In a bricks’ fabric in the German port city of Hamburg, cocoa bean shells they are processed into a black powder that stores carbon and can help counteract climate change.
The substance, called biochar, is produced by heating the shells to 600ºC in a room without oxygen.
The process captures the greenhouse gases and the final product can be used as a fertilizer or as an ingredient in the manufacture of “green” concrete.
Although still a fledgling industry, the technology offers a new solution for removing carbon from Earth’s atmosphere, experts say.
According to Intergovernmental Panel on Climate Change (IPCC) of the United Nations, biochar has the potential to capture 2.6 billion of the 40 billion tons of CO2 currently produced by humanity each year.
But bringing its use to a large scale remains a challenge.
Formerly used in America
“We are reversing the carbon cycle,” Peik Stenlund, chief executive of biochar producer Circular Carbon, tells AFP from the Hamburg factory.
The plant, one of the largest in Europe, receives the husks of the cocoa beans from a nearby chocolate factory through a network of gray pipes.
Biochar traps the CO2 contained in the husks, but the same process can be used for any other plant.
If used cocoa were disposed of without this treatment, the carbon within it would be released into the atmosphere during the decomposition of the product.
Instead, with this method, carbon is captured in the biochar “for centuries,” according to David Houben, an environmental scientist at France’s UniLaSalle institute.
One ton of biochar can store “the equivalent of 2.5 or 3 tons of CO2,” Houben tells AFP.
This substance was already used by the indigenous populations of America as a fertilizer before being rediscovered in the 20th century by scientists investigating the highly fertile soil of the Amazon basin.
The surprising spongy structure of biochar enhances the harvest by increasing the absorption of water and nutrients from the soil.
In Hamburg, the factory is enveloped by the aroma of chocolate and the heat emanating from the installation’s network of pipes.
The final product is poured into white sacks to be sold to local farmers in the form of pellets.
One of them is Silvio Schmidt, who grows potatoes near Bremen, west of Hamburg. The 45-year-old farmer is confident that biochar will “bring more nutrients and water” to his sandy land.
Everything must be local
The process, known as pyrolysis, also produces a certain volume of biogas, which is resold to a nearby factory.
In total, the plant produces 3,500 tons of biochar and “up to 20 megawatt hours” of gas each year from 10,000 tons of cocoa shells.
But the production method is difficult to bring to the magnitude envisioned by the IPCC.
“To ensure that the system captures more carbon than it produces, everything has to be done locally, with little or no transportation. Otherwise it doesn’t make sense,” says researcher Houben.
Also, not all soil types are well suited to biochar, “most effective in tropical climates,” and the raw material for its production is not available everywhere, he adds.
The cost can also be prohibitive, at “around 1,000 euros ($1,070) per tonne, which is too much for a farmer,” says the scientist.
To better use this black powder, new applications must be found, insists Houben, who points to construction.
Biochar can be used, for example, to produce “green” concrete, he says.
The sector has come up with another idea to obtain benefits: selling carbon certificates to companies that want to balance their emissions balance by producing a certain amount of biochar.
With the inclusion of this substance in the highly regulated system of carbon certificates of the European Union, “we see a strong growth of the sector”, says Stenlund, the CEO of the factory.
His company plans to open three new facilities to produce more biochar in the coming months.
Throughout Europe, biochar projects are multiplying. According to the federation of this industry, production will almost double between 2022 and 2023 to 90,000 tons.