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The Mystery of Amazonian Dark Earth

This article was written by David Zaks and Chad Monfreda in August 2006. We're republishing it here as part of our month-long editorial retrospective.

Terra PretaCarbon sequestration faces some major hurdles. Technical geosequestration methods could pump large amounts of CO2 deep underground but are still under development. On the other hand, natural methods that store carbon in living ecosystems may be possible in the short term but require huge swathes of land and are only as stable the ecosystems themselves. An ideal solution, however, would combine the quick fix of biological methods with the absolute potential of technical ones. Terra preta may do just that, as a recent article in the journal Nature reveals.

Amazonian Dark Earth, or terra preta do indio, has mystified science for the last hundred years. Three times richer in nitrogen and phosphorous, and twenty times the carbon of normal soils, terra preta is the legacy of ancient Amazonians who predate Western civilization. Scientists who long debated the capacity of 'savages' to transform the virgin rainforest now agree that indigenous people transformed large regions of the Amazon into amazingly fertile black earth. The Amazonians' techniques remain an enigma but are believed to have used slash-and-smolder to lock half of the carbon in burnt vegetation into a stable form of biochar instead of releasing the bulk of it into the atmosphere like typical slash-and-burn practices.

The difference between terra preta and ordinary soils is immense. A hectare of meter-deep terra preta can contain 250 tonnes of carbon, as opposed to 100 tonnes in unimproved soils from similar parent material, according to Bruno Glaser, of the University of Bayreuth, Germany. To understand what this means, the difference in the carbon between these soils matches all of the vegetation on top of them. Furthermore, there is no clear limit to just how much biochar can be added to the soil.

Claims for biochar's capacity to capture carbon sound almost audacious. Johannes Lehmann, soil scientist and author of Amazonian Dark Earths: Origin, Properties, Management, believes that a strategy combining biochar with biofuels could ultimately offset 9.5 billion tons of carbon per year-an amount equal to the total current fossil fuel emissions!

Indeed, there is profit to be made in this black earth, for if green is the new black, then black could be the new green. Biofuels are touted as 'carbon neutral', but biofuels and biochar together promise to be 'carbon negative'. Danny Day, the founder of a company called Eprida is already putting these concepts into motion with systems that turn farm waste into hydrogen, biofuel, and biochar.

The Eprida technology uses agricultural waste biomass to produce hydrogen-rich bio-fuels and a new restorative high-carbon fertilizer (ECOSS) ...In tropical or depleted soils ECOSS fertilizer sustainably improves soil fertility, water holding and plant yield far beyond what is possible with nitrogen fertilizers alone. The hydrogen produced from biomass can be used to make ethanol, or a Fischer-Troupsch gas-to-liquids diesel (BTL diesel), as well as the ammonia used to enrich the carbon to make ECOSS fertilizer.
We don't maximize for hydrogen; we don't maximize for biodisel; we don't maximize for char...By being a little bit inefficient in each, we approximate nature and get a completely efficient cycle.

Terra preta's full beauty appears in this closed loop. Unlike traditional sequestration rates that follow diminishing marginal returns-aquifers fill up, forests mature-practices based on terra preta see increasing returns. Terra preta doubles or even triples crop yields. More growth means more terra preta, begetting a virtuous cycle. While a global rollout of terra preta is still a ways away, it heralds yet another transformation of waste into resources.

How ironic it is that ancient humans cultivated the very fertility of Earth's most pristine places so seamlessly as to be nearly invisible. Perhaps then our challenge as planetary gardeners is not to preserve nature in a bubble but to reweave ourselves into it-to invert our footprints into handprints.

(Thanks, Garry!)

Terra Preta: Black is the New Green is a part of our month long retrospective leading up to our anniversary on October 1. For the next four weeks, we'll celebrate five years of solutions-based, forward-thinking and innovative journalism by publishing the best of the Worldchanging archives.

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A coalition of civil society groups have just released the following news release opposing Biochar plans. I'm not sure that at a large scale biochar is such a great idea...


Embargoed Until 00:01 London, England time -- 8 September 2008

International Biochar Conference Uses False Claims to Promote Dangerous
Technology in the name of Climate Change Mitigation

Joint Press Release by Global Forest Coalition, Biofuelwatch (UK) and Global
Justice Ecology Project

Campaigners today warn that an international conference on biochar, which
will be held in Newcastle, UK from 8 to 10 September, will be misleading
governments and the public with claims that biochar - a by-product of second
generation agrofuel production - can curb climate change and improve soil

The International Biochar Initiative (IBI), which is organising the
conference, promotes the idea that disastrous climate change can be
prevented of we use enormous amounts of biomass for bioenergy, obtain
charcoal as a byproduct and use that charcoal as a fertilizer. They claim
this is a "carbon negative" process, and that the charcoal improves soil
fertility and carbon sequestration. Unfortunately, their claims are
unfounded and they fail to account for the fact that vast areas of land
would have to be turned over to monoculture plantations to produce enough
biomass. [1]

From New Zealand, Sandy Gauntlett with the Pacific Indigenous Peoples
Environmental Coalition and Global Forest Coalition warns: "Biochar
proponents are speaking about enormous amounts of biomass, which will
require hundreds of millions of hectares of land being converted worldwide,
as well as removing large amounts of agricultural residues and forest
produce which are essential for maintaining healthy soils and biodiversity.
In the name of 'climate change' mitigation they want to greatly speed up
agrofuel expansion, which is already a leading driver of deforestation,
other ecosystem destruction and forced removal of indigenous peoples. This
will accelerate global warming. [2] To suggest that any massive new demand
for biomass plantations will help stem climate change is a very dangerous
false solution".

Almuth Ernsting of Biofuelwatch adds: "The IBI board members are well aware
that science does not back their claims. We were advised by the chair of
the board, Professor Lehmann, that there are no long-term experiments to
suggest that biochar actually sequesters any carbon in the ground or that it
makes soil more fertile.[3] Yet this does not stop him and other board
members from supporting unsubstantiated claims and calling for carbon
credits for biochar."

Biochar proponents also claim that their technology will help rural
communities by raising soil fertility and by giving farmers a new income
source. However, companies investing in this technology are already taking
out patents on biochar, and one of the firms represented at the conference,
BEST Energies, proclaims on their website "We are well positioned to win the
current land grab in next-generation fuels" [4], blatantly disregarding the
human rights abuses that are occurring as a result of global expanded demand
for biomass.

Dr. Rachel Smolker from Global Justice Ecology Project warns that this is
yet another scheme for profiteering off of the crisis of climate change. The
only ones who will benefit will be the plantation, forestry and bioenergy
companies, while people are further displaced from their traditional lands.
Amongst the first companies to have participated in biochar research are
three Indonesian pulp and paper companies notorious for their destruction of
rain forests and for illegally appropriating land. One of them is
implicated in 31 killings since 1998." [5]

In the UK: Almuth Ernsting, Biofuelwatch, +0044-1224-324797, mobile tel:

In North America: Orin Langelle, media coordinator, Global Forest Coalition,
office tel: +1-802-482-2689, mobile tel: +1.802.578.6980

In, Paraguay: Dr Miguel Lovera, mobile tel: +595-971-201957 (English,
Spanish, French, Portuguese and Italian)

[1] Biochar is charcoal which is a by-product of a form of bioenergy
production called pyrolysis. This involves exposing biomass to high
temperatures in the absence of oxygen. It produces mainly bio-oil, which can
be used for heat and power, for ship engines and also as a precursor to
making synthetic biodiesel for cars. Biochar has been compared to ancient
carbon rich soils in Amazonia, called terra preta, however nobody knows how
those soils were created, nor whether or how they can be replicated. We do
know that there are significant differences between those soils and modern
biochar which is highly variable depending on how it is produced. Hence
claims of its' effectiveness are based on the success and knowledge of
indigenous Amazonians who disappeared thousands of years ago.,%20381-387,%20

[2] Recent peer-reviewed studies by Timothy Searchinger et al
( and by Fargione et al ( show that
all agrofuel production results in land-use change and that the carbon
emissions from this will be far higher than any 'savings' from burning less
fossil fuels over a period of decades and in many cases centuries.

[3] Email by Professor Lehmann to Biofuelwatch, 27th March 2008


[5] The Indonesian pulp and paper companies PT Perhutani, PT Musi Hutan
Persada and PT Tenjung Enim Lestari were involved in biochar studies
( and Two of the companies have been
subject of strong national and international protest over deforestation and
over evicting thousands of people,
( whilst the third, PT Perhutani has been implicated in
serious human rights abuses, including killings (


Posted by: jim thomas on 9 Sep 08

The press release cited in comments is a mis information rant coming from the usual suspects who give the wacko left a bad name and makes no pretense of actually doing any homework.

I have investigated biochar and posted on the subject for over a year on my blog and have tackled all the objections at one time or the other.


Posted by: arclein on 9 Sep 08



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