Sustainable fuel: a real challenge for aviation

Despite recent improvements in fuel efficiency, aviation remains a major contributor to climate change. Accounting for 2.1% of all human-induced CO2 emissions and 12% of all transport-related emissions, the sector is already the world’s second biggest source of greenhouse gases. But what’s even more worrying is that, due to increasing demand for air travel, international aviation emissions are expected to triple by 2050.

If the world is to meet its ambitious climate goal of keeping global temperature rise to well below 2 degrees Celsius, the aviation sector must reduce its carbon footprint. However, as the World Economic Forum (WEF) correctly points out, it must do so without impacting the immense economic and social benefits that air travel provides:

“The aviation industry has played a large part in enabling the benefits of globalisation as well as the risks, such as the ongoing pandemic. It is in this context that the aviation industry and its entire value chain is today confronting the challenge of how to continue to deliver benefits in an environmentally sustainable way.”^[1]

The answer for striking this balance between sustainability and service is Sustainable Aviation Fuel (SAF).

SAF is a non-petroleum-based jet fuel produced by recycling sustainable raw materials or by using carbon that is extracted from plants. For example, SAF can be derived from agricultural waste, saw dust, or sewage. Even used cooking oil, which would normally be thrown away, can serve as a valuable raw material for making SAF.

“Sustainable aviation fuel is an alternative to the high pollution, high carbon emission sources that we use in aviation today,” says Marcelo Amaral, General Manager at Leaf. “With SAF, we have the opportunity to lower emissions while, at the same time, maintaining – even growing – a critical sector of the economy.”

A business unit of Lesaffre, Leaf is a leading global player in developing the industrial biotechnology that will enable a better future. For example, the BU develops industrial microorganisms and processes that allow renewable productions. In collaboration with players that are also passionate about accelerating the transition, Leaf designs and put into action high performance bio-based solutions.

Those processes are based on fermentation, that could eventually be used to produce SAF.

“Playing a key role in the production of the bio-renewable resources used by sustainable aviation fuels, fermentation will help drive SAF’s uptake and accelerate our progress towards a more sustainable aviation sector,” adds Marcelo Amaral.

 

Ready to fly

As Amaral explains, flying on sustainable aviation fuel, including those derived from fermentation-based bio-renewable resources, reduces crude oil consumption and produces lower lifecycle carbon emissions compared to conventional jet fuel. “Over its lifecycle, SAF has an up to 80% smaller carbon footprint than traditional fossil-based jet fuel,” he says.

But beyond its potential to significantly reduce an aircraft’s emissions, SAF also features a higher energy density than traditional jet fuel. And, having undergone rigorous testing, SAF is already proven safe for use on commercial aircraft.

Unlike other alternative fuel sources (e.g., hydrogen, battery electric), SAF is certified as ‘drop-in’ or ‘ready-to-use’. In other words, it possesses similar properties, qualities, and characteristics as Jet A and Jet A1 fuel (the kerosine grade of fuel used by most turbine engine aircraft).

“This means aircraft using SAF perform the same as those operating with fossil-based fuels,” says Marcelo Amaral. “More so, using SAF does not require any modifications to the aircraft or additional ground infrastructure, so any aircraft can already fly with SAF today.”

 

The need for scale

Despite these advantages, use of SAF remains low – the primary limiting factors being a lack of availability and high costs. According to the WEF, in 2019, fewer than 200,000 metric tons of SAF were produced worldwide. That’s not even 0.1% of the approximately 300 million tons of jet fuel consumed by commercial airlines every year – and it doesn’t even take into consideration the fuel used by the business and general aviation sectors.

Due to limited supply, there is also a general lack of demand for SAF. Because demand and supply remain unbalanced, the cost of SAF is more than double the cost of conventional jet fuel – putting SAF far out of reach for many operators.

To make SAF economically viable, production must be significantly scaled up – something that fermentation could help with.

According to Marcelo Amaral, high performing industrial fermentation relies on advanced microorganisms and smart technical services. Leaf provides both products and process expertise across the globe, today for renewable bioethanol and advancing towards bio-sourced chemicals. For example, its unique Comprehensive Coupled Product and Process, or CP², approach combines Leaf’s experience and recent advancements with investments in innovation and research.

“As SAF moves to commercial scale, Leaf is well-positioned to be the industrial fermentation partner for a sustainable tomorrow,” adds Marcelo Amaral. “And, as production of SAF ramps up, costs will go down and demand will increase – ultimately opening the door to the era of sustainable aviation.”

Towards the era of sustainable aviation

Helping accelerate the transition towards SAF are programmes like the Commercial Aviation Alternative Fuels Initiative (CAAFI). A public/private partnership between the aviation community and the Federal Aviation Administration (FAA), CAAFI’s goal is to promote the development of alternative jet fuel options that offer equivalent safety and favourable costs compared to petroleum-based jet fuel, while offering environmental improvement and energy supply security for aviation.

The transition to SAF is also being driven by regulatory initiatives. For example, the European Union, which aims to become carbon neutral by 2050, will require that all aviation fuel supplied to aircraft operators at EU airports contain a minimum share of SAF. When the mandate goes into effect in 2025, this minimum share is expected to be 2%, with set increases every five years, reaching a minimum volume of 63% by 2050.

Across the pond, in the U.S., the Sustainable Skies Act of 2021 aims to boost the use of SAF by providing a per gallon credit based on the lifecycle greenhouse gas savings the SAF provides. This act was followed by several additional initiatives, all of which aim to increase the production of SAF to at least 3 billion gallons per year by 2030.

These initiatives have clearly gotten the attention of industry, with Air France announcing that over 15,000 tons of SAF will be used on its aircraft this year – that’s about a 10-fold increase over what the airline used in 2021. In the U.S., United Airlines made history when a flight from Chicago’s O’Hare Airport to Washington Reagan National Airport became the first commercial flight with passengers to use 100% drop-in SAF for one of the aircraft’s two engines.

“All these initiatives and achievements highlight that SAF is the answer to aviation’s carbon challenge and the key to meeting the industry’s environmental goals,” concludes Marcelo Amaral. “SAF isn’t the future – it’s already here, now we just need to start using it.”