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Glass can be recycled infinitely. Here’s how it works in Colorado’s “closed loop.”

One glass bottle can become another in as little as 30 days, thanks to a lot of science and machines.

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The life cycle of a glass bottle — from creation to use to disposal to reconstitution — can all happen within Colorado, and theoretically continue forever. 

Glass that’s been recycled first goes to a material recycling facility, such as Eco-Cycle or GFL Environmental, along with paper, plastic, aluminum and everything else in the single-stream recycling system. While much of the recycling process is automated, humans sort through the initial stream of waste as it runs around a facility on a conveyor belt. Someone reaching into a quickly moving pile of stuff could easily cut themselves on a shard of glass, so it’s filtered out first. 

The flow of mixed materials runs over sharp, rotating gears, and since the heavy glass settles on the bottom of the materials, it gets crushed into pieces small enough to fit through a 2-inch crack and onto its own conveyor belt. From there as many contaminants as possible are removed. For example, magnets above the glass shards pull out bottle caps that also made it through the crack.

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Once the glass is separated from other recyclable items, it’s trucked to a processing plant like Momentum Recycling in Broomfield. Glass is a material that in theory can be created, used, processed and re-formed an infinite number of times. But Colorado is far from recycling every single glass bottle or jar. Rates roughly doubled once owner John Lair opened his facility in 2016, but he still estimates that somewhere between 23% and 26% of glass in the state’s waste stream gets recycled. 

“It’s kind of weird in Colorado, there’s these pockets where [recycling is] really great and pockets where it’s almost non-existent, and that needs to be solved,” Lair said. It’s not just a rural versus urban issue. There are pockets around the Denver metro area where recycling is rare or absent. “There’s a lot of room for improvement,” he said. “There’s a lot more of the glass that we could capture with some of those structural conditions improved.”

MORE: Colorado will likely miss its recycling goals again this year. What will it take to change the tide of waste?

Even if all the glass thrown out was recycled, it wouldn’t all be reused in glass bottles. About 10% of the glass pieces that make it to a processing plant like Momentum end up too small to be reused for bottles and jars. These tiny pieces get sifted out and are sent elsewhere for other uses, such as media for sandblasting, pool filters or coatings. 

Momentum glass recycling in Broomfield, Colorado on February 1, 2017. (photo by Chris Schneider for Momentum Recycling)

The desirable pieces are thoroughly washed and sorted into the three main colors — green, brown and clear — then sent to a manufacturer like O-I Glass. The international company operates two plants in Colorado and supplies bottles to many of the state’s breweries, including Molson Coors, Anheuser-Busch, New Belgium and Crabtree Brewing.

Then comes the alchemy, where old glass becomes new again, or at least mixes with new materials to create semi-recycled bottles. Jim Nordmeyer, vice president for global sustainability at O-I Glass, estimates the plant in Windsor uses an average of about 15% recycled glass. The Rocky Mountain Bottle Company plant in Wheat Ridge, a joint venture between O-I and Molson Coors, averages about 30% recycled material. 

It is possible to make a bottle entirely of recycled glass, Nordmeyer says, and the company has done it before. Some of the O-I plants in Europe regularly average 90% recycled glass per bottle because high landfill fees and fines for improperly recycling have shaped a more efficient system. The company’s two facilities in Colorado could process as much as 700 tons of recycled glass in one day, if it was available. But for the sake of realism, Nordmeyer says a 50-50 split of recycled and new materials would be considered success.

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The crushed-up pieces of recycled glass are combined with silica sand, soda ash and limestone to create new glass. It all goes into a furnace hotter than a volcano — more than 2,800 degrees Fahrenheit. That molten glass flow travels through a refiner where air bubbles can escape, then the glass gets portioned into gobs that are dropped through a series of molds. 

At that point the glass has cooled to about 1,300 degrees Fahrenheit, but the outside cools faster than the inside. A penultimate step, called annealing, reheats the whole container and slowly cools it down, which helps to strengthen the glass. The bottles get a final outside coating and, like magic, they’re ready to be filled, used and recycled all over again. 

“The beer that you enjoy today could be back on the shelf as a new beer bottle containing a different style of beer, a different brand of beer, in the state of Colorado,” Nordmeyer said, “in less than 30 days.”

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