[Note: This is a draft of an article I'm working on. Constructive criticism welcome. Or payment for publication. :) Images will be added later, if I can get permission to use 'em. And yes, I know that all of the footnotes are numbered "1". I'll fix it eventually... Thanks for reading!]
B l a c k | Can a lost civilization teach us to double crop yields M a g i c | and produce carbon-negative energy at the same time?
In 1542, Spanish explorer Francisco de Orellana described large cities, extensive roads, and fertile croplands in the heart of the Amazon Basin. These claims were long thought to be exaggerations at best. Later explorers found no traces of these complex societies. Nor did historians or archaeologists.
However, those notions are beginning to change. Orellana may well have led the first (and last) party of Europeans through a highly advanced civilization that thrived in the Amazon for centuries - a civilization whose existence was thought to be impossible. After all, even with modern farming techniques, crop yields cannot be sustained on the poor native soils. A rainforest soaks up every last drop of rain. Remove the rainforest, and the soil nutrients leach away in no time. The slash-and-burn techniques used by today's farmers in the Amazon produce a layer of ash that may only achieve a few years' worth of crop growth before all usable soil nutrients have eroded away. How could a large pre-Columbian civilization thrive where modern agriculture cannot?
Archaeologists in the Moxos Plains of Bolivia have started to unravel this 500-year old mystery. The Moxos Plains are a flat, savanna-like region on the edge of the Amazon rain forest. The plains are subject to seasonal flooding, and covered with relatively sparse vegetation. However, the landscape is dotted with "forest islands" - thousands of raised areas with highly fertile soil, covered with lush vegetation. The landscape is also criss-crossed with unnaturally straight lines and rectangular patterns, for miles on end.
The forest islands were thought to be the result of some sort of volcanic or other geological activity. But every forest island has thick, rich soil known as terra preta
, or "dark earth". And everywhere there's dark earth, there are also pottery shards, human bone fragments, charcoal, and other evidence of human life. Intricately detailed artifacts have been discovered which rival the Incan and Mayan cultures' artistry.
Evidence now suggests that the forest islands themselves were man-made earthworks. The straight lines were an extensive web of causeways connecting the islands, and canals, with fish weirs. The rectangular patterns were agricultural plots, raised to protect them from seasonal flooding. As researchers have started to map the terra preta soil throughout the Amazon basin, they're finding a strong correlation between the rich soil and the places where Orellana reported seeing villages.
Perhaps the most valuable discovery has been the rich soil itself. It appears that this vast and complex culture did not just take advantage of terra preta -- they created it. This lost civilization, apparently destroyed in a matter of decades by smallpox, influenza, and measles, has left us something valuable indeed -- a technique for creating soil with incredible properties.
Incredible - an overused word sometimes. But consider this: The terra preta soil can result in increases in crop yields of double, triple, or in one case, 880 percent1
over the native soil; the technique for creating terra preta soil can extract significant amounts of carbon from the atmosphere, and store it in the soil for millenia
; as long as an eight-inch layer of terra preta is left on the surface, it can apparently regenerate itself
to a depth of 24 inches over a period of two decades1
; and at least one plot of terra preta soil has been continuously cropped for over 40 consecutive years
In fact, several companies are trying to take the process even further. One company, Eprida
, believes that through a process called pyrolysis, it can produce bio-oil, hydrogen-based gas, and highly fertile soil, from crop residue, on a small scale, in a way that returns micro-nutrients to the soil and
removes carbon from the atmosphere.
Their prototype power plant, which is the size of a semi trailer, burns peanut shells. The heat produced is used to create steam, which is mixed with the smoke from the burning process itself. When the steam and smoke combine, a hydrogen-based gas is captured, which can then be used as a fuel, similar to natural gas. Alternately, all or part of the gaseous smoke/steam mix can be distilled into a liquid fuel. And of course, the charred material created becomes a soil amendment.
Eprida will target small farmers, since a farm can easily provide all the inputs and
use all the outputs of the process.
The researchers at Eprida actually had no knowledge of terra preta when they began researching sustainable ways to produce energy from crop residue -- but the hints were there. Danny Day, Eprida's CEO, tells the following story:
One of my employees, Nate, was instructed to bring a 55 gallon drum of charcoal from an area where we had produced and piled it up two years earlier. He came back and asked what did I want to do with the plants.
I said, "What plants?"
"The plants growing on the charcoal," he replied.
I said, "Nate, I need clean charcoal with no plants in them. Just move them out of the way and get clean charcoal with no plants or root material in it."
He quickly went away.
The next day I was puzzled and asked Nate what kind of plants were growing in the charcoal.
He said, "Oh grass, weeds... " He paused. "And turnips."
"Turnips? What kind of turnips"
He smiled as he held up his hands about a foot apart and said, "Big turnips."
I said, "Wow. That’s incredible. Go get me one."
"I can’t," he replied.
"Why not," I asked.
"You told me to move them."
"Where did they go?"
Nate replied, "Charlie, Philip, David and I took them home."
"How much did you get?"
"We each got a big garbage bag full!"
"What did they taste like?"
"They were good!"
Scientists and researchers are just now starting to unlock the mysteries of terra preta. The key ingredient, it seems, is charcoal - or more specifically, activated carbon
. A single gram of activated carbon can have a surface area of 500 to 1,500 square meters (or about the equivalent of one to three basketball courts)1
. This char material in the soil has several beneficial effects, including about a 20% increase in water retention, increased mineral retention, increased mineral availability to plant roots, and increased microbial activity. It has been shown to be particularly beneficial to arbuscular mycorrhizal fungi
, which form a symbiotic relationship with plant root fibers, allowing for greater nutrient uptake by plants. There is speculation that the mycorrhizal fungi may play a part in terra preta's ability to seemingly regenerate itself.
Biochar (sometimes called agrichar) is charcoal made from crop residue, such as corn cobs or spent sugar canes. The research into the benefits and the ultimate potential of biochar as a soil additive are being conducted around the world, in tropical, temperate, humid, and arid climates. It has been studied by such respected institutions as Cornell University, the University of Bayreuth, Germany, and the US Department of Energy. It has been reported on in journals and publications such as Nature
, Scientific American
, and Discover Magazine
It's important to remember that biochar doesn't necessarily add nutrients so much as retain nutrients, and make existing nutrients more available. The most significant crop yield increases were found when mineral fertilizers were added to poor soil in conjunction with the biochar. However, it does appear that the more char material added, the bigger the beneficial effects. The effective saturation point is not yet known. It's also important to note that the benefits may be lost when certain modern agricultural techniques are used. Mycorrhizal fungi and other soil organisms are sensitive to many agricultural chemicals, and the yields may not be as dramatic with heavily tilled soil.
More char material in the soil may mean less carbon dioxide in the atmosphere. The carbon sequestration potential of biochar is enormous. By one estimate, biochar-amended soil can contain at least two-and-a-half times the carbon of typical soil. In the Amazon's poor soil, terra preta soil has eighteen times
Unlike most soil-based carbon (organic matter), the charred matter is essentially permanently sequestered.
How much carbon can be sequestered in this manner? The limits have not yet been determined, but one estimate amounts to 150 metric tons per hectare, or, put another way, over 42,000 tons of carbon per square mile
. Bruno Glaser, a researcher with the University of Bayreuth, Germany, believes that by the end of this century, terra preta schemes in combination with biofuels could store up over one billion tons
of carbon - more than the total of all carbon emitted by fossil fuels today.1
Of course, the danger of this kind of discovery, if it turns out to hold up well under further scientific scrutiny, is irresponsible implementation. Clearcutting forests to sequester carbon doesn't seem like a practical tradeoff. And creating excessive air pollution through low-tech charring of plant material might create more problems than it solves.
However, there is so much promise, so much potential, and so many global problems that could be helped with this knowledge, that extensive trials are certainly warranted. Terra preta could provide us with:
- A way to slow, or even halt deforestation of the Amazon basin
- A way to dramatically increase crop yields, even while moving away from chemically-dependent agriculture
- A way to mitigate soil depletion problems around the globe
- A way to retain more moisture in soils, reducing the need for irrigation
- A way to reduce nutrient leaching into waterways, which in turn can reduce the "dead zone" problems such as the one found near the Mississippi delta
- A way to create energy sustainably, even on a back yard scale
- A way to permanently and dramatically reduce carbon concentration in the earth's atmosphere
- A way to do all of these things, with apparently time-tested, stone-age technologies.
There's even a small chance that particulate from creating char could temporarily re-strengthen the global dimming
effect, which might slow global warming.
Too good to be true? It's hard to say. But with all of these potential benefits, it's hard not to be hopeful. Especially since, with a little thought and creativity, it seems like much of this could be done on a homestead scale.
Sure it would be hard for a back yard hobbyist to capture, store, and use hydrogen gas. And anything involving fire and smoke would need to be thought through. The ideal situation might be an "appliance" of some sort that could filter pollutants, or even make use of the gases the way Eprida's prototype apparently does.
Even without such complexities, if the pollution question can be addressed, the potential is huge. Could it be that anyone with the motivation could dramatically improve their soil and sequester carbon in their own back yard? After all, char material can be made using little more than a steel drum with some holes in it.
There are plenty of things to do with the heat generated during the charring process. Why not use it to heat your water? Or cook your food? (Ever heard of a pit barbecue?) The heat could be used to warm a greenhouse in winter, or possibly even supplement home heating.
Maybe this was how it all started. Maybe the ancient inhabitants of the Amazon were just trying to cook their dinners or warm their water, only to stumble on one of Mother Nature's best kept secrets. Perhaps the constant rains made open fires impractical. Maybe the lack of abundant stone made pit fires the only logical choice. Or was it just that local fish tasted best when slow-cooked?
Whatever the case, it seems they discovered something akin to magic. Now that we've unearthed this deep, dark secret, are we smart enough to use it responsibly?
Labels: biochar, sustainability