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Questions Arising On Mercury In Compact Fluorescents
Posted by
kdawson
on Thu Mar 20, 2008 05:31 PM
from the now-they-tell-us dept.
from the now-they-tell-us dept.
Patchw0rk F0g sends in an article from MSNBC on how some environmentalists are having second thoughts on compact fluorescent bulbs. Their relative energy efficiency is unquestioned. The problem is the mercury — enough in one bulb to contaminate 1,000 gallons of water, even in newer low-mercury bulbs. The EPA has an 11-step cleanup process to follow when you break a CFL in your home. The specialized recycling facilities that are needed are thin on the ground — about one per county in California, one of seven states where it is illegal to dispose of CFLs in the general waste stream.
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Hardware: A Super-Efficient Light Bulb 468 comments
Chroniton writes with news of a Silicon Valley company, Luxim, that has developed a tiny, full-spectrum light bulb, based on a plasma of argon gas, that gives off as much light as a streetlight while using less power. The Tic Tac-sized bulb operates at temperatures up to 6000K and produces 140 lumens/watt, almost ten times as efficient as standard incandescent lamps, and twice the efficiency of high-end LEDs. The new bulbs also have a lifetime of 20,000 hours. There's no mention of mercury or other heavy metals, which pose a problem for compact fluorescents.
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LED lighting (Score:5, Insightful)
Re:LED lighting (Score:5, Insightful)
Parent
Re:LED lighting (Score:5, Insightful)
For me, I'd add in a cost justification as well. I'll do it when they reach a cost that justifies their purchase over a incandescent or CFL bulb.
LED house lights are a lot like electric cars...
They're just too expensive at the necessary light levels for a home. Flashlights, being both dimmer on average and portable w/limited power supplies are a different justification.
For the disposal thing, I'd say to allow them into recycling trash. At the very least, properly manufactured CFLs should drop the number of bulbs tossed in the trash by a factor of 10-20.
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Environmental Justification. (Score:5, Interesting)
If your electricity comes from coal, the power saved by a CFB prevents a greater amount of heavy metals (including mercury) from being dumped into the air, water and ground downwind of the coal plant. I like eating fish, how about you? This argument won me over, I hope it was not a lie designed to sell me a bunch of expensive light bulbs.
The service life of CFBs and regular bulbs makes me suspicious. CFBs do not last much longer than incandescent bulbs used to. I've had 2 of 12 burn out over a year or so despite the 5 year promise on the box. Incandescent bulbs used to be that good and halogen incandescent bulbs still last longer than CFBs. Ask yourself when the last time you changed your car headlights was.
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FRAUD ALERT -- Slashdot sucked in again! (Score:5, Interesting)
This is not the first time a Slashdot article has misled us about mercury in compact fluorescent light bulbs. See this comment from a year ago: Misleading article [slashdot.org]. Quote from the second link in that comment: "China is also the world's largest emitter of mercury..." China's coal-fired plants emit TONS of mercury, and the mercury travels everywhere.
Is someone at Slashdot paid to post these articles, to sell LED or other lights? Or is it just ignorance?
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Re:LED lighting (Score:5, Informative)
like daylight. Not blue, not yellow. It has 36 LEDs dotted around it, so it isn't in the
classic bulb form.
This is a similar one (Chinese products; could be countless copies):
http://evilidler.webofcrafts.net/S660E27-36D.jpg [webofcrafts.net]
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Re:LED lighting (Score:4, Insightful)
The price of the unit should be the simplest and most accurate answer of the three questions anyway, so I still want to know.
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Re:LED lighting (Score:5, Insightful)
On the one hand, they're Extremely bright for the electricity consumed, very good, they can come in any wavelength of color, for multicolored lights like Christmas lights, or for 'party bulbs' that with a little circuitry could produce a flashing swirl of rainbow colored light by switching various LEDS off and on... They're very small, and that means you can make any variety of decorator bulb configurations...
On the other hand, they NEVER BURN OUT. the MTBF on a LED is 300,000+ hours http://www.iddaerospace.com/design_development/faq_transition_flight_deck.htm [iddaerospace.com]
that's over 1305% longer than Compact Fluorescent Bulbs... in truth a LED can easily last 500,000 hours of use, the MTBF is just an estimate.... and forget them burning out from being switched on and off, Myth busters tried to do it, they tested every array of lighting combinations, and the LED array was happily blinking away 3 months later, when they finally pulled the plug on trying to get them to burn out from switching them on and off...
So, now what do you do? The government assumes that by 2012 LEDs will use 1/3 the watts per lumen VS Compact fluorescent bulbs... so it's not going to take environmentalists long to promote the usage of LED lighting...
So LEDS are a double edged sword for the lighting industry, on the one hand they're the best of the best for the environment, but on the other hand there is no turnover of bulbs. you'll be giving the LED bulbs to your grandkids before they have to replace them... For instance if you use a light 3 hours a day it will last statistically nearly 274 years. if like wal-mart you run the bulb 24/7/365 the bulbs will last an average of 34.2 years. 34.2 years.... yeah you might forget how to change a light bulb, once you get used to LEDs.
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Re:LED lighting (Score:5, Insightful)
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Re:LED lighting (Score:5, Informative)
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Re:LED lighting (Score:5, Informative)
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Re:LED's blink too! (Score:5, Informative)
No matter how much you whine, you cannot see that.
If you can, then your only deluding yourself that you can.
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Re:LED's blink too! (Score:5, Informative)
I'm using a homemade LED light as a desk lamp right now, and I can't see any flicker. The PWM chip controlling the voltage is running at around 300KHz, and I can dim it all the way to zero without any flickering. Even if it was running at a lower frequency, the filter capacitor is smoothing the voltage.
I used a 95 lumen Luxeon Rebel Star for the LED (but you can get up to 180 lumens with no additional power used) and a MAX774 for the PWM. The total cost was under $40, and it is at least as bright as a 15W halogen light. I took the circuit from a Maxim application note [maxim-ic.com].
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Re:LED lighting (Score:4, Interesting)
Right now I only use fluorescent bulbs in the basement and some places where everybody forgets to turn the light off - usually places where it doesn't matter what someone/something looks like. But still I have around 2000 W of light running in the evenings, even though my house isn't really a big place. I just love my old 80's halogen lamp pointing to the ceiling, thereby providing warm, indirect light in the entire room. This lamp sucks 1000 W alone. I would replace it if it wasn't for the fact that no other light source is able to fill this particular room with light in a better way (better as in more pleasing to the eye). I don't blame LED or fluorescent for not being able to provide similar light - it's simply because they work differently than halogen or normal light bulbs. But I think the manufacturers could do a lot more to make their products resemble the warmth and density of traditional electric light-sources. Heck even bulbs heating carbon wires are still available on the market - they were state of the art over hundred years ago and some people still buy them for their friendly red glow. They were replaced by carbon wires because they were easier to manufacture and way more efficient.
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Re:LED lighting (Score:5, Informative)
Also, 1000w bulbs only last about 2000 hours compared to 10,000 hours for the CFL.
Think about how much that Halogen costs you in power...
At california prices you'd be paying at minimum about
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Programmed Obsolescence (Score:4, Insightful)
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Re:Programmed Obsolescence (Score:5, Interesting)
Additionally, a lot of people are looking at LEDs like regular lights. They are not. They can be flexible, shock resistant, and sealed tight. They are ideal for putting light in places where we've never been able to put bulbs before. In floors. In counters. In sinks. In walkways. In door frames. As desk surfaces. You can make your slightly raised door sills out of a low-brightness LED so that they are visible to people going through. These aren't things you will ever want to replace. While very energy efficient, I think that large-scale LED production will significantly change how we light things, and those changes will necessitate "bulbs" that never burn out.
Of course, there will still be LED "bulbs" shaped like light bulbs, which fit into a standard socket. And I'm sure that some brilliant company will do as you say, and program in death. But the strips of "TruSun Dimmable"(tm) LEDs you have installed around the perimeter of your room when you re-do the ceiling won't have this "feature". They will be there for your grandkids to see.
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the common wisdom (Score:4, Interesting)
You could make the same argument about low-flow showerheads or toilets or plumbing fixtures in general (how long to those last).
People still remodel, new houses are built, old houses are destroyed, people break them, someone will come up with a new lighting mechanism (maybe that aluminum foil micro plasma lighting [physorg.com] will become popular), and people will go through another replacement cycle.
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Re:the common wisdom (Score:5, Informative)
Of course, they are still too expensive even with all that, so there will have to be some change in technology before they are used in mainstream lighting applications. Well, that and they look horrid.
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Re:LED lighting (Score:5, Insightful)
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Re:LED lighting (Score:5, Insightful)
MTBFs get estimated all the time. MTBFs of this size are almost always estimates.
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Lamplighters, Mantles, and the Grand Scheme (Score:5, Insightful)
Gas lights did not use an open flame for lighting (well, they did, but not for long). They used a special cloth "wick" called a mantle. This mantle glowed brightly when heated by the gas flame. Over time, the mantles would disintegrate, and new ones would have to be installed.
Now there were two once vibrant sectors of the lighting industry that have been virtually eliminated by progress. Sure, a few thousand people lost jobs. There were better, cheaper, safer alternatives, so people used them. The same thing will happen with the incandescent bulb makers, and the fluorescent bulb makers. LEDs are a better, cheaper, safer alternative. A few thousand people will be put out of work, and once vibrant sectors of the lighting industry will fade away. Sure, a few companies will hang on, doing specialty work, but count on GE, Sylvania, Philips, and their ilk closing a lot of bulb factories in the future.
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Re:LED lighting (Score:5, Insightful)
Depends on their proximity to my bedroom window.
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Re:LED lighting (Score:5, Informative)
http://www.superbrightleds.com/cgi-bin/store/commerce.cgi?product=MR16 [superbrightleds.com]
They have bulbs ranging in brightness from $8 to $50. I've seen this site before, but never tried out the bulbs. $50 seems a bit much, but I might go for one in the $20 range and see how it works in my desk lamp.
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Re:LED lighting (Score:5, Funny)
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Laser diodes == BAD (Score:5, Interesting)
> be combined into the proper color temperature.
That won't work. There is a good reason white LEDs aren't just tri-color LEDs without seperate leads. See the slashdot story from this weekend about the artist exploiting the monochromatic light of LEDs to produce interesting effects when illuminating paintings. If you mix primary colors to get yellow paint, paint something with it and shine a yellow LED on it you see black. Oops! Guess that is why white LEDs use a deep blue or UV LED with a fluorescent coating inside the package. A LASER diode would of course be an even more extremely monochromatic light source than a normal LED, plus the unexpected problems of illuminating ordinary scenes with coherent light.
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Re:LED lighting (Score:4, Informative)
When you dim the lights for a cozy mood, you are trying to emulate firelight or candlelight - not sunlight. Dimming CFLs just get dimmer and dimmer, not redder and cozier. The effect is somewhat like leaving your LCD monitor on in a dark room - not a warm candlelight.
Here's a neat site [cmu.edu] that lets you see the actual spectrum of all these things...
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Not New News (Score:5, Interesting)
This was on the BBC [bbc.co.uk] some months ago.
They were relatively reassuring about the health implications:
Something to be aware of, but not hugely worrying.
Re:Not New News (Score:4, Insightful)
Like when a heavy bag of groceries smashes an entire box of new CFL's in the backseat of the car while making a sudden stop? Good thing that can never happen...
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I'm dead (Score:5, Funny)
So I'll be dying soon, anybody want to buy a low slashdot ID?
Sheldon
Tag this post: getoffmylawn
Re:I'm dead (Score:5, Informative)
The powder in a CF "bulb" is the phosphor, which is toxic and hazardous in an entirely different way.
And, because basically the same stuff is in fluorescent bulbs and white LEDs, nobody wants to make a big deal out of it.
Oh, and injecting mercury is not that bad. Metallic mercury is not especially dangerous, especially because your body is already equipped to excrete a reasonable amount of it. Organic mercury compounds, on the other hand, are hideously unsafe and some of them are toxic in quantities as small as a spilled drop, largely because they have an easy time crossing cell walls.
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Probably the biggest mistake (Score:4, Interesting)
Migraine etc. (Score:4, Interesting)
Other home dangers! (Score:5, Insightful)
And now you tell me that mercury from my breaking-lightbulbs spree will kill my family tree? Good God!
The amount of mercury in a modern lightbulb is thousands of times less than what is found in a mercury thermometer or a thermostat. And let's not even begin to discuss the amount of mercury within traditional fluorescent bulbs and the amalgam in some fillings.
I don't get it (Score:5, Funny)
Hatchet Job (Score:4, Informative)
The article barely mentioned the real facts. The power production for regular light bulbs over the lifespan of a CFL generates 2-3x as much mercury as is in the CFL. They are just fine.
Now it is a bit of a problem right now finding a place that will recycle them. Ikea is doing it, and Walmart is thinking of rolling out recycling bins in their stores. But industry needs a lot more motivation to start taking these back. Ideally most municipal recycling programs would allow the bulbs to be placed in their bins (maybe in cardboard protectors or something. A decent article would have focused on this aspect of the story, and it was again just mentioned in passing.
Good grief (Score:5, Insightful)
Re:Good grief (Score:4, Insightful)
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Look overhead (Score:5, Interesting)
If you are in an office or school, look overhead and determine what type of lighting you have. There are a lot of places where it is fluorescent lighting in the long tube format.
Said tubes also contain mercury. But few, if any people, seem to consider these as part of the mercury contamination controversy.
If these tubes aren't a problem because they are disposed of properly, couldn't the CFLs be put into the same disposal chain?
And if the tubes ARE a problem because of improper disposal, shouldn't they also be mentioned along with the CFLs?
Re:Look overhead (Score:4, Informative)
So yes, CFLs could get into the same waste stream as for the tubes. But it costs money. The party with the burned out tubes pays for it.
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Do the math (Score:5, Informative)
Amount of mercury in 1 CFL light bulb: 5 milligrams (source: TFA)
Amount of energy saved by using a CFL bulb instead of incandescent, over the lifetime of the CFL:
10,000 hours * 75 watts * 75% energy savings = 0.6 megawatt-hours
(http://en.wikipedia.org/wiki/Compact_fluorescent_lamp#Lifespan)
Fraction of that energy that would be generated by coal-fired power plants: about 50%.
(http://www.eia.doe.gov/cneaf/electricity/epa/epat1p1.html)
Coal power plant energy savings: 0.3 megawatt-hours
Annual emission of mercury by US coal-fired power plants: 48 tons/year in 1999
(http://www.nescaum.org/documents/rpt031104mercury.pdf)
Power output of US coal-fired power plants: 1,900,000 gigawatt-hours in 1999 (about the same today)
Mercury emitted by coal plants: 48 tons / 19000000 GWh = 23 milligrams per megawatt-hour
Power-plant mercury emissions avoided by using a CFL bulb over its lifetime:
7 milligrams
So it's a wash. The amount of mercury in the bulb is roughly the same as what would be emitted by a coal-burning power plant, if you stuck with incandescent bulbs.
But the mercury in a CFL bulb is a lot easier to clean up than the stuff spewed into the atmosphere by power plants.
An introduction to mercury (Score:5, Informative)
Second, the speciation (division between different compounds) of mercury makes a huge difference in how the body absorbs it. The elemental form, found in old thermometers, switches and these CFL's, is practically biologically unavailable when liquid. There was a man in Taiwan who drank, IIRC, around a kilo without permanent effects. Oxidized mercury (HgCl2, Hg(NO3)2, and a few others) are also generally quite unavailable--several were used as syphilis medicine for quite some time--but led to a number of occupational hazards and poisonings. Mercury sulphide, on the other hand, is so unavailable that it's considered a "retirement path" in the mercury cycle. Among the variety of questionable Chinese medicine are "herbal balls," which have been found to contain up to 1.2 g (over a hundred CFL bulbs worth of mercury) of HgS. Finally, there are organic mercury compounds which are extremely toxic, but these are irrelevant except when they are produced by man in large quantities (though not necessarily on purpose) or when large amounts of inorganic mercury are available to anaerobic bacteria.
Almost all large-scale mercury poisoning has been due to the organic form entering the food supply.
However, though elemental, the form found in CFL's would most likely be vaporized if it got loose in your home. Vaporized elemental mercury is readily absorbed into the lungs, and can cross the blood-brain barrier, leading to temporary neurological effects in the few well-studied cases of household aspiration of the elemental form. Irritability and hyperactivity are typical symptoms.
Five milligrams is a good round number for the Hg content of a single CFL bulb. What is that for a person? 0.1 ppm? Well, the onset of symptoms in the victims of the Minamata disease (organic mercury poisoning) was a hair concentration of around 50 - 125 ppm (as mentioned, the margin of error on everything related to mercury is HUGE). Ca 100 ppm blood concentrations were found in the mothers of newborns in Iraq after an incident there with fungicide-laced grain in the 1970's. Again, uncertainty is the rule, and due to widely-varying affinities for heavy metals between different organs, there's very little one can predict in a given incident.
On a side note, while doing my thesis on a power plant mercury control system, I found my first grey hairs.
Re:Three questions. (Score:5, Informative)
2. Mercury in filling is amalgamated with other metals and practically stable against leaching or vaporisation. Some studies have suggested you absorb more mercury by having old fillings drilled out than by leaving them in for a lifetime.
To put the whole problem with the CFB mercury in relation, 100 Million light bulbs at 5 mg each contain a total of 500 kg of mercury.
The EPA estimate for mercury emissions from coal fired power plants is 50,000 kg a year.
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Further perspective (Score:5, Interesting)
If you eat 11oz of Yellowfin each week, you'll consume the same amount of mercury as eating 1 CF lightbulb each year, or 4oz of swordfish each week.
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That may be true but.... (Score:4, Funny)
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Re:Three questions. (Score:4, Interesting)
It cannot be made nontoxic (despite what the amalgum "alchemists" of dentistry will tell you.)
The ADA will lie to their graves about Mercury's toxicities in the body from the mouth and lungs the lungs. HCL acid, AKA "stomach acid", does a great job of dissolving swallowed Mercury fillings and their residues readily dispersing the Mercury into the bloodstream.
Definitions of harmless vary.
Mercury vapor is heavier than air, it will not just float away.
Please read the MSDS for Mercury..., any questions?: http://www.jtbaker.com/msds/englishhtml/M1599.htm [jtbaker.com]
Gallium OTOH is a much more expensive and LESS toxic alternative in some devices, but not all.
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Re:Three questions. (Score:4, Informative)
No. Elemental mercury at room temperatures is a liquid with extremely low vapor pressure, and will eventually (and slowly) evaporates. Long-term exposure (years) to high concentrations (break a CFL bulb and grind it onto the floor, every week, for a decade, in an unventilated room) mercury vapor is a bad thing. Oxides of mercury aren't really the point -- but for what it's worth, they're even less reactive than elemental mercury, and elemental mercury at room temperature isn't terribly bioreactive. You could swallow some (although I don't recommend it!), and you'd likely suffer no ill effects beyond some spectacularly shiny turds.
The scary MSDS sheet that someone else posted below speaks of mercury in its vapor form. Most metals, when heated to the boiling point, will present immediate dangers to life and health, and mercury is no exception. Because mercury boils at 365C (675F), liquid mercury is a Very Bad Thing to expose to fire.
The kind of mercury you really have to worry about is when it hooks up with organic compounds; dimethyl mercury [wikipedia.org] is a potent neurotoxin.
The reason we worry about CFLs being introduced into the waste stream is that the minute concentrations of elemental mercury can work their way into (and up) the food chain, and because interesting chemistry can happen when water leaches through waste dumps, and/or through fish.
The reason CFLs are still a Good Idea is because the burning of coal also results in mercury emissions. If a CFL consumes 8 watts for 10000 hours, and is then disposed of into the waste stream, its mercury must be added to that released by 80kWh of coal-burning. (Actually, more like 40kWh of coal-burning, assuming 50% of your power can come from nuclear, geothermal, hydroelectric, natural gas, solar, or wind.) In contrast, ten mercury-free incandescents (consuming 100W for 1000 hours each, times ten bulbs for the same 10000 hours of light) produce zero mercury waste by themselves -- but they also produce the waste associated with 1000kWh (at 50%, 500kWh) of coal-burning. Since (500-80=) 420 kWh of coal-burning introduces more than 5mg of mercury into the atmosphere, you're still doing the environment a favor by using a CFL, even if you just throw it into the garbage 10000 hours later when it finally expires.
2. Isn't there more mercury in a filling. In other words, we're breathing mercury vapors all the time - if we have fillings?
Yes and no. Yes, there is mercury in fillings. No, this mercury doesn't vaporize because it's a solid, locked up in the form of the other metals with which it's amalgamated. Elemental mercury is a liquid at room temperatures, and yet your fillings aren't liquid. The amalgam [ttp] in dental fillings is an alloy of mercury and other metals -- and much as bronze is an alloy of tin and copper, or solder is an alloy of lead and tin (or silver, bismuth, and copper for lead-free solder), the physical characteristics of alloys are, while well-known and researched, not intuitively derivable from the physical characteristics of their component metals.
> 3. Isn't it interesting that In the meantime, manufacturers of incandescent bulbs are not going down without a fight. and then GE is mentioned?
GE's lighting products make money for GE whether you use incandescents or fluorescents, or LEDs. If they can make an incandescent with the same energy usage and up-front cost of a CFL or LED, that'll be a winning product. GE's financial interest in MSNBC probably has something to do with it, but the sentence would be just as applicable to other manufacturers of lighting products.
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Even if every CFL gets smashed open and landfilled (Score:4, Informative)
Mercury (and uranium!) is present in the smokestack emissions from coal-burning powerplants. By reducing the amount of electricity used, CFLs actually reduce overall mercury emissions. And since the mercury they do contain is in a sealed glass tube (as opposed to being spewed into the atmosphere and settling out onto the ground), their toxic content is easily managed through recycling efforts.
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Re:MSNBC (Score:5, Informative)
However, here's the abbreviated facts (and I apologize I'm not going to go look up all the numbers again, but if you don't take my word for it, you can look the numbers up yourself):
A typical compact fluorescent light bulb has about 5 mg of mercury in it. All NEMA manufacturers voluntarily agreed to this a maximum. This is roughly as much as is contained in 50 cans of tuna. The FDA recommends consumers limit their intake of tuna to 1 serving per week, so that's about the same as a year's supply of tuna. So is this enough to be a health hazard? Not really.
First of all, the tuna contains the compound methylmercury, which is formed by bacterial action and bioaccumulates much more readily than elemental mercury. A greater portion of the latter passes through the body unretained. Secondly, you eat the tuna. Nobody eats a light bulb. Not to mention, the FDA recommendation is conservative, except in the case of children and pregnant women.
Generally, the lightbulbs don't get broken until disposal, and therefore completely contain the mercury, but if it does, it can safely be disposed of in the garbage. The EPA recommends that you not touch the pieces with your bare hands, so use a broom and put it in a bag. Most of that tiny amount of mercury is actually condensed on the phosphor that lines the bulb, and therefore fairly effectively immobilized, although it will slowly evaporate.
Is it an environmental hazard? Again, not really.
The EPA has calculated, based on the US's current power source mix, that the mercury contained in a CFL is more than offset by the power savings, which reduce the amount of mercury released into the atmosphere by burning coal. Additionally, don't forget that the mercury is trapped inside the bulb until broken. Even then it's at best a small concern. Most of the mercury in the environment is naturally occuring, although in specific areas industrial pollution has resulted in significantly elevated mercury levels.
Additionally, due precisely to disposal concerns, many CFL retailers have implemented recycling programs so you can drop off you dead CFL's and they will dispose of them properly. Not only that, but non-commercial users are actually allowed to dispose of fluorescent bulbs in the trash in most cities. Sound bad? The average US citizen produces about 4 pounds of landfill waste per day. Mix in half a dozen CFL's per year with the trash of an average household, and the amount of mercury ends up being about the same as natural occurs in the earth's crust.
Again, you don't have to believe me, but if you search around for the relevant information (natural abundance of mercury, trash produced per capita, USDA recommended limits on tuna intake, EPA datasheets on mercury and methylmercury, etc) you can verify everything I just wrote.
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Re:Mercury from power stations? (Score:4, Informative)
In 2005, coal-burning electric plants emitted 45 tons (=4.5E7 grams) of mercury in the US. That year the electric power production in the US was just over 4 billion Megawatt hours (4E12 kW-hr), so the emission is 1.1E-5 grams = 11 micrograms per kilowatt hour.
A 60-watt bulb that is on for typically two hours per day uses 44 kW-hours, so the emission of mercury due to such a bulb would be about 480 micrograms per year; or roughly 5 milligrams per ten years.
A 60-watt (equivalent) CF lightbulb has (by EPA standards, "no more than") 6 mg of mercury in it. If it is 4 times as efficient as an incandescent, it emits 120 micrograms per year, or 1.2 milligrams in 10 years. So the difference in mercury emissions is 3.6 milligrams in 10 years. So if the bulb lasts 17 years or longer, it would emit less mercury than the CF bulb.
The expected life of a CF bulb is between 6000 hours and 15,000 hours (between 8 and 20 years, at 2 hours per year), so overall, if you credit the lifetime figures, the mercury emission is roughly a wash.
The exact break even point depends on what fraction of the electrical power where you live comes from coal, as well, and whether the coal plants have scrubbers. (the numbers above are average for the US, where electricity is about 50% coal, in 2005)
Whether it's break-even or not over the lifetime of the bulb does not depend on how long you burn the bulb per day, except that CF bulbs last longer if you burn them longer-- so if you leave your bulbs on all the time, you get longer life from them.
(Unfortunately, I don't much credit these predicted lifetimes. The lifetime of a CF bulb drops the more often you turn it on or off, and my guess is that these lifetimes are for bulbs that are never turned off, not for typical household conditions nor for ratty NEO power. It's also quoted for "brand name" bulbs, not the cheapo ones you buy at the dollar store. If your CF bulb has an EnergyStar rating, by law it's guaranteed for two years. So you should keep a logbook of every time you replace a light bulb, so you can get your five dollars back, and you can email the EnergyStar program at cfl@energystar.gov to tell them about it.)
This reference goes through basically the same calculation. [grist.org]
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