The challenges of sustainable aviation fuel
SAF and the challenge of decarbonizing aviation
Sustainable aviation fuel (SAF) is central to making flight greener and is a goal that brings us together. Yet, turning this ambition into real-world impact is far from straightforward. Scaling up SAF production isn’t just a policy aim, it’s a tough engineering, economic, and regulatory challenge.
The technology puzzle
No single SAF production pathway will meet future demand. We'll need a mix of solutions, from technologies using waste and biomass to advanced synthetic options. Every pathway brings unique hurdles—solving them demands experience, creative problem-solving, and a team approach.
At AFRY, we face these challenges head-on, bringing together expertise, collaboration, and passion for real progress. Here’s a look at the main SAF and Power-to-X pathways and why understanding their strengths, limitations, and best-case scenarios and applications is so important.
Key Pathways for SAF Production
- Hydroprocessed Esters and Fatty Acids (HEFA)
- Alcohol-to-Jet (ATJ)
- Gasification + Fischer–Tropsch (FT)
- Methanol-to-Jet (MTJ)
- Power-to-Liquid (PtL) / e-SAF
HEFA is the most established SAF pathway today. It uses oils, fats, greases, and pyrolysis oils as feedstocks, which are hydroprocessed into drop-in jet fuel. Multiple commercial plants are already in operation worldwide, making HEFA the backbone of current SAF supply.
- Strengths: Mature and proven technology; commercially available; compatible with existing refinery infrastructure; relatively straightforward upgrading process.
- Limitations: Limited feedstock availability; competition with food and other biofuel markets; feedstock logistics and sustainability certification challenges.
- Best-Case Application: Best suited for regions with reliable and sustainable access to waste oils, fats, or other lipid-based feedstocks. Ideal for near-term SAF deployment, particularly where feedstock collection and logistics infrastructure are already established or can be integrated into existing refinery operations.
In the Alcohol-to-Jet pathway, sugars, starches, or lignocellulosic biomass arend fermented into alcohols such as ethanol or isobutanol. Alcohols can also be derived from gas fermentation of syngas. These alcohols are then catalytically converted into jet fuel through dehydration, oligomerisation, and hydroprocessing
- Strengths: Builds on existing bioethanol and fermentation technologies; flexible in feedstock selection; potential for distributed production.
- Limitations: Conversion yields and process efficiency are lower; higher production costs compared to HEFA; limited commercial experience.
- Best-Case Application: Suitable for regions with developed bioethanol industries or access to low-cost biomass or fermentation capacity.
This pathway converts woody biomass or municipal solid waste into syngas through gasification. The syngas is then processed via Fischer–Tropsch synthesis and hydrotreated to produce SAF. It enables the use of abundant waste and lignocellulosic resources.
- Strengths: Can utilise diverse feedstocks including waste and residues; offers large production potential; enables circular economy integration.
- Limitations: Technically complex; high capital and operating costs; syngas cleaning and process control remain challenging at scale.
- Best-Case Application: Well-suited for large-scale projects using woody biomass or municipal solid waste near industrial hubs.
Methanol can be synthesised either from syngas or from captured CO₂ combined with renewable hydrogen. Through further upgrading, methanol is converted into SAF. This pathway provides flexibility and can integrate well with renewable carbon and power-to-liquid concepts.
- Strengths: High process flexibility; compatible with renewable methanol production; can leverage existing methanol infrastructure.
- Limitations: Lower technology readiness compared to HEFA and FT; multiple conversion steps add complexity and cost.
- Best-Case Application: Ideal for projects that produce or have access to renewable or biogenic methanol, renewable CO₂, and green hydrogen. It also fits business models aiming to sell biomethanol as an intermediate product or to use it as feedstock for SAF production, depending on market demand and regional conditions.
Also known as e-fuels, this pathway uses captured CO₂ and renewable hydrogen from water electrolysis. There are two main options to create syngas:
- Reverse water-gas shift, where CO₂ and hydrogen are directly converted into syngas.
- Methanation followed by reforming, where CO₂ and hydrogen first form methane, which is then reformed into syngas.
The resulting syngas is further processed into jet fuel through Fischer–Tropsch or Methanol-to-Jet synthesis. PtL offers virtually unlimited potential, fully decoupled from biomass feedstocks, and is seen as a cornerstone for long-term aviation decarbonisation.
The resulting syngas is further processed into jet fuel through Fischer–Tropsch or Methanol-to-Jet synthesis.
- Strengths: Virtually unlimited potential; fully decoupled from biomass; scalable with renewable power availability; long-term carbon-neutral pathway.
- Limitations: High electricity demand; limited current capacity; capital-intensive electrolysis and synthesis infrastructure.
- Best-Case Application: Optimal for regions with abundant and low cost renewable power (solar, wind, or hydro) and access to CO₂ (biogenic) capture sources.
The figure below brings clarity to a topic that is often discussed but rarely explained in full: the many different pathways to producing sustainable aviation fuel. While SAF is frequently talked about as a single solution, the reality is that several distinct technological routes exist each with its own strengths, limitations, and ideal applications. This visual overview helps demystify the landscape, showing at a glance how these pathways fit together and why a diversified approach is essential for scaling sustainable aviation.
AFRY’s Capabilities
At AFRY, we support clients across the entire SAF value chain, combining market insight, technical expertise, and engineering excellence. With a track record of over 400 Power-to-X projects on the last 5 years and six ongoing e-SAF and bio-SAF developments, AFRY brings unmatched expertise across the entire value chain, from concept and feasibility to FEED and execution.
Our services include:
- Strategic Advisory – Market outlooks, feedstock studies, and business case development.
- Technology Evaluation – Independent benchmarking of SAF technologies and providers.
- Engineering & Implementation – From concept and FEED studies to EPCM delivery.
- Sustainability & Policy Insights – Guidance on regulations such as EU’s ReFuelEU Aviation and global carbon frameworks.
With deep sectoral expertise across energy, chemicals, and aviation, AFRY is uniquely positioned to help clients realise SAF projects from idea to investment decision, and from development to implementation.
How AFRY supports e-SAF project development
- CO₂ Sourcing
- Water Sourcing and Discharge Study
- Site Screening
- Front-End Loading (FEL 1–3)
- Environmental Impact Assessment (EIA)
- Land Use Planning
- Permitting (Construction, Environmental & Water)
- Appeals & Compliance Support
- Overall Project Timeline Management
- EPCM (Engineering, Procurement and Construction Management)
We help identify and assess suitable CO₂ sources, ensuring a reliable feedstock foundation for SAF or Power-to-X projects.
We evaluate water availability, quality, and treatment needs, as well as discharge requirements, to ensure projects are both technically feasible and environmentally sustainable.
Our team conducts initial site evaluations, considering logistics, infrastructure, utilities, and permitting requirements to secure the best project location.
Through FEL phases, we develop project concepts in increasing detail — from early feasibility to process design, cost estimates, and risk analysis — supporting robust investment decisions and minimizing client risks through the project lifecycle.
We prepare and manage the full EIA process, from program design to reporting, ensuring compliance with regulations and stakeholder engagement.
AFRY assists in drafting, assessing, and proposing land use plans, navigating the often complex planning and zoning requirements to secure project approval.
We manage the permitting process, including applications for construction, environmental, and water permits, helping clients avoid delays and de-risk their projects.
Our experts guide clients through potential appeals processes and compliance steps, providing reassurance that regulatory challenges can be managed effectively.
With AFRY’s integrated expertise, we coordinate all phases — from early studies to permits — to streamline the timeline and allow projects to move forward efficiently into implementation.
We deliver complete project execution support, managing engineering, procurement, and construction to turn concepts into operating facilities.
Driving the future of aviation
The future of SAF lies in a smart mix of solutions working together to secure supply and reduce emissions. At AFRY, we are committed to enabling this transition. We have supported clients across all major SAF pathways and at every stage of development.
By combining our technical, commercial, and regulatory expertise, we help bring sustainable aviation closer to reality. We believe that when brave ideas and deep expertise come together, we can build a better future.
Together with our clients, we are making future in sustainable aviation.
