Terra Preta, What?

Ancient Amazon soil could hold key to a greener energy future.

By EV World

Have you heard of terra preta? I hadn't until I listened to a radio interview yesterday in which it was mentioned in passing. The term is Portuguese for "black earth."

Why is it important? Two reasons: improving agricultural fertility without petrochemical fertilizers and sequestering carbon dioxide. In effect, terra preta -- a manmade soil originated by pre-Columbian Amazon cultures as long ago as 450 BCE -- could be one of the exciting "new" green industries of the 21st century.

Created by the slow charring (pyrolisis) of biomass vegetation by the indigenous peoples in the Amazon basin, terra preta soil solved the problem of acidic soils in the Amazon. These ancient anthropogenic soils are up to six feet deep and highly fertile even today. Research is still underway trying to better understand the composition of the soil and how to duplicate it as a way to reduce petrochemical inputs into agriculture, while also sequestering significant amounts of carbon dioxide from all the fossil fuels civilization has exhumed and burned in the last two hundred years.

The connection to alternative fuel vehicles, including EVs, is not as tenuous as it might seem. The process of creating terra preta or biochar as it is also know (another name is agrichar) involves the combusting biomass into a biogas. That biogas and the resulting heat can be used to produce a synthetic liquid fuel or power thermal turbines to generate electric power. The BEST Energy pilot plant in Australia produces both syngas and biochar. The company describes the process this way:

BEST Energies Inc. has developed a slow pyrolysis technology which consumes biomass waste streams while creating continuous syngas and carbon-rich end products. The syngas is composed of combustible gases including hydrogen, carbon monoxide, methane, and lower molecular weight hydrocarbons, as well as nitrogen and carbon dioxide. This gas is cleaned by a series of unit operations before being recycled back to the plant or exported. A portion of the gas generated is combusted and used as a heat source on the pyrolysis kiln itself. An additional portion of the gas is combusted and used to dry the incoming feed material for pyrolysis. The excess syngas gas represents the net energy output and can be utilized as a fuel for an engine, an industrial boiler, or as a feedstock for down stream processes which refine the syngas into a liquid fuel.

The electric power could be used to recharge electric vehicles. The syngas can be refined into a liquid fuel for use internal combustion engines, while the biochar -- mixed with other organic matter including poultry litter, dairy manure, distillers grain, paper sludge and nut shells -- creates a rich soil amendment that improves agricultural productivity and binds up large amounts of carbon dioxide.

Here are some additional links about terra preta.

Cornell University


Stand Center


National Geographic


Times Article Viewed: 11084
Published: 08-Jan-2009


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