Sorting through plastics

Dear EarthTalk: Why can’t plastics of all types simply be melted together instead of being initially sorted? It must be a monumental and error-prone task to separate truckloads of plastics.

– L. Schand, via e-mail

Plastics headed for sorting and recycling
Photo: Dan LaMee, Flickr
The reason plastics aren’t typically melted together is a matter of both physics and economics. When any of the seven common types of plastic resins are melted together, they tend to separate and then set in layers. The resulting blended plastic is structurally weak and difficult to manipulate. While the layered plastic could, in theory, be melted again and separated into its constituent resins, the energy inputs required to do so would make such a process cost prohibitive.

As a result, recycling facilities sort their plastics first and then melt them down only with other items made of the same type of resin. While this process is labor intensive, the recycling numbers on the bottom of many plastic items make for quicker sorting. Many recycling operations not only reduce sizable amounts of waste from going into landfills but also are profitable if managed correctly.

Manufacturers of plastic items choose specific resins for different applications. Recycling like items together means the reclaimed polymer can be used to create new items just like their virgin plastic forbearers. The seven common types of plastic are:

· No. 1 – polyethylene terephthalate (PET or PETE)
· No. 2 – high-density polyethylene (HDPE)
· No. 3 – polyvinyl chloride (PVC)
· No. 4 – low-density polyethylene (LDPE)
· No. 5 – polypropylene (PP)
· No. 6 – polystyrene (PS)
· No. 7 – other/mixed (O)

One complicating factor is trying to recycle unmarked plastics and those embossed with a No. 7 (representing mixed resins, also known as polycarbonate). According to Earth911, a leading online source for finding recyclers for specific types of items across the United States, in some cases No. 7 plastics can be “down-cycled” into nonrenewable resin; in other cases, recycling operations just send their unmarked and No. 7 plastics into local landfills.

But even though recycling operations have developed relatively efficient systems for generating reclaimed resins, many environmentalists recommend that consumers still avoid plastics as much as possible. “Simply recycling these products does not negate the environmental damage done when the resource is extracted or when the product is manufactured,” reports EcoCycle, a Colorado-based nonprofit recycler with an international reputation as an innovator in resource conservation. The group adds that the use of disposable packaging – especially plastic – has increased by more than 10,000 percent in the past 50 years.

Along these lines, products (or packaging) made from reusable metal, glass or even wood are preferable to equivalent items made from plastic. For starters, an item of metal, glass or wood can be reused by someone else or recycled much more efficiently than plastic when it does reach the end of its useful life to you. Wood products and other items crafted out of plant material – even so-called “polylactic acid (PLA) plastic” made from plant-based agricultural wastes – can be composted along with your yard waste and food scraps, either in your backyard or, if your town or city offers it, through your municipal collection system.

Happy reducing, reusing and recycling!

CONTACTS: Earth911,; EcoCycle,

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