A Sustainable Solution: Aviation Industry Embraces Eco-Friendly Fuels
For a significant period, the aviation industry has been linked to high levels of carbon emissions and ecological harm.
Nevertheless, recent progress in technology and a growing realization of the importance of sustainable practices have caused the industry to adopt advanced propulsion systems and improve efficiency in air traffic management.
In October 2021, during the 77th International Air Transport Association (IATA) annual general meeting in Boston, a resolution was passed for the industry to reach net-zero carbon emissions by 2050, in alignment with the Paris Agreement’s goal of limiting global warming to 1.5°C.
According to this resolution, it is expected that 65% of the target will be achieved through the use of sustainable aviation fuels (SAF).
This article explores the development and production of sustainable aviation fuels to achieve carbon neutrality in the aviation industry.
What are sustainable aviation fuels (SAF)?
Sustainable aviation fuels (SAF) are a type of alternative fuel made from various sources, including waste oil and fats, green municipal waste, agricultural residues, or algae.
SAF has a lower carbon footprint and emits fewer harmful pollutants compared to traditional fossil fuels, which are derived from non-renewable resources and emit large amounts of carbon dioxide into the atmosphere, causing ecological damage.
The first generation of SAF is made from fats, oils, and greases and is also known as FOGs.
For instance, in June 2020, sustainable aviation fuel manufacturing company Neste collaborated with McDonald’s in the Netherlands and utilized used cooking oil from the fast-food chain’s restaurants. This used cooking oil was then refined and turned into fuel.
The second generation of SAF is derived from biomass and municipal solid waste (MSW). Biomass includes algae, crop residues, animal waste, sludge waste, and forestry residue, which can be gasified to produce fuel.
The second generation of SAF has the potential to reduce greenhouse gas emissions by 85% to 95% over its lifecycle compared to traditional fossil-based jet fuel.
Moreover, according to data insights from BIS Research, the global emissions from commercial aviation amounted to 865.72 MMT of CO2 in 2021, and it is expected to grow at a CAGR of 3.03% and reach 1,203.42 MMT of CO2 by 2032, which is driving growth in large scale production of sustainable aviation fuels.
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Production of Sustainable Aviation Fuels: Approved Technology Pathways
Sustainable Aviation Fuels (SAF) are still in the nascent stages of development, with several technological pathways being tested and under development.
American Society for Testing and Materials (ASTM), an international standards organization, establishes technologies used to produce SAF as well as the limits for blending SAF fuels with conventional jet fuel, which is currently 50% by volume blending.
Moreover, until 2022, seven pathways have been approved by ASTM for blending with conventional jet fuel.
Three commonly used technology pathways approved by ASTM being used in the industry are as follows:
Hydro-Processed Esters and Fatty Acids (HEFA): In 2011, the HEFA pathway received official approval from ASTM. This method is used to produce SAF by refining vegetable oils, tallows, or waste greases through deoxygenation and hydro-processing. Among the different SAF technologies, HEFA is the most established and is currently the only one being utilized at a commercial scale.
Alcohol-to-Jet (AtJ): Alcohol-to-Jet pathway uses isobutanol and ethanol as feedstocks, which was approved by ASTM in 2018.
With the use of chemical processes, the Alcohol-to-Jet pathway transforms alcohol feedstocks such as sugars, starches, hydrolyzed cellulose, and industrial waste gases into SAF and other environmentally-friendly fuels.
Synthesis Gas Fischer-Tropsch (FT): FT technology offers two pathways for the production of synthesis gas (syngas), namely, feedstock gasification (Gas-FT) and CO2 electrolysis.
Approved by ASTM in 2009, the Gas-FT process involves the conversion of a synthesis gas (syngas) into liquid fuel via a Fisher-Tropsch (FT) reaction, which is a common commercial process for producing liquid fuels from both coal and natural gas.
The production of syngas involves gasifying cellulosic feedstocks or municipal solid waste, which is then transformed into a combination of hydrocarbons (the primary chemical compound in jet fuel) in a FT reactor. This is followed by additional refinement to produce SAF and other environmentally-friendly fuels.
Furthermore, production through the second pathway of FT is known as Power-to-Liquid (PtL) pathway.
While the fuels produced by the above-mentioned pathways classify as advanced biofuels, the PtL fuel is classified as electrofuel, a drop-in fuel produced using green hydrogen (H2) and sustainable CO2 through direct air capture (DAC).
PtL is a process where SAF is derived from syngas through a FT reaction. However, the syngas used in this method is generated either from green hydrogen and captured CO2 by reversing a water-gas-shift reaction or directly through co-electrolysis using solid oxide electrolysis cells and renewable energy.
Moreover, synthetic power-to-liquid fuels hold the promise to reduce greenhouse gas emissions by as much as 99% and can even create a carbon-neutral, circular system by using captured CO2 and green hydrogen.
For instance, In March 2021, Ikarus C42, a microlight aircraft belonging to the Royal Air Force (RAF), operated a short flight from Cotswold Airport powered entirely by synthetic gasoline manufactured by Zero Petroleum, which resulted in reduced emissions.
Thus, the production and widespread adoption of sustainable aviation fuels is expected to limit emissions of the aviation industry and drive growth in the emission control market.
Challenges Being Faced in Production
The use of SAFs presents significant advantages in reducing the aviation industry’s carbon footprint. However, there are several challenges that need to be addressed for the widespread adoption of SAFs, which are as follows:
Lack of Carbon Capture and Storage (CCS) Facilities: Many SAF production pathways rely on carbon capture technologies to capture carbon dioxide from industrial processes or directly from the atmosphere.
The captured carbon can then be used as a feedstock for the production of SAF. However, the current capacity of CCS is not sufficient to meet the growing demand for carbon capture.
This presents a challenge for the widespread adoption of SAF, as it could limit the availability of feedstocks for production.
Higher Requirement of Renewable Energy: SAF production requires significant amounts of energy, primarily from renewable sources, to power the waste-to-fuel conversion processes.
There is currently not enough infrastructure in place to generate the required amounts of renewable energy to meet the demand for SAF production due to the high costs of production and limited investments.
As the aviation industry transitions toward greater sustainability, the demand for renewable energy is expected to increase.
While renewable energy sources like solar and wind power have grown in recent years, more investment is required to ensure the availability of sufficient renewable energy to meet the aviation industry’s demand.
Limited Availability of Sustainable Feedstocks: The feedstock for SAF production includes materials like waste oils, agricultural residues, and municipal solid waste. This can create competition for these feedstocks, leading to price volatility and food security concerns.
As SAF production scales up, ensuring the availability of sufficient feedstock will become increasingly important, which can be addressed by developing sustainable supply chains and improving waste management practices.
Conclusion
As the aviation industry faces increasing pressure to reduce its environmental impact, SAFs are becoming an increasingly attractive option for airlines and governments looking to achieve their emissions reduction targets.
While there are still challenges to overcome, such as scaling up production and reducing costs, the growing demand for sustainable aviation fuels is expected to drive innovation and investment in this sector in the coming years.
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