Dear EarthTalk: Why can’t plastics of all types, instead of being initially sorted, simply be melted together to be separated later? It must be a monumental and error-prone task to separate truckloads of plastics.
— L. Schand, via e-mail
The reason plastics aren’t typically melted together and then separated later 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 are not only reducing sizable amounts of waste from going into landfills but are also 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 forebears. The seven common types of plastic are: #1 Polyethylene terephthalate (PET or PETE); #2 High-density polyethylene (HDPE); #3 Polyvinyl chloride (PVC); #4 Low-density polyethylene (LDPE); #5 Polypropylene (PP); #6 Polystyrene (PS); and #7 Other/Mixed (O). One complicating factor is trying to recycle unmarked plastics and those embossed with a #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 #7 plastics can be “down-cycled” into non-renewable resin; in other cases recycling operations just send their unmarked and #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 non-profit recycler with an international reputation as an innovator in resource conservation. The group adds that over the past half century, the use of disposable packaging—especially plastic—has increased by more than 10,000 percent.
Along these lines, products (or packaging) made out of 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 re-used 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!