11 Aviation Fuel

Two-thirds (66%) of the warming from flying come from non-CO₂ forcings, including contrails. Ho

Galuuci

Startup Twelve broke ground on a commercial-scale facility in Washington state, which it says will be the first in the country to make sustainable aviation fuel from CO2.

Nearly two years ago, the startup Twelve made its first batch of lower-emissions jet fuel at its lab in Berkeley, California. Using electricity, water and carbon dioxide, the company set out to make a synthetic fuel that could replace fossil-based kerosene.

Now, Twelve is ramping up to make significantly higher volumes of its ​“E-Jet” fuel. Last week, the eight-year-old startup broke ground on a commercial-scale facility in Moses Lake, Washington. Once up and running by mid-2024, the facility will be the first of its kind in the country to make alternative jet fuel from CO2 and grid power.

Airlines, Microsoft and Shopify have agreed to buy millions of dollars’ worth of E-Jet from the new plant. Twelve expects to churn out some 40,000 gallons of fuel per year before quickly expanding its production — potentially by as much as tenfold within the first year of operation.

Twelve claims its alternative fuel can cut life-cycle greenhouse gas emissions by up to 90 percent compared to petroleum-based kerosene. Burning E-Jet in engines will still emit CO2. But the goal is “recycling” CO2.

Companies are making strides to develop battery-powered planes and hydrogen-fueled jets. (Not far from Twelve’s site in Moses Lake, the startup Universal Hydrogen is test-flying a 40-passenger plane.) But both batteries and hydrogen are expected to serve mainly commuter and regional flights.

Startups like Twelve and global fuel conglomerates alike are all racing to produce ​“sustainable aviation fuel” that can be blended with, and eventually be fully substituted for, fossil kerosene in existing jet engines — but they have a long way to go. Last year, major U.S. airlines consumed some 17.5 billion gallons of jet fuel. Less than 0.1 percent of the total, or 15.8 million gallons, was so-called SAF.

the challenge isn’t just to make greater volumes of SAF but to produce it in completely new ways. Nearly all of the nation’s existing SAF supply comes from processing animal fats and used cooking oil, feedstocks that are in relatively scarce supply and are raising concerns of unintended knock-on climate risks.

Illinois-based LanzaJet, a spinoff of LanzaTech, is making synthetic jet fuel from ​“waste-based” ethanol derived from municipal solid waste, agricultural residues and biomass. The company is currently building what it says is the world’s first ​“ethanol-based alcohol-to-jet” SAF production plant in Georgia, slated to be completed later this year. At full capacity, the Freedom Pines Fuels facility is expected to produce 10 million gallons of aviation fuel and renewable diesel per year.

Another firm, New York–based Air Company, recently signed a $65 million deal with the U.S. Department of Defense to capture CO2 on military bases and turn it into jet fuel. The startup’s process involves combining CO2 and hydrogen in a chemical reactor to produce paraffins — colorless, oily liquids — for sustainable aviation fuel.

Twelve uses another method to turn CO2 and hydrogen into juice for jet engines.

To start, the company procures ​“waste” CO2 from industrial facilities. Twelve has developed its own electrochemical reactor to split carbon dioxide molecules into carbon monoxide using electricity. Engineers then use a separate electrolyzer to split water molecules into hydrogen and oxygen. The resulting mixture of carbon monoxide and hydrogen is known as ​“syngas.”

Finally, the team deploys a multistep reaction called the Fischer-Tropsch process to convert the gas into a liquid — one that’s chemically identical to jet fuel made from petroleum.

To produce SAF at its commercial-scale plant, Twelve will initially source CO2 from an ethanol refinery in neighboring Oregon and, later, from pulp and paper facilities in Washington, he said.

As the nation’s SAF supply grows from a mere drop in the bucket to a sizable share of airlines’ jet fuel use, Twelve and other producers are likely to encounter a fresh set of hurdles. Many power plants and industrial facilities don’t have the infrastructure needed to capture, store, concentrate and transport the CO2 from their waste streams. Even if they did, those plants will likely generate less planet-warming gases over time as industries decarbonize and shift to renewable energy sources. For SAF producers that rely on CO2, a potential solution is to deploy ​“direct air capture” machines that suck the gas directly from the sky, though the technology remains expensive, energy-intensive and unproven at large scales. Companies that rely on hydrogen to make low-carbon fuels or power planes directly may also struggle to procure enough “green” supply.

The availability of electricity is one of the biggest potential limitations when it comes to siting and scaling Twelve’s future SAF facilities.

Galucci (2023) This new factory will turn CO2 into sustainable jet fuel

11.1 Contrails

Gallucci

Although burning fossil jet fuel contributes about 2.4 percent of the world’s annual carbon dioxide emissions, flying may actually be responsible for 4 percent of total global warming when contrails and other non-CO2 factors are taken into account, a 2021 study found.

If scientists can accurately predict where and when heat-trapping contrails are likely to form, then airlines could adjust a plane’s path to avoid flying through the riskiest regions. The challenge, however, is that research institutions and technology companies are only just beginning to develop the tools for making such predictions.

The mechanism is fairly simple. If pilots spot a contrail left behind by another aircraft, they manually log the observation in an electronic form, noting details such as the time, altitude, temperature and humidity. That information is shared instantaneously with a dispatcher on the ground, similar to how pilots file turbulence reports during flight.

Researchers need this type of real-world data to help validate and calibrate their contrail-prediction models, Cathcart said. Satellite imagery is another important tool, though it can’t always detect contrail formations. Ground-based imagery is also somewhat limited because it generally doesn’t pick up contrails on cloudy days or over oceanic routes. The goal is to deploy in-flight reporting on many more planes to build up an industrywide database.

Recently, Breakthrough Energy and two other task force members, American Airlines and Google Research, launched a separate effort to see whether pilots could avoid creating contrails by adjusting their altitudes during flight.

Over a six-month period, a group of pilots at American flew 70 test flights using contrail forecast maps, which were developed with Google’s artificial-intelligence-based predictions and Breakthrough Energy’s open-source contrail models. After the flights, researchers analyzed satellite imagery and found that pilots were able to reduce contrails by 54 percent, according to Google Research. They estimated that maneuvering around contrail-prone zones could require airlines to burn as little as 0.3 percent additional fuel.

Virgin Atlantic’s flight will, along with informing contrail models, help to address another crucial question facing contrail researchers: whether sustainable aviation fuel itself can reduce the formation of heat-trapping clouds.

When jet engines burn fuel, they generate carbon dioxide emissions as well as particulate matter, or soot. In certain circumstances, water vapor in the atmosphere attaches itself to the soot particles and forms ice crystals, which can then become cirrus clouds that fan out and persist — contributing to global warming. A growing number of studies suggest that burning sustainable aviation fuel, or SAF, produces fewer particulate-matter emissions than fossil jet fuel, which in turn lowers the potential to create warming contrails.

If there are fewer particles, as we expect from the use of SAF, the contrail won’t last for as long and will therefore have a smaller climate effect.

Gallucci (2023) Airlines have a big climate problem, and it’s not just CO2 emissions