Thanks Tom,
Yes I agree that more gasifier chars are being used than most people
realise, the growing use of TLUD stoves can only accelerate this, and
may yet be one of the important legacy's of the good people (many on
this list) who have developed and promoted them.
Unfortunately amongst the research community in Australia a peculiar and
unwritten bias developed where only pyrolysis chars seem to be accepted
in testing trials, I suspect in part because it is easy to make and
study such chars in a lab.
The alkalinity statement came from our experience working with Bluescope
Steel on metallurgical chars, their testing showed our gasifier chars
from both softwood & hardwood chips (pine and eucalyptus) to have a
lower alkalinity compared to pyrolysis chars from oil mallee residues
which were quite alkaline (fixed carbon <60%), so much so that the
latter could not be used alone as a reductant but had to be blended with
other carbon sources.
We have since put oil malley leaf and stems through our system and came
up with fixed carbon numbers >80% similar to our original trial results
with wood chips above, though the ash analysis would be different.
Perhaps interestingly we have noted our livestock greatly prefer
gasifier chars to chew on when given two sources to choose from, and
much preferred hardwood char to softwood, results mirrored in the
Bluescope testing on steel making suitability, they all make steel
better than coke, but hardwood gasifier chars were exceptional.
However the Bluescope work example is the only one I have PH data for,
more generally you may be right and my assumptions may not hold true
either for other types of gasifiers or feed stocks. This is one the
reasons we have been trying to get gasifier chars accepted over here in
the biochar research, to get proper independently documented comparative
information.
I was told by one research source that gasifer chars would be inferior
for agronomic use compared to pyrolysis chars because of the different
crystalline structure between them, however they were unable to point me
to any work on this, published or unpublished, that supported this
conclusion. Whereas work by Greening Australia over here using our chars
showed them to have equal or superior outcomes to baseline control and
pyrolysis char plots.
Cheers,
Peter
On 28/12/2012 7:00 AM, [email protected] wrote:
Peter,
There are probably more gasifier chars used as biochar than most people
realize. I agree that gasification chars seem to be very useful for use as
biochar. I haven't really seen enough thorough analysis of gasifier chars to
be able to generalize on their characteristics as distinct from pyrolysis
chars. I do question your statement about gasifier chars being less
alkaline than pyrolysis chars. Given the same feedstock a gasifier char will
have higher ash, higher pH, and likely higher alkalinity than a pyrolysis
char.
Tom
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