Terra Preta

As each week brings new revelations about the climate, each more alarming than the one before, world leaders feel increasing pressure to declare the situation handled, and to call for increasingly ambitious reductions – 20 percent, 50 percent, 80 percent. The idea, one presumes, we will reduce our emissions to an ideal near-zero, with everyone driving electric cars and buses, our goods shipped to us in electric lorries, all running on windmills and solar panels.

If we can achieve such a world and make it work, all well and good. But those reductions aren’t of carbon dioxide – they are of new emissions. The weather already seems to be growing more freakish around the world, and as the CO2 levels take 30 years or so to be felt, that is just the effects of the cars we drove then, like the one my family sat in at the drive-in theater where we saw Star Wars.

Entrepreneurs have come up with ambitious projects for extracting the carbon – navies of floating air processors, pumping carbon dioxide into underground caverns, and so on. But any of these projects would require governments and corporations to invest enormous amounts of money, energy and resources. We are feeling a shortage of these things right now, not a shortage of grandiose spending projects.

What we need is a way that many people around the world, using simple methods, could remove carbon from the air naturally, and pack it into something that could use more carbon – like, say, soil.

We have such a method, pioneered by Amazonian tribes hundreds of years ago. Like many Stone Age peoples, they burned the brush to create fertile land – but unlike many tribes, they seem not to have allowed the brush wood to burn completely. Instead they created charcoal, crushed it and added it to the soil.

When Europeans first arrived in the area, all the tribes had died off from Old World diseases and the jungle had largely grown back – but all around they found black earth, or terra preta, that still amazes researchers today. According to a 2006 article in Nature, terra preta is three times richer in nitrogen and phosphorous than ordinary soil and 20 times richer in carbon.

Burning plants may seem like a strange way to combat climate change, but merely charring wood locks in much of the carbon and other nutrients, and is great for soil. According to researcher Bruno Glaser at the University of Bayreuth, Germany, a hectare of meter-deep terra preta can hold 250 tonnes of carbon, as opposed to 100 tonnes of carbon in unimproved soils. In addition, the biochar itself increases soil fertility, which allows farmers to grow more plants, which allows more biochar to be added to the soil.

Johannes Lehman, author of Amazonian Dark Earths, claims that combining bio-char and bio-fuels could draw down 9.5 billion tones per year, equal to all our current fossil fuel emissions. Whether or not he is right, the technique has drawn admirers like climate scientists James Lovelock and Tim Flannery.

I admit we haven’t done this ourselves, but I’d like to try. Albert Bates told me a while ago that his group, The Farm in Tennessee, was experimenting with this, but I'd like to see how easily it can be done at the household level. I’d especially like to find out if, at a time when too many of the world’s forests have been cut already, if it can be feasibly done with some commoner biomass like hay.

Is anyone doing this at home? Share.