By June Breneman | April 04, 2023
Balsam fir stands in the Superior National Forest
PHOTO: ALEXANDER MESSENGER
Balsam fir stands in the Superior National Forest
PHOTO: ALEXANDER MESSENGER
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T he Superior National Forest in northern Minnesota has piles of biomass in need of disposal. To combat the threat of fast-spreading wildfires, the park service regularly hires crews to cut young, thin balsam fir from the forest. This is referred to as “ladder fuel” because it creates a dense understory that quickly moves a fire up to the tree canopy where it more easily spreads. Balsam fir was one of the major fuels that spread the Greenwood Fire in northern Minnesota in 2021—caused by a lightning strike, it burned 42 square miles.
“Fires have been on the landscape for tens of thousands of years,” explains Patrick Johnson, Superior National Forest fire management officer. “The fire itself isn’t bad, but when it runs into someone’s house, it becomes a problem.”
Thenly way to mitigate the balsam fir fire danger is to selectively remove that species. But with no markets for this soft wood resource, the piles are left to slowly decay or are burned. Both options release carbon dioxide into the atmosphere. Recently, a demonstration project at the University of Minnesota’s Natural Resources Research Institute in Duluth turned the balsam fir into engineered biocarbon, or biochar, and then applied it to a capped coal ash landfill. It’s long been known that biochar’s porosity makes it an excellent soil amendment, improving both microbial soil health and moisture retention.
“When I heard about the biochar possibility, I got really excited,” Johnson says. “We’re always looking for new ways to treat our balsam fir problem. There’s just so much of it across the landscape. If there was a market for it, that would be fantastic.”
Sequestering Solution
Carbon offset credits are generated when the downed fir is converted into biochars and that value can be reivsted to improve wildfire management. Carbon credits are generated from net-negative carbon projects and purchased by industries that cannot meet carbon emission goals. “This is an exciting moment for biochar in that there’s a lot of interest, with big industry backing carbon sequestration and the bioeconomy,” says Brian Barry, NRRI chemist and project lead. “This project will demonstrate how biochar can be deployed in hopes that we can help grow this industry.”
Biocarbon is charred biomass, basically like a charcoal. Once transformed, the carbon is locked in, and those carbon credits can be sold in an online marketplace. One cubic yard of biochar represents about 0.7 tons of CO2 equivalents, or 0.7 of a carbon offset credit. Market prices fluctuate with supply and demand, but carbon credits currently range between $40-$80 per metric ton, according to 8BillionTrees.com.
The charring process, in a zero- or low-oxygen kiln, produces highly porous granules that are excellent material fr various water treatment and soil amendment applications. “As a material, biochar has a lot of beneficial environmental qualities–from improving the microbial health of soils for more productive crops to removing contaminants from stormwater runoff,” Barry explains. “Minnesota is poised to be a biochar leader. We’re anticipating large-scale production facilities to be built in the next few years.”
Barry and his team are characterizing biochars made under varying conditions to impart specific properties for specific applications. The kiln temperature, time in the kiln, and biomass source all impact the biochar’s performance properties.
In Action
In partnership with energy provider Minnesota Power, NRRI is applying charred balsam fir to a capped coal ash landfill at the Boswell Energy Center in Cohassett, Minnesota. The goal is to improve the soil so that native grasses can revegetate this space for new uses. “Particularly for coal ash landfills, one of the challenges for revegetaton s making sure the cover has decent water holding capacity,” Barry says. “And one of the key features of biochar is its porosity, allowing high water holding capacity.”
In late fall 2022, 12 super sacks of balsam fir biochar—about three tons—were applied to the ash landfill. This small-scale demonstration effort represents roughly eight carbon offset credits, and the removal of around 23 cords of wildfire fuel from the forest.
“If we had more financial resources, we would double or triple our capacity to remove balsam fir from the Superior National Forest,” Johnson says. “Biochar seems like a great solution where we can provide a product that’s worthwhile and find markets for it, that would be a great benefit to the public.”
A U.S. Forest Service Wood Innovation grant funded half of the $375,000 budget for this demonstration project, with the rest matched by Minnesota Power and NRRI.
Next Steps
While biochar has attracted quite a buzz, building market demand will require ongoingreserch to develop and demonstrate uses beyond agricultural applications. NRRI researchers will continue to seek partnerships with industry and government agencies to advance materials that lock away atmospheric carbon while offering enhanced performance and higher value.
