[Terrapreta] char & vascular systems

[Lloyd Helferty]

Kurt,

  You  asked a good question, but I didn't see it being answered.

 Dynamotive sells bioChar that they are claiming is "virtually sulphur free"
and thus has "EcoLogo" certification by Environment Canada's Environmental
Choice Program, although at first I had actually suspected that it may NOT
be the ideal substrate after they indicated that it is shipped as a "fine
powder".  It hadn't occurred to me that grinding the char to a fine powder
might be better than leaving it in larger bits (up to 3-5mm dia. ?), but I
recently read that this will help to "maximise moisture retention", although
I also read from Kevin Chisholm that "Crushing or breaking up charcoal will
not make an appreciable or significant difference to active surface area..."
although he did indicate that this would "permit much more uniform
distribution of the char".
I never saw any confirmation regarding this statement.  I'd like to know if
the Dynamotive char would be suitable / preferred.

Another concern regard the Dynamotive char was their chart showing an
"Example of Analysis of the Ash" in their BioChar at
http://www.dynamotive.com/en/biooil/biochar.html#what (see Table 3).
 (I also noted that on their website they are marketing it as a fuel and NOT
as a soil amendment product.)

The important point was that Arsenic concentration is supposedly "< 10
mg/kg" i.e. (<10ppm), and Cadmium <1ppm.

I've looked up Health Canada's guidelines for Canadian Drinking Water
Quality, and they have established levels of Arsenic at 0.010 milligrams per
litre (kg), based on lifetime exposure to arsenic from drinking water, which
is 1000X more stringent than the Dynamotive char, so I'm not certain that
the water flowing through this biochar would be drinkable nor whether any
veggies that might grow in the medium could be certified organic.
We are potentially planning on testing an organic rooftop garden in Toronto
using biochar and would really to know this since we were contemplating
using the char as a base medium for growing food crops and also recycling
the water running off of the rooftop garden, effectively "harvesting" the
rainwater from it for use toward the toilet flushing, maintenance water, or
even irrigation needs -- although the latter wouldn't be something we would
want to do if the runoff water were laced with Arsenic, for instance.

The question is this: Does char "lock-up" contaminants (like Arsenic and
Cadmium) that might be embedded within that carbon structure?
 And, might microbial activity help to release these contaminants (over
time)?

    Lloyd Helferty
    Thornhill, ON



-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Kurt Treutlein
Sent: June 8, 2008 1:28 AM
Cc: terra pretta group
Subject: Re: [Terrapreta] char & vascular systems

Robert Klein wrote:
>  <<snipped>>
>
>  If the temperature goes very high, we may have a less usable product.
>  I learned that coked coal is very porous but also extremely hard and 
> tough.  This returns to the problem with the use of wood charcoal.
>  The wood does not naturally breakdown into a powder which is 
> preferred for soils.

<<snipped>>

Coke is certainly very hard and tough, as I remember from my much younger
days when we fed it into a stove for room heating, but why is powdered
charcoal the preferred form for use in soil? I have the impression that
somewhere in the quarter inch lump size is considered good. ???

regards,

Kurt


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