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 isn’t the problem,” the scientist says in his office in the southern Indian city of Madurai. “We are. Plastic wouldn’t clog our oceans or our landfills if we didn’t 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 India’s 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, it’s 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 polymers similar to plastic,” he says. When molten plastic was added to stone and bitumen mix, Dr Vasudevan found that 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, India’s 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 Vasudevan’s 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. 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, we’re reducing the quantity of bitumen that is normally utilized for road laying by 6-8 per cent,” 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 kilometre, 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 India’s 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. So there is no question of toxic gases being released,” he says. Since plastic coats the stone and interacts with the hot bitumen, it’s properties change and it doesn’t break down when exposed to light and heat.
Dr Noreen Thomas, a polymer science expert at Loughborough University, said the process appeared to be an imaginative solution, but cautioned that plastic waste is often a complex mix of materials not all of which would work well with Dr Vasudevan’s operations. Some might burn up in the heat, and others, she said, might prove unsatisfactorily soft as a road surface.
“There is always a risk when heating or burning mixed plastic waste in an open environment when the composition of the plastic waste is unknown,” she said. “It is important to find more applications for mixed plastic waste but even more important to ensure that more environmental pollution is not created in doing so.”
Nonetheless, at least 16,000km of road have subsequently been paved in the state of Tamil Nadu. The national government has since approved the idea and sanctioned at least 13,000km across the country to be paved in the material as well. Of this, 8,600km have already been completed, says Dr IK Pateriya of the rural development ministry in Delhi.
Using the same process to merge waste plastic and stone with materials like limestone, ceramic waste and granite, Dr Vasudevan has created another eco-friendly building material that consumes up to 40 per cent more waste plastic than that used in the road laying process. He calls this material “plastone” and says that it is lasting, durable and cheap.
Each plastone block consumes nearly 300 plastic bags and between four and six plastic bottles.
A stone tile measuring one square metre has a manufacturing cost of Rs100; 60 plates would be sufficient to construct an eco-friendly bathroom, says Dr Vasudevan. The material could also be used to pave sidewalks, replacing cement, he says.
Today, self-help groups from various states across India, local citizens and schools are engaged in helping Dr Vasdevan collect waste plastic.
“It’s time we stop seeing plastic as the enemy and turn it into our biggest resource,” says Dr Vasudevan.