Polystyrene foam is one of the most common forms of plastic. You see it in takeout containers, beverage containers, egg cartons and the packaging peanuts used to cushion goods for shipping.
You may have stood in front of adjacent trash and recycling bins and asked yourself, "Is Styrofoam recyclable?" The term "Styrofoam" is actually the brand name of a rigid blue insulation that the Dow Chemical Company makes, not the lightweight white foam you find in takeout coffee cups. Liquid Foam For Packing
That said, polystyrene is a very versatile material, but recycling it can prove challenging.
The term "polystyrene" means that the plastic derives from styrene, a liquid hydrocarbon. When heated, monomer styrene molecules link together into long chains, creating a polymer material that's solid when it cools to room temperature. Developed in Germany in the 1930s, we use that clear, hard, brittle plastic to make CD and DVD jewel cases and plastic forks.
In 1941, Dow scientist Ray McIntyre invented extruded polystyrene foam (Styrofoam), a light, waterproof material previously used in the production of life rafts. Expanded polystyrene foam (EPS) is another, similar foam material that has found even more uses.
Because it's about 95 percent air, EPS is an excellent insulator. That's why it's in beer coolers and home insulation, and why the hot coffee in a polystyrene cup doesn't burn your fingers. Because it's light, EPS is ideal for creating buoyancy in life vests and rafts. Its lightness and malleability make it a good packing material, adding cushioning but little weight.
Also, EPS doesn't react with other materials and is resistant to heat, so it has wide use in the food industry in things like meat and poultry trays and the boxes that fast-food hamburgers are served in.
However, some of the same qualities that make polystyrene useful can also work against it when it comes to recycling.
Its lightness means the foam packing is hard to collect as part of curbside recycling programs — it often blows away, becoming litter. Because it's bulky, it's difficult and expensive to transport. Many municipal recycling programs do not accept it.
One of the problems with all plastic recycling in general is that you have to gather the same types of materials together and sort them by their material container code — a number usually found on the bottom of the container that makes it easy to identify the type of plastic in the object.
Some other plastics — like 1 (used for soda and water bottles), 2 (laundry detergent and other containers) and 4 (plastic bags) — are easier to isolate.
Polystyrene, which is No. 6, presents more problems. While water and soda bottles are relatively clean when discarded, polystyrene used for food and beverage containers often mixes with paper, food scraps and other types of plastic, like the straw that you might throw away with an EPS cup.
You usually cannot recycle Styrofoam or polystyrene at a local recycling center. Instead, it has to make its way to a centralized plant, increasing costs to the recycler and reducing the incentive to recycle.
Recycling EPS causes other problems, too. It cannot, in most cases, work for products that come into contact with food because of health concerns, even though the recycling process sterilizes the material. Instead, manufacturers might use recycled EPS to create packaging or other materials, but new EPS is always needed for coffee cups and plates.
So, what's the best way to recycle polystyrene and why might bacteria someday play a role in the process?
The polystyrene industry claims a recycling rate of about 12 percent, according to the Alliance for Foam Packaging Recycling, but that includes scraps from EPS manufacturing, which get reused immediately.
The fact is that it's often easier and cheaper to produce new polystyrene than it is to collect, transport and process material for recycling. Since simply tossing your Styrofoam containers in the recycling bin is not helpful, here are a few options.
The most direct way for consumers to recycle polystyrene is to reuse it. This method doesn't work as well with coffee cups and plastic forks, but it's ideal for packaging materials.
You can collect packing peanuts and simply use them again. Shippers may take rigid packaging and chop it into small pieces to use as loose packing. UPS accepts packing peanuts from the public for reuse.
Reprocessing, or the act of creating other products out of old polystyrene, can give the plastic a new life. For example, the Dart Container Corporation, the largest producer of polystyrene food containers, has four plants in the U.S. and Canada that receive EPS from schools, supermarkets, hospitals and other users.
Here's how the reprocessing works at their plants:
Carrying truckloads of light, bulky polystyrene to recycling facilities is usually not economical. Recyclers have found ways to compact the material to a more manageable size. Balers take foam packaging and compress it, reducing the bulk somewhat.
Another method is to use limonene, a natural solvent made from orange peels. Limonene dissolves and concentrates EPS and can itself be reused. The chemical causes the EPS foam to "melt" without heat, reducing it to 5 percent of its original size. Thermal compaction uses heat to reduce chopped EPS to a concentrated brick that's easier to ship.
When burned in municipal incinerators, polystyrene yields nothing but carbon dioxide and water vapor. It's a good fuel for waste-to-energy programs that capture the heat and turn it into useful purposes, a process known as thermal recycling.
If recycling polystyrene sounds like a lot of trouble, what's the point of doing it? Read on to find out some reasons why.
An interesting use of recycled EPS is a product that looks like wood and that builders can use for park benches and fence posts. The material costs less than hardwood and is an alternative to woods harvested from rainforests, such as mahogany and teak.
Making polystyrene requires petroleum, which is a nonrenewable resource. So recycling polystyrene reduces the amount of oil needed for the manufacturing process. This is not a pure gain, of course, because some energy will still go to transport and to reprocess the material.
The most visible benefit of polystyrene recycling is the reduction of litter both on land and in the sea. EPS — which oxygen, sunlight and water do not affect — stays around indefinitely. Municipalities have to spend money to clean it up. That's why a number of cities, including San Francisco and Seattle, have banned EPS in takeout food packaging.
Polystyrene takes up space in landfills, where it will remain for hundreds of years. The industry argues that this is not a real drawback because modern landfills are sealed from moisture and light and are not meant to encourage biodegradation. Even organic material does not break down once it reaches a landfill.
Polystyrene also poses a threat to marine life. As it wears out over time, EPS disintegrates into tiny particles, which look like food to fish, and they may eat it. The foam clogs the digestive systems of marine animals, killing them.
It's estimated that EPS makes up 60 to 80 percent of marine litter, according to a 2008 review in Environmental Research. Recycling can help reduce the amount that winds up in the sea.
Recycling consumer polystyrene also prevents the material from being burned in backyard fires or burn barrels. Polystyrene can produce toxic chemicals when burned unless efficient incinerators are used.
The benefits and the difficulties of recycling polystyrene are good examples of the complex issues that can arise when we're looking at ways to conserve resources and protect the environment. The solutions, as in the case of recycling polystyrene, are not always easy.
But we can't necessarily duck the question by turning to alternative materials, either.
For example, the paper cup that holds your takeout coffee usually has a plastic coating, meaning it's not recyclable. It also does not break down in landfills. Even reusable containers, like a ceramic cup, requires much more energy to produce than a polystyrene one and typically continues to use energy to heat the water needed to wash it.
There may be savings in the long run, but the choice is not as clear as it sometimes seems.
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