Terra Preta: Long Term Carbon Sink?

Filed in archive Earth Science on September 22, 2006

Many scientists have studied the Amazonian dark soils known as the Terra Preta and many have gained amazing knowledge from it such as restoration of degraded or poor soils, improvement of crop yields and ability to improve crop-site suitability, and most recently, technologies that may address climate change through carbon sequestration.

According to Johannes Lehmann, assistant professor of biogeochemistry in the Department of Crop and Soil Sciences at Cornell University and author of the 2003 book Amazonian Dark Earths: Origin, Properties, Management the book that gives a first comprehensive overview of the black soil, said that Terra Preta soils have been produced thousands of years ago by residents of the Amazon who used slash-and-char methods of arming rather than the present slash-and-burn. Slash-and-char uses low-intensity fires covered with dirt and straw, instead of open fire slash-and-burn.

Scientists claim that slash-and-char reduces green house gas release while slash-and-burn produces a lot of green house gases. Professor Lehmann said that the slash-and-char technology has sequestered huge amounts of carbon for thousands of years. What happens is that about 50% of the biomass carbon is retained thus making this technique a longer and more significant carbon sink than other options, say long-term forestry (but I believe that only based on carbon dioxide "sequestered" and not additional benefits).

Professor Lehmann further says that "we have calculated that up to 12 percent of the carbon emissions produced by human activity could be offset annually if slash-and-burn were replaced by slash-and-char."

Read more about Professor Lehmann's findings here.

So Terra Preta could be used as an effective carbon sink using the design that indigenous Amazonians knew. Could it the approach be improved? Tune in tomorrow...