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Terra Preta: Black is the New Green

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!)

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This is really cool. It's particularly interesting to think of this in light of Brazil's commitment to biofuels and flexi-fuel cars. One could easily imagine a Brazilian carbohydrate economy based on sustainably farmed local crops, south-south smart breeding and the soil-building techniques of an ancient Amazonian civilization.

Posted by: Alex Steffen on 14 Aug 06

This approach could be particularly useful in places where fire-adapted forest ecosystems have become overstocked and growth-supressed from decades of wildfire fighting, clearcutting, and other human disturbances. If we could harvest those small trees, cleanly burn them in biomass power plants to produce energy and biochar, haul the biochar back to the forest and reincorporate it into the soil with the long-term goal of growing big old trees for future generations, it seems like we'd have a viable, sustainable, and restorative forest/energy/carbon credit industry. It's too late for those forestlands to grow into old growth now, they've already been mismanaged for too long and Mother Nature is fighting back with catastrophic insect infestations and earth-scorching wildfires.

The timber industry and public land management agencies ought to preserve and protect the remaining old growth forests and start providing investment captial and research into this sort of innovation. If they don't - then forest communities should consider pursuing this sort of development at the local scale.

If this approach is really as good as it sounds in this article, it could be just the thing to end the timber wars, provide incentive for environmental restoration, and reverse the economic decline of rural, natural resource-based communities.

Imagine, a real restoration economy.

Posted by: John Harrington on 14 Aug 06

The ideal scheme would be to turn the biomass into char and gas either on-site or very close by, and process the gas into useful products (burn to make electricity, ferment to make ethanol, capture heavier molecules as chemical feedstocks) and truck out only high-value stuff.

Posted by: Engineer-Poet on 14 Aug 06

At we plant trees for airline passengers who are worried about their CO2 emissions.One common cricism of our project is that the CO2 will ultimately revert to the atmosphere.One idea that we've come up with is to bury the trees either deep in the soil or under water.Under these anaerobic conditions the gas might be potentially locked up for a very long time.
Think how long those shipwrecks from the spanish armada hang about for down there.

Posted by: Ru Hartwell on 15 Aug 06

Hi Ru,
I think there's room for both of you. :-)

Eprida can do it's energy, carbon locking up thing, and if they somehow start to edge in on your market for carbon sequestration, surely you'd try and switch to focussing on beautiful sustainable timber? Hey, who knows, you might even use some Eprida fertilizer and gas one day while selling them some timber!

Global warming and sustainable resources is a big, big problem. I think there's room for you both. :-)

I saw your site, and like the idea and design. More powerdown to ya!

Posted by: Eclipse Now on 15 Aug 06

Sorry, I meant to comment that your site reminded me of Tropical tree farms... I'm not from there, and it kind of looks like a signature and I just had to clarify that I don't represent them in any way. May you all "grow" and flourish.

Posted by: Eclipse Now on 15 Aug 06

Ru, have you given any thought to converting crop wastes to charcoal and plowing in the charcoal?

Posted by: Engineer-Poet on 15 Aug 06

"The ideal scheme would be to turn the biomass into char and gas either on-site or very close by..." -Engineer-Poet

It seems to me that unless you've got some mass transit bringing workers to a biomass plant in the middle of the forest, individual worker commutes to an isolated plant will contribute to the emissions problem. Also, do we really want industrial plants located "on-site" in the middle of restorable forestlands? It's all about appropriate scale and distance. If "very close by" means less than 50-100 miles, I completely agree with you.

There are some rural communties here in the PacNW that are co-locating biomass plants and other industries on abandoned mill sites within town limits. Although I think the ideal scheme for long-term forest and climate health would be to reincorporate the char into the forest ecosystem from which it came, I wonder if it might also be marketed as a valuable organic soil amendment for agricultural lands.

My main point is, there's much more potential value in what's currently considered "low value" woody biomass than many of the traditional forest industries are realizing. I think it's exciting that burning (okay, smoldering) the byproducts of forest restoration might actually produce carbon negative energy and healthier soils.

Posted by: John Harrington on 15 Aug 06

If the "industrial plant" is mounted on a set of semi-trailers, you'll have fewer issues with traffic than with the trucks removing lumber and product.  In this case, "close by" means 0-3 miles.

I can see disadvantages to mobile plants.  For instance, algal schemes to capture CO2 from the off-gas and turn it into more feedstock are going to be more difficult to make portable (I think it makes enormous amounts of sense to capture every last bit of carbon, if feasible).  But if you can turn an undergrowth problem into chipboard, liquid fuel and nearly-permanent sequestered charcoal in the soil, you've made a lot of progress.

Posted by: Engineer-Poet on 15 Aug 06

People,reading all this gives me hope for the future.Climate change will provide a learning for everyone of us and some of the lessons ain't gonna be fun.Luckily, for humans acting in concert, nothing is impossible.
The ultimate destination for all the carbon that's locked-up in our fossil reserves is probably the atmosphere because it's unlikely that, as a species, we will show the foresight to stop using it until every last drop is used up.
Our challenge,now, is to re-store it in as many ways and as many places as possible.

Our ancestors are showing us how.

Eclipse Now.Thanks so much for the positive feedback.
Engineer-Poet. Great idea.Thanks, it's just with an oak in Estonia living to 1500 years and me at 48, i dont think its me thats gonna be doing it!

Posted by: Ru Hartwell on 17 Aug 06

This potential is profound, the clock ticks on toward the impending destruction of Earth's ever weakening pulse of life. If there is hope for future generations, a turning point for mankinds exploitations, then this is surely it. We can no longer deny the outcome of our ignorance. Terra Praeta holds the solution, ancient knowledge to right the wrong, undo the damage done.
I am yearning to give what little I can to this chance of change, my knowledge is rudimentary but I have time and commitment, enthusiasm and vision. Optimism.
I am researching the current situation, searching for projects, programmes, action and momentum. A direction I can support. So it's about awareness, implementation, the resurrection of lost agricultural practice.
I want to help, I need contacts, suggestions, direction. Maybe somebody has an idea.....

Posted by: Tristan on 28 Aug 06



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