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
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
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
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
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,”