Fluorescent lamp recycling

Fluorescent lamp recycling is the recovery of the materials of a spent fluorescent lamp for the manufacture of new products. Glass tubing can be turned into new glass articles, brass and aluminium in end caps can be reused, the internal coating can be reprocessed for use in paint pigments, and the mercury contained in the lamp can be reclaimed and used in new lamps.[1] In the United States, about 620 million fluorescent lamps are discarded annually; proper recycling of a lamp prevents emission of mercury into the environment, and is required by most states for commercial facilities.[2] The primary advantage of recycling is diversion of mercury from landfill sites; the actual scrap value of the materials salvaged from a discarded lamp is insufficient to offset the cost of recycling.[3]

Mercury in lamps

The amount of mercury in a fluorescent lamp varies from 3 to 46 mg, depending on lamp size and age.[4] Newer lamps contain less mercury and the 3–4 mg versions are sold as low-mercury types. A typical 2006-era 4 ft (122 cm) T-12 fluorescent lamp (i.e., F32T12) contains about 12 milligrams of mercury.[5] In early 2007, the National Electrical Manufacturers Association in the US announced that "Under the voluntary commitment, effective April 15, 2007, participating manufacturers will cap the total mercury content in CFLs under 25 watts at 5 milligrams (mg) per unit. CFLs that use 25 to 40 watts of electricity will have total mercury content capped at 6 mg per unit."[6]

Only a few tenths of a milligram of mercury are required to maintain the vapor, but lamps must include more mercury to compensate for the part of mercury absorbed by internal parts of the lamp and no longer available to maintain the arc. Manufacturing processes have been improved to reduce the handling of liquid mercury during manufacture and improve accuracy of mercury dosing.[7]

Mercury-free discharge lamps have considerably lower production of visible light, about half; mercury remains an essential component of fluorescent lamps.[8]

A broken fluorescent tube will release its mercury content. Safe cleanup of broken fluorescent bulbs differs from cleanup of conventional broken glass or incandescent bulbs. 99% of the mercury is typically contained in the phosphor, especially on lamps that are near their end of life.[9]

Phosphors

Lamps made up to the 1940s used toxic beryllium compounds, which were implicated in the deaths of factory workers.[10][11] However, it is very unlikely that one would encounter any such lamps.[12]

Formerly, toxic materials such as beryllium, arsenic, cadmium, and thallium were used in phosphor manufacture. Modern halophosphate phosphors resemble the chemistry of tooth enamel. The rare-earth doped phosphors are not known to be harmful.[13]

Mercury containment

When discarding a fluorescent tube, the main concern is the mercury, which is an important pollutant. One way to avoid releasing mercury into the environment is to combine it with sulfur to form mercury sulfide, which is insoluble in water. One advantage of sulfur is its low cost. The reaction is shown with the equation:

Hg + S → HgS

The easiest way to combine sulfur and mercury is to cover a group of fluorescent tubes with sulfur dust and break them; when the glass is put into a bag to continue with the reaction, the mercury will combine with sulfur without any other action. The glass can be recycled where an appropriate facility exists. A quantity of 25 kg of dust sulfur is enough for 1000 tubes.

Disposal methods

The disposal of phosphor and mercury toxins from spent tubes can be an environmental hazard. Governmental regulations in many areas require special disposal of fluorescent lamps separate from general and household wastes. For large commercial or industrial users of fluorescent lights, recycling services are available in many nations, and may be required by regulation. In some areas, recycling is also available to consumers.

Spent fluorescent lamps are typically packaged prior to transport to a recycling facility in one of three ways: boxed for bulk pickup, using a prepaid lamp recycling box, or crushed for pickup. A fluorescent lamp crusher can attach directly to a disposal drum and contain dust and mercury vapor. [14] In some states, drum top crushers and self crushing lamps is not allowed. Minnesota Department of Health Drum Top Bulb Crusher Demonstration Disposal methods are regulated at both the state and federal level. Proper recycling of fluorescent lamps can reduce risk of human exposure to mercury. Companies that recycle spent fluorescent lamps include Air Cycle Corporation, Mercury Technologies of Minnesota, Inc., USA Lamp & Ballast Recycling, Inc, Waste Management, and Veolia.

References

  1. ↑ Fluorescent Lamp Stewardship Initiative, Alberta Environment, 2000, ISBN 0-7785-1730-6
  2. ↑ Release of Mercury from Broken Fluorescent Bulbs, State of New Jersey Division of Science Research and Technology, Feb. 2004, pg. 1
  3. ↑ Alberta Environment
  4. ↑ Page 183 of http://www.chem.unep.ch/MERCURY/Toolkit/UNEP-final-pilot-draft-toolkit-Dec05.pdf
  5. ↑ "Lighting Design Lab Articles - Mercury in Fluorescent Lamps".
  6. ↑ "NEMA Voluntary Commitment on Mercury in CFLs".
  7. ↑ Kane and Sell 2001 pg. 194
  8. ↑ Raymond Kane, Heinz Sell Revolution in lamps: a chronicle of 50 years of progress (2nd ed.), The Fairmont Press, Inc. 2001 ISBN 0-88173-378-4 page 192
  9. ↑ Floyd, et al. (2002), quoted on page 184 of Toolkit for identification and quantification of mercury releases (PDF)
  10. ↑ David Rosner, Gerald E. Markowitz Dying for work: workers' safety and health in twentieth-century America, Indiana University Press, 1987 ISBN 0-253-31825-4, Chapter 7
  11. ↑ http://www.nyu.edu/classes/jaeger/beryllium.htm Beryllium toxicity and fluorescent lamp manufacture, retrieved June 7, 2008
  12. ↑ General Electric Fluorescent Lamps TP 111R, Dec. 1978, says on pg. 23 that since 1949 GE lamps used relatively inert phosphates found to be safe in ordinary handling of either the intact or broken lamp.
  13. ↑ Kane and Sell 2001 page 195

External links