Wednesday, January 9, 2008

Terra Preta Commentary,Dave Yarrow,Gerald Van Koeverden,Larry Williams,Duane Pendergast

I posted yesterday’s posting on the terra preta group and got some good feed back that is helpful. Formating presents my response first before the comment and it was a bit too much trouble to get it the other way around.


I totally agree, but they can be associated with the time of manufacture and can powerfully indicate the principal crops. Their actual presence is actually anomalous for the region in any event, or at least corn is.

What I have been able to extract to date is the pollen evidence for corn and cassava culture. And yes large chunks of wood charcoal should retain cellular information that can support identification. The problem we have with effectively powdered soft plant charcoal is that it may not be that easy and could have been easily overlooked.

I would have screened the material and picked out the nice shiny chunks reasonably assuming this was representative of the fine powder and been totally misled. This is however a question that may be answered by a specialist in this type of identification who is forewarned. Do we have samples to hand and a specialist? Most identification of this type is focused on wood identification.

Actually, my kids have access to the UBC forestry faculty who would be able to do this type of work. They may even be able to char some corn stover in an oven to compare while we are at it.

does someone have good samples of terra preta?.

----- Original Message ----
From: Gerald Van Koeverden <>
To: Robert Klein <>
Sent: Tuesday, January 8, 2008 2:41:43 PM
Subject: Re: [Terrapreta] Early Terra Preta Production

Pollen evidence only tells us what plants grew in the area, not what the charcoal was made from. As you can see by the quote from a study below, scientists have the means of identifying both the age and species of the source origin of charcoal buried in the soil. Its called "soil forensics." Certainly, it must have already been done for terra pretas??

"The charcoal collections were carried out in the main massifs of present-day rainforest between latitudes 15-degrees-30'S and 19-degrees-15'S and longitudes 145-degrees-E and 146-degrees-30'E. All charcoal was collected from locations which precluded the possibility that the charcoal had been transported. Much of the charcoal retained cellular structure, and the taxonomic source was determined using an electron scanning microscope and wood identification keys. All positive identifications belonged to the genus Eucalyptus. Radiocarbon dated samples revealed ages between approximately 27,000 BP and 3500 BP with the majority of samples in the period 13,000-8000 BP."

Gerrit Van Koeverden


Hi David

That is good information and like yourself, I wonder if forensic analysis will help us. Thanks for mentioning the three sisters. I have a great deal of respect for the achievements of our agricultural forebears and the corn bean pumpkin cycle is one of the great crop innovations ever. The beans are nitrogen fixers and this allows vigorous growth in the corn. Pure genius. Now if the seed hill is made from corn biochar, I almost believe that we can crop anything.

Weed infestation is fought by close spaced weeding, and after repeating the cycle several seasons, we can expect the infestation to be much less. The seeds in the soil are depleted. Also the only soil turning will be caused by the removal of weeds in these original conditions. This will also reduce the exposure of new seeds.

In other words, aggressive weeding practices can work even in the jungle, as long as you are able to get back in almost every day. That also tells us the limiting factor for these early agriculturists in the Amazon. The problem will be much easier in temperate soils.

Thank you for this input. We today forget the labor cost of freshly clearing and initially maintaining a piece of land. It must be a bitter pill for slash and burn farmers to abandon recently cleared rain forest for lack of fertility.



----- Original Message ----
From: "" <>
Cc: Robert Klein <>
Sent: Tuesday, January 8, 2008 7:25:29 PM
Subject: Re: [Terrapreta] Early Terra Preta Production

thanks, robert, for keeping this important discussion alive. the
relax assumption is charcoal = wood. but we need a broader
perspective of likely feedstocks for char production.

35 years ago, living in new mexico, i learned the navajo method to
make pottery by firing the ots in a pit filled with dried cow pies --
areadily available and abundant resource in that arid climate. worked
wonderful. it was common knowledge how to close up the pit, and
create a reducing fire that yielded beautiful black pottery. of
course, before the spaniards appeared 500 years go, there were no cows
in the southwest.

cornstalks make excellent feedstock to make biochar -- or just for
cooking in the kitchen. especially tropical strains of corn, which
often grow 12 to 15 feet tall. i grew some guatamalan corn in my
backyard garden in upstate NY a few years ago in a classic three
sisters garden, and was startled how high the stalks grew.
unfortunately, before they tassled, the frost killed them.

however, my own conclusion is indigenous amazonians used more than
crop residues. fertile soil in a tropical climate erupts with an
abundant diversity of green growth. maintaining cropland means steady
efforts to remove weeds, bushes and saplings sprouting from the soil.
i doubt the indigenous growers -- mostly the women -- practiced the
kind of clean cultivation of modern farmers, where the soil is swept
bare except for the designated crop. indigenous weed removal would
have been more selective and thoughtful.

i would guess that the average amazon field produced far more weed
biomass each year than crop residue. and most of this would have been
non-woody weeds that will crumble easily into dust once converted to
char in a pottery kiln. how can forensic soil analysis identify this
non-woody biochar after 300+ years of residence in the soil?

david yarrow


Hi Larry

This will take a bit of trial and error to shake out properly but I can make a couple of comments. The roots can be overlapped a couple of times to get a thicker wall and better internal packing. This has to be played with in the field until we get it right. The main task is to create a thick enough wall of mud that is still porous enough to permit incoming slow airflow. This will vary with the soil type. The top of the stack can be well mudded of course.

It is a combination of slow incoming air and exiting combustion gases reducing the stover that makes this work. I suspect that slower works best as long as it is not so slow as to allow too much heat loss. It would have to be tended by a chap with a shovel to throw dirt who develops the necessary experience. Recall that a properly managed industrial system takes a good 12 hours to do its job, and then you have to wait for it to cool off.

I am skeptical about even alder since the root ball is not compact, or at least I do not think so. i never tried to pull one or if i did I was singularly unsuccessful. Corn on the other hand is a sweetheart to pull. The disc is perhaps nine inches across and the stalk with leaves is a good inch or so. It could not be designed better for a planned packing procedure. The only question is what packing plan will work best. For that we need to go do it.

Unfortunately i no longer have a corn field at my finger tips, so I need access to like minded folks to do field tests.

The main thing about corn is that we can tight pack the stalks themselves, preventing uneven burning and hotspots that would destroy a lot of product.

I am pleased that you are experimenting. There are plenty of problems with wood charcoal, but after all that work is done to make this very special product we have to actually crush it. This means the use of grinding stones to reduce tons of char each and every year to a usable powder. My sense is that this is way too hard and that it never happened that way. Corn and other soft plant residues completely eliminates this problem. And there is enough corn stover per acre to prove the value of the method the very next season.

A group of harvesters made it work the first time and it was then quickly adopted. I suspect that we will discover that this method was far more widespread that realized but used only occasionally in drier climates. It will take soil analysis to find that out but to date no one has really looked, or has misidentified any powdered charcoal seen.

A microscopic test procedure that we could trust would test that hypothesis.


----- Original Message ----
From: Larry Williams <>
To: Robert Klein <>
Cc: Miles Tom <>
Sent: Tuesday, January 8, 2008 3:04:34 PM
Subject: Fwd: [Terrapreta] Early Terra Preta Production... and a Western Red Alder fantasy

Robert-------Thanks for reposting this information. After making
charcoal with Richard Haard, I can say that it takes a lot of work to
build and manage a firing and have wondered how we could afford to
make a mound type firing with very high priced fuel or no fuel. I am
into efficiency. Richard has followed the work of John Flottvik and
has received a fine grade of charcoal as a result. With many thanks
for John's support, free charcoal is not in the cards in the future.

I fully agree that transporting organics to a distant site makes no
sense or should I say "cents". Currently, we plan to do another
firing of wood in a few months for acquiring more charcoal and to see
what we can learn about the products from a firing. It seem that we
should consider doing a field burn in the late fall with corn stalks
to learn of the difficulties of using stover material. I would assume
that freshly dug damp clayey soil is essential in the process that
you describe.

We live under some regulations concerning air quality and this may
mean that the fall timing of a test may be a problem.

Have you made stover charcoal? It would seem that the stacked roots
would need some mudding to better seal the firing chamber. I have
wondered is there is a fire proof blanket that could be used instead
of dirt if we tried a similar technic using small Western Red Alder
trees as you used the roots of the corn plants. As I write this it
comes to mind that I might be able to use a mixture of hay/ straw/
grass and clay to provide sealed surface to contain the firing
chamber. In local areas of high water tables young and old alder
trees have a flat roots mass. I might be able to use a jute mesh or
stuff the spaces between the roots with hay/ straw/ grass and clay to
assist in holding the surface together because the Alder roots are
not close knit. Using alder as the wood source would allow for a year
round firing potential... a fun fantasy. As you may be able to tell I
am writing as I work out the details.

With a stover kiln, how air tight do you think that it was? I have an
idea that it was fairly well sealed?

I much appreciate your thoughts-------Larry



The persistence of charcoal is ample evidence that charcoal resists any form of chemical weathering which makes sense but needed to be proved. Terra preta proves it. It is not resistant to mechanical weathering, however,and the type of corn char that we are proposing would start of been very fine. The remaining question is whether any particles large enough to show cell structure would survive. It is very fragile stuff.

The pottery shards may do some magic, but I think that will be a needle in a haystack, as the clay would be worked on the river bank and sun dried there.



----- Original Message ----
From: Gerald Van Koeverden <>
To: Greg and April <>
Cc: Terra Preta <>
Sent: Tuesday, January 8, 2008 6:36:58 PM
Subject: Re: [Terrapreta] Early Terra Preta Production

Nobody would bother hiring a soil forensics scientist who has to depend on finding perfect specimens encased in ceramics or preserved in amber in order to make some deductions...


Hi Duane

Not as nicely as wood, but it should be possible to take it to the high probability level while confirming the use of fast growing annuals.


----- Original Message ----
From: Duane Pendergast <>
To: Robert Klein <>
Sent: Wednesday, January 9, 2008 10:57:43 AM
Subject: RE: [Terrapreta] Early Terra Preta Production


I got that the point of the eucalyptus example was simply to point that examination of the charcoal can reveal it’s source, presumably from microscopic structure. I wonder if corn charcoal is similarly identifiable

Duane Pendergast

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