In article >,
"CSS" > wrote:

> > Here's a link that she provided me to a web page that shows a
> > graphical representation of coal structu
> >
> > http://chemistry.anl.gov/carbon/coal...roperties.html
>
>
> Frankly, I can't tell anything from that poor-quality graphic, can you?
> What are the particular PAHs that are shown in the graphic? Which ones are
> carcinogenic?
>
> My understanding is that PAHs are a generic name for any one of many
> aromatic hydrocarbons, such as naphthalene, pyrene, and others. See:
>
> http://www.ecochem.biz/PAH/pah_primer.htm

Okay, I'm going to let my wife, Giselle, respond to this one:

"As you correctly understood, polycyclic aromatic hydrocarbon (PAH) is
a generic term for any fused system of aromatic carbon rings -
aromaticity being a particular arrangement of double bonds in the
system that gives it additional stability. The number of carbon rings
(mostly 6-carbon rings) in the system can be anywhere from 2 rings
upwards. I think the graphic, from the website of the premier coal
research laboratory in the United States, Argonne National Lab, albeit
somewhat small (you can download and increase the size if you have a
graphics viewing program), does show quite clearly the large number of
fused aromatic rings in coal structure - the smaller molecules in red
being a more volatile fraction, the rest being part of a large polymer-
like macromolecular network. If you compare this structure with the
structures on the website to which you referred, the similarity is
obvious. The structure of coal is very heterogenous, and the graphic
only represents a possible combination of polycyclic aromatic units, so
one could not pick out any one in particular, claiming that it is a
carcinogenic component of all coal. Also, the toxicity of many PAHs is
not known. However, during the combustion of coal, bonds within these
units are broken as the coal reacts with oxygen, and, if the combustion
is incomplete, a large variety of smaller PAHs can also be formed, some
of them being known carcinogens.

"Charcoal does not contain PAHs. Good charcoal consists mainly of pure
carbon, the structure of which is still the subject of debate. It is
possibly amorphous, having no particular structure. Recent findings
indicate that it might consist of small curved sheets built up of 5- to
7-membered rings, not aromatic in character. If tar, a heterogenous
substance with varying composition, depending on the origin of the
charcoal, is present, it does not consist of PAHs. (The "tar" is a very
desirable product, also having medicinal applications.) It is possible
that some PAHs could form from these substances if combustion were to
take place under oxygen-poor conditions.

"Taking these facts into consideration, it seems logical to me that if
the combustion of pure charcoal is compared to the combustion of coal,
under the same conditions, as used for a BBQ, more PAHs are likely to
be emitted from the coal, as it already contains these substances,
whereas they would have to first be formed from charcoal.

Giselle Marks
Graduate Research Assistant
Dept. of Chemistry and Biochemistry
University of Southern Mississippi

> > Scroll down the page to the first graphic. (Model of Bituminous Coal)
> > See those molecules in red? Those are PAHs. Then scroll down to the next
> > graphic. (Network Model) See all the numbered ovals? Those represent
> > PAHs, also. These compounds are not typically found in sources of
> > organic carbon (wood, for instance), but - as I stated previously - they
> > are formed during the combustion of those materials. It shouldn't take
> > much of a stretch of imagination to see that burning coal produces
> > *much* more PAH than burning wood, since it is present in coal to begin
> > with, and that more of those PAHs are available to contaminate your food.
>
> I'd rather see the facts than use my imagination. Your assumption appears
> to be that because coal contains PAHs, it must emit more PAHs when it burns
> than other materials.

Yes...

> If that is indeed the case, can you explain why woodsmoke from a wood
> stove contains far more benzo[a]pyrene (BaP, a known PAH carcinogen)
> than a comparable coal fire? See:
>
> http://www.webcom.com/~bi/pah-comp-wood-coal.htm
>
> That really doesn't support your assumption, does it? In fact, it shows
> that the method of burning probably has a more significant impact on the
> amount of emitted PAH than the fuel source (fireplace versus wood stove).
> Damn- science is never simple, is it?

I think you partly answered your own question. Yes, the *method* of
burning (hence, also, the temperature) probably affects the respective
amounts of PAH. Notice that the unrestricted-air-flow, wood-burning
fireplace had the lowest overall emissions, followed by those from
coal-fired heaters. Now, being unfamiliar with coal heaters, I had to do
a search to get an idea of what this study is talking about and the
conditions under which the coal is burned. I found an interesting
article in the Mother Earth News archives, Issue # 135 -
December/January 1993 (http://tinyurl.com/ahlfl):

"...you couldn't burn coal in an airtight, oxygen-starved, and smoky
mode if you tried. Coal burns much hotter than wood, and so needs a
firebox with a heat-retaining and burnout-resistent firebrick liner.
Coal must rest on an open grate permitting a constant oxygen flow
through the bed from below, or the fire will go out. Air must also be
introduced to the top of the coal bed so combustibles in the smoke will
burn. You can't close the draft of a properly designed coal stove. You
can't improve its efficiency much either‹60 percent is about tops."

Now, to be fair, this does contradict a statement in the article you
referred to ("A wood stove or coal stove is air (oxygen) starved."), but
I wonder if the authors were very knowledgeable of the design
differences between a coal heater and an restricted-draft wood-burning
heater. In any event, coal heaters operate at hotter temps, right?
(Some, such as in a coal furnace, may even use forced-air feed to get
the temps even higher and extract the maximum BTUs.) This suggests to me
that most of the PAHs are being largely burned off, hence the low
amounts of PAH compared to restricted-draft wood-burning heaters.

Now, this brings a couple more questions to mind:

1. Do the coal particles in Kingsford burn at higher temps, or do they
burn at the lower temps of the charcoal? I don't know the answer to
that, but if the former is true, then the coal content may provide only
negligible amounts of PAH. If the latter is true , the PAH content could
be considerably higher and, therefore, more of a health risk. Until
someone proves otherwise, I'm betting on the latter instance. (...and
Giselle also thinks this may be the case.)

2. How much PAH does raw, lump charcoal produce? Again, I don't know the
answer, but (according to Giselle) it should be the lowest of all, since
most of the volatiles have been burned off, leaving mostly carbon. If we
are wrong and lump charcoal does produce significant amounts of PAH,
then stands to reason that Kingsford, with its coal and other
ingredients, would most likely produce more PAH than lump.

(BTW, for anyone else who checked that link and might have become
alarmed at the copious amounts of carcinogens emitted by those
wood-burning heaters, please note that the study in questions dates back
to *1985* - three years before the EPA imposed tighter restrictions on
such heaters in order to reduce emissions.

> The sulphur in coal varies from about 0.5 % to close to 10%. Here's an
> analysis of one particular type of charcoal:
> Fix Carbon : 80.00%
> Moisture : 12.00%
> Volatile matter: 14.50%
> Ash content : 0.25%
> Sulphur content: 0.70%
>
> This particular charcoal has more sulphur than low-sulphur coal, would you
> agree?

That depends. What is your source for these figures? (I'm certainly not
about to agree with data from an anonymous, undocumented/unreferenced
source!) And what "one particular type of charcoal" was measured? Lump?
From what kind of wood and by what manufacturing process? Briquets?
(Maybe even Kingsford? There are a lot of possible variables in
question, here.

> My point is that the research I've seen connects cancers in developing
> countries caused by coal fires to the toxic metals found in those coals.
> EPA regulations in the US prevent the burning of coals with toxic metal
> content, regulations that do not apply in developing countries. Do you have
> data that indicates these cancers are caused by PAH emitted fom the caol
> used as cooking fuel?

No, and I never claimed to have any such data. As I said before, I have
*heard* (or read) that such was the case, and I only mentioned it in
response to your idea of people "cooking over coal fires" (...as in
"grilling"?).

> >> I can look at a piece of meat and also tell that it was once a
> >> cow, but that doesn't mean it does not contain something that can
> >> make me sick.
> >
> > Sure, but can you look at a pile of ground meat and tell for sure what's
> > in it? By your own analogy, lump charcoal is a ribeye steak, and
> > Kingsford is a pile of unidentifiable "mystery meat".
>
> Now you're just being silly...

Hey, man, it was your idea!

> > Sure, I can call Royal Oak (for instance) and ask them what's in their
> > lump charcoal, and I'm pretty sure that they would answer, "Well...
> > wood! What else would it be?". I'm also sure that they would have a good
> > laugh at my expense, too!
>
> Ask them for an analysis of their product and post the result here. I'm
> sure we'd all like to know, and it's better tthan speculating about the
> quality of the product, don't you think?

Well, in case you missed it, I've already enlisted my wife to run
comparison analyses of lump charcoal and Kingsford. Hopefully, she will
be able to get to it next week. (Gotta find a couple pieces of
Kingsford, though, since I don't buy the stuff.

> > http://www.nakedwhiz.com/burntimetest/lumpcompare.htm
> >
> > Looks pretty convincing to me...
>
> Not to me. That's only one man's subjective opinion.

Subjective?? It appears to me that he is being quite objective and
methodical in his tests! What did you find lacking?

> You could also find at least another person that says lump is
> inferior to Kingsford because it burns more evenly and doesn't spark.

And others, like myself, would say that those are non-issues...

> My point is that blanket statements that certain products are
> "better" than others are always subjective, and many times are not
> based on facts.

Certainly, but to which "blanket statements" are you referring?

> >> People do know when something tastes good and when it doesn't.
> >
> > Of course, but the key word there is "taste"...something that is
> > largely subjective, personal, and unquantifiable. I'm not even
> > claiming that food cooked with lump charcoal "tastes" better than
> > food cooked with Kingsford (although I do *believe* that to be the
> > case), and I don't base my belief that lump is better than - or
> > superior to - Kingsford on my personal sense of taste. What I DO
> > KNOW, though, is really pretty simple:
> >
> > 1. Kingsford gives off a rather foul odor when it burns. Lump doesn't.
>
> You haven't started many lump fires, have you?

I've used lump charcoal exclusively for the past four years, so I have
started plenty of them! The first time I used it, I immediately noticed
that it didn't stink like Kingsford and, in fact, smelled quite pleasant.

> > 2. Kingsford contains *added* substances that are of questionable value
> > that may adversely affect the taste of food and may even be harmful to
> > your health. Lump doesn't.
>
> Oh, right, your PAH and sulphur contentions.

Yes.

> > 3. Kingsford may be cheaper, on a pound-for-pound basis, than most lump
> > charcoal, but it doesn't burn as long as most lump, which makes it less
> > economical to use in the long run.
>
> I guess, but that does that have to do with the supposed dangerous aspects
> of cooking over Kingsford?

Nothing at all. I merely mentioned it as one of the facts that I do know
about Kingsford and one of the reasons I choose to use lump.

> > 4. Kingsford produces much more ash than any of the lump charcoals
> > tested. The ash from Kingsford is also considered to be *toxic*. When
> > you buy Kingsford, consider that you are also paying for all that ash.
>
> What is your source that the ash is *toxic*?

Coal ash is toxic.

http://tinyurl.com/djytm

http://www.energyjustice.net/coal/wastecoal

Kingsford contains coal; therefore, Kingsford ash is toxic.

> > Now, we can argue this issue back and forth 'til the cows come home and
> > never convince the other that our respective stances are "right", so why
> > don't we just agree to disagree and leave it at that?
> >
>
> Agreed.

Okay, then. I'm done with it!

Stan