The airline industry is working on cleaner fuel — but how quickly can it decarbonize flying?

Our planet is changing. So is our journalism. This weekly newsletter is part of a CBC News initiative entitled "Our Changing Planet" to show and explain the effects of climate change. Keep up with the latest news on our Climate and Environment page.

Sign up here to get this newsletter in your inbox every Thursday.

April 22 is Earth Day. But as a What on Earth? reader, you know we celebrate Earth Day all year long.

This week:

Canadians love to travel, but we know that every flight produces CO2 emissions that contribute to climate change. 

While the airline industry currently contributes only 2.5 per cent of CO2 emissions, there's fear that it could increase significantly by the end of the century. The industry is looking at ways to achieve net zero emissions by 2050, and one major pathway is to explore the use of greener fuel. Here's a look at what that means, and what the challenges are.

Sustainable aviation fuel (SAF) is fuel derived from agricultural or synthetic materials (such as plants or animal fats) and recycled waste products (such as cooking oils) that can produce kerosene in jet engines. Simply put, it's cleaner fuel.

It is used as a "drop-in" additive to traditional fuels in order to cut CO2 emissions.

While there have been experiments with electrifying smaller planes, the batteries are too large for commercial planes, where every ounce of weight matters. This is why SAF is seen as vital in reducing aviation CO2 emissions.

Since SAF was first used in commercial aviation in 2011, more and more airports and airlines around the world have been integrating the cleaner fuel. The Trudeau International Airport in Montreal began providing SAF in 2016, while Pearson International Airport in Toronto began providing it in 2021. To date, globally, there have been more than 450,000 flights that have used this type of fuel.

Even so, according to a 2021 working paper by the International Council on Clean Transportation, SAF production accounts for less than 0.05 per cent of global jet fuel demand.

"The biggest criteria [for SAFs] … is something called freeze point, which is the temperature at which molecules start to solidify," said David Bressler, a professor at the University of Alberta's faculty of agricultural, life and environmental sciences.

Typically, gas-turbine airplanes use fuels called Jet-A or Jet-A1, which are special types developed for the colder temperatures found at higher altitudes. Jet-A fuel has a freeze point of –40 C, while Jet-A1 has a freeze point of –47 C. Jet-B fuel has a much colder freeze point of –60 C. (There are other types of fuel, but these are the most common.) 

Replacing traditional kerosene fuel with SAFs means ensuring that the fuel can have similar freeze points. But there are other wide-ranging challenges, says Jim Harris, a partner at the consultancy Bain & Company who specializes in aerospace.