An interesting view on how 'green' CFLs really are:

Yes, but probably not for at least another 5 years.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.theconsensus.org/ - A UK political party
http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff

Posted by Phil Hobbs on July 28, 2008, 8:37 am

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Jan Panteltje wrote:

> An interesting view on how 'green' CFLs really are:
> http://edition.cnn.com/2008/TECH/07/27/eco.flourescent/index.html
>
> So, LEDs?

The guy contradicts himself. He says that the mercury vapour escapes
from the garbage truck before it gets to the landfill, and then he says
it's locally dangerous, unlike power plant mercury.

Once the vapour is in the air, it's very unlikely to wind up anywhere
but the ocean. 100 million CFLs per year is something like 1000 pounds
of mercury, spread out over the Earth.

It's a nit, folks.

Cheers,

Phil Hobbs

Posted by Jan Panteltje on July 28, 2008, 8:48 am

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On a sunny day (Mon, 28 Jul 2008 08:37:44 -0400) it happened Phil Hobbs

>Jan Panteltje wrote:

>> An interesting view on how 'green' CFLs really are:
>> http://edition.cnn.com/2008/TECH/07/27/eco.flourescent/index.html
>>
>> So, LEDs?

>
>The guy contradicts himself. He says that the mercury vapour escapes
>from the garbage truck before it gets to the landfill, and then he says
>it's locally dangerous, unlike power plant mercury.

Well, garbage trucks wil ldrive a lot before they are full and go to
a landfil.

>Once the vapour is in the air, it's very unlikely to wind up anywhere
>but the ocean. 100 million CFLs per year is something like 1000 pounds
>of mercury, spread out over the Earth.

Plus 100 million little PCBs with all sorts of chemicals.

>It's a nit, folks.

I am not sure, it is an interesting viewpoint at least.

>Cheers,
>
>Phil Hobbs
>

Posted by Phil Hobbs on July 28, 2008, 10:06 am

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Jan Panteltje wrote:

> On a sunny day (Mon, 28 Jul 2008 08:37:44 -0400) it happened Phil Hobbs
>

>> Jan Panteltje wrote:

>>> An interesting view on how 'green' CFLs really are:
>>> http://edition.cnn.com/2008/TECH/07/27/eco.flourescent/index.html
>>>
>>> So, LEDs?

>> The guy contradicts himself. He says that the mercury vapour escapes
>>from the garbage truck before it gets to the landfill, and then he says
>> it's locally dangerous, unlike power plant mercury.

>
> Well, garbage trucks wil ldrive a lot before they are full and go to
> a landfil.
>
>

>> Once the vapour is in the air, it's very unlikely to wind up anywhere
>> but the ocean. 100 million CFLs per year is something like 1000 pounds
>> of mercury, spread out over the Earth.

>
> Plus 100 million little PCBs with all sorts of chemicals.
>
>

>> It's a nit, folks.

>
> I am not sure, it is an interesting viewpoint at least.

Let me lay it out a little clearer, then.

The abundance of mercury in crustal rocks is about 67 ppb
and in seawater 50 ppt. (http://www.webelements.com/mercury/geology.html)

So 500 kg of mercury is equivalent to the natural background abundance in

500 kg/(6.7x10**-8) = 7x10*12 kg of country rock

or

500 kg/(5x10^-11) = 1 x 10**16 kg of seawater.

Sounds like a lot. One cubic metre of water weighs 1000 kg, so 100
million CFLs per year is equivalent to the mercury contained in
10**16/1000 or 10**13 cubic metres, or 10**4 cubic kilometres--a cube
21.5 km on a side. Sounds like really a lot, but the ocean's volume is
about 1.3 billion cubic km. So if you dumped all that mercury into the
ocean and stirred, you'd increase the mercury content of seawater by

100%*10**4/(1.3*10^^9) or 0.0008% per year--and that's 0.0008% of a
barely-measureable 50 ppt to begin with.

For country rock, the picture is even clearer. That 7x10**12 kg of
crust has a specific gravity of about 3.5 for rock, so let's be generous
and say that soil is half rock and half organic matter. (I wish my
garden was that good, but that's another story.)

So figure 1.7*10**3 kg / m**3 of rock for topsoil. That 1000 kg Hg is
then equivalent to the quantity of naturally-occurring mercury in

7*10**12 kg / 1000 kg/m**3 or 4.4 x 10**9 cubic metres of soil, or a
square 66 km on a side by 1m deep. That's a big area, of course, but
the surface area of the USA alone is 10 million square km. So again, if
it's evenly distributed, all that mercury doesn't do squat.

So we can ignore mercury in the atmosphere, and we're left with
concentrations in certain areas.

There's no doubt that mercury pollution in Minamata Bay led to high
mercury concentrations in the food chain and consequently to a horrible
tragedy. That's data. Minamata fish had over 10 ppm (!) methyl mercury
at the time of the tragedy, but it got down to below 300 ppb by 1997,
so the Japanese government reopened the fishery.
(http://www.nimd.go.jp/archives/english/tenji/e_corner/qa5/q2.html)

And the total mercury effluent at Minamata was about 200 tons (i.e. 400
years' production of CFLs at 100 million per year), just dumped in one
little bay.
(http://www.nimd.go.jp/archives/english/tenji/e_corner/qa5/q3.html) And
that was methyl mercury, one of the most dangerous forms (due to easy
uptake by fish).

They dredged it all up and made an island out of it--a form of
containment far less effective than a clay-lined landfill. Yet 50 years
on, the fish in the bay are safe to eat--right next to that nasty
landfill with the hundreds of tons of mercury in it.

So mercury is dangerous, all right, but the actual level of risk to
anyone from CFLs is pretty small.

As I said, it's a nit.

Cheers,

Phil Hobbs

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Electronics Design An interesting view on how 'green' CFLs really are: