Turning trash to terra firma

A 70-year-old academician has used waste plastic to make 20,000 km of roads that are twice as durable as the normal tarred ones

It's the material everyone loves to hate, and occupies centrestage in practically every forum on environment and conservation, principally because of the huge hazard it poses to human and animal health.

Which is why an innovation by Rajagopalan Vasudevan, DEAN ECA and Professor at the Department of Chemistry at Thiagarajar College of Engineering offers a beacon of hope to municipalities battling with the safe disposal of waste plastic. Vasudevan has used it as an alternative construction material to lay about 20,000 km of roads across the southern parts of the country. He has done this both, at the state level and for private parties, such as Jayakrishna Flour Mill, Madurai, Food Grains India, Madurai and Plast India Packaging Industry, Pondicherry.

He began experimenting with the idea in 2001, by mixing some waste plastic with heated bitumen (tar). And now the 'Plastic Man', as he is known, is taking this concept to other states, training engineers on the technology. Thiagarajar College in Madurai, Tamil Nadu, where Vasudevan teaches, holds the patent for his technique but often licenses it for free.

According to Vasudevan, plastic consumption is estimated to be around 12 million tonnes, of which nearly half is used for packaging such as carry bags, cups, thermocoles and foams.

These products, which are manufactured using polymers like polyethylene, polypropylene and polystyrene, are discarded once used and form a large part of the litter in large and small cities. They mix with municipal solid waste, and since they are non-biodegradable and have limited recycling potential otherwise, are generally on the top of the list of environmental pollutants.

"Yet, these very packaging products -- either mono-layers or laminated poly-layers made out of polyethylene, polypropylene and polystyrene -- can be easily used for various uses like road construction, block making, roofing, and such like, without affecting the environment. Only polyvinyl chloride (PVC) is not used," says Vasudevan.

How does the technology work? Vasudevan elaborates that plastic waste is shredded into small pieces of 1.6–2.5mm. A granite stone is heated to around 170 degrees Celsius and the shredded plastics waste that is added it, melts to form a coat around the stone in just 30 seconds. Bitumen heated at 160 degrees Celcius is then added, and this mixture is used for road construction.

Vasudevan claims he has been using this technology to build all kinds of roads, from rural to national highways. He adds, "The use of each tonne of plastic waste avoids the entry of three tonnes of carbon-di-oxide into the atmosphere, which would otherwise result in global warming.”

Vasudevan further claims that for every one kilometer stretch of road with a width of 3.75 meters, one tonne of plastic, equivalent to a million carry bags, is used and one tonne of bitumen is saved. Each tonne of bitumen costs Rs 50,000-60,000. In comparison, each tonne of plastic waste costs Rs 5,000-6,000 if it is bought from municipalities. Flexible pavement scrap, or tar road scrap,  can also be reused effectively by coating with plastic waste. This helps reduce the cost by 50 per cent, since bitumen is already contained in the scrap. It also reduces the cost of road maintenance.

Vasudevan is being approached by other states in the country, such as Maharashtra, Goa, Himachal Pradesh, and Shillong (Meghalaya) to promote the use of plastic tar.  

He says plastic-tar roads are twice as durable as traditional ones and claims that some of the roads in Madurai have not required any maintenance for the past five years. He adds, "We laid the Jambulingam street in Chennai in 2002. It is performing well even today and entails a substantially lower maintenance cost."

Vasudevan has also developed another solution involving the use of plastic, for the construction industry. He claims the solution can be a substitute for concrete and other blocks and that industries are ready to try the process. While the technology is yet to be commercialised, the institute where he teaches has demonstrated it at a workshop conducted by Tamil Nadu government to promote entrepreneurship development in the state.