Monday 2 March 2009

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.


Erich J. Knight said...
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Robin said...

Fascinating concept. I was just reading about terra preta the other day, but had not heard or thought about applying it to current carbon problems.

Climate issues are just downright frightening these days to anyone who is looking at them head-on. And apparently these issues are meaningless to the rest of the public who have collectively chosen to stick fingers in ears and sing "la la la, I can't hear you!"

Brian Kaller said...


I have read mixed reports on how much carbon it can draw from the air, and I gather people have to really know what they're doing, but many climatologists are excited by terra preta's potential.

Talking about the climate means fighting against many things at once. Most media focuses on the immediate and irrelevant. Disinformation is widespread. And many adults have never been taught even the basics of science.

On the other hand, things build slowly and tip suddenly -- the day after the revolution, everyone is suddenly a former member of the resistance. At some point, I hope, all the people now denying climate change will, overnight, suddenly have always led the charge to fight it.

Anonymous said...

I would be concerned at differences in climate, hydrology and soils in Amazon vs temperate climates. What works in one place is not necessarily a solution somewhere else.

Anonymous said...

Greetings from your former homeland of St. Louis, Missouri!

I have been reading about terra preta and mycorrhizal fungi for the past year and am planning on trying a home-made version in my garden this year. I've picked up several bags of organic lump charcoal (from Schnucks, no less) and planned on crushing and mixing it with my soil.

But then I saw this TED presentation by Amy Smith on charcoal production from agricultural waste. What caught my eye was when she talked about it creating charcoal too fine to use w/o making briquettes.

So I picked up a half-size metal trash can, acutally just over the weekend, and plan on starting to do some testing with all those sweet gum balls that gather in my front yard.

Erich J. Knight said...

A Recent Clean Stove Project:

Brian Kaller said...


Good point -- I'd like to find that out too.


Good to hear from a fellow St. Louisan! Ah, Schnucks, gumballs -- it's all coming back to me ...

I had not heard of Amy Smith's project, but this is very interesting. I'd love to hear how your experiment goes.

I notice, though, that while she said burning charcoal requires briquettes, I didn't beleive that was true of terra preta -- it seems like her initial experiments, which did not work for cooking, would still work for that. I have not done this myself, so let me know if I am wrong.

Erich J. Knight said...

Most all biochar questions can be searched for here;

Biochar data base, TP-REPP

Nice category tabs, (also,archive of first years list posts) ie ;




Current Discussion Biochar List is at Yahoo;

Another good forum;
Terra Preta - Science Forums

Anonymous said...

Yeah, that was exactly my point. She said the result was too fine for burning as charcoal. That was my 'aha' moment for terra preta.

Erich - thanks for all those links!

Agape Farmer said...

We use a product called Char-Cal as a mineral for our organic dairy herd. It can also be used as a soil amendment. It is charcoal linked with calcium. As I understand it, the charcoal makes what ever is linked with it an organic compound. Organic compounds can easily be digested by the body as well as soil life. An example would be like when you take a multivitamin and it passes through your body with only a small amount being absorbed. With the carbon attached it is almost completely absorbed. In the soil, calcium alone can take up to three years before it is even effective if not linked with charcoal. Our herd health has dramatically improved. I plan on trying it on my garden this year and when I have the funds the whole farm.