Message in a bottle: Combining mixed-color glass an possibility to spice up recycling – TechnoNews

The glass bottles we toss within the recycling bin do not all the time find yourself the place we count on. Solely about 33% of glass is recycled in the US, in accordance with the Environmental Safety Company, partly on account of bills like sorting bottles by colour. Penn State scientists not too long ago discovered that mass-produced soda-lime silicate glass from post-consumer bottles of various colours may be safely melted collectively within the recycling course of, which may doubtlessly result in extra bottles being recycled.

The group reported their findings within the Worldwide Journal of Ceramic Engineering & Science.

“This work broadly addresses a widespread misconception that different colored glassbottles can’t all be recycled together,” mentioned Katy Gerace, who carried out the analysis as a doctoral scholar within the Division of Supplies Science and Engineering at Penn State. She graduated in 2023. “We have confirmed that you can melt all these post-consumer glass bottles together to create new, useful glass products.”

Soda-lime silicate bottles, probably the most recycled kind of glass, are was cullet—glass that has been crushed into small items, or grains—earlier than being remelted. Cullet is most frequently sorted by colour in order that producers can obtain particular colour and readability for his or her merchandise. And the provision of pristine, color-sorted glass cullet limits how a lot recycled materials is used within the manufacturing course of, the researchers mentioned.

Small-scale producers who’re targeted on recycling, and never on reaching a selected colour bottle may make the most of mixed-color cullet, protecting extra glass bottles out of landfills and lowering power prices related to manufacturing glass, the scientists mentioned.

Remelting glass cullet requires much less power than uncooked supplies, which interprets into much less carbon dioxide produced throughout the melting course of. For a ten% enhance in recycled content material, the scientists mentioned, there’s a 3% discount in power consumption.

“We are exploring how to add value to waste,” mentioned Gerace, who’s now a analysis and improvement senior engineer at Vitro Architectural Glass. “We are trying to think of this not as waste but as something that potentially could have value.”

The work stems from a partnership between Penn State and Comment Glass, a Philadelphia-based firm targeted on progressive and artistic glass recycling.

“As a small business, they are really interested in trying to remove glass from the waste stream and keep it out of landfills,” mentioned John Mauro, the Dorothy Pate Enright Professor of Supplies Science and Engineering at Penn State and co-author of the examine.

“They use only post-consumer glass bottles and so they are very interested in understanding the chemical and material properties of the raw materials that come into their business. They wanted to know if there were any technical reasons for them to be concerned about what they’re doing.”

Comment Glass supplied glass bottles for the examine, and Gerace analyzed the samples for chemical composition and thermal properties to quantify variation throughout 5 main colour households: clear, blue, amber, forest inexperienced and emerald inexperienced.

Along with demonstrating that post-consumer bottles of various colours and types may be remelted with out threat of fabric incompatibility, the researchers additionally offered varied processing strategies to manage colour homogeneity in glass produced completely from combined colour cullet from recycled glass bottles.

Gerace mentioned the particle dimension of the cullet and the temperature and time of the remelting course of have the most important impacts on colour homogeneity.

“You have to keep the glass melted for all the different ions to diffuse and move around to create a consistent color,” she mentioned. “So, you can either really extend the time of the melt and hold it at a high temperature for a long time to wait for everything to kind of equilibrate or you can decrease the particle size of the cullet into more of like a fine powder. Then it becomes a little easier to get a nice consistent color.”

This implies, for instance, that varied shades of inexperienced bottles could possibly be crushed into cullet and melted to supply a homogenous inexperienced glass. Nonetheless, if a selected shade of inexperienced is required, then the bottles can be additional separated.

“Glass is one of the best materials to recycle, but when you actually go look at the process for how it’s done, it’s very non-trivial,” Gerace mentioned. “And unfortunately, we lose a lot of what we put in our recycling bins to the landfill simply because we don’t have a good way of separating and sorting it. And that’s really unfortunate.”