Sunday, October 10, 2010

Light Banter

My post "The end of the EZ Bake Oven" got several bits of feedback on Facebook that I would like to share here. I also would like to elaborate on some of the points made that I didn't in my original post, and correct some points that appear to be in error.

 First, the feedback. Paul notes that according to Snopes:
TRUE: CFLs contain mercury, a potentially dangerous substance.
TRUE: While mercury stays safely contained in intact CFLs, it escapes from broken CFLs into the immediate surroundings.
FALSE: The amount of mercury contained in one CFL bulb poses a grave danger to a home's inhabitants.
TRUE: The breakage of a CFL bulb needs to be handled with care and certain procedures should be followed in removing the broken bulb and its contents from a home.
FALSE: The mercury dispersed by one broken CFL bulb needs to be dealt with only by an environmental clean-up crew.
If you follow the link to Snopes you will see they recommend an elaborate 16 step cleanup process, which includes shutting off the heat or AC in the house and leaving windows open for at least 15 minutes.
I replied: I never claimed you needed to call in a hazmat team, but while the snopes statements may reflect EPA information, how many families are going to follow the 16 steps, or even know about them? Who's going to shut off their heat and leave the windows open for 15 minutes in a winter storm? The EPA guidelines for safe levels of mercury in a home are 20 micrograms/m^3. The 5 milligrams from one bulb will go far beyond that in a room.

Andy commented: good article on the subject. pretty clear that the electricity needs of the old bulbs cause much more mercury (e.g. from coal power plants into the air) to be released into the environment. good info in any case.
I replied: Sorry, Andy, it is not clear at all. In fact, the opposite is clear from the link you provide.

From the article " incandescent would still contribute 4.65 more milligrams of mercury into the environment over its lifetime." But that assumes 100% of that electricity is produced by coal (the article itself states the real number is 50% but then they assume 100% coal for their calculations). Counting the non-coal power plants, instead of comparing 13.16 with 3.51 + 5, we should compare 6.58 with 1.75 + 5.

In other words, the amount of mercury released is similar. The difference is in the CF scenario the mercury is released in landfills around the country, and in the incandescent scenario it is at a power plant, where we can employ scrubbing technology or switch to a less polluting generation technology.

Incidentally, residential lighting accounts for 212TW of the 3873TW of electricity produced in this country, so even if it did save mercury, the largest amount of mercury that could possibly be saved is 3.6% of the total produced. Improving the power plants even slightly would save much more.

I still give CFs a big FAIL.

To which Andy replied: cool. Still, have to figure in HVAC loading too. now if only the guys changing all those tubes in offices would quit tossing the big tubes in the dumpster breaking them in the process ;-)
Both Paul and Andy have some good points, but I don't think either is a good argument in favor of CFs. While the mercury in one CF bulb does not present a "grave danger" (in the sense that you will die) mercury poisoning is cumulative, and if the 16 step procedure isn't followed the residual mercury may sit in the room for may years until it is eventually absorbed.
I also noted that according to the EPA (more readable article is at the Sierra club site), US Mercury emissions from power plants must be reduced to 38 tons by the end of 2010 (25% reduction) and to 15 tons by 2018. Factoring the power plant improvements into the mercury equations above yields 4.94 for the incandescent,  1.3 + 5 or 6.3 for the CF in 2010. So the CFs actually introduce more mercury into the environment over their lifetime. By 2018 that number will be 1.98 vs. 5.53 in favor of the incandescent.

The second point Andy brings up is HVAC cooling. Every watt used by these bulbs eventually becomes heat that has to be removed if your house gets too warm. So, how does that affect things? According to Mr. Electricity a 2.5 ton AC uses 3500W of power (this is a reasonably sized central air system for a residence). 2.5 tons is 30,000 BTUs, and each watt our light bulb consumes generates 3.41 BTUs. Doing the math, each watt of heat generated by our light bulbs takes another .4 watts to remove.

Assuming we run our air conditioner 3 months of the year (yes, in the south it will be more, but in the north we may not use AC at all, and some bulbs will be outdoors or in non-air conditioned areas), I estimate each watt of lighting consumes another 0.1 watts on average. Factoring this into the above equations, we get 5.4 vs. 6.4 in favor of incandescents in 2010, 1.98 vs. 5.58 by 2018.

As I noted originally, improving power plants even slightly makes a much bigger improvement. Plus that improvement is carried across all electrical usage, not just residential lighting. All of the comparisons I was able to find use the flawed logic of the Popular Mechanics article to justify the use of CF bulbs. The fact is that these bulbs increase the amount of mercury released into the environment, even in the USA, which has more coal fired electrical production than any other nation.

Thanks to all who have responded with feedback, both here and on Facebook and Plurk. I hope these articles have been informative. They certainly were for me.


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