Abstract:
How can airplanes continue to fly while reducing their environmental impact? In order to remove these obstacles, the U.S. Department of Energy’s Bioenergy Technologies Office (BETO) supports advancements in research and development of sustainable aviation fuel (SAF).
This paper explores the transformative potential of sustainable aviation fuel in aviation, covering its development, benefits, and industry implications. As a leader in patent and non-patent analytics and white space studies, SPA analysts have studied on-going developments in SAF and, the complexities of this evolving sector.
Introduction:
With the growing concerns about global climate change due to the greenhouse gases (GHG) emissions from fuel, demand for implementation of strict and feasible measures is increasing and it is very challenging to address this issue.
In this context, world’s nations pledged to try and prevent global temperatures rising by more than 1.5°C by adopting Paris Climate Agreement in 2015, however little progress has been achieved on this. According to National Oceanic and Atmospheric Administration aircraft, the contrails (white streaks following high-flying jet airplanes) and contrail cirrus (Formation of ice crystals with larger size) contribute 3.5 % of the global CO2 emission. In order for the aviation industry to become carbon neutral, sustainable aviation fuel, SAF as one of the options, has attracted a lot of interest.
What is and what is not SAF?
Sustainable Aviation Fuel is a biofuel with a smaller carbon footprint, possess similar properties as conventional jet fuel and can be used to power aircraft
EU legislation defines SAF as synthetic fuels, certain biofuels made from agricultural and forestry waste, algae, biowaste, used cooking oils, or certain animal fats. Recycled fuel made from exhaust gases and plastic waste is also considered green. In addition, renewable hydrogen can be added to the sustainable fuel mix as technology advances. However, the rules also exclude feed and crop-based fuels and those deriving from palm and soy materials, as they do not meet sustainability criteria.
Challenges and Opportunities:
There are significant challenges when it comes to adopting the use of SAF, such as large-scale production and high cost of production.
The factors affecting large-scale production are the availability of bulk raw materials, technology and conversion processes, and policy support. Similarly, the major factors contributing to high costs of production are machinery investment and operational expenses.
Many countries are providing incentive programs that facilitate innovation, scale-up, and cost challenges. In order to develop a robust strategy for scaling up novel technologies for the production of SAF on a large scale, The U.S. Department of Transportation, the U.S. Department of Agriculture, and other federal government agencies have collaborated with the Department of Energy.
The fortune companies have also announced plans to increase the production capacity of SAF to around 2.3 million metric tons by 2030, which could lead to an enhancement of SAF production and thus reduce the cost.
In order to achieve the above targets, the companies need to focus on aspects such as technological advancements, analyzing lifecycle emissions, and leveraging policy incentives. Also, collaborations and technology transfer are the key strategies for technological advancement in this arena.
Technical Pathways:
SAF is produced through various methods:
– Biomass Conversion:
Involves thermochemical treatment by processes such as gasification, pyrolysis, and hydrothermal liquefaction, which produces syngas/bio-oil, that can be further upgraded to aviation biofuels through catalytic hydro-processing.
– Synthetic Fuel Technologies:
- Fischer-Tropsch (FT) synthesis: An established process that converts the syngas in liquid hydrocarbons in the presence of a metal catalyst. The Fischer-Tropsch reaction process is carried out through tandem catalysis, which involves combining multiple reactions within a single reactor by centralizing subsequent processing reactions, which reduces the required infrastructure and aid in economic benefits.
- Hydro-Treating Process: Refines vegetable oils/waste oils/fats into SAF through hydrogenation, hydrodeoxygenation to obtain straight paraffinic molecules from which jet fuel is produced by cracking & isomerization. Honeywell developed an innovative hydrocracking technology to produce SAF which not only lowers carbon intensity by 90%, but also increases SAF production efficiency by 3-5% and a 20% reduction in operating expenses.
- Hybrid Approaches: SAF production methods combine different technologies to optimize efficiency. Integrating biomass gasification with FT synthesis is an example of a hybrid approach.
CANSTM technology, which is an integration of The Fischer Tropsch’s & Hydro-treating process, has been developed in collaboration with DG fuel, BP and Johnson Matthey, is planned to be utilized in SAF plant for commercial scale production i.e., 600,000 metric tons (MT) of SAF/year.
BP and Johnson Matthey worked together to develop a technology known as CANSTM. Three processes are combined in this integrated technology to test FT technology: a fixed-bed FT reactor, a novel compact reformer for producing syngas, and mild hydrocracking of FT waxes to produce synthetic crude. The new CANSTM catalyst carrier and optimized catalyst significantly simplify reactor design and fabrication, resulting in a 50% reduction in capital expenditure costs for the FT unit. This is in comparison to traditional fixed-bed tubular reactors, which have 95% fewer reactor tubes.
Feedstocks Types:
– Feedstock Sources: Utilizing biomass, algae, and waste materials to produce SAF.
The recent emerging feedstock in SAF is carinata, which is a non-food crop, has been listed by the International Civil Aviation Organization (ICAO) and has the potential to become one of the major feedstocks for the production of SAF due to its lower cost and abundant raw material availability. These features of Carinata could boost SAF production scalability.
Currently, Air BP Ltd. is using the oil made from Nuseed Carinata in the production of biofuels on a limited scale. Many companies are working on Carinata, which makes it a potential feedstock for SAF production in the future.
Technical Advancements:
| Company | Issues Addressed | Solution |
| Topsoe A/S | An effective process for utilising a by-product/off-gas stream rich in paraffins/olefins from a sustainable feed-to-hydrocarbon synthesis plant | Incorporation of a reforming system, in a hydrocarbon synthesis plant/process, for treating a by-product stream rich in C1-C4 paraffins/olefins |
| Chevron U.S.A. Inc | Fuels with a reduced cloud point or pour point and low carbon intensity | Hydroconversion catalyst based on zeolite SSZ-91 comprising EUO-type molecular sieve phase |
| Neste Oyj | Catalysts for catalyzing selective hydroisomerization reactions at low temperatures | A catalyst comprising a noble metal, a support and a 12-membered ring zeolite with nanopore size |
| Kepler Gtl LLC | Preventing the wastage of dry natural gas and the introduction of CO2 straight into the atmosphere without any attenuation or filtering | A Fischer-Tropsch conversion apparatus that is operably coupled to the natural gas reforming apparatus to produce SAF from dry natural gas |
Benefits of SAF:
– Environmental Impact: A reduction in GHG of up to 94% can be achieved by utilizing 100% SAF as contrails, and contrail cirrus from traditional jet fuel contributes 3.5% of global CO2 emissions. This substantial reduction is crucial to the industry’s progress towards decarbonization and combating climate change. Using 100% HEFA-SPK (Synthetic Paraffin Kerosene), a 56% reduction in ice particles per mass of fuel burned was observed compared to Jet A-1 under engine cruise conditions
– Economic Advantages: Airlines can achieve cost savings on fuel expenditures through SAF from the view point of carbon tax. By using green fuel one can save money as it will reduce the burden of carbon tax. Production of SAF from renewable resources can create economic opportunities, including new jobs and income, especially in rural communities where the raw material is available.
Biofuel Innovations in Aviation: Recent Research Developments
The performance of SAF is typically measured using metrics such as ice number concentration per mass of burned fuel. They are usually measured with two instruments: the cloud and aerosol spectrometer and the cloud, aerosol, and precipitation spectrometer. In a collaborative research project carried out by Airbus, the Deutsches Zentrum für Luft und Raumfahrt (DLR), Rolls-Royce, and Neste, a 56% reduction in ice particle numbers per mass of burned fuel was reported for 100% HEFA-SPK (synthetic paraffinic kerosene) compared to Jet A-1 under engine cruise conditions.
Reduced ice number concentrations in contrails at altitudes of 9.1–9.8 and 11.4–11.6 km from low-aromatic biofuel blends were reported by researchers from the German Aerospace Center, Johannes Gutenberg University, the University of the Federal Armed Forces in Munich, and the NASA Langley Research Center.
A continuous, two-stage catalytic process using molybdenum carbide to deoxygenate lignin into aromatic hydrocarbons with 87.5% selectivity has been developed by researchers from the Massachusetts Institute of Technology, Washington State University, and the National Renewable Energy Laboratory.
Startups in Sustainable Aviation Fuel(SAF):
Universal Fuel Technologies (2022) offers a proprietary catalyst and chemical technology, Flexiforming, that upgrades renewable naphtha and ethanol (or ethanol alone) into SAF.
Azure Sustainable Fuels (2021) is a fuel company that offers a low carbon, sustainable aviation fuel (SAF) production facility that utilizes agricultural feedstocks to produce SAF.
Metafuels (2021) powering the future of aviation with sustainable aviation fuel using path breaking aerobrew technology which provides a method for large production of e-SAF, thus overcoming higher costs.
