Is turning forest waste into black char a green solution?

This story is part of The Salt Lake Tribune’s ongoing commitment to identify solutions to Utah’s biggest challenges through the work of the Innovation Lab.

It’s new technology, but it’s been around for centuries. It’s made fiery hot, but it’s not burned. It locks down carbon dioxide, but you have to release carbon dioxide to make it.

Such are the contradictions of biochar. The charcoal-like material continues to intrigue as a possible player in everything from limiting climate change to increasing food production.

Biochar is wood waste or other plant material that has been heated in a low-oxygen environment. Denying oxygen keeps the material from releasing carbon dioxide, which causes climate change. In producing biochar, the carbon stays locked inside the material, and the material becomes more useful. In particular, biochar can be added to soil to make it hold more water and become more agriculturally productive.

“Biochar is not a magic bullet, but it’s absolutely a foundational piece,” said John Webster, Salt Lake City-based communications director for the U.S. Biochar Initiative, a nonprofit aimed at encouraging more biochar production and use.

If biochar is a key technology, it’s underused. And that prompted biochar proponents to host a “Charpolooza” at the Tooele County Landfill Wednesday to demonstrate three devices for producing it.

In Utah and the West, biochar’s biggest opportunity comes from forests that are overstocked with wood that fuels wildfires. More than a century of fire suppression, combined with a more fire-inducing climate, make forest lands vulnerable to massive wildfires.

Forest managers address hazardous fuels in a variety of ways, including removing vegetation and collecting it in “slash piles.” Historically, those piles have either been burned, releasing large amounts of carbon dioxide, or they have been left alone, where they slowly rot and release their carbon dioxide over time.

To produce biochar from the slash piles, the piles are still burned, but the burning happens in kilns that limit the oxygen. A fifth or so of the carbon dioxide is still released, mainly from the top of the burning material. But deep inside the kilns, where there is heat but not much oxygen, pyrolysis happens, breaking down the material without burning it and locking up the other 80% of carbon dioxide in the charred material left behind. That material is biochar.

From a climate standpoint, biochar represents a tradeoff. The carbon dioxide released in producing it is, in theory, more than offset by the carbon that remains in the biochar. And it will stay in the biochar for hundreds of years longer than it would if the material were just left to rot.

“We can find charcoal that is 400 or 500 years old” that was left behind by Native Americans, said Debbie Page-Dumroese, research soils scientist for the U.S. Forest Service, who has been working on biochar development. That charcoal contains carbon dioxide that would have been released had it not been burned.

Biochar has been analyzed for years as a possible solution for not just sequestering carbon but also for improving soil health. The jet black material is light and porous. When added to soils, it increases water and nutrient retention. It has also been added to livestock feed to improve animal digestion.

But there has been much debate about whether the carbon dioxide in biochar truly stays locked up. If it doesn’t, then it is not an effective climate strategy.

“In reality, the science of biochar is nowhere near a consensus point, with some studies actually calling the entire premise into question,” according to a report from Desmog, a Canadian website that challenges what it sees as faulty climate solutions. “Further, well-intentioned biochar advocates have seen their optimism paired with individuals and businesses — including Big Oil — standing to make a major profit before the science is settled on the risks and consequences.”

Page-Dumroese acknowledges that when biochar is used as a soil additive in agriculture, it’s less clear how long the carbon stays sequestered as the soil is turned over and new crops are planted. But if it is produced and kept in the forest, she is confident the carbon will stay locked up.

“On forest lands, it’s a settled question,” said “The charcoal will stay there for centuries, and so will the carbon.”

And it aids forest soil in much the same way forest fires do, she adds.

At Wednesday’s event, three different kilns were used to convert yard waste at the landfill into biochar. All three kilns share one thing in common: they’re portable. That means they can take the kilns to the waste rather than taking the waste to the kilns.

Page-Dumroese has been working with a Florida company, Air Burners Inc., in developing the “CharBoss,” a truck-sized kiln that can be fed continuously. The machine produces and then cools the biochar so it can be deposited without the risk of fire. Air Burners has applied for patents and has begun marketing the CharBoss.

Darren McAvoy, a former “hotshot” firefighter who fought the 1988 Yellowstone Park fires and now works as a professor at Utah State University extension, has developed the “big box” kiln, which is small enough to be hauled behind a pickup truck. The low-tech Dumpster-sized metal box is double-walled to protect workers and increase efficiency. McAvoy, who heads the Utah Biomass Resource Group at USU, said about a dozen kilns have been built off of his design, including one used by the Harvard University Arboretum.

McAvoy didn’t apply for any patents on the device, and he is happy to share the design with anyone. “I think we need to recognize all the values of biochar. Right now, it’s cheaper to burn piles.”

And for even smaller jobs, another inventor, Kelpie Wilson, has made the “Ring of Fire” kiln, small enough that it can be disassembled and fit into a truck bed. Her market includes farmers who burn their crop waste and property owners who want to clear brush and produce biochar instead of just burning it.

Tim Fitzpatrick is The Salt Lake Tribune’s renewable energy reporter, a position funded by a grant from Rocky Mountain Power. The Tribune retains all control over editorial decisions independent of Rocky Mountain Power.