Living Smart

II ENVIRONMENT & SUSTAINABILITY 054 055 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 Curbing plastic waste at source is key Dr. Melody LEUNG Lecturer II, Division of Life Science P lastics 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 plastic bags and organic matters separately, such as newspapers and fruit peelings, in microbe-rich soil, and comparing the results under a controlled setup.