[Terrapreta] carbon and compost

[Tom Miles]

Bob,

In our valley we harvest and process 740,000 tons of straw each year from
our grass seed crop (530,000 acres). We recover 2-3 tons per acre from the
perennial crop and leave the stubble. We used to burn all of the straw and
the stubble. Then we developed burners to burn the stubble-only (1.5 t/a)
and removed the straw. We developed markets for the straw. Now we just leave
the stubble. I can tell you from more than 32 years experience that a
pyrolysis system that meets our environmental and agro-industrial
regulations will cost about $40 to harvest and process a ton of straw, or
about $200/ton of char. ($20/ton harvest and field side/store; $20/ton to
process; 20% yield of char).            

During the last five days on my commute to work I have seen three small
houses demolished, ground up, and hauled off. Each house was probably about
120 m2 (1200 ft2) and sat on 1200m2 (12,000 ft2 ~ 0.3 acres). When the
landscaping was scraped off and everything was put through the tub grinder
the wood waste filled about three trucks of about 15 tons each. So the haul
was about 15 tons per house. I could tell by the trucks that the wood
probably was sold as fuel to one of three pulp mill boilers I work on in the
area. The pulp mill probably paid about $20/ton for the delivered fuel.
Except for permits and inspections (I saw only a water agency truck) the
public agencies were probably not involved.

Our agencies in Oregon would not permit the agricultural charcoaler that you
describe. An agricultural charcoaler in our valley would have to comply with
all of the industrial and emissions standards that are anticipated in the
ABRI pilot, and more, so I will use it as an example. The three 15 ton
truckloads could have been processed in Peter Fransham's 50 tpd Advanced
Biorefinery in a day. At 20% charcoal yield each truck (or house) would have
produced about 3 tons of char, enough to offset my personal production of
CO2 in a year (See http://terrapreta.bioenergylists.org/carbondioxide ) at a
net cost of about $125/ton char. (See

001261.html )   

If I inject the char in rows at a concentration of 6 tonne/ha (2.46 t/a) in
100 mm (3.9 in) bands like the oil mallee charcoal, which if broadcast would
equal 1 tonne/ha (.42 t/a), (See
http://terrapreta.bioenergylists.org/oilmalleeiai07 ) then I could treat
7.12 acres of crop with 3 tons (2.73 tonne) of charcoal from one house or
one 15 ton truckload of urban wood.

What agronomic benefit, and hence what economic value ($/acre), would the
char have over a 5 year period? Would it offset the $20/ton delivered fuel
cost or the $125/ton (.42 t/a x $125/t = $53/a; $10.6/a/yr at 5 years) total
char processing cost? Or, if char from straw, $200/ton, $84/a or 17/a/yr?
These are values that we have yet to determine for most applications in our
temperate soils. 

Tom
      
-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Robert Klein
Sent: Friday, July 13, 2007 1:11 PM
To: terra preta
Subject: [Terrapreta] carbon and compost

The primary municipal feedstock is wood waste in the
form of wood chips which are easily handled.

The problem is that the municipalities are used to
operating seriously over engineered and expensive
incinerators which are unnecessary and inappropriate
to the production of charcoal.

It is easy and very cost effective to simply redirect
the wood chips out to the agricultural charcoalers
that I have described.

 


       
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