In Kisumu, Kenya, start-up company Tera Carbon is collecting waste residues from sugarcane, heating this waste biomass without oxygen in a process called pyrolysis, then distributing the resulting charcoal-like substance to sugarcane growers, who mix this "biochar" into their soils. The outcome is that carbon dioxide - which had been removed from the atmosphere by the sugarcane as it grew in the fields of western Kenya - will be stored in the soil for thousands of years.
"It's a simple process, and the carbon removal is immediate," says Rob Palmer, Tera Carbon's co-founder and CEO. Without the production of biochar, he explains, the sugarcane waste, known as bagasse, would be "either combusted or left to decompose, releasing the carbon that was in the plant back into carbon dioxide or methane".
The technology is already playing a crucial role in carbon markets around the world. So far, biochar projects account for around 90 of the carbon removal credits that have been used to offset emissions and thus "retired" from the market.
Biochar projects are relatively cheap to operate, compared to technologies such as "direct air capture", which rely on large-scale industrial processes. At the same time, biochar projects are designed to permanently store carbon in the soils. This "permanence" is a distinct advantage over projects that involve planting trees or other vegetation, given that a forest could be destroyed by fire, and it is hard to guarantee that carbon will be permanently stored in wood products that might be produced.
Saving soilsThe other advantage of biochar is that the substance has significant benefits for soil health. Palmer notes that farmers across the continent typically struggle with access to the inputs they need to keep soils healthy and productive. "You get farmers either not applying anything to their soils or only being able to choose one of the inputs required," he says.