Published: 27 December, 2000

Biodegradable plastics take time to completely dissolve

If plastic is made to be biodegradable, then won't the plastic forks and spoons we use dissolve in our mouth?

Plastics are indispensable to modern life. However, every year, more than 30 billion pounds of plastic wastes are generated by American consumers, clogging our landfills and polluting our landscape. Just to give you an idea of how much waste this is, if you dumped all of this plastic waste on the Cornell University football field, it would reach about 3 miles up into the sky! Therefore a significant amount of scientific work is directed at developing polymers that degrade in the environment into non-toxic materials.

These so-called biodegradable polymers degrade in natural environments by reacting with water and/or various bacteria. One everyday example where a biodegradable polymer has taken the place of conventional plastic is in the packing 'peanuts' that surround merchandise during shipping. In the past, these were made of a non-degradable polystyrene, but are now commonly made of a natural starch-based material. My guess is that you might have found that these new 'peanuts' are soluble in water, perhaps prompting you to ask your question.

Fortunately, there are a range of biodegradable plastics, each of which has its own rate of degradation. The key is to make the plastic degrade slower than the estimated lifetime of the object, yet fast enough that it doesn't persist in the environment. There are two promising plastics in this respect: polylactic acid (PLA) and polyhydroxybutryate (PHB).

PLA is currently being commercialized jointly by Dow and Cargill, and they plan to make a range of new plastic objects, such as the clam shells that are used in the fast-food industry.

PHB has previously been used in Europe. Shown below is a shampoo bottle made of PHB that was allowed to decompose in soil. As you can see, the plastic degrades over months, not minutes! Therefore, this would be an ideal plastic to make plastic utensils.

Hopefully biodegradable forks will be common in the near future. When they appear, don't worry -- you will be able to take your time eating with these forks!