- New Plastics Made from Plants. - Darin Harris
Bioplastics are much like traditional plastics; however, instead of being made from petroleum they are made from the molecules found in living organisms. Since they are formed from organic molecules, bioplastics are biodegradable. Those formed from petroleum polymers biodegrade very slowly, sometimes taking hundreds of years.
Plastic and Petroleum
To make useful products from petroleum, the oil has to go through a process called refining. In this process it is slowly heated up. As it reaches different temperatures, various compounds, such as gasoline, kerosene and petroleum jelly, are separated out of the oil.
Other compounds that come from oil are not as well known, like ethylene and benzene. Molecules of ethylene are able to form long chains of molecules called polymers, and when these polymers are mixed with other chemicals and heated they form plastics. These long chain polymers are very complex molecules, and there are very few organisms in nature that are capable of breaking them down.
The fact that oil-based plastics are not biodegradable is not the only concern with their use. Petroleum is a nonrenewable resource, and with millions of uses of plastic in existence, finding alternative resources for making plastics is important. Currently the creation of these materials consumes approximately two million barrels of oil every day.
Making Bioplastics
Some of the very first plastics, however, weren’t made from petroleum at all. Scientists realized long ago that plastic could be made from plants. Today, scientists are going back and experimenting with plant plastics. Plants have large molecules, like starch, which are long chain polymers. These polymers are different than the polymers from petroleum, but if they are mixed with the right chemicals and “cooked” precisely they become plastics.
Though corn is the most common plant used, it isn’t the only one. In fact, many plants like soybeans and hemp create enough starch that plastics can be made from them. Scientists are even experimenting to see if some living plants can make plastics. This process hasn’t been perfected yet. Some of the plants now being used to make bioplastic include:
- Corn
- Hemp
- Potatoes
- Safflower
- Switchgrass
- Soybean
- Tapioca
- Wheat
Bioplastic from Algae
Some scientists are looking to the oceans for the future of plastics. Algae, tiny, floating plant-like organisms, create starches, like plants on land. They are much smaller than plants, but they have some advantages. Algae are able to reproduce very quickly and grow year round, so more starch can be harvested.
Cereplast Corporation is one company that is working to produce plastics from algae. According to Emily White, “Cereplast is planning to have an algae based plastic on the market early in 2011.” Cereplast already makes bioplastics from more traditional plants. “The products are fully compostable in commercial facilities within 60-180 days, leaving no chemical residue.”
Biodegradable
While bioplastics are biodegradable, most of them cannot be simply composted. The new molecules created when making them can often only be degraded in anaerobic (without oxygen) conditions. Because of this they cannot be placed in the average home compost bin for decomposition. However, commercial composting facilities and municipal landfills do provide the conditions necessary for bioplastics to biodegrade rather quickly.
Sources:
Books
Knapp, Brian. Plastics: Making Use of the Secrets of Matter. (Danbury, CT: Grolier), 2003.
Websites:
American Chemistry Council, “History of Plastics,” Americanchemistry.com Web access 6/20/2010.
Huff, E. “Plant-Based Plastics to Replace Petroleum Plastics?” Natural News.comSaturday, January 30, 2010. Web access 6/26/2010
Lupton, Emily. “Peril of petroleum-based plastics” San Diego Union Tribune 01/14/2010 . Web access 6/26/2010.
Scott, Andrew. "Down on the plastics farm," Rsc.org Web access 7/15/2010.
Shwartz, Mark. "Researchers develop biodegradable substitutes for wood, plastic bottles and other common materials," Physorg.com Web access 7/15/2010.
Society of the Plastics Industry, Plasticsindustry.org Web access 6/20/2010.
Trafton, Anne. "One word: bioplastics," Physorg.com Web access 07/15/2010.
Interview:
White, Emily. Cereplast Corporation. E-mail interview 6/28/2010.
Darin Harris - Darin Harris has spent 11 years as a high school science teacher and received a Master of Arts in Teaching from Cameron University. In ...
