Some years ago, scientists exploring the deep recesses of the Amazon basin discovered something strange. Under the surface layer of decayed leaves and wood on the jungle floor was a deep layer of black earth they called Terra Preta. It was the remnants of an agriculture practiced by pre-Columbian Amazonians who had roasted wood in an almost airless fire, smoldering until the wood turned not into normal charcoal, but into a roasted black earth that they buried to help fertilize their fields.
Soils in the Amazon basin are notoriously poor, but the addition of the charcoal, now called biochar, rendered them marvelously fertile. By the time the first Spanish conquistadores arrived, their scouts reported the existence of great walled cities housing many thousands of people. These reports were regarded as fiction until the first decade of the 21st Century, when scientists discovered the remains of those cities and their agriculture. Those ancient people grew their food on huge swaths of soil improved with biochar, from 4,800 to 500 years ago.
Now biochar is getting a second look for several reasons. First, the carbon in wood and plant wastes, turned into biochar, is sequestered in the soil for up to thousands of years, preventing its escape into the atmosphere as carbon dioxide, a potent greenhouse gas that’s promoting climate change worldwide.
In the last few weeks, hundreds of people from countries around the world converged on Sonoma State University in California to attend the first U.S. Biochar Conference, hosted by the Sonoma Biochar Initiative and the Sonoma Ecology Center.
There’s a good synopsis of the many values of biochar in this YouTube clip: http://www.youtube.com/watch?v=iKP_Dju9UK4&feature=related.
When wood is roasted in a relatively air-free environment, it gives off volatile gases that can be burned to fuel the roasting process itself, so the making of biochar uses very little fossil fuel—just enough to get the process started. Roasters are available that are portable, so the roaster can be brought to the wood waste rather than the need to transport the wood long distances to a roaster.
After the volatiles are roasted off, the tiny cells in the wood, including long tubes that carried sap up and down the trunks and limbs, are emptied. When this roasted wood is buried in the soil, microbes such as beneficial actinomycetes, fungi, and bacteria take refuge in these empty cells and tubes, giving them a safe place away from grazing predators such as nematodes that prowl the soil for microbes to eat.
Additionally, the biochar’s surfaces are negatively charged, so they attract and hold positively charged ions of plant nutrients, releasing them as needed in what soil scientists call the cation exchange capacity. And biochar has a huge surface area. Just one gram of biochar, if unfolded and flattened, would cover an area the size of two tennis courts.
Additionally still, those empty cells and tubes suck up and hold water, making the soils they are buried in resistant to drought.
Furthermore, as mentioned above, the carbon in biochar—and there’s a lot of it—is sequestered in the soil rather than dumped into the air as carbon dioxide. Nitrous oxide is also released when wood is roasted, and it’s a greenhouse gas 300 times more powerful than carbon dioxide. When it is recycled within the charring kiln, it is burnt to products that don’t affect the climate.
Trials in the field show that plant growth is much stronger in soils amended with biochar, yields are higher, and the plants are healthier–in large part because of the refuge biochar offers to beneficial soil inhabitants that support plant health.
There is a significant business opportunity in biochar. To learn more, visit Craig Sams’ website. He’s an American ex-pat living in England. He founded Whole Earth Foods, Ceres Bakery, and Green & Black’s chocolate. He’s former chairman of the British Soil Association—the UK’s organic institution—and now chairs the Soil Association Certification Ltd., which certifies organic farms and land use, and authenticates carbon sequestration. You can visit his growing businesses and products concerning biochar at www.carbongold.com.