Scrap Glass
Glass Recycling: Glass is the least finite of the non-renewable natural resources targeted by community recycling programs. Glass is made from abundant and cheap materials – sand, limestone and potash – but recycling glass still reduces pollution, conserves landfill space and reduces energy consumption.
As with aluminum and plastic, community glass recycling programs have focused on glass containers for beverages, food and other consumer products. Most glass that ends up in the municipal waste stream – 11.1 of 12.6 million tons in the U.S. in 1999 – is glass containers. The glass in glass containers is easily and repeatedly recyclable whereas the glass in some other consumer products – light bulbs, cookware and window panes among them – contain ceramic which leads to cracking and other blemishes in glass containers.
The need for a relatively contaminant-free supply of cullet – broken glass – to use recycled glass in the manufacture of new bottles has hampered glass recycling efforts. The trend in curbside recycling collection has been to mix recyclables in the collection truck and to sort them out at the end of a run at a materials recovery facility. This has contributed to an increase in overall recycling rates, but leads to a lot of breakage and contamination of glass.
Another problem for glass recycling has been the emergence of plastic in the container market.. Shipments of glass bottles dropped from 3.6 billion units in 1994 to 800 million units in 2000, a period when PET bottle shipments doubled to 25.6 billion units annually.
Glass makes up 5.6 percent of municipal solid waste in the United States, according to 1999 federal figures, and glass recycling recovered just 23.4 percent of the 12.6 million tons of glass discarded that year.
Markets for recycled glass
Glass bottle makers still provide a strong market for recycled glass containers, when they can get it in furnace-ready condition. To be recycled as new bottles, glass must be separated by color (the amber, green and blue tint to some 45 percent of glass bottles cannot be removed) and cleaned of any dirt, ceramics, window glass and other contaminants.
For glass too contaminated to be recycled as containers there are several other markets. Mixed cullet is used to make “glassphalt” for road surfaces, backfill and stormwater drainage systems. It is used as a sandblasting abrasive, as a frictionator to help light matches and detonate ammunition. It is also used to make fiberglass insulation, reflective paint, ceramic tiles and costume jewelry. One of the world’s biggest marble makers, Jabo Inc. in southern Ohio, uses all recycled glass.
The development of these secondary markets for recycled glass have helped the recycling infrastructure, and they are certainly preferable to landfilling glass, but they are a far cry from genuine recycling – turning old glass containers into new glass containers. Much of the environmental benefit of glass recycling, such as reduced energy consumption and pollution, are diminished greatly if old bottles are simply replacing sand in some engineering and industrial projects. Currently, glass containers made in America contain an average of about 35 percent recycled material.
Conservation benefits of glass recycling
• Making glass from recycled cullet uses half the energy it takes to make glass from sand, limestone and potash.
• The energy saved by recycling one glass container can light a 100-watt bulb for four hours.
• Making glass from recycled cullet reduces air pollution by 20 percent and water pollution by 50 percent.
• Recycling also means less mining and mine waste. Each ton of recycled glass reduces mining waste by 500 pounds.
• Because recycled cullet melts at a lower temperature and is less corrosive than the raw materials that make glass, glass recycling actually prolongs the useful life of melting furnaces.
17.04.2007. 09:02
This article hasn't been commented yet.
Write a comment