Plastic waste finds eco-friendly use
New Delhi, Apr 30: The plastic waste, creating pollution hazards all over the country, can be turned into an ''environment- friendly'' purpose if used in the construction of roads, according to a study sponsored by the Central Pollution Control Board.
Bitumen blended with waste polymers such as polythylene (sheets), polypropylene (sheet and film) and Polystrene (thermocol) has improved properties as binder for the road construction, experiments done by Thiagaraj College of Engineering, Madurai have proved.
Use of shredded plastic waste in bitumen for laying roads has helped in preventing creation of potholes, a common problem of Indian roads.
The technology is eco-friendly too as re-use of the plastic waste in this method is better than recycling of the material, which emits fugitive emissions. Problems like disposal of waste and blockages of waste stream would be automatically taken care of once its put to use.
Under the existing method, granite mixture is used with bitumen.
The blend cannot prevent trapping of water between the layers of the two materials, resulting in development of potholes.
The process is accelerated during movement of vehicles.
However, when polymer is coated over the aggregate, the coating reduces its affinity for water due to non-wetting nature of the polymer and this reduces the penetration of water.
During the road laying process, mixing of plastic material do not create any environmental hazards, as no burning of the waste is involved, which in turn prevents green house gases emission into the atmosphere.
The mixing of plastic waste in bitumen also reduces bleeding of bitumen in summers, as waste-polymer bitumen blend shows higher softening temperature.
The use of plastic also saves bitumen by ten per cent, thus helps in the conservation of the material.
The technology for laying bitumen-plastic road is the same as prescribed by the Indian Roads Congress specifications.
The whole process is very simple. The existing technology is only slightly modified. No new machinery is needed and the available mini hot-mix plant and central mixing plant can be used. For its use in the road construction, the waste plastic gains resale value.
Besides, it also creates jobs for ragpickers and segregators.
The consumption of plastic has increased manifold in India over the last two decades. It was four million tonnes a year in 2001 and it is expected to rise to 7.5 million tonnes till 2007. The per capital plastic consumption in the country is 3.8 kg per annum. Plastics have become a major threat to the environment because of their non-biodegradability. Their presence in the waste stream poses a serious problem as there is no efficient management of waste.
The study recommends that post-consumer plastic waste like carry bags, cups, tumblers, spoons, plates, thermocol etc thrown with domestic waste, should be segregated. The plastic waste can also be picked up from large users like Railways, hotels, airports, schools, factories, community halls, banquet halls etc. After segregation, it should be shredded and stored in a dry place to be supplied when needed for the road construction.
Mixing shredded plastic with bitumen is much better than disposing it off even by inceneration. In inceneration, the waste material is heated between 700 to 1200 Degree Centigrade and burnt completely. The gases are driven out and the residue ash is used for landfilling. For the incineration process, the maintenace of temperature is very important as the process produces toxic gasses if temperature is not properly maintained.
In India most of the waste is not burnt scientifically but in open air without maintaining temperature between 700-1200 Degree Centigrade, which cause the formation of the harmful dioxin.
The road constructed with polymer-bitumen mix has given a good performance in Chennai, Madurai, Koilpatti. Salem, Tanjore, Nagercoli and Mumbai.