How much Mercury is in Compact Fluorescent (CFL) bulbs, watch batteries, and coal-fired power plants?

In Brennn10's Compact Fluorescent Instructable there was a short discussion about the amount of mercury contained in CFL bulbs. The same topic came up in a mailing list I read, and there was some interesting analysis worth sharing.

The Stranger (the Seattle weekly) has a column called "Dear Science" where the typically quite intelligent author argued that CFL bulbs weren't all that "better" for the environment because inevitable improper disposal put more mercury-n-shit into the environment. So unless you got all your power from a mercury spewing coal plant, you shouldn't use CFL's . And Seattle, getting a majority of it's power from hydro, shouldn't use CFL's.

This was called into question for being selective analysis that encourages an attitude of "there's not currently a solution, so keep doing what you're doing", and elicited the following response:

Just so I can bore everyone with what I think is the current level of knowledge about mercury and CFLs, here's some of the current information.

NRCan did a study on how much mercury is actually in CFLs, and compares them to other typical consumer sources (e.g., watch batteries--if you throw one of them out, you've throw out five times as much mercury as in a CFL):

After reading this, I actually worked out these numbers for myself on how CFL savings compare to mercury releases a few months ago. Of course, this is all more environmental destruction brand X vs. brand Y discussion that was being talking about.

I was curious about what the numbers work out to, so I went to dig for some data; this is what I came up with.

In 1999, about 1.75 trillion kWh were generated by coal
Energy Information Administration Annual Energy Review 1999, Figure 26

In 1999, 47.8 tons/year of mercury emissions came out of coal-fired power plants.

Source: U.S. EPA, Office of Air Quality Planning and Standards.
1999 National Emissions Inventory for Hazardous Air Pollutants.

This calcs out to a figure of 0.025 mg mercury per kWh

Assuming 5 mg mercury per CFL, the equivalence point is about 200 kWh--a CFL would need to save 200 kWh before getting tossed in the trash. A quick calculation shows that this is about how much a CFL saves in half a year, if it were run 24-7: 75 W for an incandescent; 25 W for an equivalent CFL = 657 vs. 219 kWh/year, or 438 kWh/year difference.

Of course, this assumes that the coal mercury emission rate is the same as it was in 1999; I'm not sure if measures have been taken since then to reduce mercury emissions. Also, this is assuming that 100% of the power saved by the CFL would be generated by coal-fired power plants. But even with that assumption, coal is such a large fraction of the power generation (typically about half)--it would jump from six months to a year, instead. Of course, this period gets longer assuming a realistic duty cycle, but still, those numbers all seem to pencil in below typical installed lifetimes of CFLs.

Finally, there's a article from Home Energy magazine (behind a subscriber link), where somebody did a similar calculation with more current numbers, I think.

Home Energy Magazine
November/December 2007
Understanding CFLs
by Richard Benware

"Although the use of CFLs is steadily spreading, public understanding about how to dispose of them responsibly has not kept pace."

Life Cycle Benefits

In order to disprove the myths about CFLs, let's begin at the beginning. When CFLs are created, manufacturers dose the bulb with a small amount of mercury. This mercury, when electrically stimulated, releases UV light, which subsequently reacts with a phosphor coating to create visible light. Thus mercury is an essential part of every CFL; without it, the bulbs would not produce light. The typical dose of mercury is about the size of a pen tip, and these doses have been getting smaller and smaller. One reason for this is that the laws resulting from the Restriction of Hazardous Substances (RoHS) Directive have made it illegal for CFLs in Europe to contain more than 5 milligrams (mg) of mercury.

In the United States, there are no such laws limiting the amount of mercury in lightbulbs as yet, but members of the National Electrical Manufacturers Association (NEMA) have voluntarily agreed to limit the amount of mercury in the CFLs that they produce to 5 mg for bulbs of up to 25 watts and 6 mg for bulbs of 25 to 40 watts. The average CFL on store shelves today contains about 4 mg of mercury, and nearly all the CFLs in production contain less than 5 mg. The mercury used in all the CFLs produced in the United States represents 0.18% of the mercury used in all U.S. products and
industrial processes.

CFLs do not release mercury as long as they are intact. In fact, they reduce net mercury emissions in the environment by conserving energy. For every kWh of electricity used by consumers, the average power plant emits over 1.5 lb of pollutants. If a 75W incandescent is replaced by an 18W CFL, the CFL will use 456 kWh less energy than the incandescent over its 8,000 hour lifetime. The Emissions and Generation Resource Integrated Database (eGRID) contains data on the emissions of the average power plant. Using eGRID's information to calculate the average emissions per kWh, we find that this single CFL has prevented the release of 2.72 lb of sulfur dioxide, 1.05 lb of nitrogen oxide, 5.67 mg of mercury, and over 700 lb of CO2.

It is important to note that these are the reductions from the average U.S. power plant. The eGRID data show that, on average, nonbaseload emissions tend to be dirtier. And in addition to reducing emissions, CFLs save money for the consumer. The Energy Information Administration (EIA) gives a 2006 average residential electricity cost of $.1008/kWh. Using the example given above, and basing our calculation on this figure, we find that a consumer would save about $46 on energy over the lifetime of the CFL.

When these bulbs finally do reach the end of their useful life, there are several pathways they can take. In the best-case scenario, the bulbs are recycled. Recycling rates are increasing, thanks to state regulations -- California and Minnesota have banned altogether throwing CFLs in the trash -- and improved consumer awareness. In 1999, it was estimated that only 15% of all fluorescent lightbulbs were recycled. Currently, that number has increased to around 25%, with higher levels in commercial applications. Since an average of 98.9% of the mercury is successfully recovered in the recycling process, this pathway generates minimal emissions.

Even the CFLs that are discarded in the trash are unlikely to release much of their mercury. Although most of them break under current trash disposal methods, some remain unbroken, and will not release any mercury. But those that do break are not likely to release much mercury. EPA estimates that only 0.2% of the remaining mercury in a spent bulb is elemental vapor. The rest of the mercury is in the glass, the phosphor coating, and the electrodes of the bulb. Mercury absorbed in these areas is not readily released. In fact, an EPA study found that only 6.8% of the total mercury in a broken bulb will be released. Since the average bulb on the market today contains only 4 mg of mercury, it will release only about 0.27 mg, even if it breaks when it is thrown in the trash.

The only disposal option that could lead to the release of any significant amount of mercury is incineration. Today, many incinerators have advanced mercury control technologies. CFLs disposed of in such incinerators would release up to 90% of their mercury, but those emissions would then be removed by these technologies. Incinerators without these technologies are not capable of removing the mercury. But even after accounting for all of the emissions that occur via all of the routes listed above, CFLs represent a mere 0.01% of total U.S. mercury emissions annually.

It is important to note that even if CFLs released all of their mercury, the environment would still be better off than it would be if nobody used CFLs. This is true because the average power plant releases 5.67 mg of mercury to power each 75W incandescent bulb. In short, replacing incandescents with CFLs is a great way to save energy, reduce mercury emissions, and save money (see "Discounting CFLs").

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technodude9210 years ago
OK. this is my problem with just about any argument for CFL's, or "global warming". You mean to tell me that if I replace all the lights in my house with CFL's that the power plant is going to release less Hg(or CO2)? The plant is going to continue releasing the SAME amount of Hg no matter how much I draw. I'd have to be using a ridiculous amount of electricity for the plant to have to throw more coal in the burner. The only way CFL's could reduce emmissions is if the whole city used CFL's, thus drastically reducing the load, but one CFL or even a household of CFL's is not going to affect the load on the power plant, just your electric bill.
How is that a problem for you? Switching to more efficient machines benefits your bottom line and reduces your burden on the Earth. I think it's just come to be assumed as common knowledge that whenever individuals are encouraged to do their relatively small part for the good of everyone (except perhaps the few who profit from increased energy use), it won't make a difference on a global scale issue until the practice is widely adopted. Sure, one plant will probably continue to churn out as much electricity and mercury as its capacity allows. But unless you are off the grid anyway (in which case you already use the most efficient lights and appliances you can get), widespread adoption means there will be fewer power plants built and hooked into the grid in future years. If you're on a grid, your power doesn't come from one power plant, but from many different sources all at once. It's not like you're going to have a choice in a few years anyway. Unless you post an instructable on how to make your own incandescent light bulbs!
I doubt an incandescent is that hard to make... we have the technology... We just need a glass blowing instructable to tie it all up...
As a glass and light sculptor, I should support the mandating of CFL's since I could then make incandescent bulbs as "art" works which would not be banned. Could make a fortune! However, since I'm one of the few in my field that does not use mercury in their glass and light sculpture, I would feel bad about supporting all that toxic mercury getting into our environment, homes and kid's bodies.
Ah don't feel too bad the mercury would find a way anyway, it's clever and reasonably sneaky... That and you'd be able to survive the mercury poisoning...
"reduces your burden on the earth" thats my only problem. I can't understand how a houseful of CFL's will change anything. I also realize that for a whole community to adopt something new you need some people to start the move. It. I'm just not one of those people. I'm all for reducing the electric bill, but according to FPL(the electric company here)only 1% of the electricity here comes from renewable sources. So all I'll be doing is helping my wallet.
The early adopters get to decide for themselves at least. The politicians have seen which way the wind is blowing in public sentiment with the latest energy laws. In 5 years, our choice at the store will be reduced to which newer, more efficient technology to choose from - fluorescents or LEDs.
Yes but the people to start the move don't know what will and what won't work and risk spending time and money on something that can be best described as a fad. CFLs are not a fad, but what else out there is? Only time can tell.
emka10 years ago
Here’s a short critique of the bogus argument that there will be a reduction in toxic mercury into the environment with CFL’s due to the energy reduction from coal plants. (1) The old Government figures most often cited are incorrect for several reasons. The basic one is that they assume 100% of electricity in the US is from coal plants. Not true. 50% of electricity does not come from coal plants in the US and coal plants are now being mandated to reduce their mercury emissions by between 70% and 90% over the next several years. The most recent calculations from the DOE indicate that, on the average, CFL’s are worse than incandescent bulbs in terms of mercury. (2) Places like California produce little energy from coal plants, and several states produce none. So any CFL energy reductions will not cut much, if any, mercury there. (3) The 5mg of mercury generally claimed for CFL’s is largely a goal and not the current reality which is 200% to 600% higher for some major manufacturers according to suppliers of CFL’s to the State of New Jersey. (4) CFL’s are made in China with energy from mostly very dirty coal plants that emit much more mercury than US coal plants. And since China gets about 80% from coal and the US only about 50%, the comparison is even worse. It likely takes the equivalent of about 25% of the CFL’s energy savings to produce them there, plus the extra energy for the packaging and shipping compared to incandescent bulbs. That represents a lot more mercury per CFL. Oh, since fuel and power in China emit twice as much CO2 as in the US, on average, there may go up to half the CO2 savings. And since places like California are twice as clean in terms of CO2 as the rest of the US, there may be no CO2 savings realized from CFL’s in some states. (5) As much mercury is spilled into the environment in the production of CFL’s in China as goes into the CFL’s according to recent statements from industry representatives. (6) CFL’s are delivered here on ships using bunker oil, the worst mercury and CO2 producer of the fuel oils. Incandescent bulbs are still almost all made in the US. (7) There is no recycling program in place or planned that could handle the number of CFL’s proposed. Only 2% of CFL’s are recycled. And after many years, even the industrial recycling programs only handle about 25% of the mercury from fluorescent lights. (8) It is likely that if any major recycling program is set up, the CFL’s will be shipped back to China for reprocessing. Thus, when an objective and realistic lifecycle analysis is made, it is clear that a massive CFL program will put a great deal of additional toxic mercury into the environment and very likely into our kid’s bodies. And the EPA says that a sixth of them already have too much mercury in them.
Having researched and written on this topic extensively, let me discuss your points. (1)The government does not assume that 100% of energy comes from coal fired power plants. In fact, we normally take the average of all power plants in the country including nuclear, hydro, and many others that release NO mercury. However, it has found that the baseload capacity (powerplants running 24/7) comes mostly from "cleaner" energy sources like nuclear, wind, hydro, etc. Shoulder power plants tend to be coal. Thus, reducing energy consumption will be disproportionally reducing the use of coal power plants, which means the government likely underestimate the mercury released. Also, the EPA's mercury cap and trade program was just overturned in court, meaning there will be much less control of mercury release than predicted in the near future. (2)Energy conservation reduces emissions from several pollutants besides mercury. Also, while some states have very high proportions of renewables, most still import and produce at least some energy from nonrenewables. Since these are disproportionately coal, there could still be significant reductions. (3)I assume the reporting you are talking about includes industrial CFLs and regular fluorescents (which are recycled in much higher rates than the ones used in people's homes). When the government asked manufacturers for mercury data, most had a significant number of bulbs with 4 grams of mercury or less. The ones that were above 5 grams were typically not what you use in your home. (4,5,6)Most CFL manufacturers (MaxLite, TCP, etc.) are in the United States. (7)Recycling rates are higher than your estimates. Many states have also been mandating recycling/banning bulbs in the garbage. Thus, recycling rates will likely increase as more programs are adopted and improved upon in different states. Finally, I just want you to think about energy conservation in general. The U.S. needs to use demand reduction in combination with alternative energy supplies like renewables in order to solve our energy/pollution crisis.
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