Biodegradable Polymers

  A. Ecological problems

    Plasticizers and polychlorinated hydrocarbons used in the manufacture of plastics pose a health hazard and they may incorporate into the food chain, eventually getting into human body.

    Plastic wastes in the sea directly affect fishes.  Small fishes have been found dead with their digestive tracts clogged by fragments of plastic foam they had ingested.  Our sea animals also die of suffocation by plastic bags.

  B. Environmental problems

    As plastics are chemically tailored for long life, they do not generally decomposed in the landfill and remain in the environment for a long period of time.  Disposal of plastics by burning produces air pollutants such as hydrogen chloride which causes acid rain.  Also, the polychlorinated hydrocarbons in plasticizers decompose in the stratosphere to produce free radicals chlorine atoms, which is a catalyst to break down ozone.

  C. Economical problems

    The disposal of plastics requires a long term investment and the pollution problems caused by plastics also need to be solved by lots of money.  These are financial problems.  Furthermore, plastics use up the valuable space in landfills, which can otherwise be used for other purposes such as property development.

What actually are bio-degradable polymers?

As non-biodegradable polymers threaten our environment, more extensive use of environmentally friendly biodegradable polymers in Hong Kong should be promoted.  But what actually are biodegradable polymers?  And what are their advantages over non-biodegradable ones?

Plastics normally undergo extremely slow degradation because the enzymes in micro-organisms tend to attack only at the ends of the polymer chains.  Biodegradable plastics are plastics that can undergo faster and more complete degradation.  There are three main types of biodegradable polymers:

1. Biopolymers

  These are polymers made by living micro-organisms, for example, poly(hydroxybutyrate) PHB is a natural polyester made by certain bacteria.  This polymer can be broken down by aerobic micro-organisms commonly found in soil and natural water sources.  Degradation of this polymer in the environment is usually complete within nine months.

2. Photodegradable plastics

  They have light sensitive functional groups such as carbonyl groups incorporated into their polymer chains.  These groups enhance the ability of the plastic to absorb UV radiation from sunlight, which triggers a photochemical reaction.  The polymer is broken down into small fragments, which then further dissociates into carbon dioxide and water, that is, becomes biodegradable.

3. Synthetic biodegradable plastics

  The are made by incorporating starch or cellulose into the polymer during production.  Since micro-organisms digest the starch or cellulose, the plastic is broken down into tiny pieces.  The very small pieces left over have a large surface area which greatly speeds up their biodegradation.

Why using biodegradable polymers?

The answer is simple – they are environmentally friendly!  Since they are biodegradable, they impose no long term disposal problems and thus produce no pollution consequences.  Unlike non-biodegradable ones, biodegradable polymers degrade usually within one year, which is much faster than the ordinary ones.  They do not remain in the environment forever.

Another important reason is that it is increasingly easier to each biodegradable polymer and they are used to produce more common materials.  Examples include six-pack beverage rings, trash bags and disposable diapers.  These products are chosen because they entangle wildlife, make up a high percentage of litter, or cause pollution.

Act now!

So up till now, I believe you understand the significance of biodegradable polymers to our worsening environment.  To create a better environment for our next generation, use biodegradable polymers from now on!