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Currently, the majority of electronic waste is disposed of in a landfill. The remainder is either processed in energy inefficient method that only recovers a small amount of the available metals or burned to recover saleable metals such as copper, aluminum and iron. This is a problem for a number of reasons.
- This waste contains trace amounts of precious metals, and larger quantities of a variety of other metals and alloys, especially copper, aluminum and steel.
- Electronic waste contains high concentrations of heavy metals, brominated flame retardants and other plastic additives that have proven adverse effects on humans. Note: more information can be found at Electronic waste.
- The volume of electronic waste produced is high, and growing fast [1]. In 2005, the United States alone disposed of was at least 1.5 million tons of electronic waste, and at most one quarter of that was recycled [2]. The situation is similar in Canada, with more than 71 000 tonnes of waste being disposed of in 2005, with just 26% being recycled [3]. In the province of Ontario, Canada, the percentage recycled in 2004 was just 2% [4].
Materials involved
There are a wide variety of materials involved in the multitude of items that can be classified as electronic waste. Each component adds to the complexity of any recycling effort. Below is an exploration of a number of the most common components, by weight.
Printed circuit boards
A printed circuit board, or PCB, is the piece of hardware acts as a base and provides electrical connections to the mounted components. They are present in many types of electronic waste, including cellphones, computers, TVs, and printers. A PCB is made of a number of components. Each step of the productions process is outlined below, to give an idea of the variety of materials involved.
picture of a circuit board here
FR-4 is the most common base material [5] for printed FR-4 is an abbreviation of Flame Retardant 4, referring to its flame resistance and self-extinguishing properties. It is a brittle material formed by hardening a woven fiberglass sheet with an epoxy resin, usually created from ethylene clorohydrin and bisphenol-A [6]. To give it the aforementioned self extinguishing properties, a brominated flame retardant is incorporated in the epoxy. Some flame retardants can be incorporated at the molecular level, like W [7]. It can be easily coloured, with common colours including green, blue, red, and black.
The type glass used to create the fiberglass sheets is S-glass. Content ranges, by weight are, 52-56% silicon dioxide, 16-25% calcium oxide, 12-16% aluminum oxide, 5-10% boron oxide, 0-2% sodium oxide or potassium oxide, 0-5% magnesium oxide, 0.05-0.4% iron oxide, 0-0.8 titanium oxide, and 0-1% fluorides [8].
Surface mounted components
A wide variety of components are soldered to printed circuit boards. A resistor is comprised of copper leads attached to a painted ceramic or carbon core [9]. Microchips are composed of small amounts of silicon, aluminum, and copper, [10] with plastic coatings. CPUs today have aluminum heatsinks as well.
Casings
Most consumer electronic devices have plastic casings, such as a TV or a cell phone. Household appliances also have aluminum or steel cases. Other products, such as computer cases have both metallic and plastic components to them.
CRT and LCD screens
Wire
Batteries
Precious metals
Current solutions
Shredding
Municipal incineration
Open flame incineration
Proposed solutions
Thermal depolymerization
Thermal depolymerization is a process in which thermal energy, under high pressure conditions and with the aid of water, is used to decompose organic molecules. This would not be true solution for recycling electronic waste, but a step in the process. It would, in theory, render plastics and epoxies present into usable oil. The resulting solids would have much higher concentrations of metals.
Plasma arc gasification
Bioleaching
References
- ↑ http://www.epa.gov/epawaste/conserve/materials/ecycling/manage.htm Accessed Nov. 11, 2008
- ↑ http://www.epa.gov/epawaste/conserve/materials/ecycling/docs/fact7-08.pdf Accessed Nov. 11, 2008
- ↑ http://www.ec.gc.ca/wmd-dgd/default.asp?lang=En&n=F3852FB1-1 Accessed Nov. 11, 2008.
- ↑ http://www.ene.gov.on.ca/en/news/2007/061201.php
- ↑ Coombs, C., 2001, Printed Circuits Handbook Fifth Edition, McGraw-Hill, New York, section 6.
- ↑ http://www.p-m-services.co.uk/how%27s_fr4_made_.htm Accessed Nov. 7, 2008.
- ↑ Coombs, C., 2001, Printed Circuits Handbook Fifth Edition, McGraw-Hill, New York, section 6.4.2 and 6.2.3.
- ↑ Coombs, C., 2001, Printed Circuits Handbook Fifth Edition, McGraw-Hill, New York, section 6.5.1
- ↑ http://www.ecawa.asn.au/home/jfuller/electronics/resistors.htm Accessed Nov. 11, 2008.
- ↑ http://www.intel.com/education/makingchips/index.htm Accessed Nov. 11, 2008.