Jadavpur University, Kolkata in collaboration with CPCB, Delhi has reengineered a process for plastics recycling. The existing extrusion process is not considered to be environmentally sound as it causes noise and fugitive emissions. The machine developed and tested by the Department of Mechanical Engineering, Jadavpur University, Kolkata is equipped with pollution monitoring and control device and has been tested for fugitive emissions, which were found far less than traditional machines. The main components of the machine are as follows:

Phase-I: Segregation, Cutting, Cleaning & pulping: Raw materials collected from the supplier is stored at the proper place. The segregated High and low density polyethylene (HDPE & LDPE) are cut and cleaned (wherever required) with the help of detergent. The cleaned plastic wastes are taken to a machine called agglomerator with low temperature heating arrangement to convert plastic wastes in the form of pulp like shape which act as raw material for extrusion process. In some cases the cleaned and cut plastic wastes directly fed to the extrusion machine.

Phase – II, Extrusion & Palletization : It is done by a barrel and screw type extrusion machine with band electric heater. Power is supplied from a motor and the screw barrel is fed through a gearbox. Electric band heater is heated through electrical power source. Crushed raw material is fed through the hopper. Output from the extrusion machine is the wire shape plastics, which is palletized to get plastic granules.

The Extrusion and Pelletisation process have been redesigned to minimise the pollution from the process and to enhance the efficiency of the process.

It is anticipated that the reengineered machine can replace the existing to minimize pollution problems. Interactions are made with the manufactures to commercialize the developed machine

The concentration of sulphur dioxide ( SO₂), gaseous Hydrochloric Acid (HCl), Formaldehyde (HCHO) , Carbon monoxide & Dioxides ( CO & CO₂ ), NO_X and Particulate matters were measured. It has been found that in most of the cases the measured value of Carbon Monoxide & Di oxides ( CO & CO₂ ) and Nitrous Oxides (NO_X) were found below the detectable limit. However, the presence of sulphur dioxide, gaseous hydrochloric acid and formaldehyde were predominant.

A National Symposium was organised on December 15, 2004 by Jadavpur University, Kolkata in collaboration with CPCB, Delhi at Kolkata. The recommendations of the symposium are below:

1. The environmental impact assessment due to the recycling process at the unit is to be carried once in a year;
2. The existing machines are to be restructured with pollution monitoring & treatment device;
3. The operators must be trained on effective extrusion process, pollution control and monitoring process. Staff working at the unit must be given awareness on the impact of potential pollutants generating from recycling process;
4. The screw-barrel has to covered to avoid heating the ambient atmosphere;
5. Controlling process temperature to help save energy vis-à-vis cost;
6. Involvement of NGOs/institutions for collection of post-consumer plastics and transportation of recycling units/waste collection centers;
7. Establishing plastics recycling park in metropolitan cities;
8. Developing a corpus fund by the major producers of polymers in the country
9. National level Mass Awareness programmes/campaigns shall be conducted involving media and school children.

Since Plastics show binding properly on softening (heating around 140⁰ C) this property can be used to modify Bitumen, a binder for road construction. Studies are being carried out at Department of Chemistry on this line and it has been observed that polymer coated aggregate with Bitumen is a better materials for road construction in terms of strength and resistance to wands rain water. In addition, by this process, the plastic waste find a very useful disposal technique and a new technology can come into existence. Polymer blended Bitumen shows higher Softening point, lower penetration point, and better ductility. Polymer coated aggregate blended with Bitumen shows higher Marshall value and better stripping value showing that the mix is more suited for road laying.

The dry cleaned or diried plastics waste is shredded into small pieces (passing through 4.35mm sieve) The aggregate (granite) is heated to 170^oC in the Mini Hot Mix Plant and then shredded plastics waste is added, It gets softened and coated over the aggregate. Immediately the hot Bitumen (160^oC) is added and mixed well. As the polymer and the bitumen are in the molten state (liquid state) they get mixed and the blend is formed at surface of the aggregate. The mixture is transferred to the road and the road is laid. This technique is extended to Central Mixing Plant too.

It has been observed that addition of plastics waste upto 10-15% by weight of bitumen resulted into higher values of softening point and lower values of penetration, which are appreciable improvements in the properties of the binder. This has resulted and withstood higher traffic load and high temperature variation. Several experimental stretches have been laid in the State of Tamilnadu, Maharashtra, Karnataka and Pondicherry using both Mini hot-mix and Central mixing plants.

Government of India has notified "Recycled Plastics Manufacturer and usage Rules, 1999 as amended 2003, which is applicable in all the States/Union Territories. Out of 34 States and Union territories, 15 States and Union territories have brought out separate Non-biodegradable Garbage Act. These States and Union Territories are also conducting mass-awareness programmes to make the public aware about the ill-effectsof littering of plastics. As per the provisions of the "Recycled Plastics Manufacturer and Usage Rules, 1999 as amended 2003", all the plastics manufacturing/recycling units are to be registered with concerned State Pollution Control Boards/Pollution Control Committees. In this context, 17 States Pollution Control Boards/Pollution Control Committees have completed inventorisation process and started granting registration.