Biochar functions as a maximum-security prison for carbon. Charcoal can trap carbon, too, but not as effectively. Charcoal is chemically made up of carbon joined to lots of oxygen molecules but is primarily ash and has lost most of its carbon to burning. Like sorority girls in a slasher film, the oxygen is easily picked off by bacteria, which speeds up the process of decomposition, breaking the chemical bonds and leaving the carbon that does remain to drift back into the atmosphere.
Subtract the oxygen, however, and the carbon molecules get tough; they form ring structures that don’t easily shatter and are more resistant to microbial attack. Lab research suggests that these bonds have the potential to hold fast for anywhere from hundreds to hundreds of thousands of years. That means less carbon in the atmosphere. It’s also good news for anyone who’d like to see carbon-neutral or even carbon-negative biofuel production. Of course, that’s in a test tube—there aren’t many biochar studies being done in the (literal) field, and the real-world research hasn’t been conducted for very long.
That’s why—despite lots of crossed fingers—we don’t yet know whether biochar will make as good a fertilizer as it makes a carbon trap. The key question—“Does biochar-infused soil lead to more crops and better soil fertility?”—is still wide open. Yet some tantalizing data are coming out of those lab tests. It seems that by putting microbial life on slow-mo, biochar also works to trap nitrogen in the soil. Not only does that mean less nitrous oxide—another greenhouse gas—in the atmosphere, it could also mean less nitrogen fertilizer applied to the ground and less excess nitrogen leaching away into the water supply.
This is the Madelia Model in a nutshell: give farmers a reason to grow plants that are better for the land and the water supply than corn is, and then reap the benefits. In go prairie grasses, out come fuel, fertilizer, and economic development. It’s not enough fuel and fertilizer to supply the whole country or even the whole state, but that’s okay. It doesn’t have to do that. The primary goal is to prevent more of the local topsoil from blowing away, not to create a mini- empire of bio-oil production. The Madelia Model only has to work on a local scale.
Excerpted from Before the Lights Go Out: Conquering the Energy Crisis Before It Conquers Us, published in April, 2012 by John Wiley & Sons, Inc. Maggie Koerth-Baker is the science editor for boingboing.net.