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Sustainable Aviation Fuel

Sustainable Aviation Fuel


The aviation industry is significant in global transportation, connecting people and goods worldwide. However, the environmental impact of aviation, particularly its carbon dioxide (CO2) emissions, has become a growing concern. Sustainable Aviation Fuel (SAF) development and utilization have emerged as a promising solution to mitigate aviation’s carbon footprint.

Sustainable Aviation Fuel, or alternative fuel, is a renewable energy source specifically designed for use in aircraft engines. It is produced from sustainable, non-fossil-based feedstocks and has a reduced carbon footprint compared to conventional jet fuels. SAF can be synthesized from various sources, including biomass, waste oils, agricultural residues, and renewable hydrogen. Here is a more in depth look at each of the mentioned production methods.

Hydroprocessed Esters and Fatty Acids (HEFA): HEFA SAF is produced by converting vegetable oils or animal fats through a hydroprocessing technique, resulting in a fuel with similar properties to conventional jet fuel.

Fischer-Tropsch (FT) Synthesis: FT SAF is derived from biomass gasification, such as wood chips or agricultural residues, followed by a series of chemical reactions to convert the syngas into liquid hydrocarbons suitable for aviation use.

Alcohol-to-Jet (ATJ): ATJ SAF is produced by converting alcohols, such as ethanol or butanol, into a jet fuel equivalent through dehydration, followed by oligomerization and hydrogenation processes.

Power-to-Liquid (PtL): PtL SAF involves the conversion of renewable electricity into hydrogen, which is then combined with captured CO2 to produce a synthetic hydrocarbon fuel.

The production methods are only one instance of the environmental benefits of SAF. Several other ecological benefits can be attributed to the use of SAF. Some of these benefits include:

Greenhouse Gas Emissions Reduction: SAF has the potential to reduce CO2 emissions compared to conventional jet fuel significantly. Depending on the feedstock and production method, SAF can achieve up to an 80% reduction in lifecycle CO2 emissions.

Air Quality Improvement: SAF emits fewer pollutants, such as sulfur oxides (SOx), nitrogen oxides (Nix), and particular matter, resulting in improved air quality and reduce local environmental impacts.

Compatibility with Existing Infrastructure: SAF can be blended with conventional jet fuel without requiring modifications to aircraft or fueling infrastructure, enabling a smooth transition to greener aviation.

While the benefits of using SAF are substantial, there are still several challenges and concerns that must be addressed. These may include:

Feedstock Availability: Scaling up SAF production to meet the demands of the aviation industry requires a sustainable and abundant supply of feedstocks. Competing needs for biomass resources and land use consideration must be addressed.

Cost Competitiveness: Currently, SAF production is more expensive than conventional jet fuel due to various factors, including feedstock costs, limited production scale, and the need for additional refining processes. Wider adoption and government incentives can help drive down costs.

Certification and Standards: Establishing robust certification schemes and sustainability standards for SAF ensures its environmental integrity and avoids potential adverse impacts, such as deforestation or food crop displacement.

While at large, SAF has many environmental benefits, the challenges and barriers it causes must be considered. In order to do that, some steps need to be taken. Those steps should include:

Increased Production Capacity: Governments, industry stakeholders, and investors should collaborate to expand SAF production capacity and promote long-term investment in sustainable feedstock supply chains.

Research and Development: Continued research and development efforts are essential to improve SAF production processes, reduce costs, explore new feedstocks, and enhance the overall sustainability and performance of aviation fuels.

Policy Support: Governments can play a vital role by implementing supportive policies, such as financial incentives, mandates, and carbon pricing mechanisms, to accelerate the adoption of SAF usage.

ASTM International, a global standards organization, has developed pathways for the certification and approval of Sustainable Aviation Fuel (SAF). These pathways provide a framework for ensuring SAF’s quality, sustainability, and compatibility with existing aviation infrastructure. Here are the ASTM pathways for SAF:

ASTM D7566 Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons: This standard establishes the specifications and testing methods for synthetic hydrocarbon-based SAF. It covers various SAF production pathways, including Hydroprocessed Esters and Fatty Acids (HEFA), Fischer-Tropsch (FT), and Alcohol-to-Jet (ATJ). The standard ensures that SAF meets the necessary performance and safety requirements for use in aviation.

ASTM D4054 Standard Practice for Qualification and Approval of New Aviation Turbine Fuels and Fuel Additives: This practice outlines the procedures and requirements for the qualification and approval of new aviation fuels, including SAF. It provides a systematic approach to evaluating the fuel’s composition, properties, and performant characteristics. The standard ensures that new SAF formulations meet the necessary criteria for compatibility with aircraft systems, engines, and fueling infrastructure.

ASTM D7566 Annex A5 and Annex A6: These annexes to the ASTM D7566 standard specify additional requirements for SAF produced from Fischer-Tropsch synthesis (Annex A5) and Alcohol-to-Jet synthesis (Annex A6). They address specific consideration and characteristics of these SAF production pathways, ensuring their compatibility with aviation applications.

ASTM D1655 Standard Specification for Aviation Turbine Fuels: This standard defines conventional jet fuel’s specifications and quality requirements (Jet A and Jet A-1). While not specific to SAF, it is an essential reference for the comparison and compatibility of SAF with conventional jet fuel. It ensures that SAF meets of exceeds the specifications of traditional jet fuel in terms of performance and safety.

ASTM D7566 Sustainable Aviation Fuel (SAF) Evaluation and Qualification Task Group: This task group within ASTM International is responsible for reviewing and updating the existing standards related to SAF. They monitor advancements in SAF technology, assess new feedstocks and production methods, and propose revisions to the standards to reflect the latest industry practices and sustainability requirements.

By following these ASTM pathways, stakeholders in the aviation industry can ensure that SAF meets the necessary standards for quality, performance, and sustainability. These pathways provide a robust framework for the certification, approval, and adoption of SAF, facilitating its widespread use as a greener alternative to conventional jet fuel.

Airlines have several reasons for wanting to use Sustainable Aviation Fuel (SAF) in their operations. Here are some of the key motivations:

Environmental Sustainability: The primary reason airlines use SAF is to reduce their carbon footprint and environmental impact. SAF offers significant greenhouse gas emissions reductions compared to conventional jet fuel, potentially up to 80% lifecycle CO2 reduction. Using SAF, airlines can contribute to mitigating climate change and demonstrate their commitment to sustainable practices.

Regulatory Compliance: Aviation industry regulations and international agreements, such as the International Civil Aviation Organization’s (ICAO) Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), aim to limit the sector’s carbon emissions. Using SAF helps airlines meet these regulatory requirements and avoid potential operational penalties or limitations.

Corporate Social Responsibility: Many airlines view SAF as part of their corporate social responsibility initiatives. They recognize the importance of addressing environmental concerns and aim to be responsible global citizens by actively reducing carbon emissions and promoting sustainable practices.

Customer Demand and Preference: Increasingly, travelers are becoming more environmentally conscious and seeking airlines that demonstrate a commitment to sustainability. Using SAF can differentiate airlines, appealing to eco-conscious travelers and potentially boosting customer loyalty.

Hedging against Fuel Price Volatility: Conventional jet fuel prices are subject to fluctuations influenced by geopolitical events and market conditions. SAF, on the other hand, is produced from diverse feedstocks and can offer more price stability. By incorporating SAF into their fuel mix, airlines can hedge against fuel price volatility and reduce their dependence on traditional jet fuel.

Long-Term Fuel Supply Security: SAF production relies on diverse and renewable feedstocks, including waste oils, agricultural residues, and sustainable biomass. This diversity of feedstocks reduces reliance on fossil fuel reserves and enhances long-term fuel supply security for airlines.

Innovation and Technological Leadership: Airlines are motivated to be at the forefront of technological advancements and innovation in the aviation industry. By embracing SAF, airlines can showcase their commitment to sustainable aviation and position themselves as leaders in adopting greener, more efficient fuel solutions.

It is important to note that adopting SAF is influenced by various factors, including feedstock availability, cost competitiveness, and regulatory support. As the industry continues to develop and SAF production scales up, these motivations are expected to drive further adoption of sustainable aviation fuel by airlines worldwide.

US airports involved in supplying SAF:

Los Angeles International Airport (LAX): LAX has been actively promoting the use of SAF and has established partnerships with SAF producers. It has facilitated the blending of SAF into its fuel supply and has hosted SAF demonstration flights.

San Francisco International Airport (SFO): SFO has been a leader in sustainable aviation initiatives and has partnered with SAF producers to supply SAF to airlines operating at the airport. It has also implemented incentives to encourage airlines to use SAF.

Seattle-Tacoma International Airport (SEA): SEA has demonstrated a commitment to sustainable aviation practices and has facilitated the availability of SAF to airlines. It has collaborated with SAF producers and participated in initiatives to promote the use of SAF.

Denver International Airport (DEN): DEN has supported the adoption of SAF and has collaborated with SAF producers to provide a sustainable fuel supply. It has hosted SAF demonstration flights and worked to create a supportive environment for airlines to use SAF.

Chicago O'Hare International Airport (ORD): ORD has taken steps to facilitate the supply of SAF to airlines. It has engaged in partnerships with SAF producers and has been involved in initiatives to promote the use of sustainable fuels.

Please note that the availability and extent of SAF supply at airports can vary over time, and new airports may join the efforts to supply SAF.

For the first time ever, on 11/28/2023 afternoon a commercial plane flew across the Atlantic Ocean from London to New York without using fossil fuels. The fuel on this flight was made from waste fats and plant sugars and emits 70% less carbon than petroleum-based jet fuel. The main advantage of SAF is that they are “drop-in” fuels, meaning they can have an impact right away because they can be blended with standard jet fuel and poured into engines. Experts say SAF may one day play a big role in shrinking the aviation industry’s carbon footprint. SAF accounts for about 0.1% of airlines’ current fuel consumption. Airlines don’t want to buy SAF because it can be several times more expensive than standard aviation fuel.

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