[Terrapreta] Successful charcoal burn

[Larry Williams]

Sean-------Please excuse the delay in answering your questions. They  
are answered at the end of this e-mail. I wanted to first explain  
what happen so that you and other members of this list can better  
appreciate this process, our high point and those low points.

We actually had two burns in the last two weeks on the Sand Road.  
They were by the seat of our pants. We really did not know what to  
expect. After having said this, I feel that the caution exercised  
with the air taken into the the firing chamber produced some  
excellent results. I will relate the different burns so you can get a  
better picture of our procedure. We will learn far more if our ideas  
are exchanged freely so you will note that the release of carbon  
dioxide and methane is obvious.

You may have noted in Richard's comments, we have not, at this point,  
invested in the necessary instrumentation to answer some of your  
questions. Number are not my strong suit while the long term growing  
of plants is. I would like for you to know what we have done,  
separately and together. Richard's history with charcoal at the  
Fourth Corner Nursery (Sand Road firings, also) has been posted on  
the Terra Preta web site and he will answer any questions about the  
charcoal that has been used in his nursery operation. What follows is  
from my perspective.

Richard showed pictures (URL below) of charcoal from my garden  
(Southside neighborhood - Bellingham, WA) that was posted on the  
Terra Preta Web site. My garden has a history that I now feel led to  
the successful use of charcoal which Richard documented. It has been  
my practice for fifteen years to use wood chip (from a tree pruning  
company who cleared the power lines of potentially hazardous  
branches) as a mulch in my landscaping business.

The mulch would act as a weed barrier (6" or more) for three or so  
years and provided habitat for soil flora and fauna. The space  
between the pieces of chips became the home for the critters and the  
chip became the source of food for somebody. At one point, I had  
6-700 yards of green-tree sourced wood chips, reasonably high in  
nitrogen and about 150 yards of planer shavings of re-milled old  
growth Douglas Fir material with a C/N ratio around 400 to 1. So  
liberal use of these materials was used, at every opportunity, in my  
landscaping including at this Southside garden.

Woody debris in the form of wood chip was use starting around ten  
years ago at this garden. Within that period of time, for about five  
years, The garden lay fallow with a heavy layer of chips covering  
(8-10") covering it. Then two years ago I started gardening on this  
site again. This is when I started thinking about Terra Preta.

The Weber First

My first charring experience (with some charcoal) was with a Webber  
barbecue grill. I worked out of town building Urban hiking trails  
east of Seattle and was gone between two to four days a week. I  
cooked enough chicken in the Webber for the period of time I was out  
of town. The chicken was used in small meal trays and placed in an  
iced cooler for the work week. This meant that I cook a lot of  
chicken for the years that I worked trails and for the last two years  
produced a reasonable amount of charred wood and some charcoal.

This Webber material was used in my garden and produced the largest  
swiss chard that I have grown, right at 42" high. The diameter of the  
plant was large compared to other chard plants grown in previous  
years in the same location. Rich was able to take the first pictures  
of  mycelium roots and Swiss Chard roots attached to the pieces of  
charcoal. There was no commercial fertilizer. I purposefully extended  
the charring of alder branches to additional smoke after the chicken  
was cooked. Of course, chicken fat sizzled on the store-bought  
charcoal briquets. I think that that smoke was the critical step to  
the growth of the swiss chard but that is just a guess. These  
pictures are at http://www.flickr.com/photos/rchaard/sets/ 
72157594444994347/ and are the group of four pieces of charcoal in  
the upper left corner.

The Kona  Burn

My second attempt to make charcoal was on the Big Island of Hawaii at  
the beginning of April, 07' for a local garden and an organic  farmer  
above Honaunau on the Kona coast of Hawaii. I was located in a  
farming belt with 1/2 day cloud covered which means more rain than at  
the beaches below. The wind moves downhill at night and uphill during  
the day so because of a nearby home I had to be very careful that the  
wind was blowing the smoke downhill, away from the well ventilated  
house. Which is more threatening the EPA or a mad housewife who's  
clothing has been smudged?

The burn was towards 3 cubic feet of Strawberry Guava with pieces of  
wood that were less than three inches in diameter. There was very  
little dirt on this coast line (plenty of lave rock though) so it was  
difficult to seal the fire. So I improvised using the petiole of palm  
tree fronds (leaves cut off) that functioned to hold the roof of the  
firing chamber from collapsing as the wood settled. I used 3-4 inches  
of grass on top of the fronds, then cardboard which was covered with  
the little dirt that I had. It was an overnight burn (10:30 PM to  
7:30 AM). When the fire was uncovered and doused with water there was  
a rich sweet smell coming from the partially cooked grass that seemed  
significant, I believe.

There was one 5 gal bucket of charcoal and another bucket of charred  
pieces of wood that was recovered. My suggestion was that the  
charcoal be place in only one half of any vegetable rows and that the  
charred wood ends be driven into the soil around one of two Hawaiian  
pepper shrubs. Digging up one pepper plant to place charcoal around  
the root ball would slow it's growth and driving, with a hammer,  
charred wood into the soil would be less damaging to that plant's  
root system. This material has been distributed mixed in, placed on  
and pounded into the garden soil as I hear it. There has been no  
attempt to be scientific just a curiosity if there is any difference  
in the garden beds.

The Sand Road Repetitions

The third attempt at making charcoal was with Richard Haard and  
contained a little under 1.5 cords of split alder, maple, a little  
cherry and a few pieces of Douglas Fir. This wood was reasonably dry.  
Although, we took dated pictures I haven't tried to figure out the  
time sequence of the first and second part of this charcoaling  
adventure. There were two burns with three fires started to charcoal  
this 1.5 cords of wood.

First Burn---up-draft
I didn't allow enough air into the first burn (with up-draft air  
supply). Early in this Sand Road burn our curiosity had us open up  
the air supply on the down side of the sloped firing chamber to see  
what was happening and as the fire crackle away we pulled out some  
nice charcoal (mixed in sand and wet hay). We closed the lower air  
supply off thinking that there enough air leaking into the fire  
chamber to sustain a slow fire and the fire went out prematurely. No  
pipes were used nor did I spent the night camped on site to check the  
fire, an old tradition.

The Re-Burn---down-draft
The following weekend with the second burn, called the re-burn, the  
pile was re-stacked and the floor of the fire chamber had an addition  
slope of 6-8'' for a down-draft burn to pull air. I added another 15  
pieces of fresh (green) alder poles to assist in holding the roof of  
the firing chamber intact.

We added a 10' of 8" stove pipe with a 90 degree elbow (staked with  
long metal fence posts). Then we sealed the elbow and the lower 12"  
of the stack with dirt. We started the fire high in the higher end of  
the wood pile with six 1 inch pipes to provide air to the fire. The  
fire was started with a fire log and paper douse with diesel. The 10'  
stack started to draw the smoke out. We thought we had a fire. By the  
next morning the fire was out.  I now believe that the fire was hot  
enough sustain itself via the down-sloped venting stack in spite of  
the initial venting of smoke and the six 1" air pipes accessing air  
to the fire.

The remains of the fire log of this firing indicated that there was  
likely not enough draw up the stack. I still am considering the  
effects of the amount of heat available, the amount of air available  
and the additional depth required to pull air up the 10' stack. Only  
a repeat of this type of mound firing will give reflection on those  
variables.

The Re-Burn---second firing---down-draft
There was a hotspot where the previous fire was started which created  
an air hole that Richard closed in 4 hours (?) after starting the  
fire, the patched roof held for the remaining portion of the second  
burn, third firing. We added three of the 1.5 inch air intake pipes  
were low in the upper side of the mound (north end furthest from the  
stack).

When I restarted the fire, I used a fire log, 2 cups of diesel and a  
propane torch. I didn't think that I would lose the wood to ash this  
time. The reason for dropping the egress for the smoke was to capture  
more of the volatiles in the burning chamber. I believed that it work  
from the iridescent surface on the charcoal and what Rich described  
as "showing fiberous structure of carbonized vascular tissue" which  
we noticed in the south end of the mound. In the picture showing the  
smoking stack you can notice that the left side (north) of the mound  
is lower than the right side. It appears that both increased air  
supply to the lower portion of the stacked wood and the fire starting  
materials, especially the fire log, created excess heat that ashed a  
portion of the charcoal on this upper side of the burn. See: http:// 
farm1.static.flickr.com/206/458350077_eddb136e0a_o.jpg  .

Also, establishing an understanding between our use of traditional  
charcoal production and the societal burning practices is in order so  
that we do not self-limit our learning as we search for workable  
solutions to human habitation and global warming. I understand that  
capturing the wood vinegar is very important from a plant growing  
point of view and for the atmosphere. We live on the only blue-green  
globe that we know of. We have no choice but to change or change will  
overwhelm us-------Larry



P.S. See: http://www.flickr.com/photos/rchaard/458342446/in/ 
set-72157594444994347/  and http://www.flickr.com/photos/rchaard/ 
458350089/in/set-72157594444994347/  .

P.P.S. Here are the my answers to the questions that you asked:

1) Was that exhaust draft stack shown in the eddb136e0a_o.jpg picture  
venting from the bottom of the wood stack?
	You were right, 8 inches.

2) Where were the air inlets? and Was the cross-sectional area of the  
air inlet smaller or larger than the draft vent (looks like 8" vent  
pipe)?
	a) 3-1" pipes at mid-way in the pile
	b) 3-1" pipes at ground level
	c) 3-1.5" pipes on the north side of the unfinished mound before the  
pipes were installed. The pipes were later placed together between  
the pallet's boards.

3) How long was the burn before covering?
	Less than thirty minutes.

4) How long was it "pyrolizing" (small amount of air input)?
	Without looking at the time on the photos, I believe that I shut the  
air down after I realized how hot the stove pipe was as I touched the  
pipe with my forearm and realized that it was the hottest stove pipe  
I had ever touched. I was burning carbon. All the pipes that I looked  
into showed bright glowing embers. I decided to stop as much of the  
inflow as possible. The burn was pyrolizing from 6PM till it cooled  
to days later. When we opened it up there was some heat venting (no  
smoke, just hot air and not unpleasantly hot) at the top of the  
opening and I told Rich that we should get as much of the charcoal  
out as possible in case we still have glowing embers. Fortunately,  
there were no embers glowing and we removed all the charcoal.

5) Did you see the color of the smoke change from white to blue/clear  
before you stopped?
	No! And I was looking for it and was very busy closing down the fire.

6)  Was the vent stack melted at the bottom at all?
	No, although a creosote material which flowed as the lava flowed in  
Hawaii did form in the elbow. It had a puffy texture. At the top of  
the stack as some deposited out gasses that were very thin and  
fragile. This material fractured like glass and was shiny. I save  
samples of both.
  7) Were you able to make any temperature measurements?
	Not this time. I have started to look for some appropriate  
instruments. With this mound firing it would have been very easy to  
insert a sensing device down the 1" pipe.


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