Page 39 - Plastics News June 2019

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Recycling for Sustainability

Professor Dr. D. D. Kale
I ntroduction Methods of recycling

India is consuming about 16 million tons of plastics The major ways of recycling of plastic waste are:
per annum. This does not include the fiber, rubber
and coating industry. Fast growth of Indian plastic 1) Mechanical recycling,
industry may have commenced from about mid 80s. 2) Chemical recycling,
Thermoplastics can be recycled and this was put to 3) Feedstock recycling,
industrial practice in India when there was a shortage of
all type of plastics, particularly the commodity plastics 4) Pyrolysis to get gaseous fuel or liquid fuel and finally
such as polyethylene, polypropylene, or polystyrene 5) Incineration without recovery of power.
etc. Although plastic is very useful, it is being in the
bad news, of late. There appears to be a race amongst Some aspects of these can be looked into briefly.
the different state Governments to ban the plastics. Mechanical recycling
The menace of banning the plastic started with carry
bags of thickness less than 6 microns in around 1990. In mechanical recycling, the defective goods or clean waste
generated in-house is shredded, melted and extruded in
Minimum thickness of 20 micron was recommended so
that uncontrolled littering may be avoided, as rag pickers the form of pellets for reuse. These reprocessed pellets
can be mixed with virgin plastic in different proportions
may find it attractive to pick up the littered carry bags.
The new Plastic Waste Management Rules, PWM 2016, are to make new articles. The proportion of recycled material
in the in-house industrial waste is less than 10 %.
recommending that all plastic carry bags of thickness less
than 50 micron be banned. This is the only item banned The municipal waste or the waste collected and segregated
by the Central Government. by rag pickers along with other members of the supply

Ban and the reactions of different groups chain is washed to remove dirt and other contaminants
before pelletizing. These pellets are mixed with virgin
When any such ban comes in the news, there are usually material by processors to make new articles. In some
three groups. First group is plastic industry which tries cases, 100% recycled material can be used. Cheap carry
to tell everybody how good plastics are. Second group, bags can be one such example.
sometimes supported by non plastic lobby shout that
plastic is highly dangerous to the public life and even The recycling of PE and PP for 5 to 6 times does not
carcinogenic. The marine litter adds up to such cry. Third result in appreciable loss in mechanical properties
group is undecided and is prepared to accept good and of virgin material. However, this is possible only if
bad points of plastics. The sustainability and carbon uncontaminated polymer is reprocessed. Thus defective
foot print calculations add one more dimension to the films or injection molded articles produced at the
scenario. processor site can be recycled easily. If other type of
waste is to be reprocessed, it has to be cleaned and
Let us look at the connection between recycling and freed from unknown contamination. In addition, the PE
sustainability. If we look at the average consumption or PP should be segregated. The mixed plastic waste is
pattern of polymers, we notice that more than 60 not suitable for reprocessing by mechanical method of
% consumption is of PE and PP. Major application is recycling. Thus the multilayered films used in packaging
packaging films. The global consumption pattern of cannot be reprocessed easily. If composition of such films
polymers is: PE 40 % ; PP 24 % ; PVC 19 % ; PET 7 % ; Rest is known, it may be possible to reprocess them by using
of plastics 10 %. The films, sheets and injection molded appropriate compatiblizer. Thus there are limitations on
items which are found in the waste contribute to the tune mechanical recycling. Also after repeated reprocessing,
of about 64 %. The share of packaging film is about 33 % the material may not be good for mechanical recycling
while the blow molded articles contribute to about 10 %. as the mechanical strength of recycled material is poor.

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41 June 2019 Plastics News