Biochar – charcoal derived from burning plants – can boost crop yields and help fight climate change.

Andrew Tolve | July/August 2010 issue

 
In the summer of 2002, scientist and entrepreneur Danny Day sent a lab assistant to retrieve some charcoal from behind Day’s lab in Blakely, Georgia. At the time, he was researching how to turn peanut shells into hydrogen for the U.S. Department of Energy. He regularly used charcoal to preheat the reactor. When his assistant returned, he came bearing strange news: Plants had taken root in the bed of charcoal—weeds, grass, turnips as big as baseballs, enough to fill four garbage bags.
How had turnips sprouted from a pile of charcoal? Day wondered.
Charcoal is easy to make. Take biomass like wood, leaves and grass clippings, and burn it in an oxygen-free setting until all that remains is a bit of ash and a bunch of carbon. Typically, the carbon is released into the atmosphere when charcoal is burned. But if you buried the charcoal instead, the carbon would remain safely captured. And if charcoal helps turnips grow as big as baseballs, there might be a very good reason to bury it.
Such was Day’s thinking as he rushed behind his lab with a sample bag, a -microscope and a digital camera. In the eight years since that moment, “biochar”—charcoal deliberately buried to bolster crops and sequester carbon—has heated up the climate change debate.
Universities are researching the concept, and entrepreneurs are launching startups with millions of dollars of private investment. People like former U.S. Vice-President Al Gore and Virgin Group founder Richard Branson talk up biochar’s potential to offset the combined carbon outputs of all planes, cars and buses, while critics warn of unintended side effects.
“This began with nothing, zero, just a pile of charcoal,” Day says, “and now it’s all over the world. It’s wonderful.”
I traveled to meet Day at a lab in Marietta, Georgia, a suburb of Atlanta, where he was running analytical tests on various biochar feedstocks. His main piece of equipment had just broken down, but that didn’t dampen his spirits. “This might not end up being very big,” he says of biochar in his lyrical, ironic Southern drawl. “It could be like, you know, just another Internet.”
Day has reason to think big. Studies suggest biochar is excellent at retaining moisture and thus, when buried, operates as a sort of emergency reservoir, taking in and holding what water is available. Microbes love the oils in biochar, so it stimulates microbial activity and stabilizes nutrients. As an added bonus, biochar can replace nitrogen fertilizers that release nitrous oxide, a chemical compound with a greenhouse effect 300 times as potent as carbon dioxide. The net impact is sequestered carbon and higher crop yields.
Results like this have stimulated activity all across the private sector. Some startups are creating biochars that could replace or complement traditional fertilizers, targeting everything from wheat, soybeans and sugarcane to fruit, vegetables and palm oils. Many companies are hunkered down in “stealth mode,” racing for first-to-market advantage, according to David Shearer, co-founder of the biochar enterprise Full Circle Solutions in San Francisco. “This is potentially a $50 billion industry. If you factor in the agriculture benefits, the soil restoration -benefits, the carbon benefits and the -energy -benefits, it’s a huge number.”
Full Circle believes there’s a range of opportunities for its products, including in environments with degraded soil. “Biochar has the most significant impact on soils in severe need of restoration,” says Shearer. “We can take the world soil base from the UN Food and Agriculture Organization, identify where the soils are in the worst shape, and by adding our biochar products, dramatically increase crop yields to meet the planet’s food needs.”
Other startups make the machines that manufacture biochar, known as pyrolysis units. Loaded with biomass, pyrolysis units not only produce biochar but also heat, which can be used locally, and oil that can be refined for transportation.
“Two-thirds of this planet’s population lives off the grid,” says Thomas Harttung, an organic farmer and founder of the biochar firm Black Carbon in Denmark, “and there are hundreds of thousands of diesel engines out there producing electricity locally, very inefficiently, with great pollution and at great cost. So there’s a huge demand for substitutes for fossil fuels in electricity generation, and we see this as a promising way to do it.”
Harttung wants to produce pyrolysis units and distribute them in the developing world—“dropped in by parachute if need be,” he insists—to provide clean, locally produced power.
Carbonscape, a startup in New Zealand, is making biochar by way of industrial-scale microwaves, and Biochar Engineering, a startup based in Golden, Colorado, plans to release a commercial pyrolysis unit this summer. Given the commercial interest, Day is advising, startups and municipalities on how to implement biochar programs in local communities.
On the tables in Day’s Marietta lab lie shards of corn stover from Iowa, bamboo from China, tan-tan from the Virgin Islands and peanut shells and pine wood from Georgia. Day’s ultimate goal is to create a vast network of local biochar programs employing local workers and using local biomass to sequester carbon, increase local crop yields and provide energy to the region.
“Think of all the different biomass that can be turned into biochar,” Day says. “We can set up revenue models for processing organic waste that are actually profitable for cities. If we’re trying to sequester carbon, the way to do it is to extract the energy value and then take the fixed carbon back to the ground in a form that nature can use.”
Burying charcoal for its agricultural benefits is not, in fact, an entirely new concept. For years, scientists assumed the Amazon basin had wretched soil conditions because the rainforest stored all the nutrients up in the canopy. Archeologists believed the Amazon had never supported a fully developed agrarian civilization.
But in the late 1800s, they began to uncover beds of deep, dark, nutrient-rich soil that teemed with healthy microbial activity. A hundred years later, scientists realized these pockets of rich soil—called terra preta, or “dark earth”—were not a fluke of nature but the remnants of a vibrant civilization that had discovered the beauty of biochar.
“If you live and work on soils in the Amazon, you can’t help but notice the terra preta,” says Johannes Lehmann, a soil scientist who has worked on the issue of depleted soils in South America. “So we said, Okay, if there is a lot of charcoal carbon in these soils, let’s try to put -charcoal into soils today and see what it does to soil fertility.” Lehmann’s subsequent greenhouse and field experiments have created a buzz among soil scientists and environmental engineers.
Upward of 10 American universities are experimenting with biochar. In 2009, the University of Edinburgh in Scotland launched the U.K. Biochar Research Centre. That same year, New Zealand’s Massey University did the same with the New Zealand Biochar Research Center. Lehmann is now at Cornell University, where he serves as chairman of the International Biochar Initiative and orchestrates research projects worldwide.
In Kenya, he’s mapping out how much biomass local farmers have, how they use it, what biomass is best for making biochar, how local women respond to biochar stoves, what sort of emissions these stoves produce and how biochar impacts local crops. The goal: to understand the scientific and social impact of biochar before products hit the market.
Not everyone is convinced that biochar is a climate crisis game-changer. “There have been many incidences in the past where people have gotten into a lot of hype and ended up making a bigger problem than there was before,” says K.C. Das, director of the Biorefining and Carbon Cycling Program at the University of Georgia. “We’re not in that business. I like the hype, but I want to be realistic, too. Biochar will only work if it is environmentally sustainable and has economic benefits. At this point, I don’t think we’ve solved both of those problems.”
Das was speaking alongside his char maker in Athens, Georgia, where I traveled from Marietta for a tour of his lab, nestled in rolling farmland on the outskirts of town. The day I was there, Das had filled the char-maker—a large-scale batch pyrolysis unit beside a down-draft gasifier, in biochar jargon—with wood chips and was heating them to the boiling point. Das planned to send the resulting char to soil scientists to test how its chemistry -impacted soil.
“The temperatures [in the pyrolysis unit], what biomass you use, what carrier gas you use, heating rates—all these variables affect the char in subtle ways that are not very well defined and not well understood,” Das explains. “That’s what we’re trying to figure out.
Critics are wary of biochar precisely because so much has yet to be figured out. Last April, when 11 African nations approached the UN to consider biochar as an official offset for emissions, 143 non-profit groups protested that it was a “charred earth policy.” These groups worry that burying biochar amounts to a major climate intervention with unknown, and potentially disastrous, repercussions. “The evidence of [biochar] working at any scale really isn’t there,” says Almuth Ernsting, co-director of the non-profit Biofuelwatch. “There’s a complete lack of long- or medium-term field studies that look at impacts on soil -fertility.”
Critics like Ernsting point to several specific concerns. For one, theoretical models of biochar adoption assume that all char will be successfully buried in the ground. But several studies indicate that as much as 30 percent of biochar is lost into the atmosphere during transportation and application, as well as during storms as windblown dust. Black carbon in the atmosphere has a larger greenhouse effect than CO2, Ernsting notes.
A second concern is that subsidized biochar will put pressure on biomass, and companies may begin to grow and cut down trees exclusively for the production of biochar and the carbon credits that come with it. Carbonscape, the New Zealand startup, has proposed one such -tree-farming model.
“Where the market goes from here depends on whether enough policymakers believe claims made about biochar enough to incentivize commercialization,” says Ernsting. “There is definitely a case for studying the role of charcoals in soils. But this is not ready to be commercialized.”
James Bruges, author of The Biochar Debate, agrees that biochar has its risks. “If you are producing the charcoal in order to earn carbon credits, it can lead to all sorts of distortions,” he says. “The danger is that if you concentrate on the crops that capture the most carbon, companies would buy out the small-scale farmer and just plant monocultures on a large scale.”
Bruges, who works with the Indian non-profit Social Change and Development, has seen firsthand some of the complexities of making biochar a reality. In 2008, biochar helped banana farmers in southern India double their yields while halving their water use. But since then, the cost of local biochar has increased due to demand, local women have proven reluctant to use biochar cooking stoves, the introduction of larger pyrolysis units is mired in delays and organizers fear widespread use won’t happen unless the government subsidizes biochar or doles out carbon credits for its use.
Despite setbacks like these, Bruges still describes biochar as “the one technology that can save us.” Of course, it is unlikely that any single technology on its own can counter all the effects of climate change. But if its early promise pans out, biochar could become a crucial tool for sequestering carbon and repairing the planet’s degraded soils.
Andrew Tolve typed this story with fingers stained black by biochar.
To find out more, visit:
International Biochar Initiative: biochar-international.org
Black Carbon: blackcarbon.dk
Biofuelwatch: biofuelwatch.org.uk