Web edition: October 1, 2008
Fluorescent lighting uses less energy than comparably bright incandescent bulbs do. So switching to fluorescents will shave your energy bill. The big surprise: Relying on fluorescent lights may also cut how much mercury — that toxic metallic element — is released into the environment each year.
That finding was not intuitively obvious, since fluorescent lights contain mercury and the bulbs they’re replacing do not. But new calculations by a team of
Now keep in mind that producing — and ultimately discarding — fluorescent lights will release some mercury. When fluorescents accounted for only a small fraction of indoor lighting, they also contributed only minimal amounts of mercury.
government reports and public-service ad campaigns have been touting the
“green” benefits of compact
fluorescent lights — those strangely shaped alternatives to the
conventional incandescent light bulb — a renaissance in lighting has taken
place. Within a few short years, CFLs have been sweeping the market. The Energy Department has
endorsed this, noting that every home in
conserve energy equivalent to what’s needed to light more than 3 million homes for a year
avoid more than $600 million in annual energy costs, and
prevent greenhouse-gas releases equivalent to what’s emitted by more than 800,000 cars.
But the new and growing flood of CFLs into the marketplace has raised concerns about their potential to release a similar flood of mercury into the environment. Environmental engineer Julie B. Zimmerman led her Yale team to calculate whether the extra use of mercury for the expanded production of fluorescent lighting outweighs the drop in mercury releases from the electric plants that will power them.
It wasn’t an easy tally, she notes. Not only did her group have to establish what share of a region’s electricity was produced by coal, but also how efficient that coal burning was and whether the plants used controls to trap emitted mercury. The scientists ultimately tracked down numbers for most of the
They also had to calculate what share of electric energy is saved by a CFL’s long life: If it lasts eight times longer than the incandescent bulb it replaces, the industry will need to manufacture eight times fewer light bulbs (of some type). That will translate into less energy associated with shipping the bulbs to market and ultimately disposing of them. Finally, the researchers estimated what share of mercury will likely be released following a CFL’s disposal, such as in a landfill or in breakage on the way to its designated burial site.
For states like
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
Her team has quantified — and mapped — how much of a mercury advantage or disadvantage CFLs will have on a state-by-state and country-by-country basis.
They also note that fluorescent lighting’s mercury advantage gets even better where recycling — to recapture the lamp’s mercury — is high. Such as in the
But that may change soon — especially as a federal law passed last year requires a phasing out of the sale of those energy-hogging incandescent light bulbs by 2012.
Eckelman, M.J., P.T. Anastas, and J.B. Zimmerman. 2008. Spatial Assessment of Net Mercury Emissions from the Use of Fluorescent Bulbs. Environmental Science & Technology (in press). DOI: 10.1021/es800117h