When you next go shopping, you'll probably come back with a plastic bag or two. Try an experiment with it. Take a flower pot, and bury a paper bag and a plastic bag in it. Wait for a month, and dig them out. Which one had degraded?
The problem with disposing plastics
Polyethylene is considered one of the marvels of modern chemistry. It is light, waterproof and can undertake a huge amount of strain. That makes it ideal for use as a shopping bag. In fact, 80 million tones of polyethylene are manufactured every year worldwide.
Unfortunately, disposing off polyethylene bags has become a major environmental problem. They overflow dustbins and choke drains. They are dangerous to animals or children who may swallow them. They can be degraded by soil bacteria, but that can take 1000 years!
Making biodegradable plastics
Many chemical companies are now trying to make less harmful plastics. Two of the commonly made eco-friendly plastics are polyhydroalkanoate (PHA) and polylactic acid (PLA).
PHA is made naturally by a bacterium called Alcaligenes eutrophus. To make it commercially, PHA genes have been introduced from this bacterium to another one called Bacillus subtilis. These bacteria grow easily in agricultural wastes, which make the process cheap. PHA can be moulded easily, so it is used to make disposable cutlery, plastic boxes etc. Depending on their thickness, objects made from PHA take from 7 weeks to 5 years to degrade.
PLA is made in two steps. Corn or sugarcane is first fermented by bacteria to make lactic acid. The lactic acid is then used to make PLA by chemical catalysis. PLA has many uses, especially for medical purposes. It can be degraded easily by the human body, so it is used in bandages and sutures. It is also used as packaging material for food. A Japanese company even sells wedding gowns made entirely of polylactic acid!
How we can help
Biodegradable plastics are still a growing technology. Hence you may not come across them very often, though that will happen in a few years' time.
Till that happens we can help by not asking for bags when we shop, and carrying out own cloth or paper bags. Carrying a metal tiffin box to school instead of a plastic one can help too!
If you want, you can try and make your own bioplastic. Here's a video by a youngster that shows you how:-