Friday, February 17, 2006

Saving the World, Destroying the Rainforest

Soil scientists and organic gardening advocates, like those at the Rodale Institute, have for decades propounded the importance of organic matter in soils. Organic materials promote good soil structures and help retain nutrients that would otherwise be leached away.

It turns out, though, that the best organic soil component had not been properly appreciated. It's charcoal. Charcoal retains nutrients even better than the traditional organic materials derived from plant litter, manure, or compost. It binds phosphorus, which those others don't do. And, best of all, charcoal is stable in soils -- even tropical soils -- for centuries or millenia. The other organic materials quickly decompose, especially under tropical conditions.

These properties are crucially important for the highly leached and oxidized soils of the tropics. Much of the Amazon basin had been thought to be useless for agriculture because of depleted, acid soils lacked nutrients and would too quickly lose any that were applied. But within the past decade it was increasingly realized that this didn't have to be the case, and that, in actuality, pre-Colombian cultures had successfully terraformed and farmed large areas of the Amazon. Their technique, which caused the formation of so called Terra Preta de Indio, or 'indian dark earths', involved the long term addition and accumulation of charcoal and other organic materials in Amazonian soils. The resulting dark soils have remained fertile even after centuries of cultivation by farmers ignorant of its origin.

Addition of charcoal to soils is now being promoted as part of a carbon-negative biomass energy system. Biomass, when heated in anoxic conditions, pyrolyzes to make charcoal and a hydrogen-rich gas. About half the carbon ends up in the charcoal, some of which can then be added back to the soil. This carbon would accumulate over many cycles, making the soil better with time instead of depleting it.

I do worry, however, that all this will have a side effect that the advocates don't mention. If the Amazon can be made productive, there will be increasing incentive to exploit it. The tropics can be farmed year round and have plenty of water and sunlight. Already Brazil is becoming one of the lowest cost producers of grain and soybeans in the world. If biofuels become globally important as oil substitites, economic forces will drive the conversion of the rain forest to energy plantations. Sure, the Amazon could be farmed with small-scale, organic, ecologically sensitive methods. So could the US midwest -- but it largely isn't. And given how the forests of the temperate zones were converted wholesale to farmland, the previously developed countries won't be able to object without hypocrisy.


Blogger Philip Small said...

This carbon would accumulate over many cycles, making the soil better with time instead of depleting it.

I wrote about terra preta also. The patient, long term commitment is what I find most striking. It doesn't appear (but don't know) that the full Terra Preta affect could be achieved in one massive application. This creates a relationship with the land that is the opposite of slash -and-burn. Interesting that the practice devolved so thoroughly.

4:37 PM  
Blogger Paul Dietz said...

Johannes Lehmann and coauthors have a paper at the Cornell Terra Preta site in which results of charcoal addition experiments are discussed. Conversion of first growth amazon forest to charcoal would give a charcoal/soil ratio of 10 percent, a figure at which they already see benefits (although more charcoal is even more beneficial). This assumes the charcoal is mixed into the top ten centimeters of the soil, rather than the much greater depth of terra preta, but my guess is this is ok for farmers since annuals will tend to have shallow root systems.

5:22 PM  
Blogger Iain McClatchie said...

U.S. oil imports: 20 M barrels/day = 7 G barrels/year = 584 G kg/year oil, mostly carbon, mostly burned.

Spread over 956 million acres U.S. farmland, that's 151 g per m^2, per year.

Advanced crops yield 100-200 bushels per acre, about 1.7 mm. Figure the biomass waste is at least this much, 10% of which could be carbon at density 1 g/cc, you get 170 g/m^2/year. There is no way the number can be this high across all the farmland in the U.S.

So, for the U.S. to cancel it's fossil carbon contribution to the atmosphere, essentially all the chaff biomass from all the farmland in the U.S. would have to be charred and burned. But you still wouldn't make it.

I think it's a good idea anyway. I wonder if it's a better way to deal with yard waste than composting.

6:27 PM  
Blogger Erich J. Knight said...

I feel we should push for this Charcoal based, Terra Preta Soils CO2 sequestration strategy.

The economics look good, and truly great if the USA had CO2 cap & trade in place:

'Terra Preta' soils have great possibilities to revolutionize sustainable agriculture into a major CO2 sequestration strategy.
I thought, I first read about these soils in " Botany of Desire " or "Guns,Germs,&Steel" but I could not find reference to them. I finely found the reference in "1491", but I did not realize their potential .

Current issue of Nature article:

Here's the Cornell page for an over view:

This Science Forum thread on these soil contains further links, and all the new research I find I've posted here:

The Georgia Inst. of Technology page:

There is an ecology going on in these soils that is not completely understood, and if replicated and applied at scale would have multiple benefits for farmers and environmentalist.

Terra Preta creates a terrestrial carbon reef at a microscopic level. These nanoscale structures provide safe haven to the microbes and fungus that facilitate fertile soil creation, while sequestering carbon for many hundred if not thousands of years. The combination of these two forms of sequestration would also increase the growth rate and natural sequestration effort of growing plants.

Also, Terra Preta was on the Agenda at this years world Soil Science Conference !

I've sent this thread to the researchers at M-Roots, who make Mycorisal fungus inoculations for acceleration of the reestablishment of the symbiotic fungal / root relationship. Here's the M-Roots site:

Here is a great article that high lights this pyrolysis process , ( ) which could use existing infrastructure to provide Charcoal sustainable Agriculture , Syn-Fuels, and a variation of this process would also work as well for H2 , Charcoal-Fertilizer, while sequestering CO2 from Coal fired plants to build soils at large scales , be sure to read the "See an initial analysis NEW" link of this technology to clean up Coal fired power plants.

Soil erosion, energy scarcity, excess greenhouse gas all answered through regenerative carbon management

If pre Columbian Indians could produce these soils up to 6 feet deep over 20% of the Amazon basin it seems that our energy and agricultural industries could also product them at scale.

Harnessing the work of this vast number of microbes and fungi changes the whole equation of EROEI for food and Bio fuels. I see this as the only sustainable agricultural strategy if we no longer have cheap fossil fuels for fertilizer.

I would like to investigate if use of an M-Roots type fungus inoculant and local compost would speed this super community of wee beasties in populating into their proper Soil horizon Carbon Condos.

I feel Terra Preta soil technology is the greatest of Ironies since Tobacco.
That is: an invention of pre-Columbian American culture, destroyed by western disease, may well be the savior of industrial western society. As inversely Tobacco, over time has gotten back at same society by killing more of us than the entire pre-Columbian population.

Erich J. Knight
Shenandoah Gardens
(540) 289-9750

11:56 AM  
Blogger Adrian said...

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9:04 AM  
Blogger Carlos said...

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9:59 AM  
Blogger Lou Gold said...

Don't worry Paul. Terra preta is actually an excellent strategy for saving the world AND saving the rainforest. Brazil offers the perfect example.

The huge agricultural conversion of tropical cerrado (savanna)and Amazon forest was triggered by the development of new hybrids that could grow in these soils and the impact has been immense.

The new cropland often replaces degraded land used for grazing cattle and survial farming. But this only pushes the ranchers, loggers and rural poor toward more burning and deforestation. And the expanding worldwide demand for ethanol is now generating range wars in the Amazon.

Terra preta can help reduce these pressures in two ways -- 1) by increasing crop yields on existing land the need to plant new land is proportionately reduced and 2) shifting from "slash and burn" to "slash and char" farming by the rural poor will reduce the amount of fire and produce more food. What a deal !!!!!

BUT, something has to give farmers an incentive to turn char into the soil rather than into (profitable) fuel. This is where the new carbon exchange enters the picture. Revision of the Kyoto protocols to include carbon sequestration in the soil can provide the needed tipping point.

1:45 AM  
Blogger Cyril R said...

This terra preta stuff is great for enhancing poor soils, but the resource to sequester CO2 is somewhat limited.

I've been reading about mineral sequestration (olivine/serpentine) which could be a great resource to sequester CO2.

What do you think about that Paul?

1:46 AM  
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9:49 AM  
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8:51 AM  

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