The efficient destruction of CF4 - an extremely potent greenhouse gas.

[NNadir]

Carbon tetrafluoride - owing to its remarkable stability - is one of the more potent green house gases known.

The gas is a side product of the semiconductor industry and its accumulation in the atmosphere is well understood and observed, but very little is being done to address the problem.

I am very interested in the chemistry of certain kinds of salts, and I came across a paper today - something of an oldie, but a goodie - that suggests one potential way to reduce, if not eliminate the problem.

The paper is Environ. Sci. Technol. 2002, 36, 1367-1371, and was written by Lee and Choi out of the School of Environmental Science and Engineering, Pohang University of Science and Technology, Korea.

(Environ. Sci. Tech. is a publication of the American Chemical Society, the oldest scientific society in the United States.)

The authors give the back-ground as follows:

The semiconductor industry has utilized massive amount of perfluorocarbons (PFCs) such as CF4, C2F6, and C3F8 for etching silicon wafers or cleaning chambers in chemical vapor deposition processes (1). Although these gases are not toxic, they pose a serious environmental problem due to their huge global warming potentials (GWPs) (2). The Kyoto Protocol on climate change will soon require the industrialized countries to reduce the total output of heat-trapping gases (six specific gases including PFCs) by an average of 5% below 1990 levels. More than half of the total PFC gases used in semiconductor processing are discharged unreacted into the atmosphere, and they are extremely difficult to destroy due to the presence of strong C-F bonds (3, 4). In particular, CF4 represents the most recalcitrant organic gas molecule ever
made, whose atmosphere lifetime exceeds 50 000 yrs (5, 6).

The average lifetime is proportional to the half-life with a half life representing about 1.44 half-lives.

The authors expand on the problem

Currently, several methods for the decomposition of perhalogenated gases have been proposed, which include plasma (9-11), thermal (7), and catalytic (12-16) decomposition techniques. Although the plasma abatement system is effective for the destruction of many perhalocarbons, it requires costly wet scrubbing systems to remove corrosive product gases such as HF and HCl (9, 10). The thermal destruction method also requires the post-treatment systems and high temperatures over 1200 °C where NOx is formed(7).

The authors find that certain mixtures of elemental silicon and alkali metal halides, mixed with certain so called "alkaline earth" oxides, in effect destroy these pernicious compounds efficiently at relatively low temperatures, although, in fact, an energy penalty is in fact obtained.

The present study showed that alkali halides were effectively reduced to elemental alkali metals in the presence of Si as a reductant and CaO as a halide ion acceptor. Once alkali metals generated, they initiate CF4 destruction by cleaving the strong C-F bond. The PFC destruction system using these hot solid reagents has several advantages in that (1) no toxic volatile products (e.g., HF, SiF4) are generated, (2) the reagents and products are all environmentally benign, inexpensive, and safe to handle, (3) no post-treatment such as wet scrubbing of the exhaust gas is required, and (4) PFCs are destructed at relatively low temperatures. However, there are some important issues to be addressed in a practical point of view. Although the MX/CaO/Si system does not directly deal with alkali metals, the unreacted alkali metal vapors that leak out of the hot reagent bed may accumulate in the downstream...

One of the great ironies of the semiconductor industry is that during the 1970's it was hyped as a "green" industry, leading to damage - and in some cases the outright destruction - of ground water in many places, including the ground water in some areas around San Jose, California. The effects on the atmosphere have been similar, and this "green" industry now represents a huge environmental problem, particularly in China, where dangerous semi-conductor industry wastes are now dumped in huge quantities.

[WhiteTara]

1. what does this mean?

in fact, an energy penalty is in fact obtained.

[NNadir]

2. It means that you have spend energy to get environmental benefit of destroying CF4.

If you are generating this energy by burning dangerous fossil fuels, you will incur a greehouse cost by using the procedure.

[jpak]

3. US uranium enrichment plants release 200-450 tons of CFC-114 each year

*yawn*

[NNadir]

4. If you don't know what you're talking about, make stuff up.

Typically dumb anti-nukes are famous for making assumptions without citing <em>any evidence</em>.

Why not tell us that the nuclear industry releases as many tons of CFC's as say there are solar PV roofs resulting from Governor Hydrogen Hummer's brazillion solar roof plan that you were hyping here a few years back?

How about claiming that every perfluoromethane molecule in earth's atmosphere derives from nuclear power.

In fact, Giggles, I have never seen ONE indication from you that you grasp anything at all about actinide chemistry, or that you can grasp that the only sink for perfluoromethane in the atmosphere is radiolytic.

By the way, Giggles, do you have any idea how much pefluoromethane is released by a solar cell in manufacture?

Don't know?

Don't care?

Why am I not surprised?

Although the solar industry has consistently failed - even after 6 years of "world's largest solar installation" posts here to produce even ONE TENTH of an exajoule in this country - out of the more than 100 exajoules we use - its relative CF4 emissions are huge.

The matter is covered in Ind. Eng. Chem. Res. 2006, 45, 4101-4109 and Atmospheric Environment Vol. 30, No. 16, pp. 2901-2910, 1996, for instance. Since these papers involves something called "science," it is very unlikely that there is ONE dumb fundie anti-nuke who has read it.

Um, citations are something you may not have heard of. It's called a citing <em>references</em>.

Now, Giggles, you claim in your little made up scheme that uranium processing releases 450 MT of CF₄ per year. You're full of shit, but suppose you were correct. How would this compare with the other sources of this gas that you don't give a fuck about?

In fact, Giggles, the largest source of CF₄ on this planet is the aluminum industry, as a side product of the Hall process.

You know what aluminum is, don't you Giggles? That's the stuff that they would use on the frames of those brazillion solar cells on the brazillion roofs if the brazillion roofs were more than a stupid joke exercise in wishful thinking, which of course, it isn't.

From the Atmospheric Environment paper that you haven't read and don't care about, we have the following excerpts:

In the widely-used Hall-H6roult process for aluminum smelting, the oxide (A1203) is reduced electrolytically using carbon electrodes...

...The measurements of Fabian et al. (1987) in the 10-35 km region gave similar values for the mixing ratio, but showed a 12% decrease in the mixing ratio from t0 to 35 km. The atmospheric burden of CF4 as of 1984 was calculated by Fabian et al. to be (1.00 _ 0.15) × 10⁹ kg.

The measurements of the atmospheric content of CF4 can be combined with the cumulative production of aluminum up to the time of the atmospheric measurements to obtain the average amount of CF4 emitted per ton of aluminum produced. A quadratic expression for A1 production rate vs time gives a reasonable fit to the data, and by integration of this expression from 1900 to 1984 (the date at which atmospheric measurements were made) I find a cumulative
amount of 2.6 x 1011 kg.

Now, Giggles, we already know that you can't be an anti-nuke if you can compare two numbers or convert between say, tons and kg, but for those of us "in the know," a billion kilograms is a million tons.

Are you here to announce a sudden opposition to the aluminum industry, Giggles?

Um, well Giggles, if you read the literature - and you don't - in Int J Life Cycle Analysis 10 (1) 24 – 34 (2005), we have a detailed description of EcoInvent calculations on the life cycle of solar PV cells that include the following descriptions:

Solar cells are embedded in layers of ethyl-vinylacetate. The rear cover consists of a polyester, aluminum and polyvinylfluoride film. A 4 mm low-iron glass is used for the front cover. The sandwich is joined under pressure and heat. A connection box is installed and the panels receive an aluminum frame. The process data include construction material and energy consumption as well as the treatment of production wastes.

Panels are mounted on top of houses and laminates are integrated into slanted roofs and façades. The process data include the balance of plant (inverter, electric equipment, construction materials) as well as the transports to the installation site. The dismantling of the plants has been considered with the standard scenarios used in the ecoinvent 2000 project.

The bold, Giggles, is mine.

So, even if we assume that you know chemistry - which clearly you don't - and that 450 MT of CF₄ were released every year by the nuclear industry - about which you know zero - it would still be trivial, since the nuclear industry has extraordinarily high energy density.

But like I said, you don't know anything at all about actinide chemistry. You never have, and you never will.

Let's return to the Atmos. Environ. paper that you predictably know ZERO about:

Although unidentified natural sources of CF4 may exist, the input from such sources must be negligibly small compared to that from electrolytic aluminum smelting. In situ measurements of CF4 emission during this process are providing useful information about this source, but the emission rates differ so much from site to site that it will be difficult to establish the global emission rate without much additional information. The decrease in CF4 emissions from aluminum smelting within the past decade and the concurrent increase in the use of fluorocarbons by the semiconductor industry (Cook, 1995) may change the relative importance of these two sources, and should be closely monitored.

The fact is Giggles, that the abysmal failure of the solar industry to produce even one tenth of an exajoule of electricity obscures the external costs of this toy industry that exists solely for the benefit of dumb yuppies trying to absolve themselves of their consumer guilt.

Ignorance kills, Giggles. Ignorance still kills.

[jpak]

5. LOLOLOLOLOL!!!!11111

Uranium Plants Harm Ozone Layer: Kentucky, Ohio Facilities Top List of Polluters

http://www.mindfully.org/Nucs/Uranium-Harms-Ozone-Layer.htm

The uranium enrichment plant in Paducah, Ky., and its sister facility in Ohio have been by far the country's largest industrial emitters of a chemical that eats the Earth's protective ozone layer.

The emissions of the chemical coolant, which are legal, are blamed on hundreds of miles of leaky pipes at the plants operated by the United States Enrichment Corp. This year the company consolidated its enrichment operation in Paducah, making the Kentucky plant the nation's only nuclear fuel factory for commercial reactors.

The production and importation of the refrigerant CFC-114, along with many other ozone destroyers, was largely banned years ago as part of a global treaty known as the Montreal Protocol and the Clean Air Act amendments of 1990. But the chemical can still be used in industry until supplies run out.

Critics point to USEC's CFC emissions -- more than 800,000 pounds in 1999, the most recent year available -- as another example of the hidden costs of nuclear power.

<more>

http://www10.antenna.nl/wise/index.html?http://www10.antenna.nl/wise/466/4631.html

http://www.commondreams.org/views04/0817-03.htm

:rofl:

:rofl:

:rofl:

[madokie]

6. I figured as much

[Systematic Chaos]

7. So we have ourselves yet another facility which is run by

dipshit emoticon parenthetical idiots.

And since this one facility (well, one facility and a "sister facility" but they're both run by the same people) just happens to be related to nuclear energy we'll post about it here and try to equate it with demonizing the entire industry and making anything nu-ku-lur equal bad.

Apparently your dipshit emoticon parenthetical buddies are buying it, but since most of us can grok the larger picture I'd just like to present you with an amusing consolation picture:

<a href="http://failblog.org/2009/01/05/serious-text-fail/"><img class="alignnone size-full wp-image-10842" title="fail-owned-first-time-fail" src="" alt="fail owned pwned pictures" /></a><br />see more <a href="http://failblog.org">pwn and owned pictures</a>