[Announce] Ask Umbra: Still Worth It: On mercury in CFLs

Mon Jul 16 18:14:04 MDT 2007

Grist

Ask Umbra
Still Worth It
On mercury in CFLs
By Umbra Fisk 
16 Jul 2007
questionDearest Umbra,

For the past 10 years or so I have been patiently and methodically
replacing the incandescent light bulbs in my house with the more
efficient compact fluorescent ones. Even though they cost more than
incandescents, I have been confident that their lower energy
requirements and longer life span more than made up for the increased
cost. Thus I was greatly dismayed the other day when I went to our local
transfer station and was told that I must dispose of burned out compact
fluorescent bulbs as hazardous waste. I was told that this is due to
their containing some mercury.

Have I been wrong all this time by going for the more efficient bulbs? I
will certainly dispose of my burned out bulbs in a responsible manner,
but I dare say others won't know about this problem and a lot of them
will end up in landfills. Will we thus end up with more mercury (and/or
other nasties) in the environment? Please consult your oracle and tell
me which evil is the lesser.

John
Barrington, N.H.

answerDearest John,

Why add suspense to summer's heat: The answer is no. You have not gone
wrong.

Spiraling: out of control?
Photo: armisteadbooker via Flickr
For the past five years or so I have been patiently touting compact
fluorescent light bulbs and methodically deleting most of the letters
decrying the mercury they contain. Bored with the topic and tired of
repeating myself, I consulted no oracles. Until last week, when my
Hazardous Waste Oracle and I were having a social chat and he happened
to mention a nice math problem. I will convey his oracular arithmetic
and hope it helps some of you CFL holdouts correctly allocate your
mercury worries.

Compact fluorescent bulbs are an inexpensive, simple change one can make
at the household level to reduce energy use. As home energy use is
reduced, several problems upstream are addressed. For starters,
electricity generation is lessened. Electricity in the United States is
generated from dams, coal, natural gas, oil, nuclear, wind, etc., and
most regions use a mix of all these sources. Cutting electricity use
reduces the emission of mercury, a heavy metal that is a neurotoxic
byproduct of coal-burning power plants. Mercury is integral to the
functioning of fluorescent lamps, and can either be reclaimed from said
lamps upon disposal or exude into the environment when improperly
disposed. One cost/benefit calculation in buying CFLs for your home,
therefore, is whether net mercury releases increase or decrease.

My Hazardous Waste Oracle shares the following calculation: On average,
a U.S. kilowatt-hour generates .012 milligrams of mercury. So, a 20-watt
CFL running for a (shorter than expected) lifetime of 10,000 hours would
generate 2.4 mg of mercury, while a comparable 75-watt incandescent
running for 10,000 hours (you would need more than one bulb, of course),
would generate 9.0 mg. A big difference, as you can see. Add in the 5 mg
of mercury that might reside in a CFL bulb (the high average I saw) and
you get a total of 7.4 mg -- still less than the incandescent.

The American Council for an Energy Efficient Economy, an oracle
available to all of us, tells us that CFLs keep two to 10 times as much
mercury out of the environment as they contain. ACEEE calculates 6.5 mg
mercury saved from the environment by using a CFL, with numbers even
higher in states that rely heavily on coal power. The EPA's CFL fact
sheet estimates 3.6 mg of mercury avoided during a five-year period of
bulb use.

The EPA even developed a computer model for "Mercury Emissions from the
Disposal of Fluorescent Lamps." I mention it for those of you who would
like to add all the "what if" questions, such as: what if the bulb
contains 12 mg, what if the bulb falls off the truck, what if I want to
compare divalent and particulate mercury, etc. The agency was very open
about its background data, and happy to share the model itself.

What this simple math does not address (mine, I mean, not the EPA's very
large document holdings) is the differences between mercury emissions
from power generation and bulb disposal. We can all help with the
mercury issue by doing our job at the disposal end. And do I need to
point out that mercury is only one savings when we reduce energy by
using more efficient light bulbs? No, no.

Hgly,
Umbra

Yours is to wonder why, hers is to answer (or try). Please send Umbra
any nagging question pertaining to the environment -- but first check
out her FAQs!

The claims made in this column may not reflect the views of this
magazine. Neither the magazine nor the author guarantees that any advice
contained in this column is wise or safe. Please use this column at your
own risk.

Umbra Fisk is Grist Research Associate II, Hardcover and Periodicals
Unit, floors 2B-4B. 

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