After banning plastic carry bags and promoting paper bags and cups, Kerala government is now promoting the use of waste plastic in laying roads. Four such roads will be laid soon - two each in Kozhikode and Thiruvananthapuram. This follows the successful laying of one kilometer road using waste plastic in Thiruvananthapuram on an experimental basis in January 2006.

National Transportation Planning and Research Centre will be providing the plastic shredding machine, which they have procured at a cost of Rs 40,000 for shredding the plastic required for the four road projects, according to B G Sreedevi, who heads the Highway Engineering Lab of NATPAC.

Plastic shredding machines are available from Rs 40,000 upto Rs 2 lac depending on the capacity of the machine. Initially, out of the one kilometer road being laid, half will be done blending waste plastic while the other half would be laid conventionally. This is to help a comparative analysis of both the roads, Sreedevi added.

Kudumbashree, self-help groups of women in Kerala will collect the plastic required. In Thiruvananthapuram, the city corporation would also utilize the carry bags seized during the raids in shops and establishments following the ban on plastic carry bags. The waste plastic collected has to be sorted out, cleaned and dried before being fed into the shredding machine.

Only thermo-plastics can be used for road laying. This includes carry bags up to 60 micron thickness, tea cups, water bottles and ice-cream cups, according to Kurian George, Deputy Director, Kerala Highway Research Institute.

If the questions of who will collect the plastic, who will shred them and who will make it available in large quantities for road laying are successfully answered, the project will be successful, George said.

More awareness creation is needed to help public sort plastics at source rather than throwing it on roads, canals and open spaces. KHRI was involved with the maiden plastic road laid last year in Sreekariam-Gandhipuram road, which has been found to be durable with adequate compression strength and firmness.

George said imposing a ban on plastic is not a solution to deal with the problem of non-biodegradable waste. A more pragmatic solution is the use of waste plastic. One example is Tamil Nadu, where plastic has been used for laying more than 1500 kilometers of roads.

The process is comparatively simple. Plastic waste made out of Polyethylene, Polypropelene PS are separated, cleaned if needed and shredded to small pieces The coarse aggregate (granite) is heated to 170oC in the Mini hot Mix Plant and the shredded plastic waste is fanned into the aggregate. Immediately the hot Bitumen (160oC) is added and mixed well. As the polymer and the bitumen are in the liquid state, they get mixed.

The mixture is transferred to the road surface. George said that since the plastic suffers a temperature of only 160-170 degree centigrade, the issue of air pollution does not arise at all. At 600-700 degrees, harmful carbondioxide and carbon monoxide will be released in the air, he said.

George said waste plastic can be used for laying kilometers of roads but the challenge is to make waste plastic available. Thermoset plastics such as buckets, PVC pipes cannot be used for road laying. "For our project we had to bring waste plastic from Madurai, however, for such projects to be socially meaningful locally available waste plastic should be utilised," he added.

Plastic can be used from two per cent upto 20 per cent of the total bitumen weight and road strength is double than normal roads, and would not have potholes. Besides, burning of plastic can be avoided and consumption of the petroleum product bitumen can also be reduced.

Dr R Vasudevan, Head of the Department of Chemistry in Thiagarajar College of Engineering in Madurai developed the technology for this and got Patent for from the Union Government in 2002. His experiments show that plastic roads were free from wear and tear even after three years. Plastic roads can last up to 10 years as against the conventional road life of five years.