Terra preta and the future of energy: the Secret of El Dorado

There is rapidly growing interest in the development of carbon-negative bioenergy, seen by scientists as one of the most feasible strategies to mitigate climate change and strengthen energy security on a global scale. Two broad systems are being researched: a high-tech concept that involves storing carbon dioxide from biofuels in geological sites via carbon capture and storage (CCS) technologies (earlier post). The other, low-tech, is based on the ancient technique of storing charcoal or biochar into soils. This practise, known as terra preta or Amazonian dark earth, could revolutionize energy agriculture.

When biochar is added to soils, they become impressively fertile because they prevent nutrients from getting washed away by rain and erosion. Archaeologists who discovered these black soils in Amazonia are now trying to replicate the technique; soil scientists and bioenergy companies are doing the same. But some of the mystery behind these soils remains.
In an excellent documentary titled 'The Secret of El Dorado', the BBC's science program Horizon sketches the amazing story of how this ancient agricultural technique may help fuel the future. The film shows how a Spanish conquistador's 16th century tale of an 'El Dorado' hidden deep in the heart of the Amazon might have been correct after all. Researchers demonstrate that the rainforest was indeed once populated by a large civilization counting millions of people who actively transformed vast tracts of its landscape. But their real treasure wasn't gold, it was dark earth, which allowed them to flourish. The findings challenge the idea that the rainforest is a 'pristine', 'undisturbed' ecosystem - that's basically a eurocentric, romantic myth (previous post). The scientists instead found that as much as 10 percent of the entire Amazon basin is covered in man-made terra preta, a huge area.

The documentary follows archaeologists, anthropologists, historians and agronomists into the jungle where they show how exactly the Amazonian black soil worked and continues to do so to this very day. In the final part of the movie, a replication of the century-old technique shows that a combination of biochar and fertilizer boosts crop yields by an incredible 880 percent...
energy :: sustainability :: biomass :: bioenergy :: biofuels :: terra preta :: Amazon :: biochar :: agrichar :: charcoal :: carbon-negative bioenergy ::

Meanwhile, scientists and biofuel producers from various parts of the world are testing the concept in carbon-negative bioenergy systems. Dynamotive, which develops next-generation biofuels based on pyrolysis, announced it is testing terra preta in the U.S. Midwest (previous post); a set of trials from China shows the versatility of biochar, whereas agronomists in Australia already found impressive yield increases of energy crops grown in the enhanced soils (here).

References:
BBC Horizon: 'The Secret of El Dorado' - part two, three, four and part five, which shows recent trials.

In-depth info on terra preta can be found at this dedicated bioenergy list.

Biopact: Biopact to chair Sparks & Flames conference panel on carbon-negative biofuels - August 08, 2007