Biodegradable Plastics
From Chempedia
Contents |
Background
Biodegradable plastics are plastics that are produced from renewable resources and break down easily in the environment. Biodegradable plastics are becoming more popular because of their unique quality to break down a lot faster than traditional plastics. Biodegradable plastics have become increasingly common in the every day lives of many people and are replacing some of the traditional plastic products that have been known for so long. The reason why many biodegradable plastics can be broken down relatively easily is because they are being made of renewable resources. These resources can be broken down with the everyday activities of living organisms in the natural environment. When these biodegradable plastics are broken down by the microorganisms, they are decomposing into H2O and CO2. [1]Traditional plastics cannot be broken down easily because of their longer chains of polymers that are tightly bonded.
Materials which biodegradable plastics are made of
Biodegradable plastics, as mentioned above, are being made by renewable resources. One of these resources is soy concentrate. The way biodegradable plastics are made from soy concentrate involves the compression of the concentrate. This concentrate is then tested at different temperatures to determine the sturdiest, yet biodegradable, product.[2] Since this product is made from raw material, it is easily broken down in a composting facility.
Another common product that biodegradable plastics can be made of is starch. Starch is developed through the photosynthesis of plants; it is a substance of granular carbohydrates. Starch is water soluble, but it can be modified into a less soluble polymer by microorganisms. These microorganisms can then transform the starch into lactic acid. Once this is done, the lactic acid is chemically treated so it links into polymer chains.[3] These chains, however, are not as tightly bonded as the traditional plastic which leads to easier breakdown of this substance.
Bacteria can also be used in the production of biodegradable plastics. Bacteria can produce granules of plastic called polyhydroxyalkanoate (PHA) inside their cells. These bacteria, with the genes produced, can be put into the corn, and the corn consequently manufactures plastic within its cells. (Image [4])
Bacteria can also be grown in cultures and the plastic growing in the bacteria can be harvested.[5]
It is also important to notice how gelatin and casein contribute to biodegradable plastics. Gelatin is a form of collagen that can be used in sausage casings and drug capsules. Obviously each of these plastics can be broken down easily in the human body. Another form of biodegradable plastic is Casein, which is made up of natural protein. Casein is made from organic substances such as the skimming of cow’s milk, corn, and vegetable products. Casein can be used in adhesives, binders and protective coatings.
Lastly, since cellulose makes up to 40% of all organic matter, it to has been used in the production of biodegradable plastics.[6] Parkesine was the first biodegradable plastic that was made with cellulose. It consisted of cellulose, nitric acid, and a solvent. This product appeared to be much like ivory and could be molded when heated.[7] Parkesine was only the start of the production of biodegradable plastics made with cellulose.
Uses of biodegradable plastics
With the recent advancements within the industry, there are biodegradable plastics that replace virtually all traditional plastic products. Today there are biodegradable grocery bags, food packaging, disposable razors, toothbrushes, cups, suture threads, bone fixation, and many other things that are made from these environmentally friendly products.
Scientists are actually researching methods to use plastics to help people make new bones. Biodegradable plastics are being designed and implemented to be growth-inducing properties in humans. An example of these biodegradable plastics used in the human body is shown here.(Image [8])
Why people should use biodegradable plastics
Although these biodegradable plastics are anywhere from 2 to 10 times more expensive than the traditional plastics, a fact that must be considered is that it takes traditional plastics a lot longer to break down. As soon as biodegradable plastics come into contact with microorganisms, they will begin to break down. The microorganisms break down the biodegradable plastics into soil. Biodegradable plastics are actually able to break down 60%-90% in just 60-180 days in a compost setting.[9] The items in the table are traditional plastics when scattered around as litter.[10]
| Plastic coated milk cartons | 5 years |
| Plastic bags | 10-20 years |
| Plastic 6-pack holder rings | 450 years |
| Plastic bottles | Forever |
Considering everything that has been presented about biodegradable plastics, it is up to everyone on their own whether they want to contribute to the safety of the environment or save some money.
Since biodegradable plastics are becoming more familiar in this world, it is most interesting to discover the process by which they are made and what they are made of. Ultimately, the chemical structure of the materials that make up biodegradable plastics is what makes them as environmentally friendly as they are.
Footnotes
- ^ Regional Roundup: Bio Cycle. July 2005. vol 45 issue 7, p 18-18
- ^ Green Plastics: An introduction to the new science of Biodegradable Plastics. Stevens, E.S. [11] (accessed 9-24-05)
- ^ Bio-Plastics. http://www.japan-cornstarch.com/hh_13.html
- ^ Biodegradable plastics. Salt, David. http://www.science.org.au/nova/061/061key.htm (accessed 9-25-05)
- ^ Web article: Nature Biotechnology: production of polyhydroxyalkanoates, a family of biodegradable plastics and elastomers, in bacteria and plants. Yves Poirier, Christiane Nawra. [12] (accessed 9-23-05)
- ^ Plastic. Wikipedia. [13]. (accessed 9-26-05)
- ^ CNN Archives. Neo-organs: Scientists use plastic to help the body make new bone. [14]
- ^ Biodegradable. Worldwise, Inc. [15]. (accessed 10-30-05)
- Stein R.S. Polymer recycling: Opportunities and limitation. Proc. Natl Acad. Sci. USA 89
- Biodegradable Plastics Society. [16] (accessed 9-25-05)
Researched and written by: Ashley Januszewski, Carl Cabak, and Ledor Igboh
