Searching for Terra Preta

SUBHEAD: A dark horizon of terra pretas may hold the hidden secret we need to rescue Gaia’s future.

By Albert Bates on 05 August 2009 in The Great Change

Image above: Detail of book cover "Amazonian Dark Earths - Origin, Properties & Management". From

 [Publisher's Note: Terra preta (“dark earth” in Portuguese) refers to expanses of very dark, fertile anthropogenic soils found in the Amazon Basin.]

This is a very personal essay, so I am dropping the “we” convention this time and speaking in the first person singular. In an earlier post at this site I described my “Houston moment;” when I came to a full realization that ours is among the last generations of humans, and like the Elves going into the West, all life on Earth will

presently perish, possibly within two centuries, more probably over the course of a few millennia. I include in this gloomy prediction even deep sea microbes and fungi in caves. Since that glimpse of the shadow backcast by our future, I have been grappling with the internal existential crisis, and whatever should I be doing with my life now. The challenges of peak everything, nuclear winter and financial collapse pale in comparison.

This past weekend I celebrated my granddaughter’s third birthday and whenever I look into her deep black eyes, I feel a pang of sorrow, as if I were experiencing a foretaste of her sweltering hot future. Naturally I can’t share this feeling — what a party killer! — so I’m stuck with chit chat among the friends and relatives, nothing heavy.

At the other end of the denial spectrum, I have taken myself off that sweet kitesurfing beach I had planned to retire to, buckled up my Kevlar vest and first aid pouches and stepped out into the propwash. Never mind that I am Medicare-ready myself, if this Godzilla-thing devouring the planet has a weakness, I am going to find it.

The peyote prayer rings in my ears: “I am going to follow God, I am going to follow God, I am not turning back.” God’s plan, to my lights, is for Gaia not to die on this rock rotating around a medium-size yellow star, at least not until that star is ready to give it up. James Lovelock warns that we are already too late to rescue her. The signs and portents in every scientific publication are profoundly ominous.

Hell, Gaia’s fate may have been sealed before I was even born. But here is what I know: entropy is universal — things run down and bad stuff happens; but life organizes, expands, and draws unity to the whole. The human piece, as Buckminster Fuller said, is the problem-solver. I am just doing my part of that piece.

So it was that July found me flying into Manaus to attend the 61st Annual Meeting of the Brazilian Academy for the Advancement of Sciences, or more specifically, their two-day session on “Estado da Arte das Terras Pretas de Indio no Ambito Mundial” (State of the Art of Terra Preta and World Environment). At the University where we met they have to keep a 20 mph speed limit so that cars and buses don’t run over monkeys. This might be within the city limits of Manaus, but Manaus has the Amazonian rainforest for its campus.

Day one was held a stuffy classroom with fluorescent lights and powerpoints in Portuguese. Despite my language handicap, I learned plenty from listening to the speakers. I was especially interested in the explorations of Lilian Rebellato, who came at the terra preta origins from an anthropological angle.

While compositions vary, terra pretas are not always laid down uniformly, but rather show layering contours that are independent of natural terrain. In terra preta from 10 cm to 180 cm deep, the maximum phosphorus content is found at 30 to 140 cm.

Why is that, she wondered. There is a general theory that terra preta was a byproduct of village life, since it contains animal residues, house residues, humanure, bones, and pottery shards.

One theory is that since the houses are thatched with reeds and reeds have rootballs of swamp muck when pulled, the stalks then get separated to make the building material, and the discarded swamp muck is the origin of terra preta. It does explain the phosphorus. Rebellato discounted that theory by analyzing the various models of settlements, some of which would not have had access to wetland reeds.

In the Amazon, terra preta examples extend from the Atlantic coast up to the Andean plateau, so there are many different building styles used. Wenceslau Teixeira’s studies of terra preta characteristics lent support to the notion that there was a gradual learning curve in the Amazon. The deepest layers are the least rich, but by the time you reach 90 to 60 cm below the surface, there is a sharp increase in soil fertility.

This correlates to a time horizon that puts the highest carbon content at around 2500 BP, gradually falling off until 1500 AD, when traditional agriculture was discontinued because of European contact and the population crash.

 Precisely when the terra preta formula was discovered might be revealed from a dig at site called Santa Catarina.

There archaeologists have found a dark horizon in the layer of oyster shell mounds. Could this have been the Ah-ha Moment? Are we at this moment at our own dark horizon in the shell mounds? Or is it just Monsanto and Cargill from here on out? We need a 25-ton per acre increase in soil organic matter to reverse climate warming.

At the UN climate conference in Poznan last year, reknowned soil scientist Johannes Lehmann told the delegates that “biochar production from agriculture and forestry residues can potentially sequester one gigaton of carbon in the world's soils annually by 2040.” A gigaton is a billion metric tons.

Currently, powerplants worldwide emit 10 billion tons of CO2, so by Lehmann’s estimate (which I believe is overly conservative), we could knock 10% off electricity emissions globally just by charring residues (the parts other than those left in the field or forest to replenish active soil carbon) and burying the newly-minted inactive carbon as compost-amended biochar.

Moreover, using the biochar energy co-products (about 25 kWh/ton in electrical generation from kiln gas and some amount of liquid “wood vinegar,” biogas for cooking, and so forth) to displace fossil fuels, we can approximately double the prospective carbon reduction, to about 20% of global electric emissions.

The cost for installing a kilowatt of biochar producing reactors is just $1.33, compared with $4.77 for dirty coal, $3.86 for advanced coal gasification, $1870 for offshore wind and $1984 for nuclear energy, assuming the US is willing to dismantle its WMDs to fuel new nukes.

This does not solve our problem, yet, but it begins to shift us in the right direction. Human will have to teach their children to get by on lower carbon emission levels per capita, and we will have to seriously address world population, or this entire exercise will be futile.

Woody wastes are finite, and if you exceed the carrying capacity of the forests, you wind up with the same situation as a fished-out fishery. What is needed to scrub the atmosphere is more trees, not fewer.

The U.S., with over 8,000 power plants out of the more than 50,000 worldwide, accounts for about 25 percent of the world carbon total, or 2.8 billion tons of annual CO2 emissions (China is second with 2.7 billion tons).

Strangely enough, the biggest carbon burner in the U.S. is the Southern Company, which serves a geographic area with abundant solar energy year-round, and the dirtiest county in the US is Walker County, Alabama, in an area with abundant forestry residues (and closer to where I live than Nashville). On Day Two of the conference, we took a boat up river to visit a farm where the terra preta is being used to produce fruit and vegetables for the Manaus market and at the same time the ancient soils are being studied intensively.

I asked Christoph Steiner and Lilian Rebellato if the Rio Negro gets its deep black tint from terra preta. No, they said, it is from the teas, made in the river from leaves dropped in the rainforests and carried by the currents. Manaus is the “Meeting of the Waters,” where several muddy rivers converge with the black Rio Negro to form the Amazon River.

What interested me in Brazil was a chance to look at the terra preta soils close up, and to speak with some of the many scientists now studying them.

I am trying to understand how and why the ancient Amazonian cultures began the practice of carbon farming, reconciled the near-term expense with the prospect of long-term gain, and kept it going for thousands of years, creating a vast carbon sink in the Americas that perfectly balanced the rise of Amerindian civilization without desertifing the environment through farming and grazing, as happened in all the other continents where humans practiced agriculture.

As Alan Yeomans calculates, just increasing the percentage of soil organic matter an extra 1.6% in the one and three quarter acre block representing each one of us, we save our planet.

So how is it that we can effect the shift from carbon emitting to carbon farming, and do it fast enough to pull our fat from the fire? I am going to be exploring these pathways in the next several posts, and this month we are going to begin offering our carbon farming coursewares from here at the Ecovillage Training Center.

Confronted with the opportunity to go inward and slide down a vortex of despair, fretting over a wasted life, loss of historical context, and meaninglessness of every prior goal, I have chosen instead to go back into the jungle, like Stanley in search of Livingston, and pick up the faint trails that just perhaps, with long odds against, could lead to the hidden secret we need to rescue Gaia’s future.

My next stop on this trek will be the regional conference for the International Biochar Initiative in Boulder, Colorado.
see also:
Ea O Ka Aina: Soylent Black 1/11/09
Ea O Ka Aina: Black is the New Green 2/28/09

1 comment :

Erich J. Knight said...

Biochar allows the soil food web to build much more recalcitrant organic carbon, ( living biomass & Glomalins) in addition to the carbon in the biochar.
Biochar viewed as soil Infrastructure; The old saw;
"Feed the Soil Not the Plants" becomes;
"Feed, Cloth and House the Soil, utilities included !".
Free Carbon Condominiums with carboxyl group fats in the pantry and hydroxyl alcohol in the mini bar.
Build it and the Wee-Beasties will come.
As one microbiologist said on the Biochar list; "Microbes like to sit down when they eat".
By setting this table we expand husbandry to whole new orders of life.

One aspect of Biochar systems are Cheap, clean biomass stoves that produce biochar and no respiratory disease. At scale, the health benefits are greater than ending Malaria.

Secretary of Interior Ken Salazar, NASA's Dr. James Hansen
Charles Mann ("1491") in the Sept. National Geographic
Dr. James Lovelock; " Mankinds only Hope"
Tony Blair, Malcomb Turnbull, Richard Branson
Dozens of USDA-ARS Researchers

Soil Carbon Sequestration Standards Committee. Hosted by Monsanto, this group of diverse interests has been hammering out issues of definition, validation and protocol. The past week, this group have been pressing soil sequestration's roll for climate legislation to congress.

Along these lines internationally, the work of the IBI fostering the application by 13 countries for UN recognition of soil carbon as a sink with biochar as a clean development mechanism will open the door for programs across the globe.

This new Congressional Research Service report (by analyst Kelsi Bracmort) is the best short summary I have seen so far - both technical and policy oriented. .

Carbon to the Soil, the only ubiquitous and economic place to put it.

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