Remember the contaminated drywall that "must have originated" in China??

[kristopher]

http://www.huffingtonpost.com/2009/10/04/coal-ash-on-60-minutes-un_n_309268.html


Coal Ash On 60 Minutes: Lax Coal Ash Recycling Practices "An Outrage" (VIDEO)


Lesley Stahl on Sunday's 60 Minutes did an in-depth look at the problems with the by-products of coal production, commonly known as coal ash. Coal ash contains many toxic metals, including arsenic, which unchecked, can leak into ground water and be extremely hazardous to breathe. Stahl starts with a look at devastating coal ash spill that engulfed homes and destroyed whole communities in Tennessee in 2008 with a flood of a billion gallons of toxic sludge. This was the largest environmental disaster of its kind in the US. This disaster brought the issue of coal ash to the national spotlight, and Stahl moves on to how coal ash is not labeled a hazardous waste by the EPA, and is currently being used as filler in everything from golf courses to carpeting in schools to kitchen counters. Watch to the end when Stahl presses a power industry lobbyist about whether the material is being currently being handled safely and can't get a straight answer.


Read more at: http://www.huffingtonpost.com/2009/10/04/coal-ash-on-60-minutes-un_n_309268.html


The implicit assumption behind all the articles that came out was that the only possible source of potentially contaminated drywall was China - this in spite of the fact that most of the drywall was produced in the US and a large percentage of that used coal waste. While Chinese drywall was used in the affected homes, so was American drywall.

[imdjh]

1. oh my.... I guess it would be silly to wonder why there is coal waste in drywall

At least as silly as wondering why melamine powder would be anywhere near baby food.

[kristopher]

2. Not silly, no

Just an indication that the person "wondering" is totally uninformed on the topic.

The melamine powder instance is a completely inappropriate corollary since coal ash is routinely used as a legitimate source of gypsum for drywall. Melamine is NEVER a legitimate ingredient in any type of food.

[katandmoon]

3. I'm uninformed too. Why is coal ash considered a legitimate source of gypsum if it is so toxic?

[AtheistCrusader]

4. It's cheap, plentiful, and special interests have money to keep it off the hazardous waste sheets.

I think that about sums it up.


I was reading an article about how the fly ash is useful for making these wonderfully indestructible 'bricks' that might be used for things like Levees in the south.. Better than concrete. Now I'm wondering what the unforseen downside is...

[Yunomi]

5. I'm researching 'green' kitchen counter materials

and have found that several of them have fly ash as an ingredient. This is, of course, advertised as a positive thing, adding strength and durability while using what would otherwise be a waste product. I was seriously considering these counters, as they are affordable and attractive, but now I'm pretty dubious. http://www.squakmountainstone.com/

[eppur_se_muova]

6. AFAIK, the source of SrS in drywall is unclear. Could someone tell me otherwise?

I read in a CNN article that the source of the toxic, corrosive, odiferous gas hydrogen sulfide (H₂S) is strontium sulfide (SrS), which reacts with moisture in the air to form H₂S. The big question is, where does the SrS come from? It's been suggested that it was added as a phosphor, but I can't see what purpose that would serve. SrS is reportedly also added to fireworks (any Sr compound will produce a red color). Maybe the contamination occured unknowingly.

http://www.m2econsulting.com/blog/chinese-drywall/

http://www.pbchd.com/pdfs/press/2009/apr/chinese_drywall.pdf

http://www.chinesedrywall.com/

While the material source of the problem is known, the cause of the problem is unknown. Initially, the most
common theory was that the tainted drywall was manufactured in gypsum mines in China which used fly
ash, a waste material that is a byproduct from power plants using coal. Samples of Chinese drywall tested
by United Engineering, however, consisted of 5-15% organic material, which contradicts the theory that
Chinese drywall was made of waste from coal fired power plants. It is now believed that the tainted
drywall from China comes from mined gypsum, not synthetic gypsum which is made from coal ash. Mined
gypsum contains high levels of strontium, which is visible as inclusions in electron scanning microscopy.

Another theory is that Chinese drywall contains bacteria which is degrading iron and sulfur compounds to
produce sulfur odors. Drywall imported from China was kept on barges at sea for months awaiting
permission to enter the United States. While at sea, the drywall was exposed to seawater. In fact, there
are reports that the drywall was wet (and stunk) when unloaded from the ships. According to many
experts, however, if bacteria is in fact present, it is not significant enough to cause an odor.

Testing of drywall outer paper and the gypsum core has been found to release sulfur compounds. Thus,
there are potential causes aside from the drywall itself, including contaminants in the adhesive that binds
the paper to the drywall. Additionally, the drywall or outer paper may have been treated with a fungicide
after entering the United States. No one has yet to determine whether tainted drywall has been found in
China or Germany (where Knauf is based).

Most recently, some believe that Chinese drywall contains radioactive material, however, state and federal
tests so far haven't detected it.

Irrespective of the source (which is still open to debate), preliminary analytical testing of Chinese drywall
samples have revealed strontium sulfide . See Public Health Statement regarding Strontium; Statement
Regarding Health Effects. See also, EPA Drywall Sampling Analysis dated May 7, 2009).

I have my own idea about a possible source, will post later if it looks reasonable after Googling.

ON EDIT: Not a smoking gun, but China is the world's largest producer of strontium. It also turns out that the principal Sr mineral is celestine (SrSO₄), which fits with my hypothesis. http://en.wikipedia.org/wiki/Celestine Solubility decreases in the order CaSO₄> SrSO₄ > BaSO₄. Ba is found almost exclusively as the exceedingly insoluble sulfate, while calcium is more commonly found as the carbonate. One might reasonably expect, then, that Sr-rich veins of calcium minerals (such as gypsum) would also contain celestite, and that China would be more likely than any other country to find strontium in its gypsum. Now, gypsum, as mined, is calcined to convert it to "gypsum plaster", or calcium sulfate hemihydrate. http://en.wikipedia.org/wiki/Gypsum_drywall During this process, gypsum may be mixed with other components, including carbon-containing organic material, which may function as reductants. If the heat is sufficient, this may result in the reduction of sulfate to sulfide:

SrSO₄ + 2C --> SrS + 2CO₂

As it turns out this is analogous to a reaction used to recover Ba from from BaSO₄. http://en.wikipedia.org/wiki/Barium#Occurrence_and_production Quite likely, the reduction of SrSO₄is easier than that of CaSO₄, because the lattice energy is lower due to the larger Sr cation, but I haven't looked for thermodynamic data on this.

So it may very well be that there is no chicanery going on here -- Chinese mfgrs dug gypsum out of the ground, calcined it, and made it into gypsum board in the usual way. Unfortunately, the presence of natural mineral impurities resulted in an unforseen result. Of course, it may also be that some recent change in the mfgr process resulted in the formation of SrS which had not occurred before -- possible something as simple as use of higher temperatures, longer heating times, or too much organic material. No one can say at present, but it is a possible to be tested.