If you take organic waste, subject it to high heat and starve it of oxygen, you will, through a process called pyrolysis, wind up with a pile of char — also known these days as biochar — that doesn’t seem like it’d be useful for much. Turns out, plants love it.
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The residue has “huge potential” not only for agriculture, but also as a kind of natural form of carbon sequestration that can help combat climate change, said Michel Gagnon, chief executive of Airex Energy Inc. The Canadian cleantech startup is part of a group that in July committed $80 million to build North America’s largest biochar plant. Airex, along with lumber producer Groupe Remabec and waste treatment company Suez SA, plan to build the plant roughly 800 kilometres northeast of Montreal in Port-Cartier, Que.
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As its feedstck, the facility will use waste residues from lumber production, including wood chips and branches, in order to produce 30,000 tonnes of biochar a year by 2026, destined for markets in Europe and North America.
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Once it is mixed into soil, biochar quietly improves soil quality, removing contaminants and doling out nutrients to plants slowly, over time.
If left in the forest, the decomposing wood chips and branches would be ingested by organisms in the soil, which would then release carbon dioxide into the air. Biochar, on the other hand, decomposes much more slowly, so the carbon dioxide will instead be stored for decades, or even hundreds of years. The Airex project will sequester 75,000 tonnes, with each tonne representing 2.5 carbon credits which can then be sold to big energy companies, said Gagnon.
“Producing biochar has a lot of merits, because of the climate change and environmental benefit to it,” he said. Airex’s biocharwill be used not only for agricultural purposes, but also for concrete, asphalt and as topsoil for backyard gardens.
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Beware of backyard kilns
A caveat: biochar can be a high-risk, high-reward product.
If made improperly, biochar can ruin soil for generations, warned Maren Oelbermann, professor in the school of environment, resources and sustainability at the University of Waterloo. “Sometimes you talk to people, and they’re like, ‘Oh, I have biochar, I made it in my backyard, and that always makes my alarm bells go off,” she said.
Biochar at a factory in Africa. Once it is mixed into soil, biochar improves soil quality, removing contaminants and doling out nutrients to plants slowly.
Biochar at a factory in Africa. PHOTO BY MICHELE SIBILONI/AFP/GETTY IMAGES
In a backyard pyrolizer, or “kon-tiki kiln,” it is difficult to control the flow of oxygen and regulate the temperature, which can be problematic, Oelbermann said.
“Once youve added it to the soil, it’s going to be there, potentially for decades to hundreds or more years,” she added. “It is really important to understand that when biochar is added to soil, that it should be a very high quality of biochar.”
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The Port-Cartier plant will produce biochar that complies with the European Biochar Certificate, an industry standard for biochar production, which will determine the company’s health and safety procedures as well as the properties of its biochar, wrote Frederik Daneault-Duguay, spokesperson for Airex, in an email.
Once you’ve added it to the soil, it’s going to be there, potentially for decades to hundreds or more years
MAREN OELBERMANN, PROFESSOR, UNIVERSITY OF WATERLOO
One of the most important steps in making high quality biochar is selecting a reliable feedstock, Oelbermann said.
“You can’t just pyrolize anything that comes into your hands,” she said. You could use compost, for example, butits nutrient content is not always consistent, and can result in a biochar of questionable quality, she added. Biochar made from lumber waste will be better quality, but might also be more expensive for the end user.
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The specific pyrolysis process used will also affect the quality of biochar produced.
Airex, which has operated an industrial scale biocoal pellet plant in Quebec since 2016, says it has “mastered” the pyrolysis process.
“You can have the same feedstock, but you can pyrolize it using slightly different temperatures and lengths of time and you get a different product, and it looks slightly different,” said Oelbermann. “Then the question is: How do those different biochars react in the soil?”
Compressed biochar at a factory in Africa.
Compressed biochar at a factory in Africa. PHOTO BY MICHELLE SIBILONIA/AFP/GETTY IMAGES
It’s hard to say. Biochar research is still in its infancy. We don’t yet know how much biochar weshould be putting in soil, and whether it is better to add it to soil as a powder, or chunks, said Oelbermann.
Given that bad biochar could ruin soil for generations, one might ask just how “environmentally friendly” it really is.
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‘An industrial process’
The answer depends largely on the production process, said Scott Chang, professor in the department of natural resources at the University of Alberta.
“It’s an industrial process,” he said. “In that industrial process, obviously, it’s going to use some sort of energy. Hopefully not too much if (the company is) using proper biomass.”
It is essential that the wood chips not be too wet, he said, because wet wood chips will take an incredible amount of energy to char. Transporting the resulting biochar could also consume a great deal of energy, depending on the distance between the lumber producer, the processing facility, and the end user.
When all is said and done, the commercia impact of the biochar will vary. If a patch of soil is already good quality to begin, the addition of biochar might not make much of a difference.
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In general, biochar raises the pH of soil, making it more amenable to agriculture, but the pH of the soil in southern Canada is already quite high, said Oelbermann, adding that some people might question the need for biochar in our region.
But Airex and partners have global ambitions. They plan to expand to Europe, where soils tend to have a lower pH. The second project will be in Paris, Gagnon said. The companies aim to produce 350,000 tonnes of biochar in total by 2035.
