By: Mimi Martinez
As we strive toward decarbonizing multiple sectors, aviation is one of the most challenging industries to decarbonize, also known as a sector that is hard to abate. In 2023, aviation was responsible for 2.5% of global energy-related CO2 emissions, growing faster between 2000 and 2019 than rail, road, or shipping, totaling almost 950 million metric tons of CO2. The aviation industry’s rapid growth in the face of increasing demand, along with the limitations of current technological advancements, means that its emissions continue to rise. Despite new aircraft being up to 20% more efficient than their predecessors, the sector’s growth consistently outpaces these improvements. Decarbonizing aviation to meet global climate goals requires stakeholders to significantly ramp up the adoption of low-carbon, sustainable aviation fuels (SAF), improve airframe and engine design, optimize operational efficiencies, and even explore demand restraint solutions [i].
Concentrating on technical solutions and given that retrofitting airplanes to run on electricity or batteries seems far from feasible in the near future, the quest for alternative fuels is essential. Key measures must be prioritized when seeking viable alternative/sustainable aviation fuels. High energy density can help meet lightweight requirements for aviation fuel and reduce refueling constraints for long air travel [ii]. Engine and infrastructure compatibility can help ensure alternative fuels can blend with conventional jet fuel for widespread adoption. Lower emissions could allow SAFs to reduce greenhouse gas emissions by up to 94% [iii]. At the same time, flexibility could allow diverse feedstocks and production technologies to operate on the aviation fuel space [iv]; while safety [v] and cost-effectiveness are other pressing priorities [vi]. Lastly, the availability and scalability of SAF fuels will be critical for a sector-wide change [vii].
Various production routes are being explored as the search for alternative fuels continues. These routes include the reverse water–gas shift, Fischer–Tropsch (RWGS-FT), methanol, and CO2 electrolysis routes. Each method utilizes intermediate compounds like syngas, methanol, and ethylene. Research indicates that the methanol route holds promise due to its relatively low energy intensity and high CO2 efficiency, achieving up to 92% CO2 efficiency when including recycle streams. The CO2 electrolysis route, while promising near 100% CO2 efficiency, faces significant challenges due to its high energy demands [viii].
Although these routes show promising potential, the journey towards sustainable aviation fuels is far from complete. There is still much to innovate and optimize, and each step forward requires collaboration between governments, industries, and researchers. Several members of the Green Chemistry for Sustainability network are helping lead innovation in this space.
Twelve, Air Company, and Infinium Holdings, Inc. are each developing SAF technologies. Twelve is developing CO₂ electrolysis-based fuels. Air Company is innovating in this space as well, using a non-toxic, non-rare Earth minerals catalysts for its CO₂ electrolysis based fuels, now working on scaling and looking at SAF applications. Infinium Holdings is innovating with three fuel types. The eSMR Reform™ solution uses electrification instead of gas-fired heat for steam methane reforming (SMR). The Synthesize™ system converts syngas into fuels and chemicals using a proprietary catalytic process reactor technology, and their proprietary catalytic. Finally, the React Syngas Solution turns CO₂ and green or blue hydrogen into low-carbon syngas.
The future of aviation will rely heavily on the development of these types of innovative SAFs that can meet the performance demands of flight and contribute to a more sustainable world. The potential for this sector to meet global emissions reduction targets is vast—but only if we continue to push the boundaries of innovation.
[i] https://www.iea.org/energy-system/transport/aviation
[ii] https://assets.kpmg.com/content/dam/kpmg/xx/pdf/2024/07/evolution-of-alternative-fuels-for-aviation.pdf
[iii] https://afdc.energy.gov/fuels/sustainable-aviation-fuel#:~:text=Benefits,various%20feedstocks%20and%20production%20technologies.
[iv] https://afdc.energy.gov/fuels/sustainable-aviation-fuel#:~:text=Benefits,various%20feedstocks%20and%20production%20technologies.
[v] https://afdc.energy.gov/fuels/sustainable-aviation-fuel#:~:text=Engine%20and%20infrastructure%20compatibility%E2%80%94SAF,various%20feedstocks%20and%20production%20technologies.
[vi] https://assets.kpmg.com/content/dam/kpmg/xx/pdf/2024/07/evolution-of-alternative-fuels-for-aviation.pdf
[vii] https://www.reuters.com/legal/legalindustry/policies-incentives-support-sustainable-aviation-fuels-2024-09-13/
[viii]https://pubs.acs.org/doi/10.1021/acssuschemeng.4c03939
