Power-to-liquid (PtL) fuels are carbon-based liquid fuels made from hydrogen and carbon dioxide that can substitute fossil fuels in hard-to-electrify mobility sectors, particularly aviation and maritime transport, but their climate benefits depend strongly on how hydrogen, carbon dioxide, and electricity are supplied. Here, we assess global economic and environmental trade-offs for three PtL pathways: power-to-methanol, methanol-to-jet synthetic kerosene, and Fischer-Tropsch synthetic kerosene. We develop a high-resolution, spatially explicit framework that combines energy system optimization, techno-economic and prospective life cycle assessment. Low production costs and low greenhouse gas (GHG) emissions are often geographically misaligned today: renewable-rich regions such as North Africa, southern South America, and the Iberian Islands offer low-cost opportunities, whereas low-GHG grid-connected production is concentrated in regions with low-carbon power systems, such as Canada and northern Europe. Grid-connected production can be cost-effective but loses its climate advantage in carbon-intensive power systems, whereas off-grid renewable production delivers the lowest emissions at a cost premium. Configurations that combine grid electricity with dedicated renewables weaken this trade-off but remain sensitive to residual grid carbon intensity. For synthetic kerosene, Fischer-Tropsch routes are generally less GHG-intensive than methanol-to-jet routes under comparable electricity supply. Carbon pricing, sustainable aviation fuel (SAF) mandates, and fossil-fuel price volatility can narrow the cost gap, but mainly for configurations with low well-to-wake emissions. PtL deployment should therefore be guided by electricity supply, regional siting, and full life cycle impacts rather than fuel labels alone.

Pulsed electrochemical CO2 reduction has emerged as a strategy to extend electrolyzer lifetime by periodically interrupting reductive operation with short oxidative pulses. Here we investigate the effect of oxidative pulse potential, pulse frequency, and pulse duration on the selectivity and structural integrity of electrospun polymer-based silver gas diffusion electrodes over extended periods of operation. We show that the threshold potential for anodic dissolution of silver at 0.55 V vs. SHE defines an upper boundary for the pulse potential: pulses with a potential below this threshold enable periodic local acidification of the electrolyte in the vicinity of the catalyst promoting partial dissolution of (bi)carbonate precipitates, while pulses with a potential above the threshold drive a silver dissolution-redeposition cycle that restructures the catalyst into silver clusters promoting the hydrogen evolution reaction. Systematic exploration of the pulse parameter space identifies an optimal protocol consisting of 10-seconds-long oxidative pulses applied every 30 minutes, yielding a duty cycle exceeding 99%. Under these conditions, carbon product faradaic efficiency is maintained in the range of 70–80% over 100 hours of operation, representing a five-fold improvement in selectivity relative to continuous electrolysis. Our results demonstrate the potential of pulsed electrolysis to maintain high CO selectivity over long operational periods, thus representing an important step towards the industrialization of CO2 electrolysis.

The 3rd annual conference of the SWEET Consortium reFuel.ch brought together 88 participants from research, industry, and public administration at the Akademie at Empa in Dübendorf to discuss implementation options for Sustainable Aviation Fuels and Power-to-X technologies in Switzerland and abroad. For those who were unable to attend in person, the following overview compiles the key insights, findings, and takeaways presented throughout the day.

Decentralized ammonia production via electric Haber–Bosch (Haber–Bosch 2.0) could support shipping, chemical manufacturing, and local fertilizer supply chains. Unlike conventional Haber–Bosch systems, Haber–Bosch 2.0 technologies operate at lower pressures (∼30–60 bar) and temperatures (∼400 °C), enabling smaller, modular ammonia systems powered by low-carbon electricity. However, its economic viability and environmental performance under diverse conditions remain unclear. Here, we apply techno-economic and environmental life cycle assessment using a novel, open-source framework to optimally design ∼13 000 grid-connected, hybrid, and off-grid electric Haber–Bosch configurations worldwide. Our results demonstrate that decentralized ammonia production costs are between €740–4100 tNH3−1, which is substantially higher compared to centralized ammonia production (∼300 tNH3−1 historically with recent spikes up to ∼€800 tNH3−1). Hybrid configurations exhibit the lowest costs (€740–2090 tNH3−1), particularly in regions with low grid electricity prices, low capital costs, and/or abundant renewables. However, their GHG emissions vary widely depending on the GHG intensity of the local grid. Off-grid systems exhibit the lowest life cycle GHG emissions (on average 0.70 tCO2-eq. tNH3−1), but demonstrate high costs (more than €1100 tNH3−1), driven by oversized renewables and energy storage media to enable continuous Haber–Bosch operation. Cost parity may be achieved by 2050 through technology learning, especially for hybrid systems (€325 tNH3−1). To realize this potential and secure low-carbon fertilizer supply, policymakers should; (1) accelerate the decarbonization of national power grids, (2) provide early-stage deployment support for flexible, electric Haber–Bosch technologies, and (3) establish clear certification standards for low-carbon ammonia.

More than 50 participants joined a reFuel.ch coordination meeting to exchange insights and explore collaboration opportunities ahead of the upcoming call.

Carbon-neutral energy systems will rely heavily on electrification and intermittent renewables, thereby increasing the need for flexible technologies such as gas turbines. Using alternative fuels in gas turbines could reduce greenhouse gas emissions and support net-zero goals, but their full life-cycle emissions impact has not been evaluated yet. This study presents a prospective life cycle assessment (LCA) of simple cycle gas turbines (SCGTs) in Switzerland, evaluating their performance with various alternative fuels and the potential integration of carbon capture technologies. The analysis considers domestically produced biomethane (from wood chips or biogas) and four e-fuels─e-hydrogen, e-methane, e-ammonia, and e-Fischer-Tropsch (e-FT) fuels─synthesized in regions with cost-effective renewable electricity in Spain, Iceland, and the Netherlands. Regarding carbon capture, we investigate both storage (CCS) and utilization (CCU), considering storage sites in Italy and Norway. The assessment covers multiple impact categories across 2035 and 2050. The results show that domestic biomethane provides a practical and climate-friendly option, reducing life-cycle climate impacts by nearly 80% in the near term and approaching 90% in the long term. In contrast, e-methane does not exceed an 80% reduction in the long term even under its most favorable production pathways. Both biomethane and e-methane can offer net-negative emissions if combined with CCS. Domestic CCU does not offer any environmental advantage if liquefying and transporting hydrogen (H2), instead of directly importing e-methane via pipeline. Multimodal transport increases environmental impacts compared to pipeline transport across several categories. Beyond climate impacts, alternative fuel production introduces trade-offs across most categories compared with natural gas. This study underscores that minimizing greenhouse gas emissions alone is insufficient and that system-level assessments are essential to minimize overall environmental impacts in future flexible power systems.

On March 5th, representatives of the SWEET Consortium reFuel.ch initiative joined around 70 participants for the fifth Round Table in Winterthur. The event brought together researchers, industry experts, and policymakers to exchange insights on emerging energy technologies and market developments in sustainable fuels.

Low-carbon fuels (LCFs) such as green hydrogen, synthetic hydrocarbons, and biofuels are critical for decarbonizing sectors that are difficult to electrify. In this study, we present a globally harmonized techno-economic assessment of 21 LCF production pathways, including power-to-X, biomass- and sun-to-liquids, and multiple hydrogen routes, evaluated across all countries under three future scenarios for 2024, 2030, and 2050. The model integrates spatially explicit resource data, learning-driven capital cost trajectories, and dynamic, country- and technology-specific costs of capital, supported by robust scenarios and uncertainty analysis. By 2050, median levelized costs are projected to range from 0.07 to 0.10 EUR2024 per kWh for green hydrogen, 0.15 to 0.18 EUR2024 per kWh for power-to-liquid kerosene, and 0.14 to 0.20 EUR2024 per kWh for most bio-based aviation fuels, reflecting both substantial progress and persistent regional disparities. Our results show that while innovation, technology learning, and deep power sector decarbonization can unlock cost-competitive electrofuels in countries with abundant renewables, bio-based routes are frequently cost competitive for sustainable aviation fuel (SAF) production in near-term scenarios, and solar-to-liquid fuels remain constrained by feedstock availability and capital barriers. Nuclear- and methane-based hydrogen emerge as primary options in many regions, as well as the dominance of turquoise hydrogen in Russia, the Middle East, and Central Asia where carbon management is viable, which highlights the context-specific nature of future LCF systems. We also found that the least-cost logistics for global hydrogen trade will shift from ammonia shipping to pipeline transport and methanol delivery, with North Africa and Iberia emerging as leading suppliers to Europe. These findings underscore the need for integrated innovation, policy coordination, and investment strategies that address both resource and financial barriers, in order to achieve scalable, resilient, and cost-effective LCF supply chains worldwide.

Transitioning the aviation sector to synthetic aviation fuels (SAF) requires innovative catalytic processes to overcome common limitations such as insufficient activity, selectivity, and catalyst deactivation. This study presents a detailed exploration of silica-supported phosphotungstic acid (PTA/SiO2) as a robust solid acid catalyst for propylene conversion into jet fuel-range hydrocarbons (C8 to C16) at mild reaction conditions (150 °C). The catalyst with optimized PTA loading (10 wt %) demonstrates significant oligomerization performance, achieving high selectivity to jet fuel-range hydrocarbons (>80%) and propylene conversion (>90%), alongside limited aromatic byproducts formation. Compared to conventional solid-acid catalysts such as a ZSM-5 zeolite, PTA/SiO2 exhibits significantly reduced catalyst deactivation and can be regenerated through mild thermal treatment (<400 °C). Detailed structural characterization revealed that PTA island size influences product selectivity. Increasing the PTA weight loading leads to larger active phase island sizes, with larger PTA islands preferentially producing longer-chain hydrocarbons (C15+). Raman spectroscopy confirms the preservation of the PTA Keggin structural integrity across all catalyst loadings, although perturbations in terminal W═O vibrations occur due to interactions with the SiO2 support. Crucially, insights obtained through combined XPS/HAXPES analyses reveal significant electronic interactions between PTA and SiO2, characterized by pronounced bending of the energy bands at the interface between semiconducting PTA and insulating SiO2. This effect generates interfacial tungsten states, which enhance localized electron mobility and facilitate proton transfer, significantly amplifying catalytic activity. Even catalysts with minimal Brønsted acidity (1 wt % PTA loading) exhibit notable turn over, emphasizing interfacial electronic modulation, rather than bulk acidity alone, as an important performance descriptor in olefin oligomerization.

An important step for moving forward in developing a sustainable fuel production: The SWEET Consortium reFuel.ch and the Port of Sohar and Freezone in Oman are joining forces for launching a research and production facility. Their commitment to collaborate in upscaling sustainable fuel production is marked by a letter of intent, signed at the Green Hydrogen Summit in Oman in December 2025.

The fourth virtual Round Table of the SWEET Consortium reFuel.ch, held on November 19, brought together 76 participants from industry, public administration, and academia. Taking place twice a year, the event fosters knowledge exchange on technology and policy readiness and tracks developments in the emerging market for renewable and low-carbon fuels.

Hydrogen will play a critical role in decarbonizing diverse economic sectors. However, given limited sustainable resources and the energy-intensive nature of its production, prioritizing its applications will be essential. Here, we analyse approximately 2,000 (low-carbon) hydrogen projects worldwide, encompassing operational and planned initiatives until 2043, quantifying their greenhouse gas (GHG) emissions and mitigation potential from a life cycle perspective. Our results demonstrate the variability in GHG emissions of hydrogen applications, depending on the geographical location and hydrogen source used. The most climate-effective hydrogen applications include steel-making, biofuels and ammonia, while hydrogen use for road transport, power generation and domestic heating should be discouraged as more favourable alternatives exist. Planned low-carbon hydrogen projects could generate 110 MtH2 yr−1, emit approximately 0.4 GtCO2e yr−1, and potentially reduce net life cycle GHG emissions by 0.2–1.1 GtCO2e yr−1 by 2043, depending on the substituted product or service. Addressing the current hydrogen implementation gap and prioritizing climate-effective applications are crucial for meeting decarbonization goals.

The second annual conference of the SWEET Consortium reFuel.ch consortium brought together nearly one hundred participants from national and international research, administration and industry at the Paul Scherrer Institute PSI in Villigen AG.

Urban energy systems (UES) design must adapt to the multifaceted challenges of an evolving global energy landscape. This study examines ten critical questions that define current challenges, methodologies, and future priorities in UES design, providing a comprehensive understanding of techno-economic and socio-institutional aspects. It first examines the lateral and vertical interactions across spatial scales, sectors, and time, as well as the evolving needs in heating, cooling, transportation, and renewable integration. Consequently, the study critically assesses the capabilities and limitations of current energy system modeling practices, highlighting challenges related to data requirements, system complexity, scalability, and uncertainty analysis. It then discusses building energy demand and building stock modeling to provide high-resolution analyses of decarbonization pathways and to support effective demand-side management and storage solutions. As these approaches require data, the role of data availability and governance in UES design through the integration of advanced technologies such as artificial intelligence is reviewed. Moreover, it is important to consider dimensions beyond digital tools. The study discusses the inclusion of broader environmental dimensions beyond greenhouse gas emissions into UES planning to ensure sustainable pathways. It also emphasizes the role of governance, policy, business models, and social engagement in successful deployment of UES. Finally, this study analyzes how UES design can enable emerging urban visions and address the unique challenges faced by low- and middle-income countries in the Global South. By answering the ten most relevant questions on UES design, this paper aims to examine the future priorities of UES design and to offer actionable solutions for creating more resilient, fair, and sustainable urban energy futures.

Switzerland’s updated CO₂ Act mirrors the EU’s ReFuelEU Aviation regulation, setting ambitious mandates for sustainable aviation fuel (SAF) blending. However, despite regulatory clarity, significant questions remain about the industry’s readiness to meet these targets.

The reaction conditions in industrial scale chemical reactors can differ markedly from the ones in a small laboratory scale reactor. The differences are both conceptual and practical, and can at best be analysed by studying a full reactor, which requires an analytical method capable of quantifying the distribution of reactants and products in a running reactor. For this, we introduce non-destructive operando neutron imaging in combination with modelling. As a representative reaction, we studied the hydrogenation of carbon dioxide to methane selected due to the large neutron cross-section of hydrogen and hydrogen-containing species. The integration of the measurement setup/reactor into the neutron beamline enables the temporally resolved measurement of the distribution of adsorbed water on the catalyst under operating conditions (p, T). The resulting quantitatively determined partial pressure of the water thus indirectly enables the spatial and temporal conversion of the processes. The knowledge gained from this experimental approach, combined with modelling, allows the design of reactor dimensions under optimized reaction conditions. The good agreement between simulation and experimental neutron imaging warrants the method as a reliable instrument for reactor characterization and design, with the prospect of its application on reactors on the industrial scale.

Low-carbon fuels (LCFs) are crucial for achieving net-zero CO2 emission goals in integrated assessment model (IAM) and energy system model (ESM) scenarios. The absence of a standardized LCF classification system and inconsistencies in modeling approaches have obscured the integration of various LCFs within these models and makes a meaningful comparison of scenario outcomes difficult. This study addresses these issues by conducting a comprehensive critical review of the representation of LCFs in IAMs and ESMs, focusing on the fuel's role in shaping net-zero emission futures. We categorize LCFs into key groups, including electrification, hydrogen, synfuels, and biofuels. Our analysis reveals substantial gaps in technical modeling, lifecycle emissions data, incomplete modeling of environmental impacts beyond CO2 emission, and discrepancies in LCF applications across sectors. To enhance the accuracy of future scenarios, we recommend adopting a unified LCF classification system, standardized input data, and more detailed sectoral applications. Additionally, we advocate for the integration of Life Cycle Assessment (LCA) into IAMs and ESMs to improve the evaluation of LCFs' full environmental impacts, providing a more comprehensive foundation for net-zero emission pathways.

Key stakeholders and researchers gather for productive discussions on sustainable fuels

Growing demand for air travel and limited scalable solutions pose significant challenges to the mitigation of aviation’s climate change impact. Direct air capture (DAC) may gain prominence due to its versatile applications for either carbon removal (direct air carbon capture and storage, DACCS) or synthetic fuel production (direct air carbon capture and utilization, DACCU). Through a comprehensive and time-dynamic techno-economic assessment, we explore the conditions for synthetic fuels from DACCU to become cost-competitive with an emit-and-remove strategy based on DACCS under 2050 CO2 and climate neutrality targets. We find that synthetic fuels could achieve climate neutrality at lower cost than an emit-and-remove strategy due to their ability to cost-effectively mitigate contrails. Under demand reductions, contrail avoidance, and CO2 neutrality targets the cost advantage of synthetic fuels weakens or disappears. Low electricity cost (€0.02 kWh-1) and high fossil kerosene prices (€0.9 l-1) can favor synthetic fuels’ cost-competitiveness even under these conditions. Strategic interventions, such as optimal siting and the elimination of fossil fuel subsidies, can thus favor a shift away from fossil-reliant aviation.

To reduce environmental impacts from the shipping industry, the FuelEU Maritime Regulation has set a binding 80 % reduction target for well-to-wake (WTW) greenhouse gas (GHG) emissions by 2050. This article presents a prospective life cycle assessment (LCA) comparing the environmental impacts of e-ammonia, e-methanol, e-Fischer Tropsch (FT) diesel, and e-liquefied natural gas (LNG)—for maritime applications in Europe. In addition to e-fuels, traditional propulsion technologies using very low sulfur fuel oil (VLSFO) and LNG are assessed, both with and without integrating ship-based carbon capture (SBCC) systems. Key factors considered include the impact of different production locations in Europe, electrolysis technology choices, and global climate policies. Beyond analysing the environmental footprints, the study examines the economic and externality costs associated with each fuel option, contextualizing these findings within the GHG mitigation targets set by the FuelEU Maritime regulation.The results indicate that e-ammonia, e-FT diesel, and e-methanol could meet the 2050 FuelEU Maritime target, but e-LNG and SBCCS could not. Although it is the most immature technology, e-ammonia could be the cheapest option with the lowest overall environmental impacts. E-LNG shows higher life cycle climate change impacts due to ship-level methane slip but has lower impacts across other environmental categories because of low NOx emissions. E-methanol has higher toxicity risks over the life cycle and higher costs.

Hydrogen is a volatile element, both as a molecular gas and as atomic hydrogen in materials. A method is described for the detection of the corresponding dynamic hydrogen in matter, as opposed to the relatively stable bond hydrogen (“static hydrogen”). The method is based on laser-stimulated hydrogen desorption using nanosecond laser pulses in the UV optical range. The principle, already established for surface hydrogen on nonabsorbent metals has been extended to hydrogen affine bulk systems. The feasibility of the idea is demonstrated by quantifying hydrogen in hydrogen-permeable metal membranes. Model experiments, such as HD exchange, provide input to the model to extract the surface hydrogen concentration of dynamic hydrogen from laser-stimulated hydrogen desorption while eliminating the influence of the laser-matter interaction on the quantification. An estimate of the limit of detection is given.

Complex modeling of periodic excitation combined with time-resolved product detection is used to describe the complex response function of a catalytic system. We describe this concept of catalytic impedance spectroscopy (CIS) and the underlying general experimental approach and a concrete setup. The feasibility of CIS is experimentally demonstrated along the catalytic CO2 methanation reaction. The measurements confirm the theoretically anticipated rate-determining step of HCO* → CH* on Ni catalysts. Limitations and prospects of CIS to unravel reaction mechanisms are discussed.

Experts from research and industry discussed the technical and regulatory challenges of implementing sustainable fuels and platform chemicals at the first annual conference of the SWEET Consortium reFuel.ch.

This study investigates the cost and climate change mitigation potentials of fuels and chemicals from CO2 and low-carbon hydrogen produced in four sites with favorable conditions for renewable energy generation, located in Iceland, The Netherlands, Spain, and Chile. We investigate eight different chemicals, i.e., Fischer–Tropsch fuels, methanol, methane, dimethyl ether, ammonia, urea, olefins, and aromatics, considering two temporal horizons, i.e., the near future (by 2035) and the long-term future (post-2035). For hydrogen production, we explore alkaline water electrolysis, proton exchange membranes, and solid oxide electrolyzer cells. As carbon feedstock, we focus on CO2 produced via low-temperature solid adsorption direct air capture (LT DAC). Additionally, we investigate CO2 from high-temperature aqueous absorption DAC and point-source capture. We find that optimal renewable energy sites like the ones considered in this study have the potential to offer competitive costs for carbon capture and utilization (CCU) processes. These routes, when compared to the current price of their fossil-based counterparts, could achieve long-term future cost ratios ranging from 1 to 6.5 times, with a cost per ton of CO2eq avoided estimated between 150 and 750 €/t. In conclusion, this research provides valuable insights into the techno-economic feasibility of relying on fuels and chemicals via CCU processes as an energy policy strategy.

Sustainable jet fuel plays a crucial role in reducing aviation’s carbon footprint, offering a promising approach toward net-zero emissions in the aviation sector. This work investigates pathways for producing jet fuels directly from CO2. Given the early stage of many direct CO2 utilization technologies, identifying promising pathways is essential. Our investigation focuses on the three most important routes for jet fuel production, each of which employs a distinct intermediate compound. These routes are the reverse water–gas shift and Fischer–Tropsch (RWGS-FT) route, the methanol route, and the CO2 electrolysis route, which employ syngas, methanol, and ethylene as key intermediates, respectively. By performing comprehensive process simulations and analyzing the resulting energy intensity and thermal and CO2 efficiency of each route, these findings provide quantitative early-stage evaluations and allow us to identify key technical development requirements.

Developing robust supply paths for sustainable fuels and basic chemicals for Switzerland is the aim of the "reFuel.ch" consortium funded by the Swiss Federal Office of Energy (SFOE), which held its kick-off event on 8 December 2023. The consortium comprises nine Swiss universities, universities and research institutes from various disciplines as well as an industrial partner. As time is pressing for climate-friendly solutions, political decision-makers will also be involved.

A decision has been made on the call for proposals “Sustainable Fuels and Platform Chemicals”: The reFuel.ch consortium led by Empa will receive project funding.