Sustainable design: What can you make with old glass?

May 4, 2011
Most U. S. communities have recycling programs. So it should be easy to reuse common materials such as glass and plastic, right? Not quite, at least when it comes to glass

Understanding Economic and Environmental Impacts of Single-Stream Collection Systems
Container Recycling Institute
Culver City, Calif., 2009

Strategic Materials
Anchor Glass Container Corp.

Most U. S. communities have recycling programs. So it should be easy to reuse common materials such as glass and plastic, right? Not quite, at least when it comes to glass. A recent industry report claims that 40% of glass chucked into recycling bins ends up in landfills. But experts say that almost all glass is recyclable, so why does so much of it just get added to the waste pile?

Many municipalities now collect recyclables such as newspaper, glass bottles, plastic pouches, and aluminum cans in the same receptacle, using a method called single-stream collection. This lowers collection costs compared to separating glass, plastic, and so forth into their own collection containers. But by the time the mixture reaches a material-recovery facility (MRF), much of the glass is broken into particles too small to handle and, therefore, too expensive to separate for remelting into fiberglass or new glass containers. Also, any large pieces of glass that remain are typically not sorted by color, a necessity for making glass containers.

“After trucks dump their loads at an MRF, the facility uses magnets to pull steel out of the garbage, leaving everything else on the conveyor,” says Curt Bucey, president of materials processor Strategic Materials Inc., Houston. “Nonferrous magnets capture aluminum, and screens sort cardboard and paper. Lastly, air jets blow off the plastic. MRFs make individual economic decisions and sell high-value materials such as aluminum, but dump glass — typically considered a commodity — in landfills. When the MRF sells what’s left on the conveyor, we purchase the remaining mixture of glass shards, paper shreds, banana peels, and whatnot. We separate out the glass with specialized equipment and sell it to glass-container companies and fiberglass manufacturers. At this point the glass is called cullet.”

Glass recycling is mostly a free-for-all because there is no uniform definition of recycling and no meaningful way to track of discarded glass, according to Bucey. “Most people think recycling means keeping material circulating through as many product lives as possible,” he says. “But some might be surprised by uses for reclaimed glass. For example, certain cities equate the diversion of glass with recycling, as when crushed shards are sprinkled on top of a landfill to form a cover. Contrast that with the example of old bottles being remelted, over and over, almost an unlimited number of times, with the result always being a pristine bottle.”

Also, depending on a variety of factors, there are obvious differences in recycling rates from city to city, and state to state. “For example, Wisconsin has made it a goal that all materials going through MRFs must get reused and not placed in landfills,” says Bucey. “And areas with mandatory deposit laws, such as the New England states and Michigan, have much higher recycling rates — up to 90%. Contrast that with Ohio, where rates are about 5 or 10%,” he claims.

Many bottle companies are desperate for recycled glass, says vice president of Product Development Sam Wilson of glass-container manufacturer Anchor Glass Container Corp., Tampa, Fla. “Part of the problem is the lack of color processors,” he says. “Different colors of crushed glass all mixed up is almost worthless to us. Even if an MRF could remove just the glass from the other waste materials, if it’s mixed brown, green, and clear, what we call tricolor, we can only use a little of it for amber bottles — maybe 2 or 3%. But we can’t use it to make clear or green bottles. There is iron in amber glass and chrome in green glass and they cannot be mixed. When we buy cullet from Strategic Materials, it comes in separate colors.”

According to Wilson, in many areas of the country it is cheaper to buy the raw materials — sand, soda ash, and limestone — and melt them, than it is to buy good clean cullet. “If we could get cullet, we would definitely take it,” he says. “Crushed glass melts at about 2,100°F, but melting raw materials takes 2,800 to 3,000°F. So cullet reduces costs and cuts particle pollution, which helps the environment.”

The glass-container industry has shrunk substantially over the last 10 years, with 68 plants closing, according to Wilson. “So there are not as many places to recycle glass. And when the transportation costs become too high, recycling becomes uneconomical. In contrast, recyclables in Europe are collected and kept separated, and there are lots of returnable bottles. You see little plastic packaging in Europe. And, interestingly, Canada has more glass than it knows what to do with, probably because of transportation costs. There are only four glass-container plants in Canada, not many for a whole country.”

© 2011 Penton Media, Inc.

About the Author

Leslie Gordon

Leslie serves as Senior Editor - 5 years of service. M.S. Information Architecture and Knowledge Management, Kent State University. BA English, Cleveland State University.

Work Experience: Automation Operator, TRW Inc.; Associate Editor, American Machinist. Primary editor for CAD/CAM technology.

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