/em\u003e \u003cstrong\u003e1\u003c/strong\u003e, 100209 (2020).\u003c/li\u003e\n \u003cli\u003eKopp, M. \u003cem\u003eet al.\u003c/em\u003e Energiepark Mainz: Technical and economic analysis of the worldwide largest Power-to-Gas plant with PEM electrolysis. \u003cem\u003eInt. J. Hydrog. Energy\u003c/em\u003e \u003cstrong\u003e42\u003c/strong\u003e, 13311\u0026ndash;13320 (2017).\u003c/li\u003e\n \u003cli\u003eAlfian, M. \u0026amp; Purwanto, W. W. Multi-objective optimization of green urea production. \u003cem\u003eEnergy Sci. Eng.\u003c/em\u003e \u003cstrong\u003e7\u003c/strong\u003e, 292\u0026ndash;304 (2019).\u003c/li\u003e\n \u003cli\u003eSchmidt, P., Batteiger, V., Roth, A., Weindorf, W. \u0026amp; Raksha, T. Power-to-Liquids as Renewable Fuel Option for Aviation: A Review. \u003cem\u003eChem. Ing. Tech.\u003c/em\u003e \u003cstrong\u003e90\u003c/strong\u003e, 127\u0026ndash;140 (2018).\u003c/li\u003e\n \u003cli\u003eNosherwani, S. A. \u0026amp; Neto, R. C. Techno-economic assessment of commercial ammonia synthesis methods in coastal areas of Germany. \u003cem\u003eJ. Energy Storage\u003c/em\u003e \u003cstrong\u003e34\u003c/strong\u003e, 102201 (2021).\u003c/li\u003e\n \u003cli\u003eSchmidt, O. \u003cem\u003eet al.\u003c/em\u003e Future cost and performance of water electrolysis: An expert elicitation study. \u003cem\u003eInt. J. Hydrog. Energy\u003c/em\u003e \u003cstrong\u003e42\u003c/strong\u003e, 30470\u0026ndash;30492 (2017).\u003c/li\u003e\n \u003cli\u003eTreyer, K., Sacchi, R. \u0026amp; Bauer, C. \u003cem\u003eLife Cycle Assessment of Synthetic Hydrocarbons for Use as Jet Fuel: \u0026lsquo;Power-to-Liquid\u0026rsquo; and \u0026lsquo;Sun-to-Liquid\u0026rsquo; Processes.\u003c/em\u003e (2022).\u003c/li\u003e\n \u003cli\u003eLiu, C. M., Sandhu, N. K., McCoy, S. T. \u0026amp; Bergerson, J. A. A life cycle assessment of greenhouse gas emissions from direct air capture and Fischer\u0026ndash;Tropsch fuel production. \u003cem\u003eSustain. Energy Fuels\u003c/em\u003e \u003cstrong\u003e4\u003c/strong\u003e, 3129\u0026ndash;3142 (2020).\u003c/li\u003e\n \u003cli\u003eRosental, M., Fr\u0026ouml;hlich, T. \u0026amp; Liebich, A. Life Cycle Assessment of Carbon Capture and Utilization for the Production of Large Volume Organic Chemicals. \u003cem\u003eFront. Clim.\u003c/em\u003e \u003cstrong\u003e2\u003c/strong\u003e, (2020).\u003c/li\u003e\n \u003cli\u003eDoty, F. D., Doty, G. N., Staab, J. P. \u0026amp; Holte, L. L. Toward Efficient Reduction of CO2 to CO for Renewable Fuels. in 775\u0026ndash;784 (American Society of Mechanical Engineers Digital Collection, 2010). doi:10.1115/ES2010-90362.\u003c/li\u003e\n \u003cli\u003eMatute, G., Yusta, J. M. \u0026amp; Correas, L. C. Techno-economic modelling of water electrolysers in the range of several MW to provide grid services while generating hydrogen for different applications: A case study in Spain applied to mobility with FCEVs. \u003cem\u003eInt. J. Hydrog. Energy\u003c/em\u003e \u003cstrong\u003e44\u003c/strong\u003e, 17431\u0026ndash;17442 (2019).\u003c/li\u003e\n \u003cli\u003eReksten, A. H., Thomassen, M. S., M\u0026oslash;ller-Holst, S. \u0026amp; Sundseth, K. Projecting the future cost of PEM and alkaline water electrolysers; a CAPEX model including electrolyser plant size and technology development. \u003cem\u003eInt. J. Hydrog. Energy\u003c/em\u003e \u003cstrong\u003e47\u003c/strong\u003e, 38106\u0026ndash;38113 (2022).\u003c/li\u003e\n \u003cli\u003eTerlouw, T., Bauer, C., McKenna, R. \u0026amp; Mazzotti, M. Large-scale hydrogen production via water electrolysis: a techno-economic and environmental assessment. \u003cem\u003eEnergy Environ. Sci.\u003c/em\u003e (2022) doi:10.1039/D2EE01023B.\u003c/li\u003e\n \u003cli\u003eElsernagawy, O. Y. H. \u003cem\u003eet al.\u003c/em\u003e Thermo-economic analysis of reverse water-gas shift process with different temperatures for green methanol production as a hydrogen carrier. \u003cem\u003eJ. CO2 Util.\u003c/em\u003e \u003cstrong\u003e41\u003c/strong\u003e, 101280 (2020).\u003cstrong\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Footnotes","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003e With Boeing 787-9 Dreamliner\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e Average of Boeing 787-9 Dreamliner, Boeing 777-200LR, Boeing 777-3000LR, and Boeing 767\u0026thinsp;\u0026minus;\u0026thinsp;300\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e With Boeing 737\u0026ndash;900\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-3981416/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3981416/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMitigating the impact of aviation on climate change faces significant challenges due to growing demand and limited scalable mitigation options. As a result, direct air capture (DAC), a novel technology, may gain prominence due to its versatile applications as either an emissions offset (DACCS) or a synthetic fuel production technology (DACCU). Through a comprehensive analysis of cost-effectiveness, life-cycle emissions, energy consumption, and technology scale-up, we explore the conditions under which synthetic fuels from DACCU can become competitive with an emit-and-offset strategy. We find that DACCU is competitive with an emit-and-offset strategy once we explicitly include non-CO\u003csub\u003e2\u003c/sub\u003e climate impacts and under favorable conditions such as low electricity and high fossil fuel prices and emissions pricing. By highlighting strategic interventions that favor these conditions and thus enhance the competitiveness of DACCU in the aviation sector, our results provide valuable insights into how policymakers could move the aviation sector away from fossil fuels.\u003c/p\u003e","manuscriptTitle":"Synthetic fuels may be a cheaper way to achieve climate-neutral aviation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-08 12:09:41","doi":"10.21203/rs.3.rs-3981416/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f5de5f4e-698c-4fd7-9923-25b98fc16b12","owner":[],"postedDate":"April 8th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":29361483,"name":"Earth and environmental sciences/Environmental social sciences/Climate-change mitigation"},{"id":29361484,"name":"Earth and environmental sciences/Environmental sciences/Environmental impact"},{"id":29361485,"name":"Earth and environmental sciences/Environmental social sciences/Energy and society/Energy economics"}],"tags":[],"updatedAt":"2025-01-12T08:05:39+00:00","versionOfRecord":{"articleIdentity":"rs-3981416","link":"https://doi.org/10.1038/s41467-024-55482-6","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-01-11 05:00:00","publishedOnDateReadable":"January 11th, 2025"},"versionCreatedAt":"2024-04-08 12:09:41","video":"","vorDoi":"10.1038/s41467-024-55482-6","vorDoiUrl":"https://doi.org/10.1038/s41467-024-55482-6","workflowStages":[]},"version":"v1","identity":"rs-3981416","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3981416","identity":"rs-3981416","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}