How biochar — the ‘Swiss Army knife of climate tools’ — is growing in Minnesota
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It smells like a giant campfire inside a big brick building in the small northeastern city of Coleraine, in northeastern Minnesota, where researchers are making a material that can not only fight climate change, but also provide a host of other environmental benefits, from improving soil to filtering pollutants.
It’s called biochar. It’s a centuries-old technology that is now the subject of renewed attention in Minnesota and beyond as companies and government agencies look for ways to reduce their carbon footprints.
For the past several years researchers at the Natural Resources Research Institute, an arm of the University of Minnesota have experimented making different formulations of biochar in a huge kiln in Coleraine.
In a process known as pyrolysis, leftover wood chips from a nearby pallet company are cooked at nearly 1,000 degrees Fahrenheit in an oxygen-free environment.
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Researcher Cally Hunt holds the result cupped in her hands — small, easily crumbled, shards.
“It’s pretty brittle,” she said, “Basically just black wood chips, cooked down.”
Think of it as kind of advanced charcoal, said Eric Singsaas, director of the Materials and Bioeconomy Research Group at NRRI.
But this charcoal has climate change fighting superpowers.
Take a tree, explained Singsaas. When it dies, it decays. All the carbon dioxide it sucked out of the air during its lifetime returns to the atmosphere.
But the process used to create biochar, called ‘pyrolysis,’ changes the carbon into a form that doesn’t break down very easily.
“So if you put it in the ground, or in something like a building material, that carbon that was once atmospheric carbon, will stay in that form for decades to hundreds or even thousands of years,” said Singsaas.
That ability to essentially remove carbon dioxide from the atmosphere, and store it, has sparked rapid growth in the biochar industry in the past couple years.
While still small, it’s doubled in about the last three years, said Myles Gray, who directs the United States Biochar Initiative. Companies that manufacture biochar have sprouted up around the country, including a startup in Minnesota.
That growth, Gray said, has been spurred by an increased demand for carbon removal credits for biochar. Gray said combined revenues reached approximately $100 million last year.
“Essentially, large companies are buying biochar carbon removal credits to offset some of their emissions,” he explained.
Microsoft, for example, has pledged to remove all of its current and historic carbon emissions.
But biochar can do a lot more than store carbon. Researchers at NRRI and elsewhere are using it to filter pollutants, improve soils, grow trees and even make concrete and steel.
“It’s the Swiss Army knife of climate tools,” said Jim Doten, carbon sequestration manager for the City of Minneapolis.
On a vacant lot near the University of Minnesota, the city of Minneapolis plans to break ground this fall on a $1.5 million biochar plant, funded by the city and a large grant from Bloomberg Philanthropies.
Doten believes it will be the first city-owned biochar plant in the country. The feedstock for the plant will come from trees thinned by utilities under powerlines, and from millions of ash trees in the state killed by emerald ash borer.
“There’s just a huge glut of wood that’s going to be burned, and we’re trying to prevent the burning of that wood and keep that carbon stored in a safe form,” Doten said.
Doten first learned about biochar while working as a hydrologist with the National Guard in Afghanistan around 2010. Back then he wasn’t interested in its climate benefits. He wanted to improve the region’s soil for farming.
Biochar has long been recognized for its ability to boost soil health. Researchers have found evidence of biochar use dating back centuries in the Amazon rainforest to enrich the soil.
When Doten came to Minneapolis, he created a program that uses biochar and mixes it with compost to supply community gardens, plant trees and remove pollutants from stormwater.
The city plans to deliver biochar for free to residents in its green zones, and sell it to state and local agencies for their own climate mitigation work.
The city’s plant is “on the smaller scale,” Doten said. He expects it to process about 3,000 tons of wood annually, which will create about 500 tons of biochar. It’s a large scale pilot he hopes will be replicated.
“One of the big purposes here is to show that this can be done, that there are uses out here,” Doten said.
Meanwhile, an early stage Minnesota startup called Carba has developed a reactor that is able to create higher yields of biochar at a faster rate than typical pyrolysis kilns.
The company has partnered with Waste Management for its pilot-scale reactor, which it has deployed at a landfill in Burnsville. The biochar is then buried underground where it not only stores carbon, but also helps filter PFAS and other contaminants.
CEO and co-founder Andrew Jones said there’s a huge interest in companies buying carbon credits, and biochar has advantages over technologies such as direct carbon capture, which are expensive and unproven.
“It’s durable and it’s measurable and it’s available now. It’s highly scalable. And so biochar is sexy for a number of those reasons,” said Jones.
Gray, of the United States Biochar Initiative, sees a lot of opportunity in states like Minnesota, where there’s a lot of wood waste. There’s also a surprising amount of wood available in cities, he said. A large tree care company opened a biochar facility in Chicago earlier this year.
Multi-purpose biochar
University of Minnesota Duluth researchers are studying several additional ways to use biochar.
They’re testing biochar to capture E coli from stormwater runoff, and to help revegetate landfills.
Singsaas is leading a project funded by the U.S. Department of Energy that uses biochar instead of fossil fuels to make steel.
“We’re getting calls from from the steel industry all over the world, because there’s a big demand for lower carbon impact of the steel that goes into everything from our cars to our buildings to rebar and concrete,” Singsaas said.
The steel industry represents about seven precent of global carbon emissions. Biochar represents a substantial opportunity to reduce those emissions, he said.
One of the big challenges to making biochar use more widespread, Singsaas said, is the need to create unique biochars, or “engineered biocarbons,” as he prefers to call them, for various applications. “Fit for purpose” biochar, as he calls it.
Different uses, whether it’s as an additive to be used in steel or concrete, or water filtration, demand different chemistry and structure of the material, Singsaas said.
“That gap in research is what we’re trying to fill so that this can become a more widespread thing,” he said.
But there’s lots of opportunity as well. The U.S. Forest Service is interested in biochar for fuel reduction programs. It’s expensive to thin forests for fire prevention, and there typically isn’t a market for those small trees that are being thinned. Biochar could provide one.
And with more than one billion ash trees in Minnesota in the path of the destructive emerald ash borer, there’s a lot of potential unused biomass to be used as feedstock to make biochar.
“But we don’t want to go down the road of just using our forests thoughtlessly,” Singsaas cautioned. “If you create markets for more biomass than the the landscape can supply, you risk winding up creating more harm than good.”