Strategizing for a Smooth Landing

The industry must explore new avenues to meet the growing demand for sustainable aviation fuels.

- By Kevin O'Neil

The demand for sustainable aviation fuel (SAF) continues to grow as governments around the world set targets to reduce carbon emissions associated with air travel. As a result, the aviation sector and fuel producers are challenged to dramatically increase SAF production over the coming years. A key hurdle to that rampup is the limited availability of the most accessible feedstocks for SAF production.

Today, fats, oils and greases sourced from restaurant and food production waste are recycled into SAF to minimize lifecycle greenhouse gas emissions compared to traditional fossil fuels. However, SAF today accounts for less than 1% of aviation fuel production, according to estimates. There is widespread concern that there simply isn’t enough of the industry’s default feedstocks to meet the exponentially increasing demand.

The good news is that being developed and commercialized are technologies that utilize abundantly available alternative feedstocks to help fuel producers close the gap, and enable the aviation sector to meet its emission reduction goals.

What’s Driving SAF Demand?

In 2021, the Biden Administration announced its Sustainable Aviation Fuel Grand Challenge: To generate at least three billion gallons of SAF and reduce aviation emissions by 20% by 2030, and to meet all aviation fuel demand in the United States through sustainable fuel by 2050— approximately 35 billion gallons annually.

The U.S. is far from being the only nation focused on shifting aviation to more sustainable fuel sources. The European Commission released its Fit for 55 plan, a reference to the European Union’s target of reducing net greenhouse gas emissions by at least 55% by 2030. To reach that goal, the EU aims to phase out free emission al- lowances for aviation under its Emissions Trading System between 2024 and 2026. It also proposes that fuel suppliers blend an increasingly higher level of SAF into flights leaving the larger EU airports.

Ultimately, the EU targets trail only slightly behind those of the U.S., with the European Union Parliament targeting SAF to make up 2% of fuel on flights departing the European Union in 2025, 37% in 2040 and 85% by 2050.

Big Goals, Short Runway

According to the U.S. Energy Information Administration, jet fuel consumption worldwide is projected to increase through 2050. The International Air Transport Association, which itself has approved a resolution for the global air transport industry to achieve net zero carbon emissions by 2050, estimates that 6.076 billion gallons of SAF will be needed by 2030, and 118 billion gallons by 2050.

Even in Europe, with its less ambitious targets, there is a long way to go.

A study by the International Council on Clean Transportation concludes that currently, there is only a sufficient resource base to support approximately 1.04 billion gallons of advanced SAF production annually (depending on the properties of the SAF or feedstock)—5.5% of projected EU jet fuel demand in 2030. ”Production plans depend heavily on edible oils and certain wastes and residues for which there is limited supply and considerable competition,” the International Energy Agency notes. As decarbonization efforts favor increased use of SAF, the demand for feedstocks will only increase.

For SAF to see widespread adoption where government targets can be met, there’s an urgent need to investigate new and alternative feedstocks. Without these, the development of sustainable, affordable and abundant SAF will remain an aspiration rather than reality.

Alternative Feedstocks that Stand to Scale

Fortunately, there is a range of potential and promising feedstocks being explored for which emerging technologies are being developed and commercialized. It is worth considering some of the top contenders—the following are three that stand out.

• Biomass. Examples include woody pulp and other agricultural and forestry byproducts. According to the U.S. DOE, an estimated 1 billion dry tons of biomass from America’s forestry and agricultural residues alone could provide enough biomass to generate 50 billion to 60 billion gallons of low-carbon biofuels, with potential for even more—perhaps enough to completely replace the U.S.’s current fossil jet fuel consumption. New technology, such as that developed by Alder Fuels, can enable the production of SAF from biomass at scale, which can lead to a significant increase in SAF supply.

• Ethanol. Ethanol is an abundant and proven alternative already produced at scale. Producing ethanol from corn, for instance, is a mature industry. SAF can be produced from corn ethanol via emerging ethanol-to-jet technology with potentially a 15% lower carbon intensity than petroleum alternatives. According to a DOE study, ethanol-to-jet fuel conversion, along with smart farming and other existing technologies, could reduce greenhouse gas emissions compared to traditional jet fuel. Ethanol-based SAF can also use cellulose-based agricultural byproduct, which poses challenges to produce in large quantities, but offers the possibility of even greater sustainability benefits. The wheels are already in motion to advance and scale the processing of cellulosic material.

• Carbon dioxide. CO2 from carbon capture operations also offers an alterna- tive pathway to SAF production through processing scheme options known as power-to-liquids. A promising power-toliquids route combines sequestered carbon with green hydrogen produced by renewable electricity and electrolysis, to first produce methanol with low carbon intensity. Methanol can be converted to SAF via a methanol-to-jet route that uses a series of commercially proven processing steps, first converting the methanol to light olefins, then converting the olefins to heavier olefinic molecules, and finally saturating the heavier olefins to produce jet fuel.

These three feedstocks and the technologies to convert them to SAF are already realistic alternative routes to enabling significant supply of SAF. In September 2021, for instance, United Airlines and Honeywell announced a joint multimillion-dollar investment in Alder Fuels—a cleantech company pioneering technologies for producing SAF from biomass. Honeywell also launched its ethanol-to-jet technology in October 2022, making the new processing scheme available for license. Methanol-toolefins technology, meanwhile, has been commercially practiced since 2013. All three technologies are already available and bring with them a significant base of emerging feedstocks for SAF.

Continuing to Explore: Potential Future Sources

While technology developers commercialize processing technologies to expand production capabilities for biomass, ethanol and carbon dioxide, the innovation doesn’t stop, as new feedstock alternatives are also coming into focus. For example, microalgae. In 2021, Honeywell UOP’s Ecofining technology was used by Japanbased IHI Corp. to convert the company’s novel microalgal oil to SAF for a flight in Japan. The fuel met the new ASTM D7566 Annex 7 standard SAF.

Another example is solid municipal waste. Some companies are working toward the conversion of solid municipal waste, such as discarded plastics, into SAF. This kind of conversion may involve use of gasification or pyrolysis, followed by further processing to produce renewable fuels with low carbon intensities.

Others, meanwhile, are working on converting solid waste materials such as tires into jet fuel.

The demand for SAF is growing significantly and is currently pacing the availability of waste fats, oils and grease feedstocks used to produce it today. To meet adoption goals of both governments and corporations, more SAF supply is needed. New technologies are being developed and commercialized to efficiently utilize new and abundantly available feedstocks to enable a growing supply of SAF. Honeywell UOP, as a leading technology pro- vider in the renewable fuels space, considers biomass-based production using new technology, such as that developed by Alder Fuels, plus ethanol-to-jet and powerto-liquids using the methanol-to-jet route, to be very promising and anticipates these will be competitive pathways in contributing to the decarbonization of the aviation industry.