[Stoves] Characteristics of biochar was Re: [biochar] grassifier & cedar chip char

Tue Feb 5 20:18:58 CST 2013

We've been toying around with a thermogravimetric analysis (TGA) method
based on Harvey et al (2012) <http://www.ncbi.nlm.nih.gov/pubmed/22242866> that
indexes chars to graphite, as a kind of idealized end-member of "complete
charring."

The ASTM determination of "volatile matter" for coals really is not a good
fit for biochar. It's not really clear what you're measuring when applying
that method to biochar, as the prescribed heating (devised originally for
coal) alters the char. Some biochar researchers have realized that and
altered the method to try to make it more appropriate for char, but then
it's non-standard and you can't compare different researchers' datasets.

As Frank mentioned, the H:C, and I would also add O:C, ratios are sometimes
used as a proxy for recalcitrance. We measure those too, so if anyone is
interested I can let you know how they compare to results from the TGA
method.

We have not systematically measured S content in our chars (normally just
do C, N, H, ash, and O by difference) - I would assume it's quite low but
I'd like to hear from others. We could start collecting S content data if
folks think there's likely to be substantial S content. Thoughts?

Josh

On Tue, Feb 5, 2013 at 7:48 PM, Frank Shields <frank at compostlab.com> wrote:

> Alex,****
>
> ** **
>
> It’s the H/C ratio that has been considered. ****
>
> I like the term Fixed Carbon’ when we actually measure the carbon content
> in the left overs. ****
>
> ** **
>
> Regards****
>
> ** **
>
> Frank****
>
> ** **
>
> ** **
>
> Frank Shields****
>
> Control Laboratories, Inc.****
>
> 42 Hangar Way****
>
> Watsonville, CA  95076****
>
> (831) 724-5422 tel****
>
> (831) 724-3188 fax****
>
> www.biocharlab.com****
>
> ** **
>
> ** **
>
> ** **
>
> *From:* Alex English [mailto:english at kingston.net]
> *Sent:* Tuesday, February 05, 2013 3:36 PM
> *To:* Discussion of biomass cooking stoves
> *Cc:* Frank Shields; 'Crispin Pemberton-Pigott'; biochar at yahoogroups.com;
> 'Hugh McLaughlin'; 'Ron Larson'; 'Thomas Reed'
>
> *Subject:* Re: [Stoves] Characteristics of biochar was Re: [biochar]
> grassifier & cedar chip char****
>
> ** **
>
>
> Perhaps it should be called fixed-up carbon, its whats left after getting
> rid of the rif-raf that can['t tough it out in the kitchen when thing get
> hot.
>
> What other tests are there that would give a better representation of the
> biological recalcitrance of char?
>
> Alex
>
> On 05/02/2013 5:33 PM, Frank Shields wrote:****
>
> Paul,****
>
>  ****
>
> My biggest problem with the term ‘fixed carbon’ is that it is not a
> measurement of the carbon at all. Just the stuff left over after heating
> that can contain Oxygen and hydrogen. ****
>
>  ****
>
> Frank ****
>
>  ****
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org<stoves-bounces at lists.bioenergylists.org>]
> *On Behalf Of *Paul Anderson
> *Sent:* Tuesday, February 05, 2013 1:17 PM
> *To:* Crispin Pemberton-Pigott; Discussion of biomass cooking stoves;
> biochar at yahoogroups.com; Hugh McLaughlin; Ron Larson; Thomas Reed
> *Subject:* Re: [Stoves] Characteristics of biochar was Re: [biochar]
> grassifier & cedar chip char****
>
>  ****
>
> Crispin,
>
> The influence of the coal industry on the testing is not a perfect match
> for what biomass gasification is all about and the testing of biomass and
> biochar.
>
> Biomass can be 50% carbon, but with decay it will all go to CO2.
> Fixed carbon must be created in the carbonization process.
>
> In Atlanta airport about to fly to Uganda for 3 weeks.   I hope that
> others will comment, and not rely on me to reply.
>
> Paul
>
>
>
> ****
>
> Paul S. Anderson, PhD  aka "Dr TLUD"****
>
> Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072****
>
> Website:  www.drtlud.com****
>
> On 2/5/2013 10:09 AM, Crispin Pemberton-Pigott wrote:****
>
> Dear Paul****
>
>  ****
>
> **1.     **As far as I know, there is no "fixed carbon" in the biomass.
> It is fixed during the process of carbonization/pyrolysis.
>
>
>
> ****
>
> That is the problem – it you give a sample of wood to a lab and they
> perform a ‘coal analysis test’ on it you will get a report on the amount of
> ‘fixed carbon’. The point I was making is that it is a metric of
> convenience arising from the test procedure, not a reference to a material
> property.****
>
>  ****
>
>
> 2.  Some biomass such as seeds have "oils" that vaporize or are
> volatile.   They are generally not pyrolyzed.   However, the lignin and
> other "stuff" in biomass is what is pyrolyzed and gives off pyrolytic gases
> that are volatile.   At low temperatures, the future volatiles are not yet
> in a form that can be called volatile.   But they will volatize when
> subjected to higher temperatures.
>
> I will accept what the chemist eventually clarify for us.****
>
>  ****
>
> The % Volatiles are defined as that fraction that will boil (literally) at
> a given temperature. Choose you temperature. So when using a defined
> method, the result changes with the temperature your use.****
>
>  ****
>
> See for example http://www.sigmatest.org/Coal-Testing-India.html****
>
>  ****
>
> “*Proximate analysis - Moisture, Volatile matter, Ash and Fixed Carbon: **
> ***
>
> “Proximate analysis indicates the percentage by weight of the Fixed
> Carbon, Volatiles, Ash, and Moisture Content in coal. The amounts of fixed
> carbon and volatile combustible matter directly contribute to the heating
> value of coal. Fixed carbon acts as a main heat generator during burning.
> High volatile matter content indicates easy ignition of fuel. The ash
> content is important in the design of the furnace grate, combustion volume,
> pollution control equipment and ash handling systems of a furnace.”****
>
> This week we tried to get some tests of fuel content and were offered
> ‘coal analysis’ tests. It all sounds good but if you look into the
> procedure, you are not getting what you think – i.e. it is not an analysis
> of the elements that we are used to talking about in the biomass fuel biz.
> ****
>
>  ****
>
> Getting a lab test result of this type using an instrument designed to do
> ANSI/ASTM D3172 tests http://www.marsap.com/anamedinstru.com/coal.shtml and turning it into a ‘standard’ analysis is quite messy and I have a
> spreadsheet for doing that if you need it. It was necessary for the Asian
> Dev Bank (which built the SEET Lab) to do this because all that is
> available is standard coal analyses, but the HTP test method is more
> scientific in the sense that it uses the chemical composition of the fuel,
> not an approximation of it.  It is also necessary to get the ‘as received,
> ash-free’ heat content. Coal analysis methods gives AR (as received
> moisture), AD (after drying but not ‘actually dry’) and FC (fixed carbon,
> but not ‘actual carbon’ content). It also view some of the moisture as
> ‘inherent’.****
>
>  ****
>
> There are two things which come back ‘wrong’: the moisture content and the
> carbon content. Finding out what the carbon content of the volatiles was is
> nearly impossible. The right approach is XRD and XRF.****
>
>  ****
>
> To give you an idea of how far wrong the method is for determining Carbon,
> here is a standard test result of some coals and sawdust briquette. It is
> well known that the sawdust contains about 50% Carbon. It was rated as
> having 16% ‘fixed carbon’. In other words it is basically a useless
> measurement when it comes to biochar (or anything else).****
>
>  ****
>
> ****
>
>  ****
>
> Regards****
>
> Crispin****
>
>  ****
>
>  ****
>
>  ****
>
>  ****
>
>
>
>
> ****
>
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-- 
Josh Kearns
PhD Candidate, Environmental Engineering
University of Colorado-Boulder
Visiting Researcher, North Carolina State University

Director of Science
Aqueous Solutions
www.aqsolutions.org

Mobile: 720 989 3959
Skype: joshkearns
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