Curbing plastic waste at source is key| Melody Leung 12 Dec 2018
Plastics occupy a central role in our daily life. From chewing gums and toys to electric home appliances and latex paint on our walls, it is hard to imagine life without plastics.
Recently, a government-backed incentive campaign was launched with the help of three major local fast-food chains in a bid to spur diners' new habit of foregoing single-use takeaway utensils.
Plastics give us convenience, especially when everyone is used to having them in almost every facet of our living, but plastics come at a very steep cost.
The University of California has found that seven billion tons of waste plastics were produced in 2015, of which 79 percent ended up at landfills.
Scientists estimate that plastic bags will take about 500 years to degrade and become a major source of pollution. But how did scientists arrive at this conclusion when plastic bags
have been widely used only about 60 years ago?
To measure the speed of decomposition of organic matters, scientists would usually conduct a series of respirometry tests.
These tests involved researchers burying separately plastic bags and organic matters, such as newspapers and fruit peelings, in microbe-rich soil, and comparing the results under a controlled setup.
Under stable temperature and humidity, microorganisms would assimilate the sample bit by bit and produce carbon dioxide, with the resultant carbon dioxide levels serving as an indicator of degradation.
As the tests are often conducted outdoors, climatic and soil composition could affect the speed of decomposition.
Thus, there would be a slight difference in data collected in different countries. In general, newspapers and peelings would take about six weeks to be degraded completely.
Most plastic bags that we use today are made of nondegradable polyethylene. Microorganisms do not recognize them as food and they remain intact throughout.
Scientists therefore use the term "500 years" to refer to a process that would take "a really, really long time."
Even if plastics undergo photolysis under the sun, they won't be degraded and will just be "downsized."
Some may become very small hardly recognized by the naked eye, giving these tiny plastic bits a high chance of entering the bodies of plants and animals.
While it is unclear how these tiny plastics affect living creatures, we must pay more attention to the potential danger that plastic pollution poses to our society.
Today, some companies have released biodegradable plastic bags and diapers.
But since these plastic products are sensitive to temperature and humidity and their quality changes over time, reception to them in Hong Kong is lukewarm.
In her policy address in October, Chief Executive Carrie Lam Cheng Yuet-ngor said the government would launch before the end of the year a feasibility study on the control or ban of single-use plastic tableware. Reducing waste at source will still play a crucial role in curbing plastic pollution. Adopting a greener lifestyle holds the key in the next 500 years.
HKUST experts have their fingers on the pulse of a new age of science, technology and innovation