Fifteen hundred years ago, tribes people from the central Amazon basin
mixed their soil with charcoal derived from animal bone and tree bark.
Today, at the site of this charcoal deposit, scientists have found some of
the richest, most fertile soil in the world. Now this ancient, remarkably
simple farming technique seems far ahead of the curve, holding promise as a
carbon-negative strategy to rein in world hunger as well as greenhouse
gases.
At the 235th national meeting of the American Chemical Society,
scientists report that charcoal derived from heated biomass has an
unprecedented ability to improve the fertility of soil -- one that surpasses
compost, animal manure, and other well-known soil conditioners.

They also suggest that this so-called "biochar" profoundly enhances
the natural carbon seizing ability of soil. Dubbed "black gold agriculture,"
scientists say this "revolutionary" farming technique can provide a cheap,
straight-forward strategy to reduce greenhouse gases by trapping them in
charcoal-laced soil.

"Charcoal fertilization can permanently increase soil organic matter
content and improve soil quality, persisting in soil for hundreds to
thousands of years," Mingxin Guo, Ph.D., and colleagues report. In what they
describe as a "new and pioneering" ACS report -- the first systematic
investigation of soil improvement by charcoal fertilization -- Guo found
that soils receiving charcoal produced from organic wastes were much looser,
absorbed significantly more water and nutrients and produced higher crop
biomass. The authors, with Delaware State University, say "the results
demonstrate that charcoal amendment is a revolutionary approach for
long-term soil quality improvement."

Soil deterioration from depletion of organic matter is an increasingly
serious global problem that contributes to hunger and malnutrition. Often a
result of unsustainable farming, overuse of chemical fertilizers and
drought, the main weapons to combat the problem --compost, animal manure and
crop debris -- decompose rapidly.

"Earth's soil is the largest terrestrial pool of carbon," Guo said.
"In other words, most of the earth's carbon is fixed in soil." But if this
soil is intensively cultivated by tillage and chemical fertilization,
organic matter in soil will be quickly decomposed into carbon dioxide by
soil microbes and released into the atmosphere, leaving the soil compacted
and nutrient-poor.

Applying raw organic materials to soil only provides a temporary
solution, since the applied organic matter decomposes quickly. Converting
this unutilized raw material into biochar, a non-toxic and stable
fertilizer, could keep carbon in the soil and out of the atmosphere, says
Guo.

"Speaking in terms of fertility and productivity, the soil quality
will be improved. It is a long-term effect. After you apply it once, it will
be there for hundreds of years," according to Guo. With its porous structure
and high nutrient- and water-holding capabilities, biochar could become an
extremely attractive option for commercial farmers and home gardeners
looking for long-term soil improvement.

The researchers planted winter wheat in pots of soil in a greenhouse.
Some pots were amended with two percent biochar, generated from readily
available ingredients like tree leaves, corn stalk and wood chips. The other
pots contained ordinary soil.

The biochar-infused soil showed vastly improved germination and
growing rates compared to regular soil. Guo says that even a one-percent
charcoal treatment would lead to improved crop yield.

Guo is "positive" that this ground-breaking farming technique can help
feed countries with poor soil quality. "We hope this technology will be
extended worldwide," says Guo.

"The production of current arable land could be significantly improved
to provide more food and fiber for the growing populations. We want to call
it the second agricultural revolution, or black gold revolution!"

He suggests that charcoal production has been practiced for at least
3000 years. But until now, nobody realized that this charcoal could improve
soil fertility until archaeologists stumbled on the aforementioned Amazonian
soil several years ago.

Biochar production is straightforward, involving a heating process
known as pyrolysis. First, organic residue such as tree leaves and wood
chips is packed into a metal container and sealed. Then, through a small
hole on top, the container is heated and the material burns. The raw organic
matter is transformed into black charcoal. Smokes generated during pyrolysis
can also be collected and cooled down to form bio-oil, a renewable energy
source, says Guo.

In lieu of patenting biochar, Guo says he is most interested in
extending the technology into practice as soon as possible. To that end, his
colleagues at Delaware State University are investigating a standardized
production procedure for biochar. They also foresee long-term field studies
are needed to validate and demonstrate the technology. Guo noted that
downsides of biochar include transportation costs resulting from its bulk
mass and a need to develop new tools to spread the granular fertilizer over
large tracts of farmland.

The researchers are about to embark on a five-year study on the effect
of "black gold" on spinach, green peppers, tomatoes and other crops. They
seek the long-term effects of biochar fertilization on soil carbon changes,
crop productivity and its effect of the soil microorganism community.

"Through this long-term work, we will show to people that biochar
fertilization will significantly change our current conventional farming
concepts," says Guo.


[www.sciencedaily.com]