I first learned learned of terra preta while reading the fantastic book 1491 (see previous post). Terra preta or Amazonian Dark Earth was created by ancient Amazonians by burning old crop waste until it was charred rather than burning it all the way. The resulting soil retained more water and nutrients and greatly increased crop yields. Turns out it is also a great way to sequester carbon.
Bruno Glaser, of the University of Bayreuth, Germany, a sometime collaborator of Sombroek's, estimates that productivity of crops in terra preta is twice that of crops grown in nearby soilsWow! Not only do you get a soil that could increase crop productivity by 200-300%, you also have a way to sequester carbon on a scale that could offset all fossil fuel emissions. Instead of being carbon neutral, they are now talking about going carbon negative.
According to Glaser's research, a hectare of metre-deep terra preta can contain 250 tonnes of carbon, as opposed to 100 tonnes in unimproved soils from similar parent material.
That difference of 150 tonnes is greater than the amount of carbon in a hectare's worth of plants. That means turning unimproved soil into terra preta can store away more carbon than growing a tropical forest from scratch on the same piece of land
He estimates that by the end of this century terra preta schemes, in combination with biofuel programmes, could store up to 9.5 billion tonnes of carbon a year — more than is emitted by all today's fossil-fuel use.
Sounds like a sure winner, what is the downside?
One problem is that the purported benefits of char do not slot easily into the framework of the Kyoto Protocol, an international agreement to reduce carbon emissions.Cellulosic ethanol might also compete with it for crop wastes to turn auto fuel rather than char.
Then there are your risk-averse farmers.
"Can you do this in a no-till way?" is one tricky query.
Eprida is a company that is creating terra preta along with hydrogen rich bio-fuels.
All in all it looks like a very promising technology and one to keep your eyes on.
via World Changing and Nature