[Terrapreta] producing biochar on the farm

[Robert Klein]

I will be posting this on my site on agriculture and
global warming.

http://globalwarming-arclein.blogspot.com/



Let us return to the concept of the modified shipping
container.  The original intent for this design
concept was to deliver low impact incineration to a
small municipality. This is achieved by the use of a
two step burn.  The first burn inside of the fire
brick lined shipping container is held to just under
600 degrees by controlling the oxygen supply.

The flue gas, containing volatiles and other nasties
is then vented into a separate much smaller chamber. 
Fresh air is injected, immediately jumping the
temperature to 2000 degrees.  This technique bypasses
the production of intermediary combustion products
that will be an emission problem.  The high
temperature flue gas can then be sent back into the
first chamber as needed to increase the heat of its
contents.

The system was extremely successful in largely
eliminating emission problems surrounding the hospital
waste that had driven the original development of this
system.

This same system, built around a steel shipping
container and perhaps a little simplification, can be
used to produce a range of low temperature carbon
based products ranging from biochar to possibly fully
activated charcoal.  The sizing is also right for
agricultural use and the implied capital cost should
come in at under $50,000 with any level of volume
production.  I anticipate that a manufacturer will
simply supply the second chamber and the control
system, while the buyer will acquire and line a
shipping container.  This will reduce costs even
further and avoid shipping damage with the firebricks.
 A warning though, the second chamber, though
comparatively small, must withstand very high
temperatures and other stresses.  The high performance
and engineered municipal model of the secondary high
temperature burner was costing out at a lot over
$100,000 since it was cylindrical in shape and the
bricks were over twice as thick.

This system can be readily varied under operation in
order to achieve the best possible yield of product
including the option of not burning anything in the
main chamber at all.

A typical charge of biomass will likely be less than
ten tons for anything except wood for a twenty foot
container.  Something like straw could even be blown
in.

As we have posted earlier, the one crop that can
produce the most biomass per acre is corn.  Corn will
make ten plus tons of stover, while any grain crop
will make at best one plus tons per acre.  There is an
order of magnitude difference.  That also rather
obviously implies an order of magnitude difference in
haulage costs.

A farm producing enough corn stover to operate the
carbonizer for say 40 days is not likely to have
produced other types of waste that would need more
than several days of additional operation.  This means
that the facility will be operated in the fall for a
little over a month just after harvest.  The produced
carbon can be readily stored in preparation for been
rebroadcast in combination with fertilizer onto the
field originally cropped.

Our output is at least a ton of carbon for each acre
of corn grown.  We can then anticipate that the farm
will be able to add a ton of carbon each year to every
acre used for corn production.  The increased
fertility and the improved soil quality will also lead
to an increase in corn production accelerating the
process.

This new system now calls for a multi year field test
aimed at defining costs and operating parameters and
should be done soonest under an agricultural extension
program.  The visible payoff should come in the form
of both sharply increased yields and a reduction in
chemical inputs.  In other words, the economic model
is no different than the old traditional manure cycle
of a mixed farm.  It promises to just be a much better
way.



       
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