Q: On all the recycling bins at our waste facility and in the information we get from the people who pick it up, we are told that we can't recycle styrofoam. What do we do with it?
Asked by Joe Bates, Gr. '71, Noblesville, Ind.
More than 2.5 million tons of polystyrene are dumped into landfills each year. Less than one percent is recycled. The difficulty with EPS recycling is that it's expensive to transport. Ironically, the very qualities that make EPS such a great packing material—it's light and bulky—make it wildly inefficient to ship. Take a box. Fill it five percent full with oil. Seal it and ship it. That's what shipping EPS amounts to: sending a lot of empty space with very little mass.
If you can get EPS to a collection point without burning more oil than you're recovering, the recycling process is actually quite simple. They dump it into a densifier, which makes light and fluffy EPS into a brick of EPS using blades, heat and pressure. Think paper shredder followed by trash ompactor. EPS in this form is much more economical to transport.
Once those bricks arrive at the recycling center, they are broken down into smaller pieces so the EPS can be melted and reshaped. The bricks are shredded so that they fit into an auger—a long, heated tube with a giant corkscrew in it. Dumping the shreds into one end and turning the screw moves the material along the heated tube and melts it. The liquid is then pushed through a plate with a bunch of holes, like a garlic press, and cooled with water. The result is small pellets of pure polystyrene called resin pellets.
From there, manufacturers will buy the recycled polystyrene and use it as they wish. Some companies melt the pellets down again and make nonexpanded polystyrene building products, such as insulation or crown moldings for homes. Other uses include cafeteria trays, office supplies or even more EPS.
Reusing EPS means more than just repackaging. People have found practical and less-than-practical applications for their extra EPS. But hearing some ideas may inspire your own. . . .
EPS has great insulation properties, which is why it is a popular choice for transporting hot food. Even if it's been used, it still retains that property, which makes it great for keeping doghouses or sheds a little warmer. Remember that it's also flammable, so avoid using it in your own house.
EPS is waterproof so you can use it for plant drainage. Dump some packing peanuts in the bottom of a pot, add dirt and watch your plants grow. Of course, add water as needed.
Arts and Crafts
Many people suggest using EPS for crafts, such as jewelry making. Consider a styrene-studded bracelet or an EPS necklace that doubles as neck warmer (great insulator). This might be fun for kids, but adults should probably stick to wearing precious gems and metals.
More on d-limonene
d-limonene is a naturally occurring oil from citrus fruit rinds. It's great because it's renewable and safe and dissolves only EPS, not contaminants like dirt and food. Another advantage is that the d-limonene can be used again once the PS (no longer "expanded") is separated from it.
And it's not just for making glue. According to a study in Packing Technology and Science, five gallons of d-limonene can reduce 200 gallons of EPS to five percent of its original volume. This means twenty trucks' worth of EPS could be taken by one truck.
In 1998, this finding by Sony scientists led to the design of a pilot recycling program called Orange R-net. A huge truck with a vat of d-limonene ran around to different Sony stores to collect their EPS packaging. Unfortunately, the pilot program seems to have vanished without a trace—and that almost certainly means things didn't work out well, though it's unclear whether the problems were technological or economic.
We can't eat those packing peanuts, but maybe bacteria can. In 2006, scientists reported on a bacterial process that could convert polystyrene to a biodegradable plastic called polyhydroxyalkanoate (PHA). The one drawback is that you first have to use energy to melt the PS, to convert it to styrene oil. Once you have that, you can feed it to a flask of Pseudomonas bacteria and come back the next day to harvest the new earth-friendlier PHA, which can then be used in a number of medical applications, including sutures.
I went ahead and tried out the resources I found.
The American Chemistry Council has a searchable database of several hundred buyers of used plastics and ranks them by distance based on your zip code. I got contact information for the seven places on the list within 50 miles of Stanford and shot them emails. Three were bounced back to me saying the email address didn't exist—whoops. Two buyers got back to me. One said that price depends on the grade, volume and quality. The other gave me a price of $2.80 per pound if it says "CRV" or "CA Redemption" on it. That may be worth my time.
Earth911.com gave me eight pages of options, including curbside programs, drop-off sites and mail-in programs. They also gave me a map of all the drop-off centers, with the option to limit how far I'm willing to travel. The Alliance of Foam Packaging Recyclers has a PDF file with a list of drop-off centers in various cities and their phone numbers. They also have PDF files of mail-in sites and large volume recyclers. In my opinion, the Earth911.com system is easier to navigate.
I'm a student on a tight budget, so I bought an inexpensive orange instead of a $20 bottle of d-limonene. Not only did this allow me to run a crude experiment, it also allowed me to reuse my materials for a sweet post-experiment snack. I set the orange on a piece of EPS overnight. I thought I would awaken to find the orange lodged in the EPS. I was disappointed that the only effect was a small gray spot on the orange peel. Maybe this was the glue and it just dried, preventing further chemical reactions. Clearly, further studies are necessary, pending next week's trip to the grocery store.
Andrew Hellman is a PhD candidate in biology.