Terra Preta: The Benefits of the Incorporation of Charcoal into Soil

[AlecBGreen]

In reply to a previous post, I mentioned Amazonian Dark Earths (aka Terra Preta) and some of the benefits of adding charcoal to soil. Some people were interested, some unimpressed, and some scornful. In an effort to pass on what I've learned and to clarify some misconceptions, I'd like to write a short thread on this intriguing but little-understood topic.

FWIW: I am an environmentalist and conservationist, a farmer, a teacher, a Democrat and an ecologist. I am still reading and learning. I am not an expert by any means.

What is Terra Preta?

In the Amazonian basin, lush rainforests are supported by incredibly thin, acidic soil. Low in nutrients and rapidly depleted of its fertility, this soil is poorly suited to support agriculture. Still, every year vast amounts of forest are clear-cut, burned, and planted to crops. After a few years, the soil is exhausted and the farmer moves on. This is the result:



Yet there are small areas of the Amazon which have deep, rich soil, almost black with so much organic matter. These ultra-fertile areas have been continuously cropped for decades (centuries in some cases) with few to no inputs; they are virtually self-sustaining. This is terra preta, "dark soil" in Portugese.



Where did it come from?

These soils have been recognized by natives for centuries yet scientists are just now identifying their origin. According to research (too detailed to get into here), these black soils were created by the steady addition of charcoal to tropical soils by Amerindians. Though the Indians have all but vanished and the processes halted, the soils remain to this day, utilized extensively for mango and papya production.

What is charcoal?



Charcoal is wood which is “burned” without oxygen. Volatile gasses and oils are liberated and carbon is left behind. The resulting product is lightweight and extremely porous.

How does it help the soil?

Charcoal is composed almost entirely of “activated carbon,” the same material used in aquarium filters, water purifiers (and vodka distilleries! :toast: ) Without getting into too much detail, activated carbon is very good at grabbing loose ions and holding onto them tightly. So if buried in soil, charcoal latches onto loose nutrients (calcium, magnesium, potassium, phosphorous, nitrates and nitrates) and prevents them from leaching out of the soil. The more charcoal you add, the more food is held in situ for the plants to utilize. Due to the high surface-area:volume ratio, charcoal can adsorb HUGE amounts of soluble nutrients relative to its size. It functions like a sponge, soaking up nutrients and saving them for plants and microbes.



Since carbon in this form is very stable, the charcoal breaks down VERY slowly (over centuries), a very useful ability considering other organic matter breaks down rapidly in the hot, wet tropical soils. Another benefit – charcoal increases “tilth,” which makes the soil fluffier and allows for better water retention. During a heavy rain less water runs off, and during a drought more is water available.

What other benefits come from burying charcoal?

OK, so we can see how putting this stuff into the soil makes it more fertile and more stable. It grows better plants, prevents runoff, and retains moisture. What else?

Charcoal is carbon. During its creation, up to 50% of the carbon found in the woody tissue is lost as CO2. The other half is buried and remains in the soil for many years. Sequestered if you will… So if a tree has a few hundred pounds of carbon (all taken out of the air), half of that will go into the soil for a looooong time. Not only do we sequester this greenhouse gas, but we also increase the soil fertility. Sounds good so far, right?

Other current research has shown that charcoal prevents NOx and methane losses upwards of 80%. These are far more potent greenhouse gasses then CO2 and as permafrost melts, they will flood the atmosphere.

What other benefits does charcoal creation offer?

Improved soil and carbon sequestration - These two benefits alone would more than justify a second-look into charcoal. But wait, there’s more! Several companies ( EPRIDA, BEST) have created processes (Pyrolysis) that create charcoal with biodiesel and hydrogen as the byproducts! “Well Alec, that’s great, but we’re still burning fuel and adding hydrocarbons to the atmosphere...” Actually it is still a net-carbon-negative process, even taking into account the eventual burning of the diesel! So we have:

1) reduced environmental degredation (less slash-and burn)
2) increased soil fertility
3) sequestered carbon AND
4) fuel.



There are countless other benefits that are hard to quantify - more jobs (this is labor intensive), more wildlife and biodiversity, less dependence on foreign energy, more clean water, the list goes on and on. What’s not to like!? I dont believe this is a magic bullet to solve all our problems. I DO believe it is a promising avenue, and one we should explore further.

Here are some links for further study:

Wikipedia
Article on Cornell Prof. Johannes Lehmann's research
Article in Nature Magazine
Terra Preta Discussion Forum
GREAT website (lots of resources)
EPRIDA
BEST)


I hope this helped :hi:

-Alec

[madrchsod]

1. then further down the road it turns to coal....

there`s areas around northern illinois that has as much or more black dirt than those shown in those pictures. most of it was swamp land for thousands of years and was drained in the 1880`s. it`s our black gold but unfortunately it`s slowly blowing away or being paved over..

[Canuckistanian]

3. Not the same thing

The soil in the example given by the OP was created by humans adding charcoal. And one might speculate, deliberately, too.

"Swamp soil" is also black, but for a different reason. It's anaerobically decomposed plant matter. It's a good soil, but it doesn't have the same properties as Terra Preta.

It's the charcoal that makes it such a sustainable soil.

[GliderGuider]

2. The more publicity Terra Preta gets, the better.

It's been discussed here on numerous occasions. Given the problems we're facing it's one of the single best ideas I've ever seen. What appeals to me most is that it is low-tech. I have grave concerns that in an oil-depleted world high tech solutions will not be supportable. If the process was used by Amazonian aboriginals, it's obviously survivable. In addition it doesn't need to be centralized. The more the process can be decentralized, the more it will add to the resilience of the ecosphere instread of diminishing it.

Excellent summary.

[Canuckistanian]

4. Ah, I was wondering if you would weigh in on this

It is a great idea.

I'd like to try this out myself by making my own charcoal. I saw a website about how to do it, it looks fairly easy.

On edit:
I captured the page, but I have no idea what the URL is. But the information is taken from this book:

Traditional Woodland Crafts. Raymond Tabor. Published by Batsford,London,UK
ISBN 0-7134-7138-7

[Canuckistanian]

5. Good post, thanks

Looks like you've been researching this for a while.

:thumbsup:

[AlecBGreen]

6. yes and no

Ive known about it for a while but it just recently "clicked." Ive been researching and experimenting for the last two weeks.

Im making my own charcoal with a freestanding 55 gal steel drum and Im in the middle of making a retort. (it is sooo cool)

Not to sound like a total nerd, but I am so excited about this! Its fun as hell andworthwhile. What more could a progessive scientist ask for!? :shrug:

[Canuckistanian]

8. Cool!

And thanks for the link. I'd like to make a retort myself!

:hi:

[piedmont]

16. I've made about 150 lbs since March. It's a pyromaniac's delight! nt

[NickB79]

45. How do you make charcoal in a free-standing drum?

This thread has convinced be to begin making my own charcoal at my dad's farm to improve our garden soil, but I don't know if I can make a full-blown retort. I was researching how to set up a charcoal mound like people have traditionally done, but using a steel drum sounds easier. Is it as simple as placing a drum full of wood over an open fire for a few hours? Thanks.

[kestrel91316]

7. This really sounds like someting to be pursued aggressively!

My next garden is going to have a good bit of crushed charcoal incorporated into the soil - though it's not as good as the special process stuff. It's still better than nothing.......

[AlecBGreen]

9. ONE IMPORTANT THING

charcoal initially soaks up all the available nutrients, temporarily depriving your plants. I havent tried it out, but I think the best way around this is to bury charcoal in compost first or incoporate it into the soil during the fall/winter. Nutrients will have a chance to rebound before you start planting in the spring.

[formercia]

14. Low tech time-release fertilizer.

cool.

[GliderGuider]

26. Presumably EPRIDA's process gets around this problem?

Also, it should be possible to do one year of chemical or compost fertilizer for a first application of charcoal, if you don't want to wait the year for the bugs to get going.

Also, did you see the speculation in the movie posted below that Terra Preta actually grows? In Brazik they dig it up and sell it to gardeners, but if they leave some of the original Terra Preta undisturbed, over the course of 20 years or so they say it regenerates. That points to the action of the soil bacteria being important to the fertilizing effect, as well as the charcoal matrix they live in.

[AlecBGreen]

28. i know

"regenerative soil"

An inch of topsoil usually takes many decades or even centuries to form. ADE's self-replicate in a handful of years.

:crazy:

[MH1]

10. K & R - fascinating stuff!

[bahrbearian]

11. K&R

[paparush]

12. Tera Patrick unavailable for comment

[formercia]

13. I think it's a great idea.

Where I live, it's mostly glacial till and what organic matter I add breaks down quickly.

I will try it.

[piedmont]

15. When I first heard about charcoal as a soil amendment here, I was VERY skeptical...

especially since in that post it was called "fertilizer," which I don't consider it to be. But it did pique my curiosity and after some research on the web, I was convinced that it's both a great soil amendment (in acidic southern soils, at least) and a potentially powerful way to sequester carbon for thousands of years. Since March I've been making charcoal out of my yard waste (I have several hundred lbs. of limbs that I had planned to chip up) and have amended my vegetable garden's soil with it. I use the method at this link: http://www.eaglequest.com/~bbq/charcoal / to make about 30-40 lbs. at a time.

[petunia.here]

17. K&R

Hubby and I just watched a BBC Horizon ep called "The Secret of El Dorado" a week or so ago. Not sure how old it was but the coolest thing about it was the "rediscovery" of terra preta. Really exciting stuff!

http://video.google.com/videoplay?docid=-2809044795781727003&q=terra+preta+duration%3Along

Thanks for all the info in your post.

[GliderGuider]

18. I just watched it - it's an excellent movie.

But the investigators still don't have a clue about why we really need it. Terra Preta could indeed save the rain forest, but we really need it to save humanity. With CO2 still rising, soil fertility falling worldwide and oil about to deplete, a process that can provide carbon sequestration, soil fertility improvement and synthetic fuel from a low-tech process is a civilization-saver.

[HamdenRice]

19. Reality check

I'm not sure that burning trees to bury the carbon has a net positive effect on carbon dioxide in the atmosphere. As the OP points out, when you make charcoal, about half of the carbon in the wood is released as carbon dioxide. If you bury the other half as charcoal, the net effect is that you have increased the amount of carbon dioxide in the air compared to the amount that was stored in the trees. In other words, a standing, in tact forest is a better carbon sink than a burned forest with half of the carbon buried as charcoal.

If you have ever seen video of an informal Amazonian charcoal maker, they are smokey, polluting little hells. I doubt that making charcoal for the purpose of burying it is good for the environment.

Also, this proposal seems to misunderstand slash and burn agriculture and tropical soils. It is true that tropical soils tend to be thin and acidic; but the land, taken in its entirety is fertile. That's because in temperate clients, the soil nutrients tend to build up in the soil as a result of winters when nothing is growing taking nutrients out of the soil. In tropical areas, where there is no winter die off, and the vegetation constantly grows, the nutrients are drawn into the foilage until there are no more in the soil, and they remain locked up in the foilage. Hence tropical farmers burn trees and foilage to release the nutrients into the soil to make them available to their crops.

There are good methods of slash and burn, called forest fallow. The farmer burns the forest, plants his crops and moves to a new field the next year, just as in bad slash and burn. But in good slash and burn, instead of a creating a frontier continuously moving into the forest, the farmer circles back after a few years of fallow. This is actually easier for the farmer because it is easier to slash and burn secondary forest (or bush) than primary forest, which has much bigger, older trees that are difficult to cut and burn. Forest fallow appears to have been the traditional form of slash and burn in much of South America and Africa.

The Amerinds of the S. American rain forest are believed to have engaged in forest fallow. A long term result of forest fallow would be a build up of charcoal in the soil. I suspect that terra petra was a by product, not a goal, of traditional agriculture.

Modern day Amazonian farmers engage in moving frontier slash and burn because of human institutions, not out of stupidity, greed or innate environmental destructiveness. In other words, the land tenure system discourages communities from circling back after a period of fallow.

[GliderGuider]

20. Forests reach a steady state

Burying charcoal can potentially sequester very large amounts of carbon, while at the same time keeping the land used for sequestration available for agriculture, rather than retuning it to a forested state. I agree that the devil is in the details - after all, many of us initially thought ethanol would be a good idea - but at first glance it appears that the carbon that could be sequestered by this technique could significantly outstrip that sequestered in forests, at least over time. One of the problems with forests is that they sequester carbon only while they are growing. Once they reach a steady state the carbon given off by decay is approximately equal to the uptake by new growth.

Certainly the buildup of Terra Preta would have been a fortuitous byproduct of their farming techniques, but that doesn't prevent it from being one of our goals now that we understand it a bit better.

And charcoal production doesn't need to be a "smoky, polluting little hell" - we do have better technology available than the Amazonian natives did.

[HamdenRice]

21. I don't think you are seeing the balance here

The manufacture charcoal releases very significant volumes of carbon dioxide (and even worse gases by the very nature of burning wood with insufficient oxygen). It doesn't matter how good your technology is.

If you take a tree and make charcoal out of it, and buried the charcoal, you have on net, increased the amount of CO2 in the atmosphere, by half the carbon in the tree, not decreased it.

It's not about the "details"; it's about the very essense of the carbon balance in the charcoal transaction.

The only way in the long term that burying charcoal would on balance reduce CO2 would be after the tree was regrown, which would take maybe 50-100 years. Now you would have 150% of the carbon locked up 50 percent in the charcoal and 100% in the tree. But we don't have 50-100 years, and certainly not if we went on a charcoal producing binge that would actually increase greenhouse gases.

By contrast, simple reforestation of deforested areas immediately reduces greenhouse gases, without producing any new ones.

[AlecBGreen]

22. I think you're both right

When charcoal is manufactured, the process puts approximately 50% of the stored carbon (biomass) back into the air as CO2, and the other 50% of the carbon is stored in the soil. So yes, creating charcoal DOES release CO2. However, the tree which you burn has taken CO2 out of the air.

Heres an example: There is an area of open ground and you plant a fast growing tree such as a sycamore or willow. After a few years it has grown 10 feet and taken several hundred pounds of CO2 out of the air. You then turn it into charcoal via pyrolysis. (See the diagram above). As a result of this process, you 1) release half of the stroed CO2 back into the air 2) incorporate the other half of stored CO2 into the soil.

So, after 5 years we have 1) a net removal of CO2 from the atmosphere 2) increased soil fertility 3) and the production of hydrogen and biodiesel. It should be noted that even if we burn the biodiesel, the sum of this whole process is still a net negative i.e. charcoal is still being buried so carbon is still sequestered.

Another thing to note - this cycle does NOT take 50-100 years to complete. There are very quick growing trees which can be grown from seed and harvested in several years (poplars, hazel, yew, sycamore, etc). Through coppicing the results can be realized even quicker. (Coppicing also has numerous positive benefits such as biodiversity, employment opportunities, etc).

One last thing - this process works for ANY carbonaceous biomass. Grass captures carbon just like trees and it grows 100x faster. Bamboo is another good possibility, and its charcoal has been shown to be particularly effective at restoring soils. The point is, the process itself is whats important - taking CO2 out of the air, restoring soil, and creating fuel in the process. The inputs (wood, bamboo, yard waste, etc) are a secondary concern IMO.

Thanks for all the good feedback and questions. This is great!

[AlecBGreen]

23. one last point then I'll shut up

(for now ;) )

This process is a positive-feedback loop. The more charcoal we make and put into the soil, the healthier the soil and the faster the plants grow. As the plants grow faster, we are able to make more and more charcoal and sequester greater amount of CO2 in the same or less amount of time.

This is a welcome change from all the nasty feedback loops we've been hearing about regarding global warming!

[blueworld]

25. Thanks for the post - more questions

Are all the trees you've listed "equal" as far as the amount & quality of charcoal produced relative to the amount of work involved in harvesting & burning & planting it?

I thought soil nutrients were created by the decomposition of organic materials & wearing down of rocks/minerals. If the charcoal initially saps nutrients from the soil, wouldn't amendments of some kind be required for an initial period of time (or the plot wouldn't be ready for planting for several years)?

Thanks again.

[AlecBGreen]

27. not all trees are equal

Are all the trees you've listed "equal" as far as the amount & quality of charcoal produced relative to the amount of work involved in harvesting & burning & planting it?

Some grow faster and produce less-dense wood. Examples might include sycamores or pine. Some grow slower and produce much denser wood - oaks and walnuts for example. For purposes of sequestering CO2, the quickest growing would be the best i.e. whichever species of tree that can suck the most CO2 out and produce the most biomass per year. In terms of soil fertility, I couldnt tell you which is best. Scientists are still scratching their heads over the Amerindians soil-building techniques. I think the best bet would be to ues as wide a variety as possible and see what works best. I know bamboo has shown very positive results.


I thought soil nutrients were created by the decomposition of organic materials & wearing down of rocks/minerals. If the charcoal initially saps nutrients from the soil, wouldn't amendments of some kind be required for an initial period of time (or the plot wouldn't be ready for planting for several years)?

Soil itself is a mixture of weathered rocks and decayed organic matter. "Soil fertility" is a catchall phrase to describe various properties such as nutrient levels and soil structure. Fertiles soils tend to not only have high levels of organic matter, humus and humic acid, but also inorganic minerals such as potassium, phosphorous, and calcium. More importantly, though, fertile soils have these substances in plant-availible form. Here's where charcoal comes in. As I understand it, when you initially add charcoal into the soil, it's charged surface "grabs" a lot of the availible nutrients and deprives plants. Over time though the (a few weeks? months? years?) the nutrients become available. One way around this might be to soak the charcoal in compost or compost tea for a while and let it get full. That way when you add it to the soil its already STORING nutrients, not robbing the plants of theirs! This is what I plan on trying in my garden.

[GliderGuider]

24. And I likewise think you're not seeing the balance.

Let's try a crude thought experiment.

Charcoal:

In one year you grow wood that absorbs 500kg of CO2 from the atmosphere. You cut and char it, releasing half the 500 kg back to the atmosphere and burying 250 kg. The atmosphere now contains 250 kg less CO2. The next year you replant and do the same, and every year after, reducing atmospheric CO2 by 250 kg each year. Say you do this for 100 years. At the end of that time you have reduced the CO2 content of the atmosphere by 250*100=25,000 kg.

Raw trees:

What happens if you just plant a bunch of trees, leave them alone and let them grow?

A tree has a time to maturity of about 50 years, but within that time it will grow faster at first, then slow down as it reaches maturity. The 500 kg/year uptake in our thought experiment is likely to be maintained for the first 20 years or so, but will taper off to 0 as the trees mature at 50 years. Say the trees live for 100 years before they die.

During their life, the trees will absorb 500 kg of CO2 per year during their early growth phase, then some smaller amount - say on average half of that - during the later growth to maturity, then zero for the remainder of their steady-state life. That means the trees will absorb (500*20)+(30*250) = 17,500 kg over their growth, which will not change for the next 50 years of their steady-state life.

So over 100 years the growing trees have sequestered 17,500 kg of CO2 while the charcoal has sequestered 25,000 kg.

But the story isn't over yet. what happens at 100 years? The charcoal is still in the ground, but the trees fall over and decay. Within the next decade most of the 17,500 kg of sequestered CO2 is returned to the air. The result is that the raw trees have provided no net carbon reduction, while the charcoal has sequestered its full 25,000 kg.

Keep in mind too that the fastest growing organic material is not trees with lifespans of 100+ years, but woody vines etc. These smaller, shorter-lived plants could grow on marginal land that would not support large trees, as well as providing relatively higher amounts per acre of char, and leaving the arable land (which is what was deforested in the first place) relatively untouched for char-assisted agriculture.

[phantom power]

29. Very interesting. Other plants grow even faster than vines.

We can make charcoal out of any plant. Or algae. Or fungus.

[AlecBGreen]

30. not really

You can "char" almost any organic matter but to make "charcoal" we need something woody. Trees, vines, bamboo, or maybe even thick corn stalks. I dont think really small stuff would work. It'd probably just burn completely and turn into ash.

[Nihil]

31. Thanks for that explanation - it helped a lot!

I could understand that by burying half of the tree's locked CO2
you were getting a marked benefit and had also understood that a
"natural death" of the tree releases 100% of the locked CO2 but
I hadn't grasped the change in uptake over the life of the tree
(or whatever plant is used - would bamboo be a good option?).

I can now see why people are so enthusiastic about it - as long as
the burning is done in a controlled (CHP) fashion and not a "primitive"
(smoky hole in the ground) one.

Thanks for taking the time to explain.

:hi:

[HamdenRice]

32. You've changed the assumptions

Both you and Alec above are now assuming that we grow the trees first before we start making charcoal. That's fine and is in accord with what I posted -- namely that taking the growing of trees and making charcoal together you would have a net carbon dioxide reduction. That's why I said in the long run, you have 150% of the carbon stored that you did before -- but that's after the trees have been replaced. I don't think any of the upthread posts mentioned tree farming as part of the scheme.

However, charcoal is generally not made from farmed trees; it's made from already existing trees. When it's made from already existing trees, there is an initial net increase in carbon dioxide.

If your plan is to start growing trees now and then making charcoal a decade or 50 years from now, fine.

But taking existing trees and making charcoal would on net contribute to greenhouse gases before it began reducing them many years from now. We don't have many years and, moreover, we don't know whether we could survive an acceleration of deforestation and carbon dioxide loading that would result from increased charcoal manufacture.

And if you are going to grow trees now to make charcoal in the future, why not just grow trees and reforest deforested areas? Living forests have an array of benefits that tree farms don't have, and we have so deforested the Amazon, Sumatran, New Guinea and West/Central African rain forests, that there are vast, vast areas suitable for simple reforestation that would on net become carbon sinks -- even if sometime in the far future they reach equillibrium.

It's really the trees that are doing the work, not the charcoal makers.

[phantom power]

33. Farming is exactly what would be done. But harvest after 5-10 years.

I'm sure there is some optimal age after which the tree's carbon fixation rate slows

[GliderGuider]

34. It does depend on your timeframe

If you want to see an effect in a couple of years, you're better off not cutting existing trees. As Alec points out though, there are trees or other woody plants that grow much faster than your 50 year straw man, meaning that if you started growing now you could start see a net reduction of CO2 within 3 to 5 years at the most.

It's really not a case of either/or though. Why not plant new growth for charcoal AND new forests as well, each on the land most suited to the use? That way you hedge your bets and you get the advantages of charcoal plus the advantages of more trees.

[HamdenRice]

35. "your 50 year straw man"

I have no objection to tree farming for the purpose of making charcoal as well as for forest regeneration.

As for "50 year straw man," it wasn't meant as a strawman. My father's side of the family owns some land in southwest Virginia that is periodically cut for pulp. In my experience, 40-50 years is about right for scrub pine, so I wasn't just making it up to shoot it down, which is the definition of a strawman argument.

And as I mentioned, none of the upthread posts mentioned tree farming until I pointed out the carbon balance issue.

[GliderGuider]

36. Fair enough.

I guess the reason I'd never mentioned tree farming is that I've assumed since I found out about Terra Preta that farmed material is the only reasonable way to do it. Cutting down existing big trees to do it would be, as you point out, a monumentally stupid idea. That shows the danger of assuming others share your assumptions. Sorry about that.

[HamdenRice]

37. There's still something fishy about this, kinda like ethanol

So everyone now agrees that implicit in the proposal is that the trees (or biomass) would be grown first, then turned into charcoal, not that existing trees would be cut down and burned.

So imagine we had an aggressive tree planting program. Now its 40 years later (or if you think there are really fast growing varieties, 5 years later).

At this point we have locked up a tremendous amount of carbon in these trees. Do you really think that it now makes sense to half burn them to turn them to charcoal, releasing half of the carbon we have successfully locked up? At this point, our tree growing method of locking up carbon would work twice as quickly by simply stabilizing the wood and growing more trees in the place where we had just cut them down.

Most environmentalists at that point would say that from where ever we are now, carbon wise, it doesn't make sense to burn these trees and go halfway back to square one, just to create charcoal. If you are looking at wood as a carbon sink, we might as well cut the forest, dump the trees down abandoned and sealed mine shafts, or water log them and sink them into the abysmal depths of the ocean. There are still timbers in 500 year old European cities that have not completely decayed, so just stacking the wood in a dry area would be another way of dealing with it that would release the carbon dioxide much more slowly than we would be locking up new CO2.

Whatever method. I just can't see, even if it is wood from a a new forest, burning huge amounts of it just to make charcoal as a carbon sink for half of what we have already locked up.

BTW, I was in Singapore in 1998 when there were huge forest fires and slash and burn fires in Indonesia and there was a crisis because the entire region was enveloped in the smog produced by burning wood.

I just don't see it happening.

[GliderGuider]

38. If all we were looking at was carbon sequestration, you would be right.

The process as it's currently envisioned encompasses agricultural soil amendment and fuel from syngas as well. The value of those two commodities may very well be worth the reduction in total sequestration capability. Remember that if you dumped the raw logs down a mineshaft you would dump with them all the nutrients they had picked up from the soil in their growth - essentially stripping the topsoil of nutrients. By tilling in the char you improve soil fertility. In an era where fertilizer is likely to become quite expensive as the last of the natural gas sighs sighs out of the depleting fields, this could prove useful.

You keep going on about the smoke from open fires. This process will generate very, very little smoke. Modern closed commercial charcoal retorts don't look anything like a forest fire.

[HamdenRice]

39. But charcoal has no usable nutrients

I thought it is a soil conditioner and improves texture, but does not actually have the nitrogen, phosphorus or potassium in an available form. There are several posts upthread about this.

If the point is soil conditioner, there are many other carbon neutral conditioners, such as leaf litter from adjoining in tact forests.

As for the smoke, even if there is reduced smoke, there will be release of CO2 and other noxious gasses.

I guess I still just don't get the net benefit.

[GliderGuider]

40. It appears to be much more active than just a conditioner

From what I've read so far the theory is that the carbon nanostructures act as a carbon reef that harbours vast quantities of bacteria and fungi.

There's a lot of serious research going on at places like Cornell, the University of Bayreuth and Georgia Tech. That alone says the subject can't be lightly dismissed. There's a lot of research just a Google away - a search on "terra preta" gives 154,000 hits.

[piedmont]

42. The carbon in leaf litter will be mineralized (respired into CO2) within a year

Carbon in the form of charcoal will stay sequestered for hundreds, if not thousands, of years.
The benefits are multiple: Energy, soil conditioner, and sequestration of much more carbon than just growing a forest.

[AlecBGreen]

41. something fishy

lol I understand your point. It seems like every year there is another crackpot scheme coming out purporting to solve this-or-that crisis. From what I can understand with my limited understanding of biology and chemistry, however, this seems to make sense. At the least it is something worth looking into.

You point out two potential drawbacks - releasing CO2 and creating smoke/smog. I think both are solved by pyrolysis. Little to no CO2 escapes - it is converted into biofuel and hydrogen. Look at the graphic of the EPRIDA process.

[NNadir]

43. I have never heard of this idea, but it has several things to recommend it.

Charcoal is excellent of course at sequestering carbon, but it also can trap heavy metals.

It could work.

[NickB79]

44. Hmmm, I could see this on a national level

Manufacture charcoal in the forested regions of the Eastern and Western US from wood waste (or set up tree coppicing farms as well), then begin shipping them to the farms of the Midwest and Southeast on electrified rail (the electricity supplied by nuclear and wind). Use up the massive amounts of manure slurry that is constantly leaching off of fields or out of holding ponds into rivers and lakes, and even use human waste from large cities, by soaking the charcoal in the waste so that it absorbs nutrients before being applied to the fields. Offer it to farmers for very reasonable rates (subsidize the hell out of it if you must) who then plow it into their fields.

CO2 would be removed from the atmosphere, soil fertility would be improved, and a major solid waste issue would be addressed. I also have a gut feeling that this would help to improve moisture retention in soils, thereby offsetting drought conditions.