Sustainable Aviation Fuel: A Viable Option to Reduce Carbon Emissions from Air Travel

Sustainable Aviation Fuel

Sustainable aviation fuel (SAF) refers to non-petroleum based jet fuels that are produced from sustainable biomass and waste resources. SAF is designed to closely mimic conventional jet fuel in terms of performance, yet offer a significant reduction in greenhouse gas emissions over their lifecycle compared to conventional jet fuel. Some examples of potential sustainable feedstocks for SAF include used cooking oil, animal fats, algae, and plant-based sources like camelina and jatropha. Through various refining processes, these sustainable feedstocks can be transformed into synthetic paraffinic kerosene (SPK) and hydroprocessed esters and fatty acids (HEFA) which have chemical compositions very similar to traditional petroleum-derived jet fuel.

Producing SAF

There are currently two dominant production pathways for making SAF that have been approved for commercial use. The most established route is the HEFA pathway which involves hydrotreating and deoxygenating sustainable oils and fats. This produces a jet fuel blend component that is fully fungible with conventional jet fuel. The other primary pathway is SPK production which uses gasification and Fischer-Tropsch synthesis to convert biomass sources like lignocellulosic wastes into liquid hydrocarbons that can then be further refined into jet fuel. Both of these routes integrate the Sustainable Aviation Fuel feedstocks with conventional oil refining processes to yield ASTM-certified drop-in fuels that are chemically identical to regular jet fuel and thus fully compatible with aircraft engines and fueling infrastructure.

Lifecycle Emissions Analysis of SAF

Comprehensive lifecycle analyses have found that SAF can reduce greenhouse gas emissions compared to conventional jet fuel by around 60-80% depending on the specific feedstock used. The magnitude of emission reductions depends on accounting for emissions associated with growing, collecting and transporting the biomass feedstock as well as the refining processes. Used cooking oil for HEFA fuel production frequently achieves reductions over 80% since the oil was already collected and would otherwise need disposal. Algae and purpose-grown perennial grasses can also attain very high emission savings but may entail larger cultivation impacts that slightly reduce the overall reduction potential. Nevertheless, even for the most conservative estimates SAF delivers significant abatement of carbon emissions associated with aviation.

SAF Certification and Testing

Before SAF can be commercially deployed, it must undergo a rigorous certification and testing process to ensure it meets critical performance and safety standards for aviation use. The American Society for Testing and Materials (ASTM) International develops specifications for all commercial jet fuels through their D4054 designation process. Both the HEFA and SPK production pathways have been approved by ASTM and assigned D7566 and D7584 specifications after extensive evaluation of their chemical and physical properties as well as full-scale aircraft engine testing. Further testing is still ongoing for additional SAF technologies and feedstocks to expand the options for approved sustainable jet fuels. Meanwhile, international standards organizations like the International Air Transport Association (IATA) are working to align global acceptance and use of approved SAF.

Barriers to Large-scale SAF Adoption

While SAF has been demonstrated as a technically viable alternative fuel for aviation, significant challenges continue to limit its widespread commercial availability and adoption. Chief among these is SAF's higher production costs compared to conventional jet fuel. Building entirely new supply chains and refineries dedicated to SAF production adds infrastructure expenses. This cost gap must narrow before airlines can regularly substitute a high volume of SAF. Ensuring security and economy-of-scale in sustainable feedstock sourcing is also a barrier. Developing national and international policy measures like low carbon fuel standards and incentives are important to drive long term market demand and support investments needed to lower costs. Educating the aviation sector customers on SAF benefits is another necessity for growing acceptance of this new type of fuel. With concentrated effort across these fronts, SAF can play an expanded role in decarbonizing air travel.

Corporate Commitments to Sustainable Aviation Fuel Usage

Leading airlines and airports have demonstrated their support for SAF by signing purchase agreements and committing to use increasing volumes of it in the coming years and decades. United Airlines recently partnered with biofuel producers to purchase over 1.5 billion gallons of SAF over 2030. This will cut millions of metric tons of carbon emissions according to their estimates. Scandinavian airline SAS aims to replace 30% of its jet fuel with SAF by 2030. They have already conducted over 300 commercial flights using blended biofuels. Airport providers like Los Angeles International also want a share of SAF supplies. Commercial deployment has concentrated in Europe and North America so far, but usage must grow globally to achieve meaningful emissions reductions sector-wide. In parallel to volume expansion, continual cost reductions will determine the pacing and ceiling of SAF adoption across the industry.

Policy Support Crucial for SAF Scale-Up

While corporate commitments lay an important foundation, centralized policy measures will be indispensable to help SAF achieve widespread market penetration. Low carbon fuel standards which mandate average emissions intensity reductions from transportation fuels are seminal. The existing LCFS in California has demonstrated ability to stimulate alternative fuel development. Similar policies at the national and international levels would send investment signals across long planning horizons. Public procurement preferences for SAF supply at major airports supported by tax breaks would further bolster offtake. Carbon pricing or offsetting programs present avenues for direct or indirect SAF cost compensation until mature markets form. Concerted global policy cooperation on these fronts may be needed to avoid patchwork measures and ensure emissions benefits accrue from lower cost production worldwide. With enabling environments, SAF can make major inroads to aviation decarbonization by mid-century.

As a scalable drop-in replacement for regular jet fuel that leverages existing airplane and fueling infrastructure, sustainable aviation fuel represents one of the most tractable solutions available today for reducing the carbon impact of air travel. Significant research, investment and testing have validated SAF for commercial use from technical, performance and safety standpoints. Although higher costs remain a hindrance, pathways exist to gradually mainstream SAF through expanding production facilities, securing sustainable feedstock supplies, growing offtake commitments, and enacting policy measures supportive of low carbon fuels. If scaled ambitiously yet prudently in the coming decades, SAF stands ready to lower the emissions intensity of aviation while keeping this vital sector connected and growing. Continued cross-sector cooperation on technical, market and policy fronts will determine how much of aviation's future emissions reductions come from this promising low carbon fuel option.

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Money Singh is a seasoned content writer with over four years of experience in the market research sector. Her expertise spans various industries, including food and beverages, biotechnology, chemical and materials, defense and aerospace, consumer goods, etc. (https://www.linkedin.com/in/money-singh-590844163)