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Corner of TabCathode Ray Tube (CRT) Glass – A Recycling Challenge Corner of TabHighlights

Prior to the advent of flat panel displays, cathode ray tubes (CRT) displays were widely used in televisions and computer monitors. While some CRT displays are still in use today, very few new CRTs are being produced as electronics manufacturers follow consumer and business demand for flat panel TV and monitor displays. Flat panel displays are also a key component of laptops, tablets and smart phones.

As consumers and businesses replace their CRT monitors and televisions with flat panel displays, electronics recyclers receive the discarded CRT products. Prior to about 2009, CRT glass recovered from monitors and televisions was widely used for new CRT manufacturing (“glass-to-glass”) and lead smelting as a fluxing agent in the smelting process.

By 2014, the market for recycled CRT glass has become limited. Very few new CRTs are being manufactured since flat panel displays have almost completely replaced CRT displays. The demand for CRT glass by lead smelters has also fallen sharply. Recycling markets for CRT glass are limited, costly and far away making CRT glass recycling a challenge to e-scrap recyclers. As a result, some e-scrap recyclers have been “stuck” with quantities of stored CRT glass for which they are hard-pressed to find cost effective, large quantity markets.

Research continues to develop other uses for recycled CRT glass. As of early 2014, these alternative uses are small quantity “niche” products such as ceramic tile and X-ray shielding glass block which cannot use the larger quantities of CRT glass being produced by e-scrap recyclers.

CRT Monitor: Components and Lead

Figure 1 shows the parts of a disassembled CRT computer monitor. The CRT is the tube that produces the image you see when you look at the monitor. The CRT glass has a negative net value, that is, the recycler has to pay to remove it, transport it to a recycler and have it recycled. The recycler loses money on CRT glass. The circuit board, cone and copper cables have some positive scrap value, that is, the cost to remove and transport that scrap to a metals smelter is less than what the smelter pays the recycler for the scrap. The recycler makes money on this scrap. The cone is an electromagnet that encircles the electron gun at the rear (narrrow) end of the CRT. The cone directs the electron streams produced by the electron gun to the face plate of the CRT to produce the image that we see. The copper components of the cone's windings give the cone much of its scrap value. The circuit board processes the incoming signal from the computer to control the operation of the electron gun so that the correct image appears on the monitor screen. The circuit board contains copper and very small amounts of gold and other precious and semiprecious metals that give the circuit board much of its scrap value. The rest of the monitor is plastic that can be recycled with has a small positive (profit) or zero (break even) net value.

Figure 1: What's in a computer monitor?

Figure 2 shows where the lead is in the various parts of a typical color CRT used in a TV or computer monitor. The lead in the funnel and face plate glass is physically and chemically bound up in the glass matrix and does not leach very readily. The lead in the frit which joins or welds the face plate glass to the funnel glass is in the form of a lead oxide paste. The lead in the frit does leach quite readily when subjected to the Toxicity Characteristic Leaching Procedure (TCLP) test used to determine whether a discarded material is a hazardous waste or not. Research done at the University of Florida in 1999 and sponsored by the DEP showed that CRTs usually test to be a hazardous waste when subjected to the TCLP test.

Figure 2:  Where's the lead in a cathode ray tube (CRT)?

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Contacts for Reuse and Recycling

Last updated: February 13, 2014

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2600 Blair Stone Road, Tallahassee, Florida 32399-2400

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