Burn, baby, burn

Thousands of years ago in Brazilian Amazonia, indigenous peoples burned their trash and scattered the charred remains, creating a dark soil called terra preta that not only offers some of the world’s most sustainable farmland but could help control global warming.

Researchers are working to replicate this ancient technique as a way of offsetting fossil-fuel emissions—in effect producing a “carbon-negative” biofuel. Through a process called “pyrolysis,” manufacturers would burn agricultural biomass at very high temperatures in the absence of oxygen to generate heat or electricity. This would create a “biochar” that, spread on farmland, would return carbon to the earth rather than emitting it into the atmosphere.

As Robert Brown, Iowa Farm Bureau director of the Bioeconomy Institute at Iowa State University, points out, each square mile of farmland that uses biochar would negate the carbon dioxide emissions of 330 automobiles. “Like biofuels, biochar will become increasingly attractive as greenhouse gas mitigation is implemented,” he says. Brown got a $1.8 million grant from the U.S. Department of Agriculture to conduct field tests. Several other major biochar projects are underway. At the first-ever International Agrichar Initiative Conference last May, 135 scientists, entrepreneurs and academics gathered in Australia to compare notes and encourage collaborations to further the technology.

But the prospect of persuading players in the risk-averse agricultural industry that biochar can improve the bottom line remains daunting. It may take years, for instance, before manufacturers can produce enough high-quality biochar to compete with current industrial fertilizers. And even if biochar catches on, farmers would have to find a way to adapt their fertilizer-spreaders to accommodate the charcoal-like substance.

Despite those concerns, the technology has demonstrated enough promise to make the U.S. Congress take notice. Early 2007, Senator Ken Salazar drafted an amendment to the massive U.S farm bill that would allocate some $100 million to biochar pyrolysis research. And while the bill’s prospects are murky, the fact that a body beholden to industrial agriculture is considering such a measure indicates that terra preta may someday be part of our own terra firma.