Burning trees to help other trees grow? It sounds counterintuitive, but using biochar to improve soil conditions is a practice that dates back centuries.
On Arbor Day 2025, Cincinnati Mayor Aftab Pureval announced the city’s first use of biochar for tree planting to an enthusiastic crowd: elementary students at Roberts Academy in Price Hill.
“Make some noise if you love trees,” Pureval exclaimed to loud cheers. “Here’s the most exciting thing, guys — you are part of history. Today, we are using a magical ingredient for the first time in Cincinnati’s history. It’s called biochar.”
Biochar is more science than magic, but it’s pretty powerful. The charcoal-like material can enrich soil and keep climate-warming carbon out of the atmosphere.
Cincinnati has been purchasing biochar from out of state, but soon, the city will make hundreds of tons of biochar a year right here in the city.
What is biochar?
Cincinnati Parks Director Jason Barron says the parks produce a lot of wood waste, like dead trees and trimmed branches.
“And that wood waste was just decomposing and releasing that carbon back in the air,” Barron said. “And this allows us to take what we already have and turn it into something that's beneficial, not just for us, but for others.”
To make biochar, wood is burned at a high temperature with little oxygen, which traps the carbon so it can’t get out.
When it’s mixed with compost or manure, it becomes an excellent fertilizer, helping plants grow faster and taking even more carbon out of the atmosphere.
A public-private partnership
Cincinnati won a $400,000 grant from Bloomberg Philanthropies a few years ago. The Cincinnati Park Board has approved $400,000, and Great Parks of Hamilton County is kicking in $300,000.
Cincinnati is working with a local private company, Carbon Harvest LLC, to build and operate a warehouse with a machine that can make biochar on a large scale.
It’s planned for the Cincinnati Parks Sinton East Operations Center in Eden Park. Barron says the machinery produces a lot of heat, which will be re-purposed to power the biochar facility as well as the operations center.
The goal is to produce at least 300 tons of biochar a year. About two-thirds will be sold, making the project financially self-sustaining in the long-run.
What’s left will be mixed with manure from the Winton Woods farm and equestrian center, where Great Parks is constructing a $600,000 composting facility. The mixture will be used to plant trees.
“I've been thinking about it as a quilt,” said Carbon Harvest owner Sam Dunlap. “We're trying to restore soil health with one patch of land at a time … and we can make ourselves, our city, much more climate resilient and healthy by building this quilt of healthy soils.”
Neighborhoods with fewer trees experience more flooding and higher temperatures. And in Cincinnati, lower-income neighborhoods tend to have the fewest trees.
Crystal Courtney is trying to change that. She manages the city’s urban forestry with Cincinnati Parks, and just last month helped plant 27 trees at an elementary school in Over-the-Rhine, which has just 13% tree canopy.
“The biochar and the compost will provide more nutrients than what you see kind of in our very clayey soil here,” Courtney said. “So it will hold more nutrients and moisture close to the root system over time.”
Newly planted trees often struggle in urban environments. Research says a biochar and compost mix helps urban trees grow faster and live longer.
Its worldwide potential is much broader.
‘Everything is on the table’
Making biochar can also produce a type of renewable energy. And when it comes to resource-intensive agriculture, biochar can increase crop yields while decreasing dependence on climate-polluting fertilizers.
So, could biochar save the world?
Not quite, says Rattan Lal, distinguished university professor of soil science at the Ohio State University.
“Climate change is such a humongous problem that humanity and planet Earth has never seen before,” Lal said, adding the first step is to stop burning fossil fuels.
“For this humongous problem, there is no one solution. Everything is on the table,” he said.
That includes biochar — and Jason Barron says Cincinnati wants to lead the way. He’s hoping other cities follow in their footsteps and start making biochar, too.
“Ultimately, that will lead to not just healthier, faster-growing trees in Cincinnati, but faster-growing trees throughout the region,” Barron said. “And then growing that industry and growing that technology across the country.”
Learn more about biochar in Cincinnati
WVXU's Cincinnati Edition will feature a discussion about Cincinnati's biochar project on Tuesday, May 19.
You can tune in live at noon, or listen to a replay at 8 p.m., on 91.7 WVXU. The audio will be available on-demand at wvxu.org/cincinnati-edition.
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