Glass containers are made from sand, limestone, soda ash, cullet (crushed bottles) and various additives, including those used to "color" brown, green and blue bottles.
Fifty-three percent of the glass bottles produced in the United States are clear (flint), 38 percent are brown, 8 percent are green and 1 percent are blue or other colors. Half of the green bottles used in the United States are imported wine and beer bottles.
The amount of glass bottles used in the United States increased by 4.4 million tons between 1960 and 1997, for a 58 percent increase. However, the glass container market share of MSW declined in the same time period by 30 percent as lighter weight aluminum and plastic containers replaced glass bottles.
Other glass products include flat glass such as windows, fiberglass insulation and glassware. These products use different manufacturing processes and different additives than container glass. This "Profile in Garbage" does not cover non-container glass.
Glass Container Solid Waste (MSW) Facts:
Generated: * 10.6 million tons or 4.9% by weight.*
* 78.5 pounds per person per year.*
* The average glass bottle weighs 8 oz.
* 82% of glass bottles are generated from homes; 18% from businesses.*
Recycled: * 2.9 million tons for a 27.5% recycling rate.*
* Industry data shows a 35% recycling rate in 1997. This figure includes refillables at a trippage rate of 8 times per bottle.
* 10 states require deposits on glass beverage containers.
Recycled Content: * 26% U.S.-produced bottles.
Composted: * Glass does not compost.
Burned or Landfilled: * 7.7 million tons or 4.9% of discarded MSW by weight.*
* Glass is non-combustible and generally forms a slag.
Landfill Volume: * 5.5 million cubic yards or 1.3% of landfilled MSW.*
Density: * Landfilled glass bottles weigh 2,800 pounds per cubic yard.
* Loose glass bottles have a density of 600 pounds per cubic yard.
* Crushed bottles have a density of 1,000 pounds to 2,000 pounds per cubic yard.
Source Reduction: One hundred, one-way, 16-oz. glass bottles weighed 75.7 oz. in 1972 and 48.04 oz. in 1992, for a 36.5% weight reduction.
A new beer bottle using 20% less glass now is available.
Markets: The glass container industry used 79% of the cullet recycled in 1997 as a raw material in making glass containers.
Fiberglass products are the second largest market for cullet. Other secondary markets include abrasives used in sand-blasting; aggregate substitutes used in road construction including "glasphalt;" glass beads for reflective paint; fiberglass; filler in storm drain and French drain systems; frictionators used for lighting matches; glass foam and fluxes; and other additives.
A minimal amount of glass is exported for recycling.
End-Market Specifications: Glass containers fall under the Institute of Scrap Recycling Industries (ISRI) Guidelines for Glass Cullet: GC-98, with color-specific specifications for unprocessed and processed (furnace ready) container glass cullet.
Unprocessed cullet should be free of excess moisture and may not be pulverized. Prohibited materials include non-container glass, metals, rocks and ceramic closures. Unprocessed clear cullet must be at least 95% clear glass; brown cullet must be at least 90% brown glass and green cullet must be at least 90% green glass. After processing, the cullet must be suitable for glass container production.
Glass bottles often break when collected in curbside programs. Breakage solutions include installation of interior baffles or nets in collection trucks, special glass-only truck compartments, and limiting the number of times glass is transferred after collection before final processing.
Recycling Cost and Value: * Collection costs range from $54 to $77 per ton.*
* Processing costs range from:
$37 to $105 (clear glass)*;
$70-$149 (brown glass)*;
$58-$134 (green glass)*; and
$29-$76 (mixed color glass).*
Sources: Characterization of Municipal Solid Waste in the United States:
1998 Update, 1999. U.S. Environ-mental Protection Agency Office of Solid Waste, Washington, D.C. Website: www.epa.gov/osw
Glass Packaging Institute, Washington, D.C. Website: www.gpi.org
Measurement Standards and Reporting Guidelines:
National Recycling Coalition, Alexandria, Va. Website: www.nrc-recycle.org
National Solid Wastes Management Association's Waste Recyclers Council, Washington, D.C., Processing and Collection Cost Studies.
Rhode Island Department of Environmental Management, 1990.
Scrap Specifications Circular 1997: Guidelines for Paper Stock, Institute of Scrap Recycling Industries, Washington, D.C. Website: www.isri.org