Whatever be its method of disposal, plastic poses a huge threat to the environment. Burial causes soil contamination while burning releases poisonous gases into the atmosphere. Even incineration — burning plastic in a controlled, scientific manner — leads to environmental problems if the temperature isn’t maintained properly.
Calcutta generates about 500 metric tonnes of plastic waste daily. In an attempt to deal with this problem, a conference was recently organised by the West Bengal State Council of Science & Technology (WBSCST) and the Department of Science & Technology, Government of West Bengal, to discuss a novel technique of safe disposal developed by Alka Zadgaonkar, head of the department of applied chemistry, G.H. Rasioni College of Engineering, Nagpur.
“Plastic waste has become a menace and we need to get rid of it in an eco-friendly way,” said Dr Hemanta K. Majumdar, WBSCST working chairman.
Zadgaonkar has of late been in news for her method of degrading waste plastic to produce fuels. The process, invented and patented by her, is capable of dealing with all kinds of plastic — from carry bags, broken buckets and chairs to PVC pipes, CDs, computer keyboards and other e-waste as well as aluminised plastic bags. No sorting is required. The stuff is shredded and fed into a conventional extruder. Here, the waste is plasticised (converted to plastic polymers) and melted at a relatively low temperature. The melt is then stripped of chlorine and led to a reactor. The melt now interacts with proprietary catalysts invented by Zadgaonkar. The stable, continual chain of carbon found in all plastics is destabilised by a depolymerisation reaction and rendered ready for a rich harvest.
Three streams of produce are obtained. A part of the gaseous cloud is condensed to form a liquid hydrocarbon. This is fuel oil, a sulphur-free equivalent of industrial crude oil. The other products are gas (an LPG-equivalent that can be used to generate electricity) and coke.
Zadgaonkar’s method is being widely put to use in Nagpur. A plant has been set up that can process five metric tonnes of plastic waste everyday. The fuel oil obtained is sold for Rs 25 per litre. Zadgaonkar has also signed an MoU with the Indian Oil Corporation for optimisation and upgradation of the process, and development and economic analysis of the demonstration plant.