May 12, 2021

Two dudes on an 8,000-year-old mission to resuscitate ... dirt?

The BioChar Guys
By Craig Manning | April 25, 2020

“Very few cultures worldwide have really learned how to build soils. Most cultures rise and fall, and when they crash, they've usually taken their soils with them.”

That’s the wisdom of Tim Overdier, a retired Northport-based soil scientist who has spent his career getting to know the differences in soil types across the country. He’s worked in 10 different states and on 24 different Indian reservations, trying to understand how different soils affect everything from plant growth to groundwater quality. Over time he’s come to a realization: soil is society’s purest and most important currency, and we as a population aren’t treating it well — at least not yet.
Saving the Soil

A few years ago, Overdier was introduced to Paul May of The May Farm in Northport, a grazier who rears cattle, lambs, and chickens. The two found they shared a passion for the idea of “biochar,” a type of charcoal produced by burning organic plant matter that can then be put back into the soil. Biochar is rich in stable carbon molecules and can theoretically store that carbon in the ground for hundreds or thousands of years. Comparatively, even naturally decaying plants emit carbon dioxide into the atmosphere.

In a completely natural cycle, other trees would absorb this CO2 in a sort of “circle of life.” In our current global scenario, where CO2 emissions from human activities are already too much for our forests to absorb, plant decay only adds to problems with greenhouse gases and global warming. Biochar, by stabilizing the carbon and sequestering it in the soil for an extended period of time, helps remove carbon dioxide from the atmosphere while also delivering side benefits, such as improving the fertility of the soil, boosting agricultural outcomes, and protecting water quality.

Overdier and May ultimately joined together to launch “The BioChar Guys,” a business aimed not only at selling biochar materials to growers and environmentalists throughout northern Michigan, but also at educating the public about biochar and the importance of soil-building techniques.

“There's a book by a guy named David Montgomery called “Dirt: The Erosion of Civilizations,” and it tells extensively how, worldwide, we have depleted our soils over time,” Overdier said. “Right now, we are doing the same thing in the United States, and it's because of our commercial agriculture. Our agriculture is usually an extractive technique, using plows and chemicals and things like that. But a few cultures have learned how to build soil, and we can too. It's just a matter of choice and understanding.”

Right now, Overdier and May are on a mission to spread that understanding throughout northern Michigan — even though biochar is anything but a new concept. On the contrary, Overdier says that the science behind biochar dates back 8,000 years, to Amazonian cultures that burned biomass “into a carbon-dense char material” and then put it back into the soils. In the Amazon Basin, these biochar-aided soils are known as “terra preta,” which translates to “black soil” in Portuguese. These dark soils are known worldwide for their high levels of minerals and nutrients and their high fertility for plant growth.

Despite this long history, biochar is largely an obscurity in Michigan — particularly Up North. The BioChar Guys are working to change this narrative — in part because northern Michigan soils have some commonalities with the soils that Amazonian cultures were treating with biochar thousands of years ago.

“Here, we're actually not all that different from the tropics in that we have highly acidic soils,” Overdier explained. “It's just that, unlike the tropics, where they have clay soils, we have sandy soils.”

For agricultural applications, sandy soils are far from ideal. Sand lacks the structural stability of other types of soil, which means it is low on nutrient-holding capacity, has little “buffering capacity” to protect against pollution or toxicity, drains rapidly when wet, and is highly vulnerable to erosion.

These issues can pose challenges for growers, property owners and developers, and environmentalists alike. Overdier notes that, because of its low water-holding capacity, sandy soil requires a lot more irrigation to keep plants from drying out in the sun — hence the need to water your lawn daily in northern Michigan come summertime.

Limited nutrient-holding capacity makes it difficult to grow healthy plants or crops, while fast drainage means nutrients and toxins can leach quickly from the surface of the ground to groundwater sources, risking contamination. As for erosion, the lack of stability in sandy soils renders them particularly vulnerable to issues such as rising water levels — a problem Michigan is currently contending with statewide.

Biochar, in many ways, is the direct opposite of sandy soils. Overdier says that the key characteristic of  biochar — beyond its carbon density — is its “incredibly porosity.” The porous nature of the charred material enables it to absorb virtually anything it comes into contact with. It absorbs water, which keeps soils moist and reduces the need for constant irrigation. It absorbs minerals and nutrients, which help foster greater health for plants grown on biochar-enriched ground.

It absorbs pesticides, nitrates from fertilizers, and other chemicals, slowing their drainage through the soil and preventing groundwater contamination. Biochar even provides a home for bacteria, fungi, and other microbes, which help increase its carbon content over time, improve soil fertility, and propagate natural soil-building decomposition of grasses and other ground-level biomass.

The process of creating biochar, Overdier says, can be either high-tech or low-tech. Research institutions like Cornell University use expensive kilns to execute a controlled burn of organic material, measuring emissions figures and other key metrics along the way.

The BioChar Guys, meanwhile, use a makeshift kiln made from old oil tanks, which they cut in half and bolted together to create a 10-foot-long trough for burning branch material ranging from 0 to 3 inches in diameter. Overdier says the key is to get a hot fire going and continuously add material on top to allow for “pyrolysis” — defined as the burning of organic materials at high temperatures in an oxygen-deprived environment to bring about chemical decomposition. Finally, The BioChar Guys “inoculate” their char with manure or compost, to ensure what Overdier calls a “reef-like home for a lot of biological diversity.”

In addition to selling their own biochar and coaching locals on how to execute a controlled pyrolysis burn on their own, The BioChar Guys have also been ramping up local outreach efforts in hopes of making more of a mark. Some of those efforts — including a half-dozen public speaking engagements — were canceled due to COVID-19. However, Overdier still thinks local growers and environmental organizations are starting to see the benefits of biochar.

The BioChar Guys currently have five landowners lined up who want to learn how to use dead tree material on their properties to create biochar-enriched garden plots. Recently, Overdier and May consulted with the Glen Lake Water Association about utilizing compost-inoculated biochar in resident lawns, to prevent fertilizer nitrates from leaching into Glen Lake and causing algae blooms.

Perhaps most notably, Overdier and May have been approached by numerous local wineries interested in using biochar to help establish “terroir.” A French term that translates to “taste of the place,” terroir refers to how the environmental factors in an area where wine grapes are grown — from climate to soil health — can impart a specific flavor identity to the wine itself. Overdier says that northern Michigan wines don’t have a terroir in the same way that, say, wines from California’s Napa Valley wine region do. Better soils could, theoretically, improve the health of wine crops while also establishing a more distinct regional flavor.

“In most places, the flavor of the wine is characteristic of the soils that the grapes are grown on,” Overdier said. “California understands that, which is one of the reasons that they are looking at biochar a lot more than we are.”

Despite these potential benefits and others, Overdier says more research is needed to understand the effects of biochar — particularly in places like northern Michigan, where its use has been minimally tested. Biochar skeptics say that it can work very differently depending on the soils in which it is applied, hence the need for testing. Critics, meanwhile, tend to raise a wide range of concerns about biochar, from the possibility that it may deplete atmospheric oxygen to fears that the dark color of biochar can increase reflectivity of soil and potentially lead to negative implications for climate change.

More testing and research in a broader range of industries could help answer some of these questions and determine the role biochar should play going forward. In turn, these conversations could get more people thinking about how to build and protect soils as part of the bigger picture. Ultimately, Overdier thinks there’s still time to save North America’s soils. To make it happen, though, we need to get to work. Even if biochar is the key, it’s not ready for the spotlight just yet.

“Right now, we don't have the infrastructure, the financing, the policy, the research, the education, or the production techniques to adopt biochar widely,” Overdier said.

Interested in learning more? You can find The BioChar Guys online at


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