Mercury: A Light-Bulb Moment

July 1, 2008

"So, what's the big deal about mercury? When we were kids, we used to break thermometers and play with the little liquid drops of silver." I hear this comment more often than not when giving presentations on LEED, especially from folks my age and older. So, what is the big deal about mercury? With too much exposure, mercury can cause brain and kidney damage. But, if those of us who played with it seem to still have our wits about us, again, "What's the big deal?" Well, it's used in far more than thermometers these days - and we're disposing of more mercury than ever before.

Mercury is present in fluorescent light bulbs, some types of batteries, thermostats, thermometers, and switches. When these items hit the dumpster and are incinerated, the mercury vapors enter the air we breathe. Even though coal-fired electricity plants are the largest source of mercury emissions in the United States, municipal landfill incinerators also contribute to overabundance of mercury in our environment. 

Most of our lakes and streams are polluted with mercury, contaminating aquatic life and the animals that depend on fish. Mercury builds up in the environment, where concentrations increase as the mercury moves up the food chain. Birds that are predominantly fish-eating are highly affected by mercury, suffering from neurological damage and higher incidences of disease. Most states have Fish Consumption Advisories because a diet rich in mercury-tainted fish can severely damage the nervous systems of children and fetuses.

The folks at the U.S. Green Building Council (USGBC) created credits in the USGBC LEED rating system to encourage reduction in the amount of mercury going to landfills and incinerators. The less we throw away, the better off are we - and the planet, too. Thus, the LEED rating system requires the recycling of 100 percent of a building's mercury-containing lamps. 

Regulations governing the disposal of mercury-containing products vary by state. For example, in Maryland, it's illegal to dump a single fluorescent bulb in the dumpster; however, in Texas, it's okay to discard your used lamps in the dumpster unless you are dumping a large quantity.

Regardless of state and local laws, LEED requires 100-percent recycling. Recycling occurs through bulb recyclers and mercury lamp drum-top crushers also known as bulb eaters. Bulb recyclers provide a recycling certificate. Though not allowed in all states, bulb eaters are a good solution for facilities where the payback makes sense. Bulb eaters run between $3,500 and $5,000, and reduce the risk of breakage during storage, handling, and transportation of spent bulbs - not to mention the emissions resulting from the transport of the bulbs from the facility to a recycler. Important to note is that, because mercury is a regulated substance, recycling mercury reduces the liability of the property owner. 

The folks at the USGBC also designed credits to encourage us to purchase wisely and, thus, even though 100-percent recycling is required, fewer lamps will need to be recycled. The LEED for Existing Buildings: Operations & Maintenance Rating System, Materials and Resources Credits 4.1 - 4.2 cover sustainable purchasing for reduced mercury in lamps. The intent of the credit is "to establish and maintain a toxic material source reduction program to reduce the amount of mercury brought onto the building site through purchases of lamps." To earn points under this credit, the project team must develop a purchasing plan that specifies an average target picogram of mercury per lumen hour of either 90 or 70 for the project building and associated site. The latter target achieves 2 points; the former achieves 1 point. In addition, a third point for exemplary performance is available to projects that achieve 50 picograms per lumen hour or less. 

For this credit, the average picogram per lumen hour must be computed. Four variables are needed to calculate the average picogram per lumen hour for the project building and associated site:

  1. The number of light bulbs of each type.
  2. The total mercury content of the bulbs (mg).
  3. The rated life of the bulbs (hrs).
  4. The rated output per bulb (lumens).

To obtain an average picogram per lumen hour, the total weight of mercury in all the mercury-containing light bulbs is divided by the sum of the lumen-hour output of all the light bulbs. The lumen-hour output is derived by multiplying the rated hours of life by the mean light output in lumens. Therefore, picograms per lumen-hour vary directly with mercury content and inversely with life and lumen output of the bulbs. In other words, the overall picogram per lumen hour will decrease as mercury content decreases, the life of the bulb increases, or the lumen-hour output increases.

The intent is to find the best balance of lamp life, output, and mercury content for all the lamps in a building. We have to think about the life-cycle of the bulb - from its creation to its disposal. A common misunderstanding is focusing on just the mercury content of the lamp. But, if the lamp does not have a long life or produce the needed light output, we do not accomplish the goal of reducing the amount of mercury in the environment. 

Naturally, LEED does not require you to throw away your current bulbs. The key is to establish a bulb-purchasing plan for every fixture so that, when a bulb or lamp is replaced, it's specified to ensure the lowest amount of mercury per lumen hour of output for the entire building. Developing a purchasing plan that reduces the amount of mercury content entering a building is one of many steps the project will use to establish and maintain a toxic material source reduction. Less mercury purchased means less mercury entering the environment and the waste stream.

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