Module 51 Only Humans Generate Waste

Module 52 The Three Rs and Composting

Module 53 Landfills and Incineration

Module 54 Hazardous Waste

Module 55 New Ways to Think About Solid Waste

553

Polystyrene is a plastic polymer that has high insulation value. More commonly known by its trade name, Styrofoam, it is particularly useful for food packaging because it minimizes temperature changes in both food and beverages. Polystyrene is lighter, insulates better, and is less expensive than the alternatives. However, a number of years ago, polystyrene was deemed harmful to the environment because, like all plastics, it is made from petroleum and because it does not decompose in landfills. In response to public sentiment, most food businesses greatly reduced or eliminated their use of polystyrene. All over the country, schools, businesses, and public institutions have purged their cafeterias of polystyrene cups and most have replaced them with disposable paper cups.

But was the elimination of polystyrene actually an environmental victory? It is hard to quantify the exact environmental benefits and costs of using a paper cup versus using a polystyrene cup. For example, because a paper cup does not insulate as well as a Styrofoam cup, paper cups filled with hot drinks are usually too hot to hold and vendors often wrap them in a cardboard band that becomes additional waste. To fully quantify the environmental costs and benefits of each type of cup, one must create a list of inputs and outputs related to their manufacture, use, and disposal. This input-output analysis of all energy and materials is also called a cradle-to-grave, or life-cycle, analysis. When we make a list of all the materials and all the energy required to produce and then dispose of each type of cup, we find that it is not easy to determine which choice is better for the environment.

554

One study found that making a paper cup requires approximately 2 grams of petroleum along with 33 grams of wood and bark, which are renewable materials. A polystyrene cup requires 3 grams of petroleum, a nonrenewable material, but no wood or bark. Manufacturing the paper cup requires about twice as much energy, and much more water. A paper cup of the exact same size as a polystyrene cup is substantially heavier, which means it requires more energy to transport a paper cup to the location where it will be used. Air emissions are different in the manufacturing of each type of cup and it is difficult to say which emissions are more harmful to the environment. Since more energy is needed to make and transport a paper cup, it is reasonable to assume that using it generates more air pollution. A paper cup is normally used once or at most a few times while the polystyrene cup can, at least in theory, be reused many times. However, both types of cups are usually thrown away after one use. There has been concern among some scientists—but no consensus—that a polystyrene cup might leach chemicals from the plastic into the coffee; if this is true, using a paper cup could pose less risk to human health. However, without proper disposal, the bleach used to make paper cups in a paper mill, along with small amounts of the associated by-product, dioxin, can cause harm to aquatic life when the water is discharged into rivers and streams. Incineration of both types of cup could yield a small amount of energy. In a landfill, the paper cup will degrade and eventually produce methane gas, while the polystyrene cup, because it is made of an inert material, will remain there for a very long time.

Weighing these and other factors, one study concluded that a polystyrene cup is more desirable than a paper cup for one-time use. However, critics of that study felt that the author did not consider the toxicity of emissions from making polystyrene, the exposure of workers to those emissions, the impact of both cups on global carbon dioxide emissions, or the possibility of making the cup from materials other than petroleum or paper. Today, there is still no definitive answer as to whether the paper cup or the polystyrene cup causes less harm to the environment.

These types of studies illustrate that analyzing the environmental effects of the products we use is complex since it involves the synthesis of many aspects of environmental studies. Not only does it include science, ethics, and social judgments, it also necessitates a systems-based understanding of waste generation, waste reduction, and waste disposal. There is widespread agreement that paper and Styrofoam are not the only options. Reusable mugs are a possibility but they would require consideration of a host of different life-cycle issues such as greater inputs for manufacturing, and energy consumption, as well as the water and other resources needed to clean them after each use.

Sources: M. B. Hocking, Paper versus polystyrene: A complex choice, Science 251 (1991): 504–505, DOI: 10.1126/science.251.4993.504; M. Brower and L. Warren. The Consumer’s Guide to Effective Environmental Choices (Three Rivers Press, 1999).