People often express concern when they learn that fluorescent lamps contain mercury. In areas where electricity is produced using coal, the mercury release to the environment from incandescent bulbs is almost always higher than the equivalent fluorescent, even if the fluorescent bulb is not disposed of properly and its mercury ends up in the environment.
Where I live, our electricity comes from a coal-fired power station (Sunbury) which emits about 135 kg of mercury per year and produces around 1.7 TWh of electricity per year. That's an emission rate of about 0.079 mg/kWh. Sunbury has one of the highest mercury emission rates on any power station in the U.S., there are only a few plants which are higher, one being Reliant Energy's Shawville plant in Clearfield County, PA with a staggering 0.126 mg/kWh (highest in the nation).
Let's say I have a 26-watt CFL that lasts for 4000 hours...
That would be about 6 100-watt incandescent bulb lifetimes, adding up to a grand total of 400 kWh of electricity.
The CFL would only use 104 kWh over those 4000 hours, saving 296 kWh of electricity.
So burning 4000 hours of incandescent on Sunbury electricity releases 31.6 mg of mercury into the environment.
Burning 4000 hours of CFL on Sunbury electricity releases 8.2 mg of mercury into the environment. If the bulb is broken and its mercury released then it is 14 mg (assuming 5 mg Hg in the CFL, which is about the norm).
Despite the mercury content of the CFL, it is still far below the levels of the equivalent incandescent bulb. Most coal-fired power stations in the U.S. are emitting in the range of 0.015-0.05 mg/kWh. The effect would be less profound, but in the end the CFL still wins most of the time. Disposing of them properly means there will be even less mercury emissions. There is also a fourfold SO2, NOx, and CO2 production cut when using CFLs. A fourth of the electricity, a fourth of the pollution.
