[Gasification] [biochar] ICM gasifier project comes to a close

[Mark Ludlow]

The question I have (what have I missed?) is why the char from either
pyrolysis or gasification, from identical feedstocks, would have higher or
lower ash? I realize that feedstocks that slag on grates during gasification
could affect this, but that aside: are we claiming that a ton of chips
gasified v. a ton of chips pyrolyzed would have substantially different
effects on soil pH? Potassium hydroxide is hard to gasify; where does it go
or why is it less available? Or are we saying because gasifier char is a
smaller (%) by-product--than pyrolysis char--its ash components will be at a
lower concentration? Certainly, kg-for-kg of feedstock the  total amount of
ash will remain constant...won't it?

Mark

-----Original Message-----
From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of Peter & Kerry Davies
Sent: Thursday, December 27, 2012 4:17 PM
To: gasification at lists.bioenergylists.org
Subject: Re: [Gasification] [biochar] ICM gasifier project comes to a close

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, gasification-request at lists.bioenergylists.org 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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