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

[Kevin C]

Dear Peter

"Observations trump intuitive beliefs." :-)

# Assuming that it is the "alkaline ash" that drives the pH of  
biochar, then intuitively, a "gasifier char" with lower yield, and  
consequently higher residual ash content, should yield a higher pH in  
a biochar application. Equally, one could intuitively reason that with  
a pyrolysis char, containing more tars, the tars would "coat the ash  
and hid the ash activity", also giving a lower pH for chars with  
higher weight based yields.

# Your actual observations suggest different mechanisms at play. Is it  
possible that there are organic compounds produced in pyrolysis char  
making that are strongly alkaline in nature, and that they are absent  
in gasifier char that was produced at higher temperature?

Best wishes,

Kevin


Quoting Peter & Kerry Davies <realpowersystems at gmail.com>:

> 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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