[Stoves] [biochar-production] Re: Stoves Digest, Vol 14, Issue 17

[Paul Olivier]

Let us suppose that the proximate analysis of a rice hull sample is:
15.80% fixed carbon
63.60% volatile matter
20.60% ash.
If we remove all volatile matter, the remainder would be:
43.41% fixed carbon
56.59% ash
Should this material not be called biochar?

Paul Olivier

On Thu, Oct 27, 2011 at 3:54 AM, Frank Shields <frank at compostlab.com> wrote:

> Dear Crispin, Tom,
>
> I think we need to define a minimum *carbon* content for a material to be
> called *biochar*. We can't call something a biochar if it has less than 1%
> carbon for example. So where do we draw the line? We need to include all
> natural biomass made into biochar like rice hulls. The material needs to
> have enough carbon to be useful. So I say 50% carbon a minimum to be
> 'excellent' biochar knowing that most all natural, clean biomass will
> produce a biochar with greater than 70% carbon. But open to other values to
> make a scale. This makes it a product with enough value for a grower to
> purchase and spread.
>
> I think the product should have the carbon content defined for quality (not
> DAF). We should not include the oxygen and hydrogen and ash. We should
> calculate the percent carbon content on the biochar sample dry weight (200
> deg C). If we base quality on percent fixed matter (C-H-O) after
> subtracting
> the ash I think there is a mistake. Because we 'make' more ash when we
> change the cations into carbonates (increasing weight) during the process.
> More cations from vegetative matter the more the problem. And this quantity
> of ash is not what we are spreading on the field. Also the carbon trapped
> in
> the ash (as CO3) is not included in the fixed carbon fraction - it should
> be
> because it comes from the organic carbon in the raw sample. These are just
> details and perhaps not that important. To do what I think is needed we
> must
> determine the carbon using a Leco CHN analyzer. More work with expensive
> equipment. But if we want to get carbon credits in the future we need to
> start off accurately measuring the potential CO2 we are fixing. When money
> is involved these details need to be addressed. Now is the time or we will
> be back here again at a later time.
>
> Just because the carbon content is 0.1% and the ash is 99.9% doesn't mean
> the product is not beneficial for an ag field. But I don't think we should
> call it biochar even if someone did add a spoonful into a soil mix. This
> rating has nothing to do with benefit to a field. That is site specific. It
> has something to do with label on the bag (or may in the future).
>
>
> Regards
> Frank
>
>
>
>
>
>
>
>
> Vegatative plant material is 10 to 20 percent. We test a lot for nutrients.
> It is very hard to get the customer to bring us a clean sample as it takes
> so very little dust and dirt to bring the ash concentration up. I think
> harvesting biomass for biofuel and one will not be careful to harvest clean
> samples.
>
> If you have 15% ash in a dry organic material. Loose 60% of the organic
> fraction during pyrolysis you have something like 20+ percent ash. And, as
> you point out, there can be biomass with much greater than 20% ash.
>
> I suggested the 50% thinking this would be high enough to include most all
> biomass that is made into biochar. Thinking we need some limit that if
> there
> is less than 50% carbon
>
>
>
>
>
>
> Frank Shields
> Control Laboratories, Inc.
> 42 Hangar Way
> Watsonville, CA  95076
> (831) 724-5422 tel
> (831) 724-3188 fax
> frank at compostlab.com
> www.compostlab.com
>
>
>
> -----Original Message-----
> From: stoves-bounces at lists.bioenergylists.org
> [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Crispin
> Pemberton-Pigott
> Sent: Wednesday, October 26, 2011 12:42 PM
> To: Discussion of biomass cooking stoves
> Subject: Re: [Stoves] [biochar-production] Re: Stoves Digest, Vol 14,Issue
> 17
>
> Dear Frank
>
> Apart from the special case of rice hull, how could you get a 50% ash level
> in char?  Trees are about 0.5% ash. There is not much left of the fuel if
> the char is 1% of the initial mass.
>
> Regards
> Crispin
>
> Frank,
>
> I see the ash/carbon content as a sliding scale with relative changing
> benefits rather than a threshold level. If biochar has less carbon than ash
> is there still an agronomic benefit?
>
> It is not clear how the IBI guidelines will be used. The guidelines should
> list those components that should be measured. The recommended levels of
> those components for different purposes could be separate recommendations
> from IBI to a certification agency.
>
> If the purpose is stability and carbon sequestration why limit counting
> recalcitrant carbon even if it is 0.1% carbon or, 99.9% ash?
>
> Tom
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-- 
Paul A. Olivier PhD
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Dalat
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