Key takeaways
- Depending on the feedstock and production pathway, SAF can reduce life cycle greenhouse gas emissions by 80–90% compared with conventional jet fuel.
- There's no universally optimal SAF production route. HEFA, alcohol-to-jet, Fischer-Tropsch, and power-to-liquid each bring different advantages and constraints, making local feedstock availability, infrastructure, energy availability, and policy conditions critical to technology selection.
- Brownfield conversion can accelerate SAF deployment, but existing infrastructure creates value only when it’s technically suitable for the new duty and doesn’t introduce disproportionate modification costs, operating constraints, or reliability risk.
- The SAF projects most likely to move forward will be those that can sustain high-quality production despite feedstock variability, utility constraints, catalyst degradation, maintenance requirements, and other real-world operating conditions.
Commercial aviation is facing one of the energy transition’s toughest decarbonization challenges. The sector’s carbon footprint accounts for roughly 2%–3% of global CO2 emissions, yet very few practical decarbonization pathways exist, especially for medium- and long-haul flights.
Commercial aircraft need fuels with exceptionally high energy density, meaning they carry substantial energy at the lowest weight possible, leaving more weight available for payload and range. Electrification and hydrogen propulsion could eventually help decarbonize aviation, especially on shorter routes. But even once electric and hydrogen aircraft are ready for production, replacing the global fleet will take decades, as today’s aircraft typically stay in service for 30 to 40 years before being retired.
Meanwhile, improvements in engines, airframes, and fleet efficiency will continue to reduce fuel consumption incrementally, which means liquid fuels will remain necessary for the foreseeable future. And with passenger air travel projected to more than double by 2050, the industry must accommodate growth while materially reducing the carbon intensity of its operations. Right now, the only viable solution is sustainable aviation fuel (SAF).
The SAF opportunity centers on supply rather than demand
SAF is jet fuel produced from renewable or waste-based sources—used cooking oil, waste fats, agricultural and forestry residues, municipal solid waste, alcohols, renewable hydrogen combined with captured CO2—rather than from petroleum. Developers can convert these feedstocks into usable jet fuel through several certified pathways, each relying on distinct chemical or biological processes that vary in cost, scalability, and emissions impact.
While SAF is chemically very similar to standard jet fuel and does release CO2 when burned, much of that carbon originates from recently absorbed atmospheric CO2 or from waste streams, rather than from newly extracted fossil resources. That distinction—recycled carbon versus newly extracted carbon—is what reduces its net carbon footprint. Depending on the specific pathway and feedstock, SAF life cycle greenhouse gas emissions can be 80%–90% lower than fossil-based jet fuel.
Another advantage of SAF is that airlines don’t have to modify existing aircraft engines to use it. Most commercial aircraft today are approved to use a fifty-fifty SAF blend with standard jet fuel. Engine and aircraft makers operate within blending limits set by specific production pathways and technical standards, though they’re working toward 100% SAF certification. Airbus, for instance, has pledged that its commercial aircraft will be certified for 100% SAF by 2030. Airports offering SAF can also use existing fuel storage, handling, and distribution systems with little or no modifications. San Francisco International Airport is a good example; it was the first airport to receive SAF via the same pipeline originally built for conventional jet fuel.
Recent policy developments and market activity also reflect SAF's potential, with many governments now introducing blending mandates, tax incentives, subsidies, and other financial support mechanisms to accelerate adoption. The European Union’s (EU) ReFuelEU aviation regulation is among the best-known. From 2025, it’s called for a minimum SAF share of 2% at EU airports, rising to 70% by 2050.
Airlines are also expanding long-term offtake commitments, or contracts to purchase a set volume of fuel over multiple years. Air France-KLM agreed to purchase up to 1.5 million tons of SAF through 2035. Similarly, International Airlines Group contracted for 785,000 tons over 14 years to support its five European airlines, including British Airways, Iberia, and Aer Lingus.
These measures, combined with the industry’s own ambition to decarbonize, are spurring substantial demand growth. What remains uncertain is whether SAF producers can create enough supply at a price the market can sustain.
SAF scale-up is an execution challenge
Several SAF production pathways have now reached technical maturity. Hydroprocessed esters and fatty acids (HEFA), alcohol-to-jet (AtJ), Fischer-Tropsch (FT), and power-to-liquid (PtL) can all produce fuels suitable for flight, although they differ in feedstock requirements, process configurations, and potential for large-scale development.
Choosing a pathway is only the first decision. Developers must also determine how well that pathway integrates with a facility’s feedstock supply, logistics, utilities, hydrogen, supporting infrastructure, and plant operations. Constraints or underperformance in any one of those areas can materially affect a project's bankability—its ability to secure financing and achieve final investment decision (FID).
For example, early-stage project models often assume steady feedstock volumes, predictable quality, and secure long-term supply agreements. In reality, feedstock availability fluctuates considerably, while quality variations introduce operational challenges that directly affect plant performance.
Developers also tend to underestimate the impact of contaminants. Metals, phosphorus, water content, and solids can shorten catalyst life, increase maintenance requirements, reduce yields, and disrupt downstream operations. Facilities that lack sufficient pretreatment investment may be exposed to operational instability that can’t be solved further downstream.
Infrastructure dependencies create additional obstacles. Hydrogen availability, utilities access, transportation networks, storage capacity, and product distribution channels all influence project viability. Those factors are often identified late in development, when changes become expensive and difficult to implement.
Financing adds another layer of complexity. Investors increasingly scrutinize feedstock security, operational flexibility, technology integration, and project execution risks. A technically sound concept may struggle to achieve FID if assumptions around supply chains, logistics, or plant integration are uncertain.
Overall, economics continues to be one of the biggest barriers to scaling SAF. While airlines will need increasing volumes to meet regulatory requirements and decarbonization commitments, SAF continues to command a substantial premium over conventional jet fuel. This price differential limits voluntary uptake beyond mandated blending requirements.
Over the next few years, the pace of industry growth will closely tie to policy support mechanisms, including tax incentives, subsidies, contracts for difference, and other funding schemes that bridge the gap between production costs and market demand. Until production scales enough to narrow the cost gap with conventional aviation fuel, or new policy frameworks emerge to support demand, commercial viability will remain every bit as important as technological readiness.
Validate constraints before choosing an SAF production pathway
Selecting an SAF production pathway is arguably the most consequential strategic decision a developer faces. As with any industry, and particularly in the energy sector, there's a natural tendency to choose the most mature technology and then build the project around it. But we argue the reverse is a lower-risk approach.
In practice, that means validating local constraints on feedstocks, infrastructure, utilities, markets, and policy in a given region, and then determining which pathway best aligns with those conditions.
Today, that means choosing among four dominant routes:
- Hydroprocessed esters and fatty acids—Mature but feedstock constrained. HEFA accounts for the majority of commercial SAF production and is the most technologically mature of the four pathways. Its primary constraint is feedstock. Facilities depend on access to suitable lipid-based materials, such as used cooking oil and waste fats. Where those resources are abundant and competitively priced, HEFA provides an attractive route to market. But maturity alone can’t overcome poor feedstock economics where supply is constrained or competition is intense.
- Alcohol-to-jet—Opportunity but market-dependent. AtJ offers another route to expanding SAF supply, particularly in regions with established ethanol or other alcohol production. Existing agricultural, logistics, and fuel infrastructure can strengthen the business case, but project economics are highly dependent on feedstock cost, availability, and carbon intensity, as well as regional market conditions. As with HEFA, the technology alone doesn’t determine success—the system around it does.
- Fischer-Tropsch—Flexible but more complex. FT pathways can access a wider range of resources, including biomass, waste streams, and municipal solid waste. That broader feedstock base can diversify feedstock supply and potentially improve long-term resilience. The trade-off is complexity. Gasification, synthesis gas conditioning, FT conversion, upgrading, and supporting utilities create a more integrated process with additional interfaces that developers must engineer and operations teams must manage effectively.
- Power-to-liquid—Promising but infrastructure-heavy. PtL could become an important contributor to future SAF supply because it's less dependent on limited biological feedstocks. Instead, it combines renewable hydrogen with a carbon source to produce synthetic hydrocarbons. PtL’s primary hurdles are infrastructure requirements, which can be prohibitive. Access to abundant low-cost renewable electricity, electrolyzer capacity, reliable CO2 supply, water, and supporting grid infrastructure will typically determine project viability before considering the fuel synthesis process itself.
Greenfield vs. asset conversion for SAF production
Beyond selecting an SAF production pathway, developers must determine whether to execute the project as a greenfield development or as a conversion of an existing industrial asset. That decision has significant implications for process design, capital intensity, integration complexity, and long-term operability.
Greenfield projects provide the greatest degree of design freedom. Developers can engineer them as an integrated system around the specific requirements of the selected SAF pathway:
- feedstock receiving and pretreatment
- conversion units
- hydrogen production and distribution
- utilities
- storage
- offsites
- product logistics
That freedom can simplify process integration and improve overall plant efficiency, but it typically entails higher capital requirements, a broader infrastructure scope, and longer permitting and execution schedules.
Brownfield conversions offer a different value proposition by leveraging existing processing equipment, utility systems, tankage, logistics infrastructure, site services, and workforce capabilities. Matching an existing asset to new process requirements can reduce capital scope, shorten development timelines, and lower execution risk—which is why we see a significant share of early SAF capacity developed through refinery conversions, coprocessing configurations, and projects integrated with existing renewable fuels infrastructure.
The challenge is that reuse potential is highly site-specific and can be overstated during early-stage development. Take a refinery’s existing hydrotreater, for example. On paper, it can appear ready for HEFA conversion, but its metallurgy—built for crude-derived feedstocks—may not be rated for the corrosivity of used cooking oil or waste fats, and retrofitting it can be costly. Systems that appear suitable for reuse at the conceptual stage may require substantial revamping, derating, or complete replacement once detailed engineering confirms actual operating conditions and integration requirements.
In all cases, developers need rigorous techno-economic assessments to determine which assets can be viably repurposed, where modifications are required, and whether the overall conversion project can deliver a competitive business case.
Success with SAF depends on a systems-level perspective
Like most downstream facilities, an SAF plant isn't simply a collection of independent technology packages. It's a tightly connected production system, with each part of the process closely dependent on those that lie upstream of it. Feedstock handling and pretreatment must deliver a consistent input to the conversion process. What comes out of conversion, in turn, must align with downstream upgrading and separation, while hydrogen supply keeps pace with process demand.
At the same time, developers must size and coordinate supporting utility and logistics systems to maintain stable operation across a range of feedstocks and operating conditions.
Problems, when they emerge, typically appear at the interfaces rather than within individual pieces of equipment, which explains why rated plant capacity can be a misleading measure of project attractiveness. Plants that achieve consistent uptime and stable performance frequently outperform facilities chasing aggressive production targets that real operating conditions can’t support. Likewise, investments in pretreatment, separation technologies, and operational flexibility often generate greater long-term value than attempts to minimize upfront capital costs.
Few, if any, organizations have expertise across every part of the SAF production system. Licensing the technology, supplying feedstock, engineering the plant, and running it day-to-day typically involves four different parties with four different contracts. Each may be highly capable within its own scope, but fragmented responsibility can create gaps at the interfaces between those scopes. That’s where integration capability becomes particularly valuable.
As SAF projects grow in size and complexity, a systems-level perspective matters more than ever. The technologies themselves are the easier part. Connecting them into an operable industrial facility is where the real work—and the real risk—lives.
SAF diligence must extend to integration risk
The implication for developers and investors is clear: Integration risk deserves the same scrutiny as pathway selection and feedstock security. Pathway maturity and feedstock security get the most scrutiny in due diligence today, and rightly so. What gets far less scrutiny is whether the pieces of a project, once assembled, will work together as designed. That gap matters because integration failures are rarely visible at the conceptual stage. They surface only after engineering—or worse, operations—exposes what the paper design missed.
For developers, this means treating systems integration as a bankability criterion in its own right, not a downstream detail to be resolved after financing closes. For investors and lenders, it means asking a different question earlier—not just “does this pathway work,” but “who owns the interfaces between technologies, and what happens if one of them underperforms?” The projects most likely to reach FID and perform well once built will be those whose developers turn the diligence lens toward integration.
That’s good news, because of all the variables standing between SAF and industrial scale, integration is one developers can act on now, well before shovels hit the ground.
