Activated Charcoal, Hardwood Charcoal?

[Ruth_10]

I'm coming late to this discussion, but I'll put my lab coat on and throw in my two cents worth.

-Most people say "carbon" when they mean carbonaceous materials. Big difference.

-Elemental carbon has many forms and all of them are difficult to derivatize. Think diamonds and pencil leads (graphite). They sit around unchanged for eons.

-One step up from elemental carbon is carbon with some hydrogen atoms attached to it: gasoline, methane, ethane, buckyballs, for example. Still not very easy for plants or animals to use (note how difficult it has been to find microbes to digest oil from oil spills).

-Wood ash has a lot of stuff in it. Before it has been rinsed many times with water, it is very basic (lye soap is made from wood ashes and grease). Eventually the soluble materials will be washed out and most (but not all) of what is left behind will be compounds with high carbon content but not elemental carbon.

-Activated charcoal is made from wood or bone by heating it at very high temperatures in the presence of steam, air, or carbon monoxide (i.e. a source of oxygen). This process makes it very porous (high surface area). With this high surface area it can adsorb other molecules. It works well for adsorbing organic molecules (molecules containing carbon), but not for inorganic molecules (like water or sodium chloride). Thus it works well to remove poisons derived from organic molecules from one's stomach but wouldn't work well to remove all that salt you swallowed when you ordered the large margaritta.

It seems to me it would remove from the soil things you'd rather have available to organisms in the soil. It will hold on to these molecules for a long time (they won't be available as a nutrient), but on the other hand, you will saturate all the pores pretty quickly, too. At that point, the charcoal is an inert filler. It might help aerate the soil or it might help drainage, but it won't itself hold water in the soil and to the extent it is elemental carbon, organisms (microbes, plants) can't use it either.

[dice]

(Resurrecting this thread to report some research results.)

I noticed in a BIM ("Beneficial Indigenous Microorganisms") document whose URL was
posted in a thread fairly recently (
http://tribes.tribe.net/effectivemic...8-51fdf4f013ad
) that the authors had a formula for "Designer Compost" that included Charcoal Dust.
The reason cited was that it functioned as a substrate for beneficial microorganisms.

Some research reported recently on the effects of adding wildfire-produced
charcoal to various soils:
http://soil.scijournals.org/cgi/cont...ract/73/4/1173
(Cannot read the whole article without a subscription, but the abstract sums up
the general conclusions.)

[aninocentangel]

Fascinating stuff!
I found a documentary that discusses terra preta here.
Really really interesting. I do think that the pot shards found in terra preta play a part too, they're also porous and the minerals they release as they break down would have a good input.
This is, however, my own conjecture.
Worth, did you ever try creating your own terra preta?

[dice]

I still think Terra Preta the product is mainly hype.

The conclusions of the research report were that the charcoal
from forest fires does provide a substrate for bacteria, but there
is also nitrogen drawdown from the carbon in it, with this effect
being the least pronounced in coniferous forest soils (which does
not describe the soils of the Amazon Basin). The Wikipedia article
on Terra Preta soils mentioned that there was practically zero
unbound nitrogen in it, because the carbon content was so high.

Plants need nitrogen to grow, so where does it come from in a soil
with that much carbon in it? My guess would be that it washes down
out of decaying organic matter in the layer of dead leaves and other
vegetation (and dead bugs, birds, lizards, animals, etc, plus all of their
droppings) on top of the soil. Without that thick layer of rapidly
decaying humus on top, the carbon-rich Terra Preta soils would be
poor soils to try to grow crops in. They would be severely nitrogen
deficient.

(I think the potshards are just archaeological artifacts, basically,
something left behind where they lived by every human civilization
since pots were invented. Finding them where people lived and
farmed for thousands of years does not seem to me especially
related to some function that the shards may have had in the soil.)

[Structure]

Interesting discussion and thank you everyone for your contributions. Since reading 1492. I've also been fascinated by the potential of terra petra.

However, let's separate or interest in temperate gardening from an slightly arcane debate about Amazon basin population levels. Some (most?) of the academic interest in terra petra in South America derives from debates about population levels upon contact. More recently these estimates have tended to consider carrying capacity. An Amazon inhabited by swiden agriculture tribes or one with large, stable fixed populations? The differnce can be millions. For anthropologists, archeologists, and historians, not to mention Latin Amerian politicians this matters.

But I'm less convinced that amending temperate soils with charcoal has a significant benefit. That shouldn't cause us to dismiss claims of the benefit in river basin tropical soils, but it should cause us to pause before dumping bags of charcoal in our garden.

The hype surrounding "terra petra" for modern agriculture and temperate soils seems driven by James Lovelock's embrace of "biochar" as a solution to global warming.

Myself, I'd love a panacea. It would make life, and gardening so much easier. In the meantime, my panacea in the ol' sub-tropics is good old compost.

my 2 cents.

[aninocentangel]

In regards to the pot shards I was referring to the ongoing garden trials in the documentary where their results using charcoal and mineral fertilizer increased yields more than 800% over mineral fertilizer alone and what appears to be a million or more times over the slash and burn method. I believe that the pot shards could be a source of minerals, like the mineral fertilizer. They were growing what the scientist called corn, but unless it was a less evolved corn like teosinte it more closely resembled millet to me.
I do understand your view points. It does seem unlikely that there's some miracle earth that is going to save the world, and I don't know that this can be replicated or even made useful for everyone, however I have to wonder if the soil is fertile due to rotting debris then why isn't there fertile soil besides the areas that have charcoal. Why wouldn't the soil retain it's fertility for more than one crop like the terra preta does. Why would the bed that had the charcoal and fertilizer added produce more than the one that just had the fertilizer? It does make me think that there has to be some sort of connection, something in the soil that uses the charcoal in some way that benefits the plants. They're looking at the bacterias and fungii living in the soil as a possible link.
I did have some activated charcoal (medical grade, not the hardwood charcoal that was used in the Amazon) on hand and mixed a level 1/4 cup into the hole when planting a sage and a sweet marjoram today, along with rounded 1/8 cup tomato tone, since it was the only fertilizer I have on hand. I'm interested in how/if it will effect them.

[dice]

My view is simply that the plants in Terra Preta have a short
window for absorbing nitrogen before the bacteria trying to
digest all of that carbon glom onto it and make it insoluble.

If it is not flowing down with the rain, it is not there at all as
far as the plants are concerned. Remove the top humus layer,
and what soluble nitrogen was there is gone with the next
couple of tropical downpours (along with other nutrients that
have good soil mobility).

I have not researched this recently, but I remember hearing
decades ago about effective desertification of areas in the
Amazon that had been clearcut logged. When the trees are
removed, the humus is not restocked with leaves, and the
heavy rainfall rapidly washes soluble nutrients out of the soil,
leaving a nutrient poor soil that takes a very long time to
recover. The rainfall still comes, but nothing much grows.
Vegetation builds up very slowly starting with plants that can
live on air, more-or-less, that only use the soil for an anchor.

(This was long before I ever heard of Terra Preta or biochar,
but it fits.)

[aninocentangel]

I agree with you. The rainforest does not have enough nutrients to support more than one seasons worth of growth, if that, once it's been denuded, and then it becomes a barren wasteland. I have an idea that the land is so poor/the rainfall so heavy that it requires simply far more biological material to produce crops than humans can provide.

The trials that they were conducting proved that the clearcut land won't support sustainable agriculture. They said that the first year the slash and burn plot produced a crop, when they showed it was during it's third year and all the plot had to offer was one measly twig that did not have any produce on it. The charcoal and mineral fertilizer bed had plants with nice big heads on them. It isn't logical that adding charcoal would have a positive effect. It doesn't fit into what we know should happen, yet it does work for them and if developing the techniques helps support that area and prevents more rainforest from being destroyed, that's a fantastic benefit for the whole world. I find that fascinating, and intend to try to keep track of research.
Prior to this morning most of the research that I had done on terra preta was on the scientific databases the college I attend subscribes, between doing class research and keeping my kids entertained. Today I started digging into the internet, and wow...now I understand what you're talking about when you mention the hype around it. I'm not buying into that, my interest is more of the science is fun and isn't nature fascinating bent, hence my own little experiment.