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Glass
EPA Links and Publications
Comprehensive Procurement Guidelines (CPG) site provides recycled-content recommendations for various glass products.
- Just the Facts
- Recycling Glass
- Collection and Processing
- Markets for Recovered Glass
- Source Reduction/Lightweighting
- Case Studies
For centuries, glass has served as a universal packaging container, holding precious commodities like wine and olive oil. Today, manufacturers use glass to hold everything from soda and peanut butter to champagne and perfume. Glass manufacturers and consumers continue to appreciate glass for its aesthetic value but also recognize its practicality. The glass in many items, from your soda bottle to your computer, can be recycled over and over while retaining its strength.
Just the Facts
- Americans generated 13.6 million tons of glass in the municipal solid waste (MSW) stream in 2007.
- About 24 percent of the glass was recovered for recycling.
- Recovery increased from 750,000 tons in 1980 to more than 3.2 million tons in 2007.
- Soft drink, beer, food, wine, and liquor containers represent the largest source of glass generated and recovered for recycling.
- Glass in durable goods, such as furniture, appliances, and especially consumer electronics, round out the sources of postconsumer glass.
Recycling Glass
More Glass Information
The Glass Packaging Institute (GPI) 
, represents the glass container industry in Washington, DC, and in state legislatures across the country.
The Institute of Scrap Recycling Industries (ISRI) is a trade association representing the scrap processing and recycling industry. ISRI represents 1,400 companies that process, broker, and industrially consume scrap commodities, including glass.
The Clean Washington Center (CWC) , in Washington state, works to develop markets for recycled materials, including glass.
The glass containing your soda today might be the glass containing your spaghetti sauce tomorrow. That's because glass, especially glass food and beverage containers, can be recycled over and over again. In fact, 90 percent of recycled glass is used to make new containers. Other uses for recycled glass include kitchen tiles, counter tops, and wall insulation. Glass makers have always known the material's recyclability, but glass recycling has grown considerably in recent years. This growth is due to both increased collection through curbside recycling programs and glass manufacturers' increased demand for recycled glass.
Today, most glass manufacturers rely on a steady supply of recycled crushed glass, known as "cullet," to supplement raw materials. To make glass, manufacturers mix sand, soda ash, limestone, and cullet; heat the mixture to a temperature of 2,600 to 2,800 degrees F; and mold it into the desired shape. Sand is the only material used in greater volumes than cullet to manufacture glass.
Using cullet saves money and helps the environment, because:
- Cullet costs less than raw materials.
- Cullet prolongs furnace life since it melts at a lower temperature.
- Cullet demands less energy from power sources like electricity, natural gas, and coal.
- Less energy used means reduced emissions of nitrogen oxide and carbon dioxide, both greenhouse gases.
Collection and Processing
Although all glass is made of silica and soda, the type and quantity vary slightly with different types of glass. These differences frequently cause manufacturing problems due to different melting points and chemical incompatibility. In addition, since neither brown nor amber glass is used to manufacture clear glass, it is important to sort glass by color. Glass separated by color, whether this takes place at the curbside or drop-off facility or at a materials recovery facility, yield glass cullet of higher economic value.
Sorting also can help reduce common contaminants, such as ceramic cups, plates and pottery, clay garden pots, crystal and opaque drinking glasses, heat-resistant ovenware, lead collars from wine and champagne bottles, stones and dirt, light bulbs, metal caps, lids and neck rings, and mirrors. Finally, sorting can keep broken glass from contaminating other recyclables, like newspapers.
In the materials recovery facility, workers remove large contaminants by hand and sort the glass by color where possible. Then, glass is typically crushed and travels by conveyor belt through a series of refinements. Magnets pull out metal, and air currents remove lightweight material such as paper. Some cullet suppliers use sophisticated equipment such as lasers to sort colors of crushed glass and further remove small contaminants. Scientists continue to develop mechanisms to improve materials sorting, and, therefore, the quality of the cullet.
Markets for Recovered Glass
Glass container manufacturers need a steady supply of quality cullet to make glass containers. Ninety percent of recycled glass is used to make new containers, and the demand for quality cullet is greater than the supply. Due to factors like contamination, cullet can be either high-quality or low-quality by the time it is sold. High-quality cullet is free of contaminants that can jeopardize the integrity of an entire batch of glass. The Glass Packaging Institute (GPI), a trade association representing glass and glass product manufacturers, lists a number of secondary uses of high-quality cullet: abrasives, aggregate substitute, bead manufacturing, decorative applications, fiberglass, frictionators (match tips), and fluxes in metal foundry work.
Lower-quality cullet—that is, mixed-color glass from container and non-container recycled glass—is increasingly used in secondary applications, such as in the manufacture of fiberglass insulation, roadbed aggregate, driving safety reflective beads, and decorative tile.
Source Reduction/Lightweighting
Source reduction is the process of reducing the amount or toxicity of waste that is generated. Lightweighting—reducing the volume of material used to make a specific product—saves a considerable amount of energy and raw materials. Money and resources saved by reducing the volume of glass containers help make glass more cost effective for glass container manufacturers, who face competition from aluminum and plastic container manufacturers. Using advances in design and manufacturing technology, the glass container industry continues to reduce the weight of glass containers. For instance, manufacturers reduced the weight of non-returnable glass containers by about 44 percent from 1972 to 1987, according to a 1992 Franklin Associates study, "Analysis of Trends in Municipal Solid Waste Generation."
Case Studies
Waste Management Recycle America (formerly Recycle America Alliance) constructed an automated, optical glass sorting line at its California facility that removes ceramic and metal contaminants from color-separated clear, brown, and green glass. The new sorting technology also has the ability to convert three-color mixed glass into clean, usable cullet.
The goal of the Department of Defense (DOD)/Federal Facility/Ohio Pollution Prevention Partnership is to create a working relationship to promote and implement pollution prevention as the preferred strategy for protecting the environment. The partnership increased glass and plastic recycling by 99 percent, from 30 pounds to 27,000 pounds, by allowing DOD employees to recycle household materials on base.
More than 15 Minnesota counties have used reclaimed glass as aggregate. While many different applications have been demonstrated in Minnesota and other states, the use of 10 percent blend for road base is the most common, well proven, and safe.
