As the world struggles with the ever-increasing plastic waste, the making of plastic-tar roads offers a way out—if you can’t beat plastic, use it! There may be some scepticism, but by and large the feasibility of such roads is widely accepted. Some roads have already been built in India with this concept. Will 2024 see more such roads, using tonnes of the notorious non-biodegradable material, to help curb pollution? TreeTake takes a look …
One of the biggest challenges confronting mankind today is waste plastic management. Despite curbs, there is rampant use of plastics in the form of disposable cups, polythene bags, and various other things that are non-biodegradable. In fact, there has been a massive increase in global production and consumption of plastic since the 1960s. A large part of global plastic production is for packaging and the rest is single-use. Although demand for plastic is likely to continue rising, the growth in production and consumption is unmatched by an efficient global waste management system, which means less than a fifth of plastic waste is recycled. As plastic does not break down naturally, it ends up polluting natural ecosystems, including soil, rivers, and oceans. The production, use, and disposal of plastics also create significant greenhouse gas emissions throughout the different stages of the plastic value chain.
According to research by the Centre for International Environmental Law, greenhouse gas emissions from plastic could represent 10-13 percent of the entire remaining carbon budget by 2050 (in the context of the 1.5-degree goal of the United Nations Framework Convention on Climate Change Paris Agreement). As the environmental consequences of plastic become increasingly apparent, regulation and consumer behaviour have also started to change, albeit there is no significant impact.
Plastic waste management
Normally, plastic waste management involves the following:
Recycling: Collection, sorting, washing, shredding, melting, and then remolding into new products.
Energy recovery: Energy recovery is the process of converting non-recyclable waste materials into usable heat, electricity, or fuel through various processes, including combustion, gasification, pyrolization, anaerobic digestion, and landfill gas recovery.
Landfills: This is the least desirable method where plastic waste is dumped in designated areas. While it does keep waste out of sight, it’s not an eco-friendly solution.
Plastic waste to fuel: In this process, plastic waste is converted into fuel like gasoline, kerosene, or diesel. This is an innovative method, but it requires careful execution to ensure it doesn’t cause further pollution.
Problems in plastic waste management
The disposal of plastic waste is not entirely hassle-free. Indiscriminate littering of unskilled recycling /reprocessing and non-biodegradability of plastic waste raises the following environmental issues:
• During the polymerization process, fugitive emissions are released.
• During product manufacturing, various types of gases are released.
• Indiscriminate dumping of plastic waste on land makes the land infertile due to its barrier properties.
• Burning of plastics generates toxic emissions such as carbon monoxide, chlorine, hydrochloric acid, dioxin, furans, amines, nitrides, styrene, benzene, 1, 3-butadiene, CCl4, and acetaldehyde.
• Lead and cadmium pigments, commonly used in LDPE, HDPE, and PP as additives are toxic and are known to leach out.
• Non-recyclable plastic wastes such as multilayer, metalised pouches, and other thermoset plastics pose disposal problems.
• Sub-standard plastic carry bags, packaging films, etc. pose problems in collection and recycling.
• Littered plastics lead to garbage pile-ups in cities and choke drains and sewage systems.
• Garbage mixed with plastics interferes with waste processing facilities and causes problems in landfill operations.
• Recycling industries operating in non-conforming areas are posing a threat to the environment through unsound recycling practices.
PLASTIC ROADS: A PATH LESS TRAVELLED
As the world struggles to find an answer to the plastic waste conundrum, some stakeholders are also exploring new options to use it as a partial substitute for raw materials. The use of plastic waste as a bitumen modifier in road construction, referred to as ‘plastic roads’, is one option being explored.
The technology was initially developed and patented by Rajagopalan Vasudevan of the Thiagarajar College of Engineering. In January 2018, Vasudevan was bestowed with one of India's most prominent awards, the Padma Shri, for his research on plastic research and reuse. The plastic-bitumen road-laying technique was covered under a patent held by the Thiagarajar College of Engineering in 2006. The installation of plastic roads comprises the collection of waste plastics, including plastic carry bags, cups, soft and hard foams, and laminated plastics. These are then cleaned by washing, shredded to a uniform size, melted at 165°C, and then blended with hot aggregates and bitumen. This unique mixture is thereafter used, as a main component, in the eventual construction of a plastic road.
Since plastic roads are a relatively new idea, construction processes vary. In Jamshedpur, India, roads are created from a mix of plastic and bitumen. In Indonesia, roads are also being built using a plastic-asphalt mix in many areas. These roads are made from recycled plastics and the first step in constructing them is to collect and manage the plastic material. The plastics involved in building these roads consist mainly of common post-consumer products such as product packaging. Some of the most common plastics used in packaging are polyethylene terephthalate, polypropylene, and high- and low-density polyethylene. These materials are first sorted from plastic waste. After sorting, the material is cleaned, dried, and shredded. The shredded plastic is mixed and melted at around 165°. Hot bitumen is then added and mixed with the melted plastic. After mixing the mixture is laid as one would with regular asphalt concrete.
As per VP Srivastava, engineer-in-chief (rural), PWD, Lucknow: “Plastic roads are a good option. They are durable and safe. There is no question about their durability. But the availability of raw materials is a problem. Collection of plastic waste, its segregation, shredding, and then making it ready for use requires a plant.” He said one such plant had been set up in Varanasi and added that there was provision for the use of plastics in one road in each district under the Pradhan Mantri Sadak Yojana. In reply to a question, he said a plastic road, once made, was the same as a normal bitumen road. “Since plastic is used on the surface if a cave-in is from underneath, it cannot be checked. But otherwise, it is a very feasible concept and very advantageous in checking pollution.”
So far, no large-scale, systematic approach has been employed to build roads entirely of plastics in any country. However, India has been leading the world in experimenting with plastic-tar roads since the early 2000s. But a growing number of countries are beginning to follow suit. Building plastic into roads and pathways is helping to save carbon emissions, keep plastic from the oceans and landfills, and improve the life expectancy of the average road.
By 2040, the world is likely to see approximately 1.3 billion tonnes of plastic in its environment. India alone generates over 3.3 million tonnes of plastic waste per year. Needless to say, this was a key factor that led Vasudevan to evolve a system to use plastic waste in roadmaking. It has the benefit of being a very simple process, requiring little high-tech machinery. First, the shredded plastic waste is scattered onto an aggregate of crushed stones and sand before being heated to about 170C – hot enough to melt the waste. The melted plastics then coat the aggregate in a thin layer. Then heated bitumen is added on top, which helps to solidify the aggregate, and the mixture is complete.
Many different types of plastics can be added to the mix: carrier bags, disposable cups, hard-to-recycle multi-layer films, and polyethylene and polypropylene foams have all found their way into India's roads, and they don't have to be sorted or cleaned before shredding. This not only ensures that these plastics don't go to landfills, incinerators, or the ocean but there is also some evidence that the plastic also helps the road function better. It helps slow down wear and tear and minimises the chances of the roads developing craters and potholes. The plastic content improves the surface's flexibility, and after 10 years Vasudevan's earliest plastic roads showed no signs of potholes. Though many of these roads are still relatively young, their long-term durability remains to be tested. Vasudevan’s calculations also say that the process would save three tonnes of carbon dioxide per kilometre of road. It would also economise on the cost of roadbuilding.
In India, the technology was first adopted in a big way in Chennai. Since then, all major municipalities have experimented with the technology, Lucknow being one of them. Chennai has used nearly 1,600 tonnes of plastic waste to construct 1,035.23 km of roads in recent years, which include N.S.C Bose Road, Halls Road, Ethiraj Silai Street, and Sardar Patel Street. Using bitumen technology on waste plastic, the Pune Municipal Corporation constructed a 150-metre stretch of Bhagwat lane at Navi Peth near Vaikunth Crematorium in 2016. The other trial patches in Pune include Dattawadi Kaka Halwai Lane, Katraj Dairy, Magarpatta City HCMTR Road, Kavade Mala Road, Koregaon Park Lane No 3, and Yerawada Shadal Baba Darga Road from Chandrama Chowk. Jamshedpur Utility and Services Company (JUSCO), which is a subsidiary company of Tata Steel, constructed a 12–15 km road in the steel city, as well as Tata Steel Works using the plastic road, including a nearly 1 km stretch in Ranchi, 500m stretch each in Dhurwa and Morabadi, 3 km of roads in Chas and Jamtara each and 500m stretch in Giridih. In 2014, the Madhya Pradesh Rural Road Development Authority (MPRRDA) constructed around 35 km of roads in 17 districts with plastic waste.
The idea of using a plastic-bitumen mix was executed in Surat in 2017. The problem of potholes was significantly got reduced as no cracks developed in areas where roads were layered with waste plastic. The technology has penetrated deeply and has found application even in far-flung Meghalaya, where a village converted 430 kg of plastic waste into a kilometre-long road in 2018. In December 2019, 21,000 miles of roads were built in India using plastic waste. Until now, the country has almost 33,700 km of plastic roadways which means every 1 km road uses one million plastic bags. As of 2021, only 703-kilometre of National Highways were constructed using plastic roads. In neighbouring Pakistan, a one km stretch of Ataturk Avenue in Islamabad was entirely re-laid with plastic in 2021. The process involved the use of 10 tonnes of plastic waste. Several other countries too are making forays into plastic roadmaking.
Notwithstanding the pros and cons, plastic roads may be the ‘in thing’ in the future. However, many are sceptical about the concept, worrying over the potential risks to the environment in the long run. There are questions like: how will they exactly damage our roads over time while suffering from the passage of cars and weather conditions? What would be the consequences for the environment of the tiny particles being released in the air and dragged by the rainwater? Prof Venkatesh Dutta, School of Earth and Environmental Sciences, Babasaheb Bhimrao Ambedkar University (BBAU) Lucknow, is of the view that the concept is very feasible and would not harm the environment if exercised judiciously. It is a good use of waste plastic. “The plastic road approach should be site-specific, that is, such roads should be made only in places where the water table is low, or where there is no water body, river or wetland or danger of the erosion of any kind so that the microparticles do not contaminate water. It would be better to make such roads in dry areas and not saturated zones.” On the question that plastic would still be there in the environment, even if mixed in road material, he said: “Like charcoal, plastic is also a petroleum-derivative. So, if it is mixed with bitumen, it works fine. After all, plastic products have also to be recycled or re-used and it is very difficult to dispose of them. So plastic roads are a good option to tackle the problem of plastic waste management.”
Advantages of plastic roads
Plastic roads can have hollow spaces built in to allow ease of wiring, connecting pipes, etc.
Since plastics come with various chemical and physical properties, roads can be engineered to meet specific requirements (e.g. weather and wear resistance)
Plastic roads can be built from waste plastic --- the majority of which is usually put into landfills, incinerated, or polluted into the environment. Land-filling and incinerating plastic are both problematic methods of managing plastic waste. Plastics in landfills can leak pollutants into the surrounding soil; incinerating creates gaseous pollutants, such as carbon dioxide.
Plastic-bitumen composite roads need not be especially discriminating with the plastics used, thus increasing the reuse of plastic. Most plastic waste is not recycled because it is usually mixed with other garbage and segregation is labour-intensive.
Using less asphalt saves on cost and resources. Asphalt concrete requires petroleum which is becoming scarce.
The addition of plastic in asphalt can reduce the viscosity of the mix. This allows a lower working temperature, which lowers CO emissions.
Plastic-bitumen composite roads have better wear resistance than standard asphalt concrete roads.
They do not absorb water and have better flexibility which results in less rutting and less need for repair.
Road surfaces remain smooth and require lower maintenance.
Pure plastic roads require use of compatible plastics because, when melted, plastics of different types may phase-separate and cause structural weaknesses, which can lead to premature failure.
Plastics in the road can break down and find their way into the soil and bodies of water, absorbing other pollutants.
Every time maintenance is performed on these modular roads the flow of power, water, and internet that has been installed within will be interrupted.
IRC identifies benefits
The Indian Roads Congress ( IRC) laboratory and field performance studies/investigations in India have identified benefits like higher resistance to deformation, higher resistance to water-induced damages, Increased durability and improved fatigue life, improved stability and strength, and adequate and environment-friendly disposal of waste plastic. Speaking at a technical session of the Indian Roads Congress in 2022, Mahesh Kasture, chief manager corporate, the Bharat Petroleum Corporation, said what was a wonder material was now notorious, and one good solution was to use it for road construction. He was delivering a talk on “Utilisation of plastic waste in the road and allied construction”. “Using plastic waste for road construction is an effective solution for end-of-life plastic utilisation in an environmentally friendly manner, thereby saving such plastic from entering the food chain,” he said. “The success of the process has been proven by laying several stretches across India and these are operational today also. Its success will lead to achieving the goal of the Swachh Bharat Mission and generate carbon credits for green utilisation of waste plastic,” he said.
As per experts, plastic-tar road construction will be easier and quicker, possible even in difficult or sandy terrain. The cost of transportation of material will go down as less fuel will be used, plastic being light. The roads will be longer lasting, easy to maintain, and might pave the way for other innovations. Overall, plastic roads offer promising prospects in waste management and road construction, but addressing the doubts associated with them through research and continuous improvement is important for their successful implementation and long-term viability. By carefully weighing all variables, it is possible to encourage their effective implementation as a long-term method of handling plastic trash in road building.
Here’s to hoping the revolutionary concept is put to more use this year and plastic waste does something useful for mankind, instead of just adding to the litter.