Can this 'burnt toast'-like substance be a key tool in the fight against climate change?

It might be considered an odd retirement hobby, but Greg Porteous spends his spare time making biochar. 

Biochar is a black, charcoal-like substance created by applying high heat to organic materials such as wood, plant matter and even sewage sludge.

He makes it in his own backyard in Courtenay, B.C., where he has a kiln that he bought online. In goes the organic matter, like brush or old wood pallets, high heat is applied with little to no oxygen and, since there is minimal fire, the fuel is turned into biochar. 

Porteous got the idea after looking into ways he could help fight climate change and reading that making biochar was a good option. He started doing it for himself and his neighbours. 

"It's just win, win, win. It's a cascade of positive benefits," said Porteous.

"The property owner, he gets his woody debris dealt with, the soil gets a beautiful additive put into it, the atmosphere gets the carbon sequestered so it doesn't go into the atmosphere. It's great for me, too. It's a great physical activity to get outside," he said

It's a carbon removal tool that has been picking up steam over the past decade. The United Nations has said biochar is a good way to deal with wood waste because it can hold carbon in the soil. Its report on mitigating global warming said biochar can be "used to store carbon away from the atmosphere for decades to centuries." 

That has corporations and countries turning to biochar as they look at their own climate solutions. 

Biochar is made through a process called pyrolysis. 

"Think of it as burnt toast," said Kathleen Draper, who sits on the board of the U.S. Biochar Initiative and is the U.S. director for the non-profit Ithaka Institute for Carbon Intelligence.

"Imagine you put any kind of organic material in an oven, you close the door to limit the oxygen … and if you turn up the heat, what happens? You get this black substance that is very unappetizing."

Unappetizing to eat, yes, but there are benefits. A plant, for example, absorbs carbon dioxide over its lifetime. When it dies, that carbon is released. But through pyrolysis, Draper says at least half of that carbon doesn't get released, and instead is put into that "burnt toast"-looking substance. 

Biochar has all sorts of uses. Draper says it can be used as an additive to make greener concrete and asphalt or to clean up lakes and ponds that have too much phosphorus. 

It's also very good for soil, according to Annette Cowie, a researcher at the New South Wales Department of Primary Industries and an adjunct professor at the University of New England in Australia.