Can a Kind of Ancient Charcoal Put the Brakes on Global Warming?

Popular Mechanics
By Jeremy Jacquot
Published on: December 30, 2008

Biochar was first created and used thousands of years ago to help plants grow. Researchers have found that this charcoal-like substance traps carbon and is a renewable source of fuel. Nine countries are pouring research dollars into the charcoal-like substance to see if it can sequester carbon, improve the soil and produce biofuels all at once—on an economically competitive scale. Could this ancient fertilizer really put a dent on global warming?

When pre-Columbian natives in the Amazon Basin first began to use biochar—a fine-grained, carbon-rich type of charcoal made from burning bone fragments and other food remains—some 7,000 years ago, they knew that it helped their crops grow. But they didn't realize that this charred biomass was extraordinarily good at absorbing and storing carbon dioxide, and that the process that made it released chemicals that could be used as fuel. (At the time, chemistry was still a few thousand years away.) Today, private companies, universities and government organizations in nine countries—Vietnam, Belize, Cameroon, Chile, Costa Rica, Egypt, India, Kenya and Mongolia—are setting up demonstration trials to evaluate biochar's ability to improve various types of soils while trapping carbon and making fuel to find out if this ancient substance is an economically viable solution to global warming.

Biochar is different from the dry charcoal that you'd burn in a grill: It is produced by heating plant waste to 400 to 500 degrees C in the absence of oxygen—a process known as low-temperature pyrolysis—which makes a substance that has a greater number of smaller pores than charcoal. (The better to trap carbon dioxide with.) The process used to make biochar is a closed, sustainable one: Biomass is fed into the oxygen-free burners and turned into the char. The gases that are released during the reaction is then captured and converted into electricity (from combustible gases) or biofuel, while the remaining char is safe to throw directly into the soil. Biochar does the rest of the work underground. The substance improves the ground's composition and fertility by locking in water and nutrients, thereby reducing the need for fertilizers while boosting crop yields. It also stores the carbon from the plant materials that made it— around 50 percent of the carbon produced from converting biomass into biochar can be trapped—and traps even more carbon from decomposing plants in the soil.

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