A Beacon for the Future

A Beacon for the Future
"We hope the reinvention of our 100-year-old waterfront home as a model of green building will educate and inspire both the building industry and the general public.” - Homeowners Dave and Anna Porter (rendering by Craig Thorpe).

Saturday, January 26, 2013

What the bottom line on mercury?

The Green Market Oracle reported this week on a new treaty signed by more than 140 nations limiting mercury emissions.  The negotiations for this treaty, which limits acceptable mercury emissions from industrial boilers and power plants, was nearly 5o years in the making.  It also sets rules on phasing out certain products that have high mercury content and mining and storage.

We have known for centuries that mercury is poisonous.  It is particularly dangerous to women and babies.  The good news is that we have come a long way in technology that would help lower or eliminate mercury emissions.  

So, you might ask, what about the push to replace incandescent light bulbs with compact fluorescent light bulbs when CFLs contain mercury?  Glad you asked...

Lighting accounts for close to 20 percent of the average home’s electric bill. ENERGY STAR qualified CFLs use up to 75 percent less energy (electricity) than incandescent light bulbs, last up to 10 times longer, cost little up front, and provide a quick return on investment.

CFLs contain a very small amount of mercury sealed within the glass tubing – an average of 4 milligrams (mg). By comparison, older thermometers contain about 500 milligrams of mercury – an amount equal to the mercury in 125 CFLs. Mercury is an essential part of CFLs; it allows the bulb to be an efficient light source. No mercury is released when the bulbs are intact (not broken) or in use.

Most makers of light bulbs have reduced mercury in their fluorescent lighting products. Thanks to technology advances and a commitment from members of the National Electrical Manufacturers Association, the average mercury content in CFLs has dropped at least 20 percent or more in the past several years. Some manufacturers have even made further reductions, dropping mercury content to 1 mg per light bulb.

EPA estimates the U.S. is responsible for the release of 103 metric tons1 of mercury emissions each year. More than half of these emissions come from coal-fired electrical power. Mercury released into the air is the main way that mercury gets into water and bio-accumulates in fish. (Eating fish contaminated with mercury is the main way for humans to be exposed.)  

Most mercury vapor inside fluorescent light bulbs becomes bound to the inside of the light bulb as it is used. EPA estimates that the rest of the mercury within a CFL – about 11 percent2 – is released into air or water when it is sent to a landfill, assuming the light bulb is broken. Therefore, if all 272 million CFLs3 sold in 2009 were sent to a landfill (versus recycled, as a worst case) – they would add 0.12 metric tons, or 0.12 percent, to U.S. mercury emissions caused by humans.

Electricity use is the main source of mercury emissions in the U.S. CFLs use less electricity than incandescent lights, meaning CFLs reduce the amount of mercury into the environment. As shown in the table below, a 13-watt, 8,000-rated-hour-life CFL (60-watt equivalent; a common light bulb type) will save 376 kWh over its lifetime, thus avoiding 4.3 mg of mercury. If the bulb goes to a landfill, overall emissions savings would drop a little, to 3.9 mg. EPA recommends that CFLs are recycled where possible, to maximize mercury savings.

Because CFLs also help to reduce greenhouse gasses, other pollutants associated with electricity production, and landfill waste (because the bulbs last longer), they are clearly the environmental winner when compared to traditional incandescent light bulbs.

(Source: EPA ENERGY STAR.  http://www.energystar.gov/ia/partners/promotions/change_light/downloads/Fact_Sheet_Mercury.pdf)