[Stoves] Clean coal burning stoves Re: History of clean Chinese stove development.

Tue Sep 15 23:11:22 CDT 2015

Crispin and stovers,
Its hard to disagree with you Crispin, for a variety of reasons:) Many of
them are because I agree. However, I don't feel that the very recent (shall
I singular example)  Mongolian experience of very excellent combustion of
processed coal used in heating stoves ....negates concerns about real world
combustion of many less processed fuels used in chimneyless cooking stoves.
  How many orders of magnitude worse (combustion) is the best mass produced
raw wood chimneyless cook stove? It may not strictly correct of criticize a
fuel for incomplete combustion but if there isn't a real world example of
excellent combustion with a given fuel used for a given purpose then I
don't have a huge problem with
being critical of fuels.
Best in class can still be a looser.
Alex

On Tue, Sep 15, 2015 at 1:35 PM, Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

> Dear Dean
>
>
>
> Thanks for that.
>
>
>
> Paul: note carefully the difference between the impact of the products of
> incomplete combustion and the inherent emissions.
>
>
>
> What has happened, and Berkeley is not exempt from this, is the
> attribution of incomplete combustion products as an inherent aspect of the
> fuel. This is incorrect and the confusion should be corrected whenever it
> arises. ‘Smoke’ is not a property of wood. Some wood stoves don’t make
> smoke, or barely any. ‘Smoke’ is unburned fuel. Burning it makes it
> ‘disappear’. We do not discuss the combustion of wood as if we have to
> forever deal with ‘smoke and what to do about it because it will always be
> there’.
>
>
>
> There are people who present smoke to be inherent in the fuel, and it is a
> misunderstanding on their part. Fine, they do not get to lead the parade.
>
>
>
> Let’s looks are what comes out of a coal fire that is related to the
> combustor and what is related to the fuel. That way we will be able to
> avoid fuels (whether coal of wood or ethanol gels etc) that contain
> something that could be emitted at a concentration that is toxic to the
> user of the stove.
>
>
>
> Here is a list of wood fuels that can be used for smoking meat. It is the
> sort of information that we want to have about coals and charcoals.
>
>
>
> http://www.smokingmeatforums.com/a/guide-for-woods-used-to-smoke-food
>
>
>
> Here is a short list of really dangerous fuels:
>
>
>
> http://23thorns.com/2013/05/31/33-the-poison-tree/
>
>
>
> Now, we do not go round listing the poisonous trees and say that because
> there are toxic trees, therefore no one in the world should burn wood. So
> why should one get away with saying that about coal, as if all coal is the
> same?  Whose interest is served by misrepresenting coal (or charcoal) like
> that? The union of wood vendors?
>
>
>
> Remember that the first occupational disease recorded is testicular cancer
> in chimney sweeps. It is caused by coal smoke, i.e. particles of incomplete
> combustion. It is not caused by any of the emissions from complete
> combustion, it is caused directly by the carcinogenic nature of what is not
> properly burned.
>
>
>
> Here are the emissions that are bad (provided by Dean citing the WHO):
>
>  • There is sufficient evidence in humans for the carcinogenicity of
> household combustion of coal. Household combustion of coal causes cancer of
> the lung.
>
> Huh? That is saying that the emissions are from *burning* the coal, not
> from a *failure* to burn the coal. Obviously the knowledgeable reader
> will understand that it is from incomplete combustion, but it is attributed
> by the WHO to ‘burning coal’ not to ‘failure to burn coal’. Here it is
> again, misleadingly and plainly stated:
>
> • There is sufficient evidence in experimental animals for the
> carcinogenicity of emissions from combustion of coal.
>
> Well, now it looks as if the authors really believe that burning coal
> creates ‘unavoidable emissions from incomplete combustion’, i.e. that the
> emissions are inherent in the coal. But then:
>
>  • There is sufficient evidence in experimental animals for the
> carcinogenicity of extracts from coal-derived soot.
>
> Not even soot, but extracts derived from coal-derived soot. Well, that is
> how toxicity is indicated. No numbers are given, but let’s assume the
> ‘exposure’ (as modelled) is equal to the toxicity rating of the soot
> extracts (as tested) and ‘exposed’. It is a model based on a model, and you
> can complain about that, but the bigger issue is that it is not based on
> either the combusted products from the fire or the analysis of the fuel.
> With Tambuti wood, there really is an issue with the combustion product. A
> regular fire doesn’t destroy the compound. I guess in theory it *could*,
> but there is a good reason to issue a warning. The same can be said about
> Jatropha oil. These are examples of molecules, note elements, and molecules
> can be destroyed, so it is different, but dangerous. Does this apply to
> coal?
>
> >It is noted that the type of coal used by households in most, if not
> all, of the epidemiological studies in this assessment, was raw
> (unprocessed)1 coal. The overall evaluation concluded that indoor emissions
> from household combustion of coal are carcinogenic to humans (Group 1).
> This evidence was assessed as being of high quality.
>
> Again, there is an inference that the combustion, not the incomplete
> combustion, is responsible for the emissions, and therefore the toxicity.
> Coal *as a fuel* is blamed for the failure of the stove to burn it
> completely. It is very clear in the above paragraph that the intention is
> to assign the stove’s performance to be an inherent property of the fuel.
> On that basis, we should not burn wood or ethanol gel or kerosene or
> gasoline or diesel or methane or biogas or natural or propane, because
> somewhere there is a useless stove failing to burn these fuels completely.
>
> A6.1.3 Toxic contaminants -
>
> Review 8 identified studies reporting on health effects of five toxic
> contaminants in coal, arsenic, fluorine, selenium, mercury and lead.
>
> Stop there for a moment. This is a clear attempt to associate the
> incomplete combustion to the inherent contents of one or more coal fuels.
> This is clearly a misdirection, and tries to embed in the reader an
> association between the performance of the stove and the elemental analysis
> of the fuel. It is quite true that coal contains arsenic, fluorine,
> selenium and mercury not to mention lead. Coal also contains uranium, zinc,
> chrome, iron, and every other trace element on earth. The question is
> whether or not they are present in the fuel in ‘toxic quantities’ and
> whether or not the ‘smoke’ is emitted in the room or outdoors, and whether
> the exposure level is from breathing in the home, outdoors, or as
> demonstrated by the case of the chimney sweep, during routine maintenance.
>
> The toxic effects of Tambuti and Euphorbias are well known – it is related
> to the exposure level. Similarly the elements listed above. What is
> misleading is to relate the elemental content of the fuel to the products
> of incomplete combustion which are complex molecules. For the vast majority
> of toxic compounds that a stove can manufacture, the five items listed are
> not significant carcinogens at ‘normal’ exposure levels, are they? They are
> associated with health issues in sufficient dosage, but the carcinogens in
> the products of incomplete combustion are far more related to the formation
> of carbonaceous or chlorine based materials. Dioxins are really
> carcinogenetic. That is a chlorine compound created by wood fires so they
> can be formed in a coal fire in conditions are right.
>
> Let’s follow their argument:
>
> >These studies provide evidence on toxin content of coals, combustion and
> emissions chemistry, exposure routes (i.e. food, air, water), air pollution
> and exposure levels, and health impacts.
>
> Well here again the ‘toxin content of coals’ is being related to the
> exposure of the householders to the smoke from not burning it. They have
> not made any direct reference to the fact that the emissions from soot are
> or are not related to the ‘toxic content’. An essential part of fear
> mongering is to confuse the reader about what should be a clear
> differentiation. Just because the people working on the WHO committee are
> not clear about the difference doesn’t mean the stove designing community
> should be.
>
> >Of the contaminants, the risks and effects of arsenic and fluorine are
> the two most comprehensively investigated and reported. Most of the
> evidence on the effects of contaminants derives from studies in China.
>
> I believe nearly all the work available in English is from Berkeley and it
> is about the terrible consequences of burning arsenic and fluorine
> contaminated coals in SW China. There are an equal number of works that
> deal with the contamination of water from the same area. Arsenic pollution
> of water in Bangladesh has received a lot of attention, the problem being
> solved by a Canadian researched who devised a simple method of removing
> it.  We cannot do that with contaminated coal unless it is being turned
> into liquid fuels (per SASOL). So such contaminated fuels should be
> avoided, like Tambuti wood.
>
> I have not seen any study of the combustion of other coals that show
> anything like the effects from the combination of water and stove emissions
> in China. Are there any? How do we separate the effect of water
> contamination from the incomplete combustion of coal?
>
> >[Dean] The assessment of evidence for health risks from toxic
> contaminants of coal was based on an overall evaluation of the available
> studies covering all of the aspects noted above.
>
> If that is the case, where is the differentiation of incomplete combustion
> (no carcinogens produced that were not already available in elemental form
> in the coal) from the inherent components? Will the authors go to the
> trouble of clearly differentiating between what is the product of the coal
> and what is the product of the stove? No. They do not. They confabulate the
> smoke with the toxic elements in the coal, and step carefully around the
> issue, creating the impression in the mind of the reader that coal ‘cannot
> be burned cleanly because it contains (at least some detectable) toxins’.
> Well, that is doing a disservice to the policy makers. Why are they doing
> that?
>
> An answer may be that they really don’t know the difference. They have
> mixed in the text the products of incomplete combustion and the elemental
> composition which any rural African cook knows is not reasonable. How is it
> they don’t know? How did they get on that committee?
>
> >[Dean] The data obtained on the content of toxic contaminants in coal,
> the fact that these are not destroyed on combustion, measurements of toxins
> in air and food (which are the main routes of exposure), and some dose
> measurements (e.g. in blood) strongly indicate that use of contaminated
> coals in the home puts members of the household at risk.
>
> Of course there is ‘risk’ but how much? It depends completely on the
> analysis of the coal (which varies hugely) and whether or not the stove has
> a chimney. Exposure to the elemental composition is not measurable by fuel
> analysis. Products of incomplete combustion are note measureable by looking
> at the fuel. You have to look at the emissions and they are produce by the
> fuel in combination with the operating behaviour, fueling behaviour, fuel
> condition and appropriateness for the combustion chamber and the stove
> itself, not only the fuel.
>
> You can imagine what the reaction would be if someone were to discover a
> new particularly poisonous tree in Papua New Guinea and then declare that
> all biomass combustion should cease because the precursor elements, carbon,
> hydrogen, oxygen and chlorine are contained in all biomass! That would be
> ridiculous.
>
> The outcome of a proper and balanced analysis of coal burning will find
> that there are some high value, excellent coals that should be used in
> preference to others. It will be shown that coals considered ‘low quality’
> are among the highest quality coals available and a premium will be paid
> for products made from them, such as pellets, powder and briquettes. The
> ‘quality’ would include the ability to be ignited easily, burn extremely
> cleanly and to produce low quantities of inherent toxins.
>
> It is then that common sense will prevail. Chasing away coal on trumped up
> charges is not going to fly in those nations that know better.
>
> Burn it clean, all of it.
>
> Crispin
>
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