What Sheffield Proved — and What It Did Not

The University of Sheffield study, led by Professor Meihong Wang and published in Nature Communications (DOI: 10.1038/s41467-025-67977-x), is a rigorous piece of process engineering modelling. The core innovation is replacing natural gas combustion in the liquid direct air capture (L-DAC) calciner with concentrated solar energy delivered through a hydrogen-fluidised calciner heated by a field of mirrors. Conventional L-DAC using Carbon Engineering technology emits approximately 0.58 tonnes of CO2-equivalent per tonne of CO2 captured because natural gas combustion at 800-900 degrees Celsius accounts for more than 90% of total energy consumption. Solar heating, in principle, eliminates that emission entirely.

The model projects a minimum selling price (MSP) of $4.62/kg for the resulting SAF, compared to $5.60/kg for fossil-heated DACCU, a 17% cost reduction. The five geographies identified as optimal for production are the United States, Chile, Spain, South Africa, and China, selected for high solar irradiance combined with relatively low green hydrogen and land costs.

What the study did not prove is that any of this works at scale. The paper is a computer simulation. There is no physical pilot plant. The broader DACCU category is currently in the R&D phase. The L-DAC base technology developed by Carbon Engineering does carry a relatively mature technology readiness level (TRL 7-8), with large-scale plants under construction in the United States and United Kingdom. But the integration of solar heating into that process via a hydrogen-fluidised calciner is a novel configuration that has not been demonstrated at any meaningful scale. The Sheffield result should be read as a proof of concept with credible underlying physics. It is not a deployment roadmap.

Where $4.62/kg Sits in the eSAF Cost Landscape

The Nature Communications paper references a 2022 SAF market price of $2.40/kg and conventional jet fuel at $1.10/kg. As of January 2026, HEFA-SAF produced from used cooking oil is trading at approximately $2.00/kg ex-Netherlands, according to Fastmarkets pricing data. Against those benchmarks, the Sheffield projected MSP of $4.62/kg is 2.3 times the current HEFA-SAF price and 4.2 times the cost of conventional jet fuel.

That gap is not a rounding error. It represents a structural cost problem that modelling improvements alone cannot solve. Even if the solar DACCU process works exactly as designed, aviation fuel buyers cannot voluntarily absorb a 130% cost premium without blending mandates, carbon pricing mechanisms, or direct subsidy support significant enough to bridge the gap.

Every serious eSAF pathway today is converging on the same expensive neighborhood. The Sheffield result narrows the gap with HEFA but does not close it, and it depends on green hydrogen infrastructure that does not yet exist at the required cost or scale.

The European Power-to-Liquid cost range projected for 2030 sits at approximately 1.22 euros per litre, equivalent to roughly 1,525 euros per tonne, according to RSC Publishing analysis from January 2024. That figure is broadly consistent with the Sheffield projection, suggesting the entire class of electrofuels and solar-driven SAF pathways faces the same affordability challenge, not just this one paper.

Bottlenecks Between the Model and the Market

Three categories of bottleneck sit between Sheffield’s simulation and any commercial solar SAF operation: technology integration risk, cost of green hydrogen, and geographic and infrastructure constraints.

On technology integration: the solar heating integration via a hydrogen-fluidised calciner requires precise thermal management at sustained temperatures above 800 degrees Celsius, delivered intermittently by solar to a process that has historically run on continuous fossil combustion. Thermal storage, process stability, and materials durability at those temperatures in a solar configuration have not been demonstrated in this context. Each of those engineering challenges represents real capital and time to solve.

On green hydrogen: the Sheffield model’s cost competitiveness depends on access to low-cost green hydrogen. Green hydrogen supply chains at the volumes needed to support commercial SAF production are nascent almost everywhere. A solar SAF plant that requires cheap green hydrogen is betting on a commodity market that does not yet exist at scale.

On geography and infrastructure: the five identified optimal countries span three continents. Airlines require fuel at airports in Europe, North America, and Asia-Pacific. Producing solar SAF in Chile or South Africa and transporting it to Frankfurt or Singapore adds logistics cost and supply chain complexity that the MSP model likely does not fully capture.

How Sheffield Compares to Metafuels and Twelve

Metafuels is building the Turbe plant at the Port of Rotterdam, which it describes as the first commercial eSAF plant in Europe. In April 2026, the project received a 1.92 million euro grant from the Dutch government. The aerobrew process uses green methanol as feedstock and converts it to SAF via a methanol-to-jet pathway. Metafuels has not published a cost-per-kilogram figure for its output. What the Turbe plant demonstrates is that the path from model to plant is achievable. It just takes years and real capital.

Twelve’s AirPlant One project in Moses Lake, Washington, uses CO2 electrolysis with water and renewable electricity to produce SAF intermediates. The company raised $645 million in September 2024, including $400 million in project equity from TPG Rise Climate and a $200 million Series C. Twelve has not published a cost-per-kilogram figure for commercial-scale output. Academic modelling of CO2 electrolysis-assisted SAF pathways published in ScienceDirect in June 2025 projects a levelized cost of fuel in the range of $3.88 to $4.46/kg, which is below the Sheffield $4.62/kg projection but still well above current HEFA pricing.

All three pathways are converging on a similar cost range in the mid-to-high $4/kg band. None of them have published verified commercial cost figures. What this convergence suggests is that the eSAF cost challenge is not pathway-specific. It is systemic. Any pathway that relies on renewable electricity, green hydrogen, or CO2 capture at current technology and energy costs will land in roughly the same expensive neighborhood. The differentiation will come down to which technology reaches commercial scale first and which operates in geographies where policy support is most favorable. Sheffield’s solar DACCU pathway is the furthest from that finish line. Twelve and Metafuels are building real plants now.

What Would Need to Be True for Solar SAF to Matter by 2035

First, green hydrogen costs would need to fall substantially. The IEA and most credible analysts project green hydrogen potentially reaching $2 to $3 per kilogram in favorable locations by 2030, down from $4 to $8/kg today. If that trajectory holds, it would pull down the input costs in the Sheffield model meaningfully. But cost projections for green hydrogen have a poor track record. The same optimistic curves were drawn for battery storage and offshore wind in prior decades, and while those technologies did fall in cost, they consistently took longer than forecasts suggested.

Second, policy support would need to materialize and hold. The EU’s ReFuelEU Aviation regulation includes a 1.2 percent sub-mandate for synthetic fuels from 2030, which creates a floor of demand for power-to-liquid pathways in European markets. The United States has no equivalent PtL-specific mandate. Without a mandate that carves out demand specifically for synthetic fuels, solar DACCU cannot rely on policy to bridge the price gap in the largest aviation market in the world.

Third, and most fundamentally, the technology still needs a physical demonstration. The Sheffield model is built from credible component-level data, but solar-thermal integration with DACCU and Fischer-Tropsch synthesis at co-located commercial scale has not been demonstrated in a single facility. No techno-economic analysis resolves system integration problems. A pilot plant is the only way to find out whether the integrated system performs as the model predicts.

That brings the timeline question into sharp relief. 2035 is nine years away. Novel energy technologies at the pre-pilot stage typically require 10 to 15 years to reach commercial-scale deployment. Solar DACCU has not yet completed the first of those steps. The Sheffield paper is a meaningful signal that the pathway deserves serious research investment. It is not a signal that commercial relevance by 2035 is achievable.

Key Takeaways

• The University of Sheffield modeled solar-driven DACCU at a projected MSP of $4.62/kg of SAF, using concentrated solar heat via a hydrogen-fluidised calciner to replace fossil fuel combustion. The result is 17% lower than fossil-heated DACCU but 2.3 times the current HEFA-SAF market price of approximately $2.00/kg.
• The study is a computer simulation. No physical pilot plant exists. The solar heating integration is a novel configuration not yet demonstrated at any meaningful scale, and DACCU as a category remains in the R&D phase.
• All serious eSAF pathways are converging on a similar high-cost range: Sheffield at $4.62/kg, academic CO2 electrolysis models at $3.88 to $4.46/kg, and European PtL projections at roughly $1,525/tonne for 2030. The binding constraint is expensive inputs, not pathway choice.
• Commercial relevance by 2035 would require green hydrogen falling from $4-8/kg to $2-3/kg, a successful integrated pilot demonstration, and policy mandates for synthetic fuels in key markets. The EU has a 2030 PtL sub-mandate; the US does not.
• The Sheffield result is a credible contribution to the research literature that justifies continued investment in solar DACCU as a long-term pathway. It does not support a near-term commercial timeline.

Source: Nature Communications — Solar-driven direct air capture to produce sustainable aviation fuel (DOI: 10.1038/s41467-025-67977-x)

Sources:

1. Wang, M. et al. (2026). Solar-driven direct air capture to produce sustainable aviation fuel. Nature Communications. DOI: 10.1038/s41467-025-67977-x
2. University of Sheffield. Press release: Solar energy could be key to making sustainable aviation fuel. March 2026. sheffield.ac.uk/news
3. Fastmarkets. HEFA-SAF spot price assessment, ex-Netherlands. January 2026.
4. Metafuels/Evos. Partnership announcement and Dutch government GroenvermogenNL grant of €1.92 million. April 2026. metafuels.ch
5. Twelve. $645 Million in Funding Led by TPG. PR Newswire, September 19, 2024.
6. ScienceDirect. CO2 Electrolysis-Assisted SAF production: Cost optimization. June 2025.
7. RSC Publishing. Future costs of power-to-liquid SAF from hybrid solar PV-wind plants in Europe. January 2024. DOI: 10.1039/D3SE00978E