How to Recycle ‘Weird’ Glass

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When it comes to recycling, knowing what not to put in the bin is sometimes just as important as getting the right materials in there in the first place.

From the nuances of pizza box recycling to knowing what forms of plastic you can recycle in your local program, there’s no shortage of rules to keep up with.

This author had her own epiphany about recycling rules while researching this particular article: Not all glass is created equal.

“It’s just like dealing with different polymers in the plastic industry,” said Joe Cattaneo, president of the Glass Packaging Institute (GPI), the trade association representing the North American glass container industry. “Just because it looks the same doesn’t mean it is all the same.”

broken drinking glass

A broken drinking glass like this typically can’t be processed in container recycling programs. Photo: Duke LeNoir/Flickr

Additives = Contaminants

Most recycling programs are set up to process container glass, like beverage bottles or condiment jars. This class meets certain regulations to be certified safe for food.

But the glass that makes up everyday household items like ovenware, drinking glasses, incandescent light bulbs, windows, windshields, and mirrors contain materials like lead and plastic that cannot be mixed with container glass.

Let’s take the example of windshields, for example. According to a representative working in the windshield recycling industry, windshields have a layer of plastic “sandwiched between the glass.” This plastic is a contaminant in the recycling stream and is very difficult to remove. There is a machine called a windshield stripper,” he tells Earth911. “It’s an expensive piece of equipment, upwards of $100,000. It basically liberates the plastic from the glass.”

Windshields, like other types of non-container glass, have specific, and sometimes limited, recycling options. For example, this representative’s company recycles glass from obsolete or broken inventory from manufacturers and does not accept materials directly from consumers.

“[A] consumer with a windshield more or less has to throw it away because to bring it to us costs more money than that glass is going to be worth,” he says.

Additionally, because glass is recycled using a heat-intensive melting process, the different chemical compositions and tempering found in non-container glass can vary.

“The issue with glass containers, or soda lime glass, is that it can get contaminated by other types of glass such as ovenware, because [ovenware is] a much stronger tempered glass that’s made to be reused and in the oven and microwave,” says Cattaneo. “It’s a higher durable glass that won’t melt at the same temperature as typical bottles and jars. It will cause stones that will make the ‘regular’ soda lime glass break.”

This goes for your coffee mug, too, because ceramics have different chemical compositions than container glass.

Stronger forms of glass made to withstand high levels of heat and environmental stress can also damage equipment in recycling facilities.

“In fact, glassware, ceramics, window panes, or mirrors can pose a threat to equipment in a glass recycling plant,” according to the Washington State Department of Ecology.

broken mirror

You can’t recycle them, but materials like broken mirrors are fodder for fabulous DIY projects like sun catchers and mosaics. Photo: zen Sutherland/Flickr

What You Can Do

So what does this mean for the rest of us, exactly?

Just like other recycling streams, it’s better to not add materials to the recycling bin that may cause problems down the line than assuage your “green guilt” for creating more trash. You’re likely to just contaminate your recyclables.

Cattaneo’s advice is also not leave it up to chance whether or not your glass will actually get recycled.

“There certainly are some types of drinking glasses, for example, that could be mixed with soda lime glass, but “it’s so difficult to discern one from the other. The issue is that often they could be decorated, or they could have lead in them. Lead crystal isn’t meant to be recycled; it’s meant to be reused over and over and then thrown away.”

Don’t let the word “lead” make you nervous though. According to Cattaneo, “Glass does not contaminate landfills; it’s inert.”

Cattaneo also cautions against being too general. “[Potential glass recyclers are] probably going to have to look in their own community on where they can get that taken care of.” In other words, check with your local recycling facility to find out what types of glass they accept and don’t accept.

Glass Projects Abound

While it may be a bit tough to find ways to reuse a broken windshield (We’re open to suggestions!), drinking glasses and ovenware pieces can be reused in a number of facets.

A word of caution: Do be careful when crafting with glass. Here’s some helpful advice from Associated Content: “If you want to use them [broken pieces of glass] for something that requires you to smooth the edges and make them safe, you can do so by squeezing hot glue along the edges or by covering the edges with masking tape. You can also use a Dremel or other small sanding tool to smooth down the edges. Be sure to wear safety goggles and heavy duty gloves to protect your hands.”

Check some of these cool projects the next time you get hit by a clumsy moment:

Earth911 partners with many industries, manufacturers and organizations to support its Recycling Directory, the largest in the nation, which is provided to consumers at no cost. The Glass Packaging Institute is one of these partners.

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