Editorial Feature

The Future of Using the Air and Sun to Produce Sustainable Aircraft Fuel

Shipping and aviation combined account for around 8 percent of total anthropogenic CO2 emissions. Swiss researchers at ETH Zurich have developed a rooftop refinery that turns sunlight and air into fuel. The aim is to produce carbon-neutral fuels for transportation, with an emphasis on aviation, because it is one of the hardest sectors to decarbonize.

aircraft, aviation, air, sunlight

Image Credit: petrmalinak/Shutterstock.com

Paris Climate Agreement and COP26 Glasgow

The 2015 Paris Climate Agreement, adopted by 196 parties, is a legally binding international treaty, aimed at tackling climate change.

A key part of the agreement was to limit global temperature rise to below 2 ºC, preferably 1.5 ºC, pre-industrial levels.

COP26 in Glasgow 2021 was the follow-up to Paris to review progression, raise new agreements, and secure agreement to reach global net-zero by 2050.

Researchers, such as those at ETH Zurich, are working diligently to develop new technologies, trying to provide solutions to achieving net-zero, including aviation fuel.

Aviation for tourism and domestic flights shows no signs of slowing down, despite repeated demands from campaigners to cut subsidies and tax exemptions (2021 Taming Aviation Coalition), and a brief interruption in the number of flights being taken due to the COVID-19 pandemic.  

As air travel produces more carbon dioxide per kilometer than any other form of transport, ETH Zurich decided to create a jet fuel refinery. The researchers see no reason why the technology cannot be funded by the small number of wealthy frequent fliers, who are responsible for the high emissions that flying creates.  

Sunlight and Air Chemical Process

The new process takes water and carbon dioxide directly from the air, reducing it to carbon monoxide and hydrogen using solar power, which is then made into fuel.

Water and carbon dioxide are captured using an amine-functionalized sorbent from Climeworks, a company founded in 2009 by two engineers as a spin-off of ETH Zurich. The gases are then fed into one of two solar reactors.

The first reactor thermally reduces the redox material and cerium oxide, with oxygen as a by-product. The resulting syngas is then reoxidized with carbon dioxide and water to generate carbon monoxide and hydrogen.

The second reactor receives concentrated sunlight, so both reactors run simultaneously, with one creating solar energy and the second performing oxidization of water and carbon dioxide.

The last stage takes the syngas mixture of hydrogen and carbon monoxide and converts it to methanol at the rate of around 50 ml per day on a sunny day.  The syngas mixture can also be used to create other fuels such as kerosene.

Scaling Up Sustainable Aircraft Fuel Plants

Carbon-neutral fuels, such as methanol or kerosene and other hydrocarbon fuels are vital for the future of aviation if air travel is to become sustainable.  

Commercial, large scaling-up of the technology and investment is needed to achieve sustainable aviation. Desert locations are ideal because of solar resource availability, and available land.  

Hydrocarbon fuels are also better for the planet and people than biofuels because unlike many biofuels, they do not compete with agricultural land, which is needed to produce food or manage livestock.

To scale up and meet the demands for global aviation fuel, which was 414 billion liters in 2019, production plants would require 45,000 km2 of space, which equates to around 0.5% of the Sahara Desert.

The researchers, writing in Nature said “….bringing such solar fuels to the market will require substantial process optimisation and upscaling, and this should be supported by policy schemes that enable market introduction at commercial scale.”

The technology is mature enough to use in industrial applications and would cost 1.2 to 2 euros per liter. The cost is expensive for the first generation of fuel created due to the initial setup costs of solar plant installations, but ETH Zurich is calling on the European Union to adopt a European technology-specific quota system for aviation fuel. 

This would require airlines to purchase a specific amount of fuel generated by solar. Current emissions trading and offsetting support instruments do not currently encourage market demand for solar-generated sustainable fuels.

Researchers at ETH Zurich claim such a quota system would barely affect the cost of flying but would promote scaling-up of production facilities, leading to further developments and reduced costs.

There are several other companies also creating jet fuels from air and sunlight, most of which are operating at a small scale to begin with, to test both the technology and gain market support and investment.

One such company is Dimensional Energy, which has been piloting a project in Arizona but has plans to scale up to fuel flights to Hawaii. Hawaii officials have agreed to accelerate a policy to switch to renewable energy by 2045.

Hawaii is supporting 19 businesses with funding, Dimensional Energy being one of them, as part of its Elemental Excelerator initiative. The not-for-profit model launched in 2009 provides training and funding of up to $250K each to companies involved in climate technology development, teaching them how to scale up and develop their businesses. Elemental Excelerator has so far awarded $49.3M to companies pursuing sustainable technologies.

Similar localized initiatives and financial support packages are happening elsewhere, but it is only a large scaling up that will really make any significant difference in tackling aviation emissions.

References and Further Reading

Drop in Fuels from Sunlight and Air (pdf) (2021) Schappi. R, Rutz.D, Dahler. F, Muroyama. A, Haueter. P, Lilliestram. J, Patt. A Furler. P, Steinfield. A in Nature online (accessed 02.12.2021) https://www.nature.com/articles/s41586-021-04174-y

Making aircraft fuel from sunlight and air (11.04.2021) Institute for Advanced Sustainability Studies e.v (IASS) in Science Daily online (accessed 12.02.2021) https://www.sciencedaily.com/releases/2021/11/211104115245.htm

Paris Climate Agreement 2015 (pdf) in UNFCCC online (accessed 12.02.2021) https://unfccc.int/sites/default/files/english_paris_agreement.pdf

COP26 Goals 2021 in UKCOP26 online (accessed 12.02.2021) https://ukcop26.org/cop26-goals/

250,000 tell EU to end airline subsidies, tax breaks, night flights (11.30.2014) in Transport & Environment online (accessed 12.02.2021) https://www.transportenvironment.org/discover/250000-tell-eu-end-airline-subsidies-tax-breaks-night-flights/

Mini-refinery makes jet fuel from just sunlight and air (11.09.2021) King. A in Chemistryworld online (accessed 12.06.2021) https://www.chemistryworld.com/news/jet-fuel-from-sunlight-and-air-could-decarbonise-the-aviation-industry/4014727.article

Researchers create fuel from thin air and sunlight (11.03.2021) Massey. N in Evening Standard online (accessed 11.06.2021) https://www.standard.co.uk/news/uk/scientists-aviation-nature-writing-switzerland-b964194.html

New Era of Energy Challenge (2021) in Elemental Excelerator online (accessed 12.06.2021) https://elementalexcelerator.com

This Company makes Jet Fuel from Water, Sunlight and CO2 (10.05.2021) in CiviliBeat online (accessed 12.06.2021) https://www.civilbeat.org/2021/10/this-company-makes-jet-fuel-from-water-sunlight-and-co2/

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Georgie Lyng

Written by

Georgie Lyng

Georgie Lyng is a freelance writer, with a strong interest in environmental issues, a focus on sustainable technologies, climate change science, improving biodiversity, and protection of natural ecosystems. Georgie completed an Open University BSc Environment Studies degree in 2016, enjoys researching environment issues, and writing about the latest scientific developments in the industry and sustainable solutions to help protect the environment.


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