As the aviation industry intensifies efforts to reduce its carbon footprint, Sustainable Aviation Fuel (SAF) has emerged as a pivotal solution for decarbonizing flight operations. In our previous article, we examined the regulatory drivers propelling SAF adoption. This time, we take a closer look at the technological pathways enabling SAF production and their potential to scale this innovative solution within the growing landscape of Green Molecules™ technologies.

‍

Emerging SAF Pathways

As the aviation industry accelerates its transition to decarbonization, four primary technological pathways are poised to dominate Sustainable Aviation Fuel (SAF) production in the coming years. These methods, categorized by their feedstocks and production processes, offer unique advantages and challenges:

1. Hydroprocessed Esters and Fatty Acids (HEFA) – "The Fats Way"
   HEFA is the most widely adopted SAF production technology, utilizes feedstocks such as vegetable oils, waste oils, and animal fats, which are combined with hydrogen under high heat and pressure to produce biodiesel, later refined into jet fuel. A notable example of progress in this space comes from Cemvita, which earlier this year announced a breakthrough in producing substantial quantities of its Sustainable Oil from waste carbon sources—a pivotal step toward scaling low-carbon-intensity feedstocks for HEFA-based sustainable aviation fuel.
   • Pros: Proven and scalable technology with an established production infrastructure.
   • Cons: Limited by the availability of waste oils and fats, which may compete with food and forestry needs.
2. Fischer-Tropsch (FT) – "The Garbage Way"
   FT technology converts diverse feedstocks, including agricultural residues, woody biomass, and municipal solid waste, into syngas through gasification. The syngas is then refined into high-quality jet fuel.
   • Pros: Highly versatile feedstock options and produces high-quality fuel.
   • Cons: High capital costs and an energy-intensive production process.
3. Alcohol-to-Jet (ATJ) – "The Grain Way"
   ATJ technology transforms agricultural crops or waste into ethanol, which is further processed into jet fuel through dehydration, rehydration, and other chemical reactions.
   • Pros: Can leverage existing ethanol production infrastructure and offers high greenhouse gas (GHG) reduction potential.
   • Cons: Currently costly, with variable carbon intensity depending on the feedstock and processing methods.
4. Power-to-Liquid (PTL) – "The Air Way"
   PTL captures carbon dioxide (CO₂) directly from the air and combines it with water using renewable energy to synthesize jet fuel. This pathway offers the highest potential for emissions reduction, achieving up to 90% lower lifecycle emissions.
   • Pros: Significant GHG reduction with minimal land and water usage.
   • Cons: Requires large-scale renewable energy deployment, making it the most expensive SAF pathway currently.

In addition to the four leading technologies, several innovative pathways are being explored to diversify SAF production:

• Hydroprocessed Fermented Sugars to Synthesized Iso-Paraffins (HFS-SIP): Uses genetically modified microorganisms to ferment sugars into farnesene, which is then processed into jet fuel.
• Catalytic Hydrothermolysis (CH): Converts fats into biodiesel through high-temperature, high-pressure processes, which are then refined into jet fuel.
• Hydrotreated Depolymerized Cellulosic Jet (HDCJ): Utilizes lignocellulosic biomass (e.g., forestry and agricultural waste) to produce bio-oil, refined further into jet fuel.

Most pathways, except HFS-SIP, produce Synthetic Paraffinic Kerosene (SPK), which can achieve up to 50% blending with conventional jet fuel under current regulatory standards. These advancements highlight the critical role of SAF technologies in meeting aviation’s decarbonization goals.

‍

Scaling Sustainable Aviation Fuel (SAF) to Meet Future Demand

As outlined in our previous article, global demand for Sustainable Aviation Fuel (SAF) could exceed 16 million metric tons (Mt) by 2030. To meet this demand, production of these Green Molecules™ must rapidly scale from the current level of just 1.5 Mt per year.

Diversifying SAF production pathways will also be critical. Currently, nearly all SAF is produced using the HEFA pathway due to its cost advantage and scalability. However, feedstock limitations significantly constrain HEFA’s long-term potential, with projections from the International Energy Agency (IEA) and Energy Transitions Commission indicating that HEFA-based SAF will only account for ~10% of future production. Despite this, HEFA represents 85% of announced SAF capacity for 2030.

Emerging technologies such as Alcohol-to-Jet (ATJ) are gaining traction, with forecasts suggesting ATJ could capture 8% of the SAF market by 2030. Meanwhile, Fischer-Tropsch (FT) and Power-to-Liquid (PTL) technologies are expected to contribute approximately 7% of capacity combined.

Looking ahead to 2050, global SAF capacity could scale to 250 Mt annually, provided investments accelerate. Achieving this ambitious target would require the construction of 500-800 new SAF production facilities, with cumulative capital expenditures nearing $1 trillion, or $40 billion annually through 2050. However, HEFA will remain limited to ~10% of total SAF production due to constraints on waste-based feedstocks. Other bio-based solutions could supply an additional ~40% of production but are restricted by land and water availability.

The remaining 50% of future SAF demand must be met through Power-to-Liquid (PTL) technology, which leverages renewable electricity to produce synthetic jet fuel. Scaling PTL will be essential to bridge the gap and drive the aviation sector closer to net-zero emissions.

‍

Economic Considerations and Market Dynamics

Today, just 14 airlines account for half of global jet fuel consumption and nearly all of the Sustainable Aviation Fuel (SAF) use worldwide. In 2024, SAF production is expected to reach approximately 500 million gallons (1.875 billion liters), equivalent to 1.5 million metric tons (Mt), or roughly 0.53% of total jet fuel consumption. With SAF priced at an average of $6.70 per gallon ($1.77 per liter), total spending on SAF is projected to reach $3.4 billion this year.

This cost is significantly higher than conventional Jet A fuel, which typically fluctuates between $2 and $4 per gallon ($0.53 to $1.07 per liter), creating a notable "green premium" for SAF. Due to the tight margins in the airline industry, much of this premium has historically been passed on to customers via SAF certificates, selling for $300-$325 per metric ton of CO₂ avoided.

While these costs may seem steep today—especially when compared to short-term carbon credits, which can sell for $100 per metric ton—they are expected to become more reasonable over time. Bloomberg analysts project that by 2050, the market price for offsetting 1 metric ton of CO₂ could reach $238. At the same time, SAF production costs are anticipated to decline as technologies mature:

• HEFA: Already near the bottom of the cost curve, offering a cost-effective option today.
• ATJ and FT: Expected to see a 33% reduction in costs by 2050.
• PTL: Projected to achieve a 50-60% cost reduction, potentially reaching parity with other SAF pathways.

These anticipated cost reductions, combined with rising carbon credit prices, suggest that the green premium for SAF could soon be less expensive than offsetting emissions from burning conventional jet fuel.

According to a survey conducted by RMI, the willingness to pay for SAF—assuming a 75% reduction in carbon intensity—is estimated at $2.34 to $3.93 per gallon. This places the target price for SAF, when paired with conventional Jet A fuel priced at $3 per gallon, between $5.34 and $6.93 per gallon.

Currently, SAF production costs range from $6.40 to $19.01 per gallon, putting them at the higher end of this range. However, as technology advances and costs decline, SAF is expected to fall well within this target price range by 2050. Additionally, policy incentives such as the IRA tax credit of $1.75 per gallon further mitigate the economic challenges associated with SAF. By mid-century, all SAF technology pathways are projected to align with this pricing model, particularly when factoring in the growing willingness to pay for abated emissions.

‍

The evolution of the SAF industry hinges on diversifying the technological pathways used to produce Green Molecules™. While HEFA dominates production today, the future of SAF will increasingly depend on the scalability of ATJ, FT, and PTL technologies to address feedstock constraints and deliver deeper emissions reductions at a competitive cost. Achieving net-zero aviation by 2050 is an ambitious goal, but it remains within reach with sustained investments, technological advancements, and robust policy support.