Published: 1 July, 2009

Plastic cutlery: its impact on environment

How long does it take for the so-called biodegradable plastic cutlery that is now on the market to decompose? What is the energy cost to produce it in the first place? Are they truly an environmentally responsible product?

This is an excellent question, one that many scientists have spent many hours discussing. As has been mentioned in this column in the past, plastics are also known as polymers in the scientific community. The word "polymer" comes from Greek words meaning "many parts," because plastics (polymers) are actually long chains of small molecules, much like a long chain of people holding hands. Therefore, the cutlery we are discussing is made from long chains of molecules. The biodegradable plastic cutlery available today is commonly produced from poly(lactic acid), which is a plastic that begins in the form of small molecules derived from corn. If you look for plastic containers with the recycling symbol 7, and the letters PLA below, you have a plastic made from poly(lactic acid). Some food containers at Wegmans are made from this plastic and have that symbol on them.

Research has shown that under optimal conditions (such as an industrial compost center), this plastic will degrade in 45-100 days. However, when poly(lactic acid) plastics are disposed in the trash and sent to the city landfill, the plastic won't degrade any faster than any other plastic, which is estimated to be at least hundreds of years. This is because heat, sunlight and oxygen are required for the decomposition of the poly(lactic acid) and it is difficult for sunlight and oxygen to penetrate the tons of soil and thick plastic liners of a landfill. It is also difficult to achieve the required composting conditions in the compost pile in ones backyard. Because of these difficulties in achieving optimum conditions, some stores selling products packaged in containers made of poly(lactic acid) have a program where customers can bring their used containers back to the store for the appropriate composting, rather than throw them in a landfill with the rest of the trash.

There are other issues with turning corn into plastics besides disposal. Some people question whether we should be using food products (corn) to produce materials or if it is more responsible to use it to feed people. Also, it is unclear how much energy it takes to grow, harvest and process the corn to produce the polymer and then eventually recycle it. Some scientists have argued that it is actually more energy efficient to just use petroleum resources to produce plastics as, overall, this process might produce less greenhouse gasses such as CO₂ and consume less energy. One could also question why we need so many disposable containers that are only used for an hour or two and then disposed of in the landfill to sit for hundreds of years.