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Difference between revisions of "Viability of recycling semiconductors in Dell LCD PC monitors"

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(Part A)
(Cost For Recycling, Collecting, and Transporting Semiconductors)
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=Cost For Recycling, Collecting, and Transporting Semiconductors=
 
=Cost For Recycling, Collecting, and Transporting Semiconductors=
 
The cost to transport to recycling center is estimated at 0.0172 dollars per kilogram. From our calculated total amount of world wide recovered amount of semiconductors is 43,885.29 Kg. So the total cost of transporting semiconductors is 0.0172*43,885.29 = $745.83. The cost to sort semiconductors is 0.140 dollars per Kg. The total cost to sort semiconductors = 0.140*43,885.29 = $6,143.94 . The cost to dismantle them is 0.315 dollars per Kg. Total cost to dismantle = 0.315*43885.29 = $13,823.9 . Cost to recycle monitor is 0.110 dollars per Kg, so the total cost to recycle monitors is 0.110*43885.29 = $4,827.38
 
The cost to transport to recycling center is estimated at 0.0172 dollars per kilogram. From our calculated total amount of world wide recovered amount of semiconductors is 43,885.29 Kg. So the total cost of transporting semiconductors is 0.0172*43,885.29 = $745.83. The cost to sort semiconductors is 0.140 dollars per Kg. The total cost to sort semiconductors = 0.140*43,885.29 = $6,143.94 . The cost to dismantle them is 0.315 dollars per Kg. Total cost to dismantle = 0.315*43885.29 = $13,823.9 . Cost to recycle monitor is 0.110 dollars per Kg, so the total cost to recycle monitors is 0.110*43885.29 = $4,827.38
 +
<ref>"Economics of PC Recycling"<ref>
  
 
==Resources==
 
==Resources==
 
{{Reflist}}
 
{{Reflist}}

Revision as of 17:18, 9 October 2012

Asi.png This page was part of a project for MY3701 -- an MTU class on semiconductors.

This page is now open edit -- please fix mistakes or feel free to leave comments using the discussion tab.



Authors


Overview

The technology that me and my colleagues have chosen to examine as a possible semiconductor recycling project is the LCD PC monitor. We have chosen Dell[1] to take a closer look at the viability of recycling semiconductors. Hydrogenated amorphous silicon is the typical choice of semiconductor material in the manufacturing of LCD monitors. It is the best choice of semiconductor material because it can be "grown" over large areas. The structure of this silicon is not that of a crystalline material. It lacks the long range order that is present in crystalline silicon. Within the material there are vacancies that form, leaving behind dangling bonds; these free bonds are free electrons from the silicon that have not bonded with another silicon atom. However, the addition of the hydrogen atoms reduces the amount of dangling bonds because hydrogen consists of one free electron and can attach to the vacant bonds. This can be seen in Figure 1. [2]
Fig 1: Shows the gaps and dangling bonds with hydrogen atoms in the structure of the silicon.
The process of which the hydrogenated amorphous silicon is deposited onto a substrate is called plasma-enhanced chemical vapor deposition (PECVD). This process uses silane gas which enters the chemical vapor deposition chamber and dissociates into a cloud of plasma. This plasma is induced by a radio frequency power generator; the chamber that holds this process must be in a vacuum to eliminate any impurities in the process. Similiar to an electron beam deposition process,the silicon and hydrogen atoms condense on a substrate, in LCD monitors this would be the glass, and make the thin layer of hydrogenated amorphous silicon. The setup of this process is shown in Figure 2. [3]
Fig 2: Shows the setup for the production of amorphous hydrogenated silicon

Scale of market

The production of PC LCD monitors on the worldwide market shows Dell, Samsung, and LGE at the top of the market selling most for the 12 Brands selling from as low as 10 million units in a month to nearly 15 million units a month for 2010. Dell was ranked number one in the production of LCD for 2010. (Fig 3) In Figure 3, we were capable of determining the amount of units sold by Dell, which is estimated at 22.5 million units in 2010. [4]


In the total amount of PC LCD monitors that the top 12 brands sold between January 10 2009 and January 10 2010 was approximately 139 million units. (Fig 4)[5]


The growth for the production of LCD screens is expected to slowdown in the next two years. The growth in production of LCD panels for LCD has decreased, by the slow economic recovery, which is causing consumers to buy less and is predicted to slow down further for the next few years. (Fig 5) [6]

Recycling practices

Dell


Yes, LCD monitors are recycled.

Scrap LCD monitors are sold for recycling of the actual LCD panel when its not cracked, if it is cracked, its value drops dramatically to almost 0 since the only thing that is left to recycle is the actual printed circuit board and the circuit board in the LCD monitor is usually lower grade. [7]


HOW to recycle your LCD monitors…

To prevent your old electronics from being melted down over a rudimentary stove in Guiyu, China, or being tossed into a landfill in Lagos, Nigeria, you’ll want to choose a reputable recycler. [8]

Recycling LCD monitors is easy if you do not have to go through the process yourself. There are multiple companies that allow you to send in your monitors for free, for a price or you can even drop them off at specific locations and they will handle it all for you. Some of these companies include Apple, Staples and Dell. Michigan Technological University allows people to drop off their monitors and the Apple store will recycle it all. If you want to go straight through Apple, their recycling process is to purchase any Apple computer or monitor and receive free recycling of your old computer and monitor no matter what the brand is.

WHY it should be recycled…

Electronics consist of valuable resources, such as precious metals, copper, and engineered plastics, all of which require considerable energy to process and manufacture. Recycling electronics recovers valuable materials, conserves virgin resources, and results in lower environmental emissions (including greenhouse gases) than making products from virgin materials. For example: Recycling one million desktop computers prevents the release of greenhouse gases equivalent to the annual emissions of 16,000 passenger cars. By recycling 100 million cell phones, approximately 7,500 pounds of gold could be recovered - allowing that amount of gold to go into new products. Recovering the gold from cell phones, rather than mining it from the earth, would prevent 12,000,000,000 pounds of loose soil, sand, and rock from having to be moved, mined, and processed. [9]


DANGERS of not recycling properly...

Electronic waste isn’t just waste, it contains some very toxic substances, such as mercury, lead, cadmium, arsenic, beryllium and brominated flame retardants. When the latter are burned at low temperatures they create additional toxins, such as halogenated dioxins and furans – some of the most toxic substances known to humankind. The toxic materials in electronics can cause cancer, reproductive disorders, endocrine disruption, and many other health problems if this waste stream is not properly managed. Many of the toxic constituents are elements, which means they never disappear, even though they may change form. Other toxic chemicals in electronics do not break down over time and instead, accumulate in the food chain and biosphere. Not only do these toxins present risks to communities and the global ecosystem, but also to electronics recycling workers, even in developed countries.

An estimated 70-80% of the e-waste that’s given to recyclers is exported to less developed countries. Once there, primitive technologies such as open air burning and riverside acid baths are used to extract a few materials. The rest of the toxic materials are usually dumped. Unlike other countries in the world, the U.S. sends a significant portion of its hazardous e-waste to U.S. prisons to process in less-regulated environments without the worker protections and rights afforded in the private sector. Moreover, such operations amount to government subsidies, undermining the development of responsible private-sector recycling infra-structure and distorting the economics of recycling. [10]


What can the recycled be used for…

Flat screen LCD monitors and televisions contain toxic substances that can wreak havoc on the environment, but they may also have a silver lining -- or in this case, a silver nanoparticle and PVA lining.

British scientists have discovered that by separating the films of LCD screens, they can remove the polyvinyl-alcohol (PVA) and turn it into a disinfectant. According to the researchers, the substance can kill harmful bacteria including strains of Escherichia coli and Staphylococcus aureus.

Andrew Hunt of the University of York says, "We can add significant value this waste...that has great potential for use in biomedicine. Now we have gone a step further by enhancing its anti-microbial properties through the addition of silver nanoparticles, with the result being that it can destroy bacterial infections."

Previous research of theirs has found that pure PVA might be useful in human tissue regeneration and possibly in treatments to transport medications to specific areas of the body. By adding a dash of silver to the screen material, they hope to potentially make antibiotic cleaning solutions for hospital use.

And what to do with the rest of the toxins leaking from our technotrash? The EPA estimates that in 2005, the computers, TVs, VCRs, monitors, cell phones and other electric items ditched by Americans amounted to almost 2 million tons. That’s a whole lot of lead, mercury, arsenic, beryllium, cadmium, and other dangerous substances. That's why it's so important to recycle your old electronics. [11]


Amount of semiconductor in market

The amount of hydrogenated amorphous silicon is all dependable on the thickness of the thin film layer. These layers can range from nanometers to micrometers, and for the LCD monitors an average between the two will be used to determine the thickness. [12]


Thickness=((1x10^-9)+1x10^-6))/2=5.005x10^ -7 meters

To determine the total volume in each monitor that Dell sells, we took the average height and width of the monitors that are offered. [13]

Width=(18.5+4*21.5+3*23+24*4+27+30)/14=23.32

Height=(13.74+4*12.84+3*12.73+4*15.47+16.7+18.95)/14=14.34

Converted to meters, the average size of the screen is: .592x.364 meters

Total volume=(5.005*10^-7)*.364*.592=1.0785*10^-7 meters^3

To determine the mass of the silicon present, we took the average volume of the monitors and multiplied it by the density of silicon.

1.0785*10^-7 meters^3 * 2330000 grams/meters^3=.2513 grams per monitor

Finally, the total amount of silicon that could be possibly extracted from the 22.5 million units sold is:

.2513 average grams per unit * 22.5 million units sold=5,654,250 grams

5,654,250=12,465.487 lbs

Methods of collecting lost semiconductor materials

The methods for collecting the liquid crystals from the LCD panels are: 1. Supercritical Carbon Dioxide Fluid Technology extracts the liquid crystals from the glass. This method uses iso-thermal and a depressurization method to remove the liquid crystal from the glass panel, by converting carbon dioxide gas to its supercritical fluid state, thus dissolving the liquid crystal. Then the temperature is dropped, the carbon dioxide reverts back to gas, leaving the liquid crystal [14]. 2. Ultrasonic cleaning uses ultrasonic waves, which causes pressure against the liquid, thus removing the liquid crystals by force from the glass substrate[15]. After the liquid crystals have been extracted and removed and cleaned using a solvent, they can be recycled back into a different LCD [16] [17].


Potential for Post-Consumer Recycling

It has been decided that the semiconductor material found in Dell LCD PC monitors is a viable resource that should be recycled post-consumer.

Part A

Cost For Recycling, Collecting, and Transporting Semiconductors

The cost to transport to recycling center is estimated at 0.0172 dollars per kilogram. From our calculated total amount of world wide recovered amount of semiconductors is 43,885.29 Kg. So the total cost of transporting semiconductors is 0.0172*43,885.29 = $745.83. The cost to sort semiconductors is 0.140 dollars per Kg. The total cost to sort semiconductors = 0.140*43,885.29 = $6,143.94 . The cost to dismantle them is 0.315 dollars per Kg. Total cost to dismantle = 0.315*43885.29 = $13,823.9 . Cost to recycle monitor is 0.110 dollars per Kg, so the total cost to recycle monitors is 0.110*43885.29 = $4,827.38

Cite error: Closing </ref> missing for <ref> tag
  1. "Dell Monitors." : Computer Monitor, LCD Display and Screen. N.p., n.d. Web. 25 Sept. 2012. <http://www.dell.com/monitors>
  2. Kasap, S. O. Principles of Electronic Materials and Devices. Boston: McGraw-Hill, 2006. Print.
  3. Kasap, S. O. Principles of Electronic Materials and Devices. Boston: McGraw-Hill, 2006. Print.
  4. "LCD Monitor Production Will Continue to Soar." TechEye. N.p., 07 June 2010. Web. 29 Sept. 2012. <http://news.techeye.net/business/lcd-monitor-production-will-continue-to-soar>
  5. "LCD Monthly Desktop Monitor Production Rate Highest Since Mid-2008 - DisplaySearch." LCD Monthly Desktop Monitor Production Rate Highest Since Mid-2008 - DisplaySearch. N.p., 01 Feb. 2010. Web. 29 Sept. 2012. <http://www.displaysearch.com/cps/rde/xchg/displaysearch/hs.xsl/100201_lcd_monthly_desktop_monitor_production_rate_highest_since_mid_2008.asp>
  6. Dash, Sweta. "Market Watch." LCD Panel Market Growth Slows in 2011. N.p., 19 May 2011. Web. 29 Sept. 2012. <http://www.isuppli.com/Display-Materials-and-Systems/MarketWatch/Pages/LCD-Panel-Market-Growth-Slows-in-2011.aspx>
  7. Grossman, Elizabeth. Salon. N.p., 10 Apr. 2006. Web. 16 Sept. 2012. <http://www.salon.com/2006/04/10/greenguide/>
  8. "LCD Monitors recycling." B.W Recycling Inc.. B.W. Recycling, Inc, 1 Sept. 2012. Web. 20 Sept. 2012. <http://www.computersrecyclingcompany.com/lcdmonitors.htm>
  9. "Reuse & recycle." U.S. Environmental Protection Agency, 16 Apr. 2012. Web. 18 Sept. 2012. <http://www.epa.gov/epawaste/partnerships/plugin/reuse.htm>
  10. "Reuse & recycle." U.S. Environmental Protection Agency, 16 Apr. 2012. Web. 18 Sept. 2012. <http://www.epa.gov/epawaste/partnerships/plugin/reuse.htm>
  11. "LCD toxic trash: useful antibiotic?." Smart Planet. Ed. Melissa Mahony. N.p., June 2010. Web. 7 Sept. 2012. <http://www.smartplanet.com/blog/intelligent-energy/lcd-toxic-trash-useful-antibiotic/1663>
  12. <http://www.csun.edu/~rdconner/630/slides/Amorphous%20SC%20and%20Solar%20Cells.ppt>
  13. <http://www.dell.com/content/topics/segtopic.aspx/monitor_segselecter?c=us&cs=04&l=en&s=bsd&ST=dell%20monitors&dgc=ST&cid=245312&lid=4445170&acd=sTvOmguLW,26522075259,901w1k7137>
  14. "Study on Method Recycling Liquid Crystal from Waste LCD Based on Supercritical CO2 Fluid Technology" Scientific.net N.p., 27 Feb. 2012. Web. 29 Sept. 2012. <http://www.scientific.net/AMR.479-481.2165>
  15. "Recovery of Valuable Material from Waste Liquid Display Panel" Sciencedirect.com N.p., 7 Jul. 2009. Web. 29 Sept. 2012. <http://www.sciencedirect.com/science/article/pii/S0956053X08004315>
  16. "Recovery of Valuable Material from Waste Liquid Display Panel" Sciencedirect.com N.p., 7 Jul. 2009. Web. 29 Sept. 2012. <http://www.sciencedirect.com/science/article/pii/S0956053X08004315>
  17. "Recycling Liquid Crystal Displays (LCD)" voices.yahoo.com N.p., 11 Sept. 2006. Web. 29 Sept. 2012. <http://voices.yahoo.com/recycling-liquid-crystal-displays-lcd-78361.html>