[Terrapreta] Earthen Kiln Conjecture

[Robert Klein]

Ihave reposted an article by David Bennet with Lehmann on Terra Preta publishedin 2005.  This outlines the most criticalinformation as well as describing the original scope of the Indian civilizationitself. It is at:http://globalwarming-arclein.blogspot.com/2008/04/earthen-terra-preta-kilns-and-pollen.htmlAgainthis lays out the limiting factors and fully supports my earthen kilnconjecture, particularly the following quotation.“There has been some pollen analysis. It suggests manioc and maize were
being grown 2,000 to 3,000 years ago. In the pollen bank, these crops didn’t
pop up sporadically but in large numbers.”
Ihave also polished my description of the protocol and am activelypromoting  field trials.Firstly,the maize or corn exists in an environment that mitigated against its use forpurely food production.  There werealternatives far better suited. to the non terra preta environment, startingimmediately with manioc which I think is a rainforest friendly plant. Secondly,the only viable source of meat protein to these peoples at this populationdensity was through fish.  Withoutconfirmation, a pond with tilapia makes great sense. It was a staple for the Maya.The waste from the daily meal could be readily folded into any growing seedhill.  Human waste could simply have beenburied in the field itself avoiding any storage.  This is common practice to this day. Themaking of the earthen kiln is no more difficult than uprooting the dehydratedcorn stalks after harvest and properly stacking them to form an earthen walledkiln with a wall thickness of two to three root pads
 and an interior of tightlypacked corn stalks.  Obviously, any otherplant material, including wood can be built into the stack as available.  The earthen wall nicely restricts air flowduring the burn phase and lends itself to optimization by changing the wallthickness.  It also minimizes the amountof human effort needed which is through the roof if you are attempting to coveror bury a ten ton pile of stubble or branches. Thisgives you a kiln with vertical earthen walls and a possibly domed top that canbe easily covered with earth.  Again,field trials will optimize this protocol very easily.  The kiln could be squared off or perhaps evencircular though unlikely. The only tool to this point is a strong back ortwo.  We have gathered several tons ofcorn stover over perhaps an acre of land with only a little more effort thanthat annually required to clear the field and burn the waste. Nowwe must fire the kiln.  The easy way isto take a clay lined old basket
 and fill it up with coals from a woodfire.  Carry this ember charge to thecenter of the kiln top and tip the charge onto the exposed center and place thebasket as a cap to the newly forming chimney. 
More clay may be necessary to widen the chimney cap.  Throw more earth on top of this to preventbreakout of the fire.  Keep throwingearth on any breakout points that start. 
The chimney will serve to burn all the volatiles produced as the hotzone expands to fill the collapsing kiln until they are exhausted.  Thereupon the hot zone will cool off leavinga blend of biochar, ash and earth and some root ends for the next kiln.  And yes, we should have a lot of fired clay. Thebiochar itself will be a range of nonvolatile combustion products that willrange from even dried vegetation to activated charcoal following a nice bellcurve.  The material can be then gatheredin baskets and redistributed into the field onto the seed hills again reducingwastage and effort. Irealized originally that the only ancient plant that could accommodate a highenough volume of terra preta production was good old maize.  It just seemed an unlikely option fortropical rainforests. That is when I started looking for references to thepollen record.  The article by DavidBennett and Lehmann is one of those reverences that then emerged. Iwould like to get a full
 spectrum of the pollen profile since it seems verylikely that while the fence rows held the food trees, it seems more likely thatthey also used a variation of the three sisters using some form of convenientlegume.  Squashes also, of course, butnot nearly as important. Thekey point of all this is that a family can convert a field into terra preta inone short season, allowing them to repeat the process thereafter as necessaryuntil the field is completely transformed to depth.  Today, we can do the same thing using shovelsand a garbage can lid.




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