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January 2005
Multiple uses for recycled glass found in Minnesota
Glass supply, once contamination has been eliminated, is available in abundance and the state of Minnesota has creatively found alternatives to landfilling this valuable resource.
Glass containers that are brown, green and clear are commonly recycled in Minnesota. The majority of this glass is recycled back into new containers to package food and beverages. However, many companies and counties are exploring alternative recycling options for post-consumer glass.
Glass as an Abrasive
Glass beads are used in blasting and surface cleaning applications.
Blasting with glass beads made of recycled glass can perform better
in certain applications than virgin glass beads. The abrasion of the
crushed glass can improve the quality of the blast. Beads sold in Minnesota
range from 95-100% recycled post-consumer content.
Decorative Glass
Decorative products like stepping stones, coasters and trivets
are new recycled products. Winona ORC Industries is one of a few companies
in the U.S. making such products from recycled container glass. They
were looking for better end-uses for the volumes of glass collected
in the region, which was expensive to ship to the Twin Cities for recycling.
Success Story: Winona ORC Industries (WORC)
WORC developed decorative garden stepping stones, trivets, coasters,
plant stands and plant caddies made from recycled container glass (95%
post-consumer content). Clear, green and amber bottle glass collected
from residential and business recycling programs are crushed, cleaned,
mixed and placed into molds, then fused in a kiln. Each stone is uniquely
designed with flowers, vines, fruit and animals.
WORC formed a partnership with the Southeast Minnesota Recyclers Exchange (SEMREX), an alliance of local public and private recyclers that operates a program to assist the region in marketing its recyclables to end-users. In 1994, WORC received a grant from the OEA to demonstrate that they could locally manufacture garden pavers made from recycled glass.
Their manufacturing method is an internationally recognized ground-glass/fire-kiln process — the only one like it in the world. Much like works of art, the products made with this process are unique; background hues vary with the mixing of colored glass. The non-porous glass is strong and durable, does not absorb water, and can withstand extreme heat and cold. Independent testing has proven them to be virtually chip and crack-free under hundreds, or even thousands of pounds of stress.
Glass as Road Aggregate
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% blend for road base is
the most common, well-proven and safe.
Success Story: Ramsey County
For several years, the Ramsey County Public Works Department has
experimented with different applications of glass in cooperation with
Super Cycle of St. Paul. Ramsey County has found glass to be an excellent
aggregate amendment and has actively pursued new and different engineering
applications for the material. Ramsey County has used glass in shouldering,
a 10% mix in base, asphalt and a 100% use in base.
Success Story: Otter Tail County
Otter Tail County’s Highway Engineer, Rick West, made an
early commitment to use recycled glass for use in a road resurfacing
project in the county.
In 1996, the county recycling program began stockpiling glass containers collected for recycling. In 1997, because the glass was dedicated to use in highway construction, the glass-recycling program was expanded to include non-container glass, including dishes, window glass and glass cookware.
The project to re-construct a four-mile section of Highway 74 began in September 1998. Bid specifications required the contractor to include a 10% blend of recycled glass (by weight) in the aggregate used in the road base. The County Solid Waste Administrator, Mike Hanan, and the County Engineer, Rick West, worked closely with the contractor to ensure that the material used in the base course was clean and of high quality. Engineers determined that the glass could be crushed as it was blended with gravel. The finished product was a MnDOT Class 5 aggregate base with a one-inch maximum particle size. Some salvaged asphalt pavement was also included in the blend.
This mixture performed well during construction, with no need for special equipment. The county has found that this use is an excellent way to recycle glass locally, avoiding the high transportation costs and color separation of the glass required for recycling back into container glass. “We will do these kinds of things (aggregate amendment) until the market says that trucking glass to be used for new glass makes sense,” says West.