Indian chemistry professor shows that repurposed plastic can be good for the environment
At 73, Dr Rajagopalan Vasudevan is roughly as old as the mass production of plastic. But that is not the reason why the chemistry professor has a soft spot for the much-maligned material.
Plastic isnt the problem, the venerable scientist says in his office in the southern Indian city of Madurai. We are. Plastic wouldnt clog our oceans or our landfills if we didnt throw it there in the first place. And there is so much we can do with it instead.
He should know. In January this year, Dr Vasudevan was honoured with one of Indias highest civilian awards, the Padma Shri, for his groundbreaking research on re-using waste plastic in a very unusual way.
The idea emerged from his workshop at the Thiagarajar College of Engineering in Madurai as far back as 2001. Disturbed by calls to ban plastic, which he believed was important to poor people, he wanted to find a solution to the growing environmental challenges it raised.
Ban plastic and it can severely affect the quality of life for a low-income family, he says. But if you burn it or bury it, its bound to affect the environment.
And so, he began a series of experiments in his workshop to discover effective disposal techniques. In a molten condition, he found that plastic had the property of an excellent binder. Acting on the principle that like attracts like, Dr Vasudevan looked at another chemical of similar nature: bitumen, a black tarry substance that was being combined with gravel to lay roads.
Bitumen, a highly heterogeneous mixture of hydrocarbons is in effect, composed of polymerssimilar to plastic, he says. When molten plastic was added to stone and bitumen mix, Dr Vasudevan found that, true to its nature, plastic stuck fast and bound both materials together.
The bitumen-modified plastic improved the tensile strength of the road by making it more durable and flexible. Plastic also prevented pothole formation. When the layer of molten plastic filled the space between the gravel and bitumen it thwarted rain water from seeping in and causing structural defects.
When late Dr Abdul Kalam, Indias former president and scientist visited Thiagarajar College, he encouraged Dr Vasudevan to lay the first plastic paved road within the campus. He asked me to make the roads grey, since black roads absorb and trap heat, says Dr Vasudevan. In 2002, he paved a 60-ft road within the campus with plastic-modified bitumen. The road is still intact today. He received a patent for the process in 2006. Since then, almost 10,000km of Indian roads have been paved using his technique.
At Dr Vasudevans workshop, shredded plastic in big bins shines like bright confetti . These are the remains of the plastic material that we use (and throw away) in our everyday lives. Plastic from water bottles, notebook liners, single-use bags with a thickness of less than 50 microns; all kinds of plastic waste is fed into his shredder and reduced to strips.
An assistant demonstrates on a much smaller scale how the plastic road-laying process works.
Asphalt is heated to a temperature of 170C (338F). Shredded plastic below 70 microns (including the multi-layer plastic shreds) is then sprinkled over it. The bits of plastic seemingly disappear, melting into the red heat. Heated bitumen is added next. The molten plastic then moulds with the bitumen and stone and results in a shiny tar surface.
When using plastic as a binder, were reducing the quantity of bitumen that is normally utilized for road laying by 6-8%, says Dr Vasudevan.
A regular road requires 10 tonnes of bitumen for each kilometre. A plastic road however, requires only nine tonnes of bitumen and one tonne of waste plastic for coating. So, for every km, the plastic roads save as much as one tonne of bitumen.
Our planet is drowning in snack-food packaging that is non-recyclable, says Almitra Patel, a member of Indias supreme court committee for solid waste management. If (this technology is) seriously adopted in all cities for all multi-film laminates, it has the potential to achieve near-zero landfill, leaving almost nothing for final disposal.
The real challenge lies, she says, in collecting all of the voluminous post-consumer packaging.
To environmentalists who believe that the technology could be harmful because of toxic fumes from plastic residue, Dr Vasudevan points out that the plastic used is softened at 170C. Plastic decomposes to release toxic fumes only if it is heated at temperatures above 270C (518F). So there is no question of toxic gases being released, he says. Since plastic coats the stone and interacts with the hot bitumen, its properties change and it doesnt break down when exposed to light and heat.