[Cob] Joe Kennedy comments on biochar in earth ovens

[Shawn King]

Hi Joseph, thanks for the feedback.  I am hoping some of these designs
will be helpful to others. I look forward to hearing more about your
project as it rolls along, and I appreciate your willingness to get
experimental with your current project.

As far as getting heat from the char making, since the biochar
canister is inside the oven, the heat from combustion of the pyrolysis
 gasses does go into heating the oven, it is not wasted.  I am certain
that there is a net heat benefit, as the amount of energy needed to
start and sustain the pyrolysis will be less than the total released
when the gasses burn.  This would be true if the canister is in any
combustion chamber.  The only loss is the volume for fuel displaced by
the canister in the oven chamber or firebox.  You can add the canister
when the fire is burning down to coals to avoid this issue.

My hope is that people who already have earthen oven or masonry
heater/mass heater can start making biochar, right away, no
alterations needed.  Twigs are poor fuel otherwise, so you get to make
use of this easy resource, and get the soil-amendment benefits of
biochar, and it is super fast and easy. Ideally, a separate chamber
would be better, I agree, and I intend to make a fired-cob mass heater
with a biochar component as part of the small cob house I am building
in Sacramento.  Much mad scientist activity in my near future, I
suspect :)


On Mon, Apr 25, 2011 at 12:03 PM, Joseph Kennedy
<livingearth62 at hotmail.com> wrote:
> Dear Shawn,
>
> I have been inspired by your low-tech stuff, and am going to integrate
> the door design into my new oven under construction with high school
> students.
>
> However, it seems a waste to make biochar unless you are using that heat to
> heat up the oven for other purposes.
>
> To me the ideal would be to make a biochar chamber below the oven (like in
> Ray Cirino's example) to create efficient heat and biochar at the same
> time.  Any ideas on this option?  I can play around with this idea, since my
> oven is still under construction.
>
> I love the mad science going on!J
>
> All the best,
>
> Joe Kennedy
>
> PS.  I just published an article of my earth oven odessey at Kiko Denzer's
> site.  It has the plans of my latest oven.
> http://www.handprintpress.com/ovens/an-earthen-oven-odyssey-by-joe-kennedy/
>
>