Composition of Waste Electrical and Electronic Equipment (WEEE) /E-waste is very diverse and differs in products across different categories. It contains more than 1000 different substances, which fall under “hazardous” and “non-hazardous” categories. Broadly, it consists of ferrous and non-ferrous metals, plastics, glass, wood & plywood, printed circuit boards, concrete and ceramics, rubber and other items.

Iron and steel constitutes about 50% of the WEEE followed by plastics (21%), non ferrous metals (13%) and other constituents. Non-ferrous metals consist of metals like copper, aluminium and precious metals ex. silver, gold, platinum, palladium etc. The presence of elements like lead, mercury, arsenic, cadmium, selenium, and hexavalent chromium and flame retardants beyond threshold quantities in WEEE / E-waste classifies them as hazardous waste. The possible substances of concern, which may be found in selected E-waste item are given as follows:

Table 1: Possible Hazardous Substances in Components

The substances within the above mentioned components, which cause most concern are the heavy metals such as lead, mercury, cadmium and chromium (VI), halogenated substances (e.g. CFCs), polychlorinated biphenyls, plastics and circuit boards that contain brominated flame retardants (BFRs). BFR can give rise to dioxins and furans during incineration. Other materials and substances that can be present are arsenic, asbestos, nickel and copper. These substances may act as a catalyst to increase the formation of dioxins during incineration. The description about some of these substances where uncertainty exists regarding their “level of concern” based on literature review are given below.

Plastics containing Brominated Flame Retardants (BFRs)

Two families of BFRs have been used in EEE. The first is polybrominated diphenyl ethers (PBDPEs), which includes DBPE (decabromodiphenyl oxide), and PBPE (pentabromodiphenyl oxide). In the electronics industry, BDPE is the dominant PBDPE BFR and is used primarily in computer housings. The second family of BFRs is the phenolics, which includes TBBPA (tetrabromo-bisphenol A). TBBPA (also referred to as TBBA) is used primarily in printed circuit boards.

Insulation

Materials of concern in these components are ODS in insulation foams, asbestos and refractory ceramic fiber.

Asbestos

Asbestos has been used in older appliances such as coffee pots, toasters and irons. Asbestos was also a component of some heaters and other item that benefit from the heat resistant properties o f the material. Modern appliances do not contain asbestos. However, if a heating appliance is very old (ex. pre 1985), the chances of finding asbestos are high.

Refractory Ceramic Fibers (RCFs)

Respirable RCFs are classified as category 2 carcinogens, which takes into account observation from recent studies involving laboratory animals that suggest these fibers may have potential to cause lung cancer or mesothelioma in humans. This classification, which became effective in January 1999, does not represent a ban on use. However it does mean that any work with RCF is subject to stringent controls.

Liquid Crystal Display (LCDs)

LCD consist of liquid crystals, which are embedded between thin layers of glass and electrical elements. A cellular phone display can contain about 0.5 mg of liquid crystals, a notebook display about half a gram. The LCD, first used predominately in notebook and laptop computers, is now moving into the desktop computer market. Most LCDs have a lamp. For small LCDs, the main consideration for the dismantler will be whether or not there is a lamp present. Liquid crystals come under suspicion of being a health hazard. About 50,000 liquid crystal substances are known, but only about 500 are key components for LCD technology. Examples are MBBA (4-methoxybenzylidene-4-butylaniline) and 5CB (4-penty1-4-cyanobipheny1). Currently there appear to be no toxicological tests results on liquid crystal materials.

Components containing Plasticisers/Stabilisers

The concerns here include the use of phthalate plasticizers and lead stabillisers in plastics and rubbers. For example, dibutyl phthalate and diethylhexyl phthalate are considered “Toxic for Reproduction” at concentrations >=0.5%.

Circuit Boards

While most boards are typically 70% non-metallic, they also contain about 16% copper, 4% solder and 2% nickel along with iron, silver, gold, palladium and tantalum. Approximately 90% of the intrinsic value of most scarp boards is in the gold and palladium content. Consequently, traditional reprocessing of circuit boards has concentrated on the recovery of metals values. Some of the components found in circuit boards are described below.

Flame Retardants

The circuit board laminate consists of a glass fibre reinforced epoxy and is likely to contain flame retardant substances at a level of about 15%. The main flame retardant material used in circuit boards is tetrabromobisphenol-A (TBBPA). TBBPA is claimed to have a lower dioxin generation potential than PBDE (pentabromodiphenylether).

Lead

The typical Pb/Sn solder content in scrap of printed circuit boards ranges between 4-6%, consequently lead represents 2-3% of the weight of the original board. The concerns about lead in circuit appear to relate to the possibility of lead leaching from circuit boards disposed of in landfills.

Mercury

It is estimated that 22% of the yearly world consumption of mercury is used in electrical and electronic equipment (ex. in fluorescent lamps). Its use in EEE has declined significantly in recent years. It has been used in thermostats, (position) sensors, relays and switches (ex. on printed circuit boards and in measuring equipment), batteries and discharge lamps. Furthermore, it is used in medical equipment, data transmission, telecommunications, and mobile phones. The estimated concentration level of mercury in computers is 0.002%.

Beryllium

Copper beryllium alloys are used in electronic connectors where a capability for repeated connection and disconnection is desired, and thus where solder is not used to make a permanent joint. Such connectors are often gold plated, so that copper oxide is not created on their surfaces, and does not form a non-electrically conductive barrier between the two connectors. A second use of beryllium in the electronics industry is as beryllium oxide, or beryllia. Beryllia transmits heat very efficiently, and is used in heat sinks. These sinks project heat-generating devices by rapidly distributing their heat to a much larger volume and surface area, where it can be further safely discharged into a moving air stream. Beryllia heat sinks have been used in specific designed parts, which are attached to a heat source, and have also been built into specific microelectronic devices as integral parts of the substrates of those devices. Beryllium oxide (BeO) or beryllia is found in some power transistors, transistor and valve bases, and some resistors.

Capacitors

Capacitors containing hazardous substances have been classified into two types i.e. electrolytic capacitors and capacitors containing Polychlorinated Biphenyls.

Electrolyte Capacitors

Aluminum capacitors are small and cheap for their capacity and can be found in sizes from <1 uF to over 1 farad. They are commonly available up to 450 volts working voltage, with some up to at least 600 volts, much higher than other types of electrolytic capacitors. Aluminum electrolytic capacitors use a layer of aluminum oxide grown on aluminum foil. The aluminum foil forms one electrode the rest is a non-aqueous electrolyte in thin paper separator, and another foil layer for the cathode. The original electrolyte formulae usually comprised a glycol or amine, in which a conductive salt (e.g. sodium borate) is dissolved, plus a trace (1-2%) of water. Many variations on this have been used over the years, although glycol is still often used. Typical contents of a 100µF 10V aluminum capacitor are given in table 3.

Table 3: Contents of a 100µF 10V aluminum capacitor

The capacitor is rendered hazardous if an accompanying threshold concentration is more than 25%. Thus, with electrolyte accounting for <17% of a typical capacitor, the glycol content would not render the capacitor hazardous.

Capacitors containing Poly Chlorinated Biphenyls (PCBs)

PCBs were extensively used in electrical equipment such as capacitors and transformers. Their use in open applications was widely banned in 1972 in Europe and they have not been used in the manufacture of new equipment since 1986. Capacitors containing PCBs fall into two categories, according to size. Small capacitors were used in fluorescent/ other discharge lamps and also with fractional horsepower motors used in domestic and light-industrial electrical equipment. Large capacitors were used for power factor correction and similar duties.

Source:

Central Pollution Control Board