Black Gold

October 14, 2009 07:00 PM

Deep in the Amazon basin, there is a rich loam known as terra preta, or "dark earth.” Studies show that this soil, which early farmers created by mixing charcoal and fish bones into their fields, can be 10 times more fertile than unaltered soil.

University of Georgia scientist Brian Bibens' metal chamber cooks biomass to temperatures near 1,000°F and forms the material into char pellets.
Today, scientists are working to recreate this high-fertility soil by adding charcoal made from biomass, called biochar, back to crop fields.
"Biochar requires less fertilizer per acre. It lowers the negative impact that crops have on the  environment by reducing nitrous oxide emissions, phosphorus runoff and nitrogen leaching,” explains Troy Wragg, founder, chairman and CEO of Mantria Corporation, which produces EternaGreen, a biochar product that sells for 25¢ per pound (
The bigger benefit of biochar may be its potential to lock away carbon, helping reduce greenhouse gas emissions and combat global warming. Biochar is a fine-grained product, high in organic carbon and resistant to decomposition. This resistance creates a nearly "carbon-negative” footprint when biochar is recycled as a fertilizer product, Wragg says.
How it's made.
Biochar is typically produced through advanced pyrolysis and gasification technology. Pyrolysis is a thermal process that rapidly heats biomass in an oxygen-free environment and then quickly cools the volatile products formed during the reaction.
Brian Bibens, a scientist at the University of Georgia, has developed a metal biochar cooker that heats the biomass to temperatures approaching 1,000°F. After a few hours in the cooker, the resulting material can be formed into char pellets.
The pyrolysis procedure not only creates char but also liquid and gas. These biochar coproducts can be turned into electricity and fuel, Wragg adds.
Research revving up.
There is still more research needed on biochar as a fertilizer product, including how much farmers should use, how they should apply it and which feedstocks work best. Although field trials are currently in process, Wragg says his company's product is showing effectiveness at as little as 25 lb. to 50 lb. per acre.
Iowa State University researchers are studying the yield impact of biochar made from switchgrass and cornstalks. Scientists at the University of Georgia are testing biochar from peanut hulls and pine chips.
Several companies are already producing biochar for sale commercially to vegetable growers.
In the end, biochar's potential is unlike any other fertilizer product, Wragg adds. "Biochar has the potential to increase yields while decreasing global warming,” he says. "It's a win-win product.”


You can e-mail Jeanne Bernick at

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