Lighting the Way

In today's Business section, the New York Times highlighted Wal-mart's efforts to push the not-so-popular compact fluorescent light bulbs or CFLs as part of its broader initiative to get green. The bulb's advocates claim it is environmentally superior to the more familiar incandescent bulb because CFLs use a third to a quarter of the energy for the same amount of light and the bulb itself lasts up to ten times longer.

Aesthetics aside, there are tradeoffs. The main environmental strike against the energy efficient bulbs is that each one contains about five milligrams of mercury; incandescents don't contain any mercury. Mercury is a heavy metal that bioaccumulates, which means that once it gets into an animal it tends to stay there. This results in increased concentrations of mercury in animals higher in the food chain (eg. humans). Mercury can damage the nervous system and causes birth defects. For these reason, the Environmental Protection Agency (EPA) has strict regulations about mercury emissions from chemical and power plants. It is also why there has been a push for years to get mercury out of common household items like thermometers and thermostats.

So why is the mercury in compact fluorescents acceptable? The EPA claims that because the CFLs consume less energy, less electricity has to be generated to power the bulb. Less electricity means less coal is burned to produce the electricity. Less coal means less mercury is emitted from coal power plants. The result is that the amount of "mercury savings" from the power plant is greater than the mercury contained in the bulb. According to the numbers given by the EPA, it's about a 30% savings.

But an analysis of the energy efficiency to mercury tradeoff is not that simple. With the additional complexity of a CFL bulb, how much more energy is required to make them? With the increase in weight per bulb how much more energy is required for transport? How much mercury, if any, is emitted in the manufacturing of CFLs? How much mercury does coal burning emit? Even this last question is not simple to answer. It depends on factors such as the type of coal burned and how well the mercury released is captured by control devices. The type and effectiveness of the control device may depend on the age of the power plant and the federal and state environmental regulations it is subject to. Also, according to the Energy Information Administration (EIA) only about half our electric power in 2005 came from coal. It is not apparent that these considerations have been included in EPA's 30% mercury savings estimates.

Not all the mercury in CFLs will necessarily find a way directly to the environment. The EPA recommends that consumers bring expired CFLs to a recycling center for mercury recovery. But if it is taking Wal-mart, a giant in retail marketing, so much energy to get folks to simply buy the bulbs, what kind of heroic effort would be required to get folks to go to their recycling centers with the old bulbs? It is likely that some percentage of these bulbs and the mercury in them will end up in a landfill or in an incinerator, giving the mercury a potential pathway into the food chain.

This is not to say CFLs are bad, or that Wal-mart's intentions are ill placed. With the energy saved with CFLs, there is the added benefit of fewer emissions of the other pollutants generated from power plants - nitrous oxides, sulfur oxides, carbon monoxide, particulate matter, and carbon dioxide from non renewable sources, to name a few.

So what is the answer? A technical analysis, such as a life cycle assessment (LCA), can be used to compare the environmental impacts of the two bulb technologies. However, the results will be limited to the analysis' scope and will be as accurate as the data and the assumptions used to build it. Then there are social and commercial impacts that are more difficult to quantify. In their current incarnation and use, compact fluorescent bulbs are more energy efficient than their incandescent cousins, but they are not yet sustainable. Getting to sustainability, however, is an ongoing process and CFLs could be a transitional technology along the path to sustainability. For instance, Wal-mart's goal of increasing CFL sales may promote industry competition, generating even more research into energy efficient technologies. This research could lead to other types of lighting that contain less hazardous materials. With the public awareness of energy efficiency created by the promotion of CFLs, these next generation technologies could be adopted more quickly and the next step toward sustainability taken. So there is no clear and single answer, there is a path. And the next time you walk down the lighting isle at a Wal-mart store looking to replace a bulb, what you'll find is a fork in the road.

Sources:
Wikipedia Compact Fluorescent Lamp entry
EPA on mercury
EPA's Energy star on CFLs
Mercury Technology Services website