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Plastic waste

  Sep 12, 2017

Plastic waste

The menace
The quantum of solid waste is ever increasing due to increase in population, developmental activities, changes in life style, and socio-economic conditions. Plastics waste is a significant portion of the total municipal solid waste (MSW). The plastics waste constitutes two major category of plastics; (i) Thermoplastics and (ii) Thermoset plastics. Thermoplastics, constitutes 80% and thermoset constitutes approximately 20% of total post-consumer plastics waste generated in India. The Thermoplastics are recyclable plastics which include; Polyethylene Terephthalate (PET), Low Density Poly Ethylene (LDPE), Poly Vinyal Choloride(PVC), High Density Poly Ethylene (HDPE), Polypropylene(PP), Polystyrene (PS) etc. Recycling of plastics should be carried in such a manner to minimize the pollution during the process and as a result to enhance the efficiency of the process and conserve the energy.

The menace
The Task Force on plastic pollution, set up by the Planning Commission in 2014 had estimated that 60 cities across the country generate over 15,000 tons of plastic waste every day—almost 6 million tons per year. Cattle and other animals, which freely move around the streets, unknowingly devour some of this plastic material, which is not digested but stays put in their stomachs leading to their eventual death. It is time that India ban plastic bags and related stuff before the water bodies, land and seacoasts are choked and menace turns into a manmade disaster.

The landlocked African country Rwanda has banned plastic bags since a few years; Kenya has just announced a ban on plastic bags; Morocco has had such a ban for almost a decade.

Plastic degrading microbes
A lot of plastic waste from across the world eventually ends up in the oceans, which cover over 70% of the earth’s surface and hold 97% of the earth’s water. The amount of plastic rubbish reaching the oceans is 8 million tons per day. By 2050, there will be more plastic in the world’s oceans than fish. The huge amounts of plastic thrown in the oceans that keeps floating is hardly 1%, the rest sinks way down and/or are slowly being degraded or broken down.

Researchers have partially succeeded to identify, isolate and study the biological species that seem to degrade plastics into small molecules. These plastics can be used for safer purposes. Scientists have identified certain species which are responsible for biodegradation of plastics, these are some fungi and bacteria. Two strains of the fungus aspergillus spp, found in the waters of the Gulf of Mannar degrade the plastic HDPE which is used to make milk and fruit juice bottles, grocery bags and such. These fungi release some enzymes which degrade HDPE, essentially breaking up the polymeric molecule into smaller pieces.

Also, enzymes from the microbe named, Ideonella sakainesis are capable of breaking down the polymer PET (polyethylene terephthalate, used in making packaging trays, polyester clothing and others) into its basic monomeric molecules terephthalic acid and ethylene glycol which are used as building blocks for a variety of chemicals. The microbe is found in soil, sediment, waste water and similar material.

Recently, scientists have shown that the fungus Aspergillus tubigensis can degrade plastic material called polyurethane or PU (used in the manufacture of car tyres, gaskets, bumpers, fibres, plastic foam, synthetic leathers).

Scientists have concluded that microbes can be genetically modified to suit any intended purpose. This type of research will bring a great deal of benefit to not only terrestrial life forms but those living under water as well.