Renewable fuels from sunlight and thin air? Here’s what the airline industry is concocting to become planet-friendly

(Editor’s note: This article has been updated as of August 24, 2021)

CoViD-19 crisis or not, one of the critical goals of the aviation industry has been environmental sustainability. Truth be told, the aviation industry is one of the few businesses to have established agreed-upon carbon-emission-reduction standards for both equipment and operators internationally.

Three goals were declared through representative organizations in 2009 to mitigate the industry’s effect on climate change. First is to achieve carbon-neutral growth by 2020, followed by improving fuel efficiency by 2% per year from 2010 to 2020. Finally, to reduce CO2 emissions by 50% by 2050, relative to 2005. Now, to aid in achieving these targets, four pillars were disclosed. These are technology improvements in airframes and engine efficiency; the modernization of air traffic control; operational changes such as adopting single-engine taxiing and streamlined flight planning; and the use of renewable fuels. reported that the single-largest potential reduction in aviation’s greenhouse emissions would result from the broad adoption of Sustainable Aviation Fuel (SAF) in place of the current fossil-based jet-A. That is according to the Business Aviation Guide to the Use of Sustainable Alternative Jet Fuel.

“The price of SAF is today not competitive with petroleum jet [fuel],” Commercial Aviation Alternative Fuels Initiative (CAAFI) executive director Steve Csonka noted. “I could say that a couple of months ago when oil was sitting at $60 to $70 a barrel, and you’ve seen what has happened in the last couple of days with the price of oil, which just completely exacerbates the issue,” he added.

The cost of a gallon of blended SAF depends on many factors. “We are now up to seven production processes, and each of those has a different price point that is baked into the operating economics, driven by the capital expense of the facility and the vagaries of the feedstock that you’re using in that facility,” Csonka explained.

Csonka also explained that one misconception about SAF is that its main environmental benefits stem from its use in aircraft. While the SAF fuels do not contain sulfur—which is released into the atmosphere in the form of sulfur oxides, a component of acid rain—what’s lost on a lot of people is that the actual amount of CO2 coming out of the tailpipe is nearly identical to the amount of CO2 that comes out of the exhaust for a plane flying on petroleum-based jet fuel.

He also added that the difference lies in the benefits inherent in the production of each, which could potentially result in CO2 emission reductions of more than 100% over the life cycle of the fuel. “Fundamentally, this is what we’re talking about. Instead of continuing to pull carbon molecules out of the ground, burning them, and turning them into additional CO2 in our atmosphere. What we’re trying to do is pull carbon molecules out of our biosphere from different plant matters and recycle those carbon molecules so that in the long run we abate or even potentially reduce the amount of carbon that we’re exposed to in our biosphere.”

CAAFI assessed that after four years of sustained commercial use of SAF, renewable jet fuel production would increase from 36 million gallons per year (GPY) to 43 million GPY in 2020 and to nearly 10 times the latter figure by 2022. And with the anticipated opening of a major production facility in Asia, the value would double again, to more than 800 million gallons, by 2024 as more facilities come online and others are expanded.

An article published in April 2021 in reported that the “amount of SAF used by commercial aircraft rose 65% between 2019 and 2020, despite the devastating financial impact of Covid-19 on airlines.” It added that in 2021, this is expected to “jump another 70%”, quoting Robert Boyd, IATA Assistant Director of Aviation Environment and Head of SAF.

Boyd estimates that on the current trajectory, SAF production could hit 2% of the total fuel demand by 2025. At that level, the price gap between SAF and regular kerosene would start to close. (

Renewable jet fuel from sunlight

Yes, you read that right. recently reported that the Lufthansa Group had signed a letter of intent with the Swiss Federal Institute of Technology Zurich (ETH Zurich), along with its two spin-offs Climeworks and Synhelion to develop renewable jet fuel from sunlight.

Initiated by Lufthansa Group subsidiaries, the collaborative partnership with SWISS and Edelweiss will include cooperation in technology and economic efficiency. Including an intention to agree at a later date on shares of the renewable fuel to support demonstration projects. ETH Zurich’s researchers and engineers have developed methods possible to extract CO2 from the atmosphere, which along with water and concentrated sunlight, will convert it into a synthesis gas that can be used to produce jet fuel. In turn, this fuel will release only as much CO2 as was previously extracted from the atmosphere.

“In contrast to other modes of transport, air transport will depend on sustainable liquid fuels in the foreseeable future. Their market launch requires a joint effort by fuel manufacturers and airlines,” said Professor for Renewable Energy Carriers at ETH Zurich Dr. Aldo Steinfeld. “This letter of intent is intended to support the energy turnaround in aviation.”

On the part of Synhelion, its CTO Philipp Furler explained: “The pure water and CO2 splitting process we proved is our long-term vision, but it still requires quite some development and its product is more expensive than the current fossil fuel price. So, it is currently too far away from the market.” In this more advanced pure thermochemical route, we are putting in 1500°C of heat to drive the chemical process. We aim to introduce this technology by 2030,” he explained, whose solar fuels research at ETH Zurich formed the basis of the technology.

“But we also plan to introduce a product before that time. To enter the market much faster, we want to launch a simpler solar reforming-based route first. The solar reforming approach is more efficient than the pure water and carbon dioxide splitting process and is based on existing industrial technology. It is why we are developing both processes in parallel,” Furler added.

According to Synhelion, jet fuel made through a solar reforming-based approach would be commercially viable in the short term and cost a little more than today’s jet fuel because reforming is a mature, standard technology.

Meanwhile, this is not the first time Lufthansa has ventured into power-to-liquid projects recently. It also signed a letter of intent with Raffinerie Heide (Heide Refinery) for the development and use of synthetic kerosene produced from renewable energy, water and CO2 just early 2019. This type of fuel is to be provided by using surplus wind energy generated locally.

“The Lufthansa Group has been working hard for years to make flying ever more sustainable,” said Executive Board Member of Deutsche Lufthansa and Customer & Corporate Responsibility Christina Foerster. “Thanks to the forward-looking technologies and the cooperation with innovative partners in two of our home markets, we are on the right track.”

Watch how sunlight and the Earth’s atmosphere are actually harnessed to convert CO2 into synthesis gas and jet fuel here: