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Sunday, 05 October 2008 23:12

Toxic mercury: fluorescent or incandescent light bulbs. What's better?

Researchers from Yale University have conducted a study showing compact fluorescent lamps (CFLs) instead of incandescent bulbs produce a net global reduction of toxic mercury emissions. However, not all parts of the world should use them—instead they should stay with incandescent bulbs. Why? Find out below!

Their article “Spatial Assessment of Net Mercury Emissions from the Use of Fluorescent Bulbs” was published in the journal Environmental Science and Technology.

The authors of the EST paper are: Matthew J. Eckelman, Paul T. Anastas, and Julie B. Zimmerman, all from Yale University, New Haven, Connecticut, U.S.A.

The purpose of their research is to highlight the concern of mercury in fluorescent light, which, as they say in their abstract, “is an important technology for reducing electrical energy demand.”

Fluorescent bulbs save energy when compared to incandescent bulbs, but they also contain a small amount of mercury. Such a tiny amount of toxic mercury is not a danger to individuals who use them, but all of them, as a group, can be a serious problem to the environment if they are not recycled but, instead, just thrown away into landfills and other such waste deposal spots.

And, they may become an increasing problem because we are using larger amounts of mercury within these greater numbers of CFSs.

Incandescent bulbs do not contain mercury, but coal–fired power plants, which help to manufacture these incandescent bulbs, does emit mercury in their processes.

CFLs are found as compact fluorescent light bulbs, which are intended to replace incandescent bulbs because they can fit into existing light fixtures previously used by incandescents.

Read page two for comparisons of fluoresent and incandescent bulbs, and the conclusions of this Yale study.

According to Energy Star research (a part of the U.S. Environmental Protection Agency and the U.S. Department of Energy), a CFL can save over US$30 in electricity costs over the lifetime of the fluorescent bulb when compared to an incandescent lamp.

It also saves about 2,000 times its own weight in greenhouse gases. CFLs also use up to 75% less electricity than incandescent bulbs, and have a lifetime up to ten times longer than incandescents.
However, like all fluorescent bulbs, CFLs contain the toxic metal mercury. The average amount of mercury in a compact fluorescent bulb (CFL) is four milligrams, while the amount of mercury ranges from 1.4 to 5 milligrams.

According to Energy Star, the amount of mercury saved by using CFLs rather than incandescent bulbs is eight milligrams. This would seem to indicate that it is better to use CFLs rather than incandescents. However, this is not always the case.

The researchers used state data from all fifty states of the United States and national data from the United States and 130 other countries around the world. The data came from the year 2004.

They state within their paper, “Combustion of coal for electric power generation is generally the largest source of atmospheric mercury pollution; reduction in electricity demand from the substitution of incandescent bulbs with fluorescents leads to reduced mercury emissions during the use of the bulb.”

Their analysis, “… considers the local mix of power sources, coal quality, thermal conversion efficiencies, distribution losses, and any mercury control technologies that might be in place. Emissions of mercury from production and end-of-life treatment of the bulbs are also considered, providing a life-cycle perspective.”

Their conclusions are: “Net reductions in mercury over the entire life cycle range from −1.2 to 97 mg [milligrams] per bulb depending on the country.” Thus, they found that fluorescent bulbs reduce mercury emissions to the atmosphere in "many" but not "all" countries of the world.”

According to the study performed by these Yale researchers, whether it is better to use CFLS or incandescents depends on what type of system powers primarily your local homes and businesses.

People who live in places that use coal primarily for electricity should use CFLs because they reduce the overall mercury emissions in the environment. These CFLs do not need coal-fired power plants to manufacture them.

According to the October 1, 2008 Science News article “Fluorescent bulbs offer mercury advantage,” “For states like North Dakota, West Virginia and New Mexico — big coal burning regions — swapping out CFLs for incandescent lights should result in a net drop in local mercury releases.”

It adds, “The same is true for many countries, especially China, where electricity production relies on high-mercury coal burned in plants with few or no controls on mercury emissions.”

What was their conclusion is a person lives in a clean-burning-power-plant area? Please read page three.

However, if a person lives in a region that uses cleaner burning power plants (when compared to coal), then such persons are better off to use incandescent bulbs because in the long-run they emit less mercury into the environment.

The Science News article states, “The opposite would be true — overall mercury emissions to the environment would rise — as CFLs replace incandescent bulbs where the local power primarily comes from hydro, nuclear or other virtually mercury-free electricity sources (even some low-mercury coal). Think Alaska, California, Oregon, Idaho, Vermont, New Hampshire, Maine and Rhode Island.”

Julie Zimmerman, a co-author of the study, states, “The places known for sustainability are the places that have the potential to do the most harm by bringing this technology in.” [American Chemical Society: “Do compact fluorescent bulbs reduce mercury pollution?”]

She adds, “If we want to be truly sustainable, we can’t be dependent on materials that use toxic substances. We need to look toward safe LEDs [light-emitting diodes] or better CFLs.”

The research, the first of its kind, is not the final verdict as to whether incandescent light bulbs or compact fluorescent light bulbs are better for the environment.

However, their research does indicate that, overall, the use of compact fluorescent light bulbs will reduce mercury emissions from coal power plants and generally reduce the amount of mercury emitted into the atmosphere (and the environment, in general).

However, they do not decrease mercury emissions in all parts of the world.

The researchers also state that better technologies will build more efficient, safer CFLs with less mercury (and maybe ultimately without any toxic materials), which will eventually help to reduce the emissions of greenhouse gases into the environment by such light bulbs.

In addition, they state that the further increase of recycling of such CFLs, along with all other fluorescent bulbs, will help to reduce the amount of mercury that goes back into the environment.


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