Biochar: A New/Old Technology Gains Ground

By Elizabeth Saito | September 15, 2010
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Joe Hackler and his wife Karen Schwalbe keep a small organic farm in Falmouth on a piece of land collectively owned by the co-housing community, Alchemy Farm. Farming is not their main occupation.  Hackler has a job calculating carbon emissions from global deforestation at the Woods Hole Research Center, and Schwalbe works there part-time helping to figure out how the Earth can possibly sustain a population of 9 billion people by the year 2050. This is the background they bring to their hobby farm, which supplies them with fresh eggs, goat’s milk and vegetables. In past years they’ve sold a small amount of produce at the Falmouth Farmers’ Market, but this year Hackler has devoted a large amount of their growing space—and his time—to an agricultural experiment.

“This is my first scientific experiment,” Hackler told me when I met him at his house on a cloudy day in late spring. That morning, he and Tina Praprotnik, a summer intern at the Woods Hole Research Center, were preparing to mix approximately one thousand pounds of charcoal into a series of soil test plots. Given the right conditions, charcoal can greatly improve soil structure and fertility, help retain water and increase fertilizer efficiency, all while sequestering carbon within charcoal’s strong, stable, molecular bonds. When charcoal is used this way, as a deliberate soil amendment, it’s referred to as biochar.

Before we talked about biochar, Hackler wanted me to understand the bigger picture, which he explained while feeding weeds chopped from beside his barn to a herd of five Nigerian Dwarf goats. Society has to work on bringing its resources circles closer to home, he said, as the goats nibbled their greenery. “I mean, food is trucked onto the Cape, and then hauled off to be burned—that’s insanity.” Our finite ecological resources and expanding population “don’t add up”.  Modern, industrial society is founded on the “cheap subsidy of fossil fuel”, which won’t last. “I’m looking at the direction things are going and saying ‘holy crap!’”

The biochar rested in a large heap in an old manure spreader, where it had been mixed with an equal amount of leaf mulch and a bit of soy meal. At first glance, the mixture just looked like a dark pile of compost, but up close you could see small pieces of charcoal ranging from a half inch to an inch in size. Praprotnik picked through the pile, crushing larger pieces with her fingers. Although odorless from a few feet, the mixture had a sharp, ammonia-like smell when I put my nose up to it. To Praprotnik, it smelled like “microbial activity.” Hackler explained that biochar’s porous structure provides “lots of little spaces” for beneficial soil microbes to colonize.

That morning, Hackler and Praprotnik worked out the location of a central reference line through their test plots. Hackler bounded among the soil beds with an orange 165-foot measuring tape, and then rototilled the reference line with a biodiesel-powered tiller (he used to make his own biodiesel, before Loud Fuel began selling it).  “We’re basically just learning how to conduct a biochar experiment,” he said. Colleagues at the Woods Hole Research Center are helping with the soil analysis, and Praprotnik’s labor comes free of charge, but otherwise this is an unfunded project born of personal curiosity.  Around 9:30 A.M. Hackler donned a motorcycle helmet and began the 7-mile ride to work on an electric bicycle he’d built himself.  Praprotnik would spend the day mixing some 200 buckets of biochar into the soil.

Biochar is both a new and old technology. The ancient Amazonians deliberately added large amounts of charcoal to their fields, creating pockets of dark, rich earth in the midst of the agriculturally unproductive Central Amazon. These soils, known today as “terra preta” (“black earth” in Portuguese), remain incredibly fertile even hundreds of years after the civilization that created them was decimated by European diseases. It was the archeological discovery of this lost agricultural practice that got modern researchers thinking about biochar in the first place.

Biochar is made by heating organic matter (wood, manure, lawn debris, cornstalks) in a closed container in the absence of oxygen, a process called pyrolysis. Instead of burning, which leaves mostly ash, the material “thermally decomposes” into charcoal. As it does, the organic feedstock—say, wood—gives off gases that can be captured and turned into biofuel. Roughly half of the carbon that formed the wood is left behind as charcoal. Joe used waste wood from around his property as feedstock for the biochar. If, instead of making biochar, he had simply burned the wood, this would have sent all the carbon back into the atmosphere immediately as carbon dioxide (CO2). He could have left the wood to be decomposed by microorganisms, which also returns the carbon to the atmosphere because the microorganisms eat the wood the same way we eat food: breathing in oxygen to convert their carbon-rich lunch into energy and breathing out CO2. (Of course, plants do the opposite during photosynthesis: absorbing CO2 and solar energy to create organic matter, with oxygen as the byproduct.) Because charcoal does not decompose for hundreds to thousands of years, Joe has effectively sequestered half of the carbon content of the wood.

If biochar production were widely adopted, it has the potential to divert some of the huge amounts of carbon that annually cycles between plants and the atmosphere—trees grow leaves, they fall to the ground—by locking it into the soil. Johannes Lehmann, a leading biochar researcher at Cornell University, estimates that converting one percent of annual plant uptake into biochar would be the equivalent of reducing human carbon emissions by ten percent. Thusly, the attractions of biochar are fourfold: it can improve soil fertility, produce biofuel, mitigate climate change and turn waste products into a valuable resource.

Five years ago, Bob Wells of Eastham read about the terra preta soils in the book 1491: New Revelations of the Americas Before Columbus. At the time, he was beginning to clear a six-acre plot of land abutting the National Seashore to start his own farm. I stood with Wells out in his fields on a mild evening in late June. “This is what I was starting out with,” he said, picking up a handful of sandy earth and letting it run through his fingers. “Washed out, sandy soils.” Without any additional research, Wells decided to try adding some charcoal to his soils, which he knew how to make from building model rockets in his youth. He planted a crop of turnips with biochar. “And [the turnips] went crazy,” Wells said. “They were, like, twice as big. At that point, I got really excited.” He began reading everything he could about biochar, and testing different designs for pyrolysis machines. In January of this year, Wells and his business partner Peter Hirst founded New England Biochar. The business is threefold: they sell a biochar and compost mix at the Orleans Farmers’ Market; build smallscale pyrolysis units (Wells estimates they’ve sold about a dozen so far; Hackler rented one of Wells’ machines to char his wood); and also give paid seminars throughout New England on biochar and biochar production. “There’s so much opportunity to use this stuff,” Wells said. The business has been successful enough that Wells now hires someone to work his farm so he can concentrate on biochar full-time.  “I’m amazed it isn’t more well known,” Wells said. “And I’m amazed I don’t have gobs of competition for building machinery.”

One reason that biochar hasn’t shown up at your local Agway is that not a lot of people are making it. Thayer Tomlinson, with the International Biochar Initiative (IBI), a non-profit that lobbies for biochar-friendly energy policies and provides information and field support for farmers, says she knows of only about 40 small-scale producers throughout the country, Wells being one of them.  Producing biochar on a large scale isn’t an attractive investment because the transportation costs associated with bringing the organic feedstock from far and wide to a single biochar plant are prohibitive.   “That’s an odd concept for Americans,” Wells told me, “We think ‘how can I build a big biochar factory?’ And [biochar] doesn’t fit that picture.” Wells believes that biochar should be practiced on a small scale, by local producers (such as a single farmer, or a farming cooperative) who can make use of on-site or nearby materials. From a sustainability perspective, that certainly makes sense: keep the “resource circle” small.

There’s an active debate about whether biochar should be eligible for carbon credits, because it’s a “carbon negative” technology. As far as Wells is concerned, “Carbon credits aren’t even an afterthought.  Carbon credits are aimed at big companies doing big things. For me, it’s not worth the paperwork.” He pointed out that it costs $200 per ton to dispose of waste wood in Eastham—“people will pay me to take it!”—and then he makes more money turning it into biochar, as well as boosting his own farm’s productivity, and getting some extra energy in the process. He balks at the idea of growing grasses or other crops specifically to make biochar, as some enthusiasts have proposed.  “There’s so much waste already available,” he said.

An important thing to understand about biochar is that it’s not a single, standardized substance. Biochars have very different physical and chemical properties depending on what feedstock was used and what temperature it was pyrolized at. And biochar does not affect all soils equally. There’s evidence that it can hurt the productivity of soils that already have a high pH, because biochar tends to act as a liming agent. And biochar can’t really boost the fertility of soils that are already highly productive. Johannes Lehmann, the Cornell scientist, put it this way during a presentation at Stanford University, available on YouTube: “Biochar is not a miracle, it will only improve a soil that has a problem, and a problem that biochar can address.” But the sunny side of that, as Lehmann wrote in testimony to the Congress, is that “crop yields can be significantly increased in soils that have productivity constraints.”

The USDA is currently conducting large-scale biochar field trials in Iowa. I spoke by phone with the scientist leading the study, David Laird. Two years after applying large quantities of biochar to roughly ten acres of “well-managed farmland,” there’s been no appreciable change in plant yield. Laird said this was not surprising, “We have some of the best soils in the world here in Iowa. It’s difficult to improve upon a good thing.” Although the biochar did not boost plant growth, Laird said that lab experiments indicate it could dramatically reduce the leaching of phosphorous. A key nutrient for plants, phosphorous is a major source of water pollution due to fertilizer runoff from farms. Laird said biochar has great potential to improve crop yields in degraded and nutrient-poor soils in the tropics, and sandy, acidic soils in temperate regions. Laird said identifying what biochars are appropriate for which soils is a major research question yet to be worked out.

Back in Falmouth, at the time this article was written in midsummer, the Japanese millet Joe Hacker had planted in his fields was growing vigorously, but with no visible difference between the control areas and those treated with biochar. There was still a lot of work ahead, harvesting and weighing the grains, and conducting various soil tests. When the study is complete, Hackler plans to publish his results, and perhaps try to secure funding for additional experiments.  Personally, he’s hopeful the biochar will improve his soil over the long term, helping him to save money—and time—by decreasing the amount of compost and other soil amendments he has to add every year. What would he like the future of biochar to look like? “If it makes sense to put [biochar] in soil in a wholesale manner, then I’d like to see an efficient system put in place to recycle waste biomass as biochar—that would be a seriously sustainable thing to do.” Hackler doesn’t see biochar as a silver bullet for addressing climate change, but perhaps he says, it’s a silver BB.

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