When it comes to solving our climate-change pickle, it might be time for deus ex machina-type proposals to take a back seat to something a little more homegrown: biochar. While the charcoal-like substance has often been pooh-poohed as a crackpot hippy idea — burning organic matter to capture carbon dioxide, really? — a new study in the August issue of Nature Communications concludes that the black stuff could sustainably offset as much as 1.8 billion metric tons of carbon emissions annually, or up to 12 percent of global greenhouse-gas production.
When left to its own devices, biomass (such as plants, wood, and livestock manure) breaks down and releases its carbon into the atmosphere within a decade or so. Subjecting that same biomass to high temperatures and creating biochar, however, locks the carbon in a stable state for hundreds, even thousands of years.
Biochar’s amazing properties don’t stop there. It’s also great for soil fertility and agricultural productivity, as ancient civilizations have long known. About 2,500 years ago, farmers in the Amazon improved their soil’s ability to retain water and nutrients by tilling it with charcoal. (Portuguese settlers later dubbed this terra preta, or “black earth.”) Plus, the addition of biochar can also reduce the amount of methane and nitrous oxide released by decaying plant matter in the soil.
But growing crops for the sole purpose of producing biochar could prove problematic, not to mention generate more carbon dioxide than it saves if, say, old-growth forests are stripped for plantations. Much like the debate over ethanol and other biofuels, socio-political economics are also at play.
“Using biochar to reduce greenhouse gas emissions at these levels is an ambitious project that requires significant commitments from the general public and government,” says James E. Amonette, a geochemist at the Pacific Northwest National Laboratory and one of the study’s co-authors. “We will need to change the way we value the carbon in biomass.”