When most glass bottles are recycled, they’re dumped in a pile and pulverized until they turn back to sand. These sand-like leftovers, called aggregate, are an unsophisticated mix of glass, metal caps, paper labels, and other scrap. And it can only be used in low-grade construction materials and as a layer to cover landfills. The bottle someone took the time to recycle, with hopes of making a cleaner Earth, ended up back in a landfill anyhow. But recent technological advancements have made it possible to turn a recycled bottle into an entirely new bottle.
NPR‘s Planet Money team went to a recycling plant in Jersey City, New Jersey how old glass can be converted into a new bottle.
The first step is to take the aggregate and sort out all the non-glass materials. The mix is passed through a magnet which pulls out basic metal scrap. But not all metals are magnetic, so the mix then moves through an eddy current machine which creates a magnetic field inside non-ferrous metals like aluminum and copper and ejects them from the mix, leaving only glass.
Clear glass is more easily converted back into bottles than other colors. Optical sorters take instant photographs of glass on the conveyor belt to analyze the color of each fragment. Jets of air are used to push the pieces around and sort them by color. A task that would take many humans hours of labor is accomplished in seconds.
The sorted glass fragments are then sold to bottle manufacturers, in this case the Ardagh Group in Salem, N.J, who makes Snapple bottles and mason jars. The glass is shipped and delivered, ready to be reused.
The recycled glass is mixed with soda ash, sand and limestone and melted together in a furnace at 2700 degrees Fahrenheit. Because recycled glass melts at a lower temperature than the raw materials used to make new glass, less energy is used per bottle. Companies like the Ardagh Group simply can’t get enough of the glass. Ardagh alone goes through 150 tons of recycled glass daily, making their new bottles 20-25 percent recycled. If more was available, they’d happily double that percentage.
The molten glass is cured and then then transfered to forming machines where it is cut into drops or “gobs,” which are immediately shaped into a glass container.
The glass-blowing machines are used to shape the “gobs” into bottles, which are then moved to an oven. After the bottle is completely made, it goes through an automated inspection process. The machines can blow up to 400 bottles per minute.
As Gary Shears, the general manager at the Ardagh plant said, “The beauty is if you recycle one Snapple bottle in New York City, we now have the ability to make another.” Finally, when an old bottle goes in, a new bottle can come out.
NPR Planet Money
Images by Lam Thuy Vo, NPR