The virtues of biochar: A new growth industry?

CHARCOAL has rather gone out of fashion. Before the industrial revolution, whole forests disappeared into the charcoal-burners’ maw to provide the carbon that ironmakers need to reduce their ore to metal. Then, an English ironmaker called Abraham Darby discovered how to do the job with coke. From that point onward, the charcoal-burners’ days were numbered. The rise of coal, from which coke is produced, began, and so did the modern rise of carbon dioxide in the atmosphere.

It is a sweet irony, therefore, that the latest fashion for dealing with global warming is to bring back charcoal. It has to be rebranded for modern consumers, of course, so it is now referred to as “biochar”. But there are those who think biochar may give humanity a new tool to attack the problem of global warming, by providing a convenient way of extracting CO₂ from the atmosphere, burying it and improving the quality of the soil on the way.

Many of those people got together recently at the University of Colorado, to discuss the matter at the North American Biochar Conference. They looked at various ways of making biochar, the virtues of different raw materials and how big the benefits really would be.

The first inkling that putting charcoal in the ground might improve soil quality came over a century ago, when an explorer named Herbert Smith noticed that there were patches of unusually rich soils in the Amazon rainforest in Brazil. Most of the forest’s soil is heavily weathered and of poor quality. But the so-called “terra preta”, or “black earth”, is much more fertile.

This soil is found at the sites of ancient settlements, but it does not appear to be an accidental consequence of settlement. Rather, it looks as though the remains of burned plants have been mixed into it deliberately. And recently, some modern farmers—inspired by Wim Sombroek, a Dutch soil researcher who died in 2003—have begun to do likewise.

Char grilled

The results are impressive. According to Julie Major, of the International Biochar Initiative, a lobby group based in Maine, infusing savannah in Colombia with biochar made from corn stover (the waste left over when maize is harvested) caused crops there to tower over their char-less peers. Christoph Steiner, of the University of Georgia, reported that biochar produced from chicken litter could do the same in the sandy soil of Tifton in that state. And David Laird, of America’s Department of Agriculture, showed that biochar even helped the rich soil of America’s Midwest by reducing the leaching from it of a number of nutrients, including nitrate, phosphate and potassium.

All of which is interesting. But it is the idea of using biochar to remove carbon dioxide from the atmosphere on a semi-permanent basis that has caused people outside the field of agriculture to take notice of the stuff. Sombroek wrote about the possibility in 1992, but only now is it being taken seriously.

In the natural carbon cycle, plants absorb CO₂ as they grow. When they die and decompose, this returns to the atmosphere. If, however, they are subjected instead to pyrolysis—a process of controlled burning in a low-oxygen atmosphere—the result is charcoal, a substance that is mostly elemental carbon. Although life is, in essence, a complicated form of carbon chemistry, living creatures cannot process carbon in its elemental form. Charcoal, therefore, does not decay very fast. Bury it in the soil, and it will stay there. Some of the terra preta is thousands of years old.

Moreover, soil containing biochar releases less methane and less nitrous oxide than its untreated counterparts, probably because the charcoal acts as a catalyst for the destruction of these gases. Since both of these chemicals are more potent greenhouse gases than carbon dioxide, this effect, too, should help combat global warming. And the process of making biochar also creates beneficial by-products. These include heat from the partial combustion, a gaseous mixture called syngas that can be burned as fuel, and a heavy oil.

Read more . . .

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Tags: amazon rainforest, ancient settlements, biochar, black earth, carbon dioxide in the atmosphere, charcoal, charcoal burners, greenhouse gases, Industrial Revolution, Innovation, rich soils, soil quality, sweet irony

This entry was posted on Thursday, August 27th, 2009 at 2:16 pm and is filed under BBC, Economist, Innovation, Science Digest / Science Daily, TechCrunch, The Food Challenge, environment. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.