Fluorescent lamp recycling is the recovery of the materials of a spent
fluorescent lamp
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet ligh ...
for the manufacture of new products.
Overview
Glass tubing can be turned into new glass articles, brass and aluminum 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. 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.
[Release of Mercury from Broken Fluorescent Bulbs](_blank)
State of New Jersey Division of Science Research and Technology, Feb. 2004, pg. 1 The primary advantage of recycling is diversion of mercury from landfill sites, but the actual scrap value of the materials salvaged from a discarded lamp is often insufficient to offset the cost of recycling.
Mercury in lamps
The amount of mercury in a fluorescent lamp varies from 3 to 46 mg, depending on lamp size and age. Newer lamps contain less mercury and the 3–4 mg versions are sold as low-mercury types. A typical 2006-era T-12 fluorescent lamp (i.e. F34T12) contains about 5
milligrams
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...
of mercury. 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."
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.
Mercury-free discharge lamps have considerably lower production of visible light, reduced to about half; thus, mercury remains an essential component of efficient fluorescent lamps.
Broken lamps
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, avoiding the use of vacuum cleaners, in favour of sticky tape to recover small particles, and ensuring that fans and air conditioning are turned off. Approximately 99% of the mercury is typically contained in the
phosphor, especially on lamps that are near their end of life.
[Floyd, et al. (2002), quoted on page 184 o]
Toolkit for identification and quantification of mercury releases
( PDF)
Phosphors
Lamps made up to the 1940s used toxic
beryllium
Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form m ...
compounds, which were implicated in the deaths of factory workers.
Today it is very unlikely that one would encounter any such lamps.
[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.'']
Other toxic elements such as
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...
,
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
, and
thallium
Thallium is a chemical element with the symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes an ...
were formerly used in phosphor manufacture. Modern
halophosphate
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet, ult ...
phosphors resemble the chemistry of
tooth enamel
Tooth enamel is one of the four major tissues that make up the tooth in humans and many other animals, including some species of fish. It makes up the normally visible part of the tooth, covering the crown. The other major tissues are dentin, ...
. The
rare-earth
The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silve ...
doped phosphors are not known to be harmful.
Mercury containment
When a modern fluorescent tube is discarded, the main concern is the mercury, which is a significant toxic pollutant. One way to avoid releasing mercury into the environment is to combine it with
sulfur to form
mercury sulfide
Mercury sulfide, or mercury(II) sulfide is a chemical compound composed of the chemical elements mercury and sulfur. It is represented by the chemical formula HgS. It is virtually insoluble in water.
Crystal structure
HgS is dimorphic with ...
, which will prevent vapor release and 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 (sometimes called "
flowers of sulfur
Flowers of sulfur (British spelling flowers of sulphur) is a very fine, bright yellow sulfur powder that is produced by sublimation and deposition. It can contain up to 30% of the amorphous allotrope of sulfur, which is the noncrystalline structu ...
") and to break the tubes; when the glass fragments are 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 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
An environmental hazard is a substance, state or event which has the potential to threaten the surrounding natural environment or adversely affect people's health, including pollution and natural disasters such as storms and earthquakes. It can i ...
. 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, by using a prepaid lamp recycling box, or crushed onsite before pickup. A fluorescent lamp crusher can attach directly to a disposal drum and isolate the dust and mercury vapor. In some states, drum-top crushers and end-user crushing of lamps are not allowe
Minnesota Department of Health Drum Top Bulb Crusher DemonstrationDisposal methods are regulated at both the state and federal level.
Proper recycling of fluorescent lamps can reduce risk of human exposure to mercury.
References
External links
NEMA paper on recycling household compact fluorescent lampsLampRecycle.orgInformation and directory from the National Electrical Manufacturers Association (NEMA)
ALMR.orgAssociation website for the Association of Lighting and Mercury Recyclers (ALMR)
Mercury-containing Light Bulb (Lamp) Recycling
Midwest Lamp RecyclingQuick tips for Light Bulb (Lamp) Recycling
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Recycling by product
Types of lamp
Electronics and the environment