Safer Reuse of Waste Plastics
Bhaskar Deka
(The writer can be reached at bhaskar_deka4u@yahoo.co.uk)
When needed, plastic is found to be very useful, but after its use, it is simply thrown away, creating all kinds of hazards. Plastic garbage is commonly seen around the country and has started causing several problems. Plastic waste clogs drain, causing floods. It chokes animals that eat plastic bags, packets etc. Plastic found in fields blocks germination and prevent rainwater absorption. Plastic is non-biodegradable that remains as a hazardous material for more than centuries. Recycling of plastic can be done only 3-4 times and melting of plastic for recycling releases highly toxic fumes. Prime Minister Modi in his 73rd Independence Day speech urged the people to go for lesser and lesser use of plastic, to make the country free of single-use plastic and use of jute or cotton bag instead and for coming up with ideas to reuse waste plastic in the country.
The quantities of plastic waste in Municipal Solid Waste are increasing rapidly years after year. Over the period from 1950 to 2015 the amount of waste plastic rose to 7.5 billion tonnes from roughly 1.8 million tonnes in the world in 1950. As per April 2018 statistics, India generates around 5.6 million tonnes per annum, which is about 15,342 tonnes per day. According to an authentic NGO report, Assam produced about 13,505 tonnes of plastic waste in the year 2018, i.e. 2.99 lakh kg of plastic per day. Concurrently, Guwahati generates 37,000 kg of plastic waste per day in the same year.
Now, coming to the point, how we can reuse these waste plastic for its future safer use, especially in the construction industry so that the huge piling up of this kind of waste can be reduced drastically. Plastic wastes, mainly plastic carry bags, disposable cups and Polyethylene Terephthalate (PET) bottles that are collected from garbage dumps as important ingredients of the construction materials. By using plastic waste as modifier, we can reduce the quantity of cement, bitumen and sand by their weight, hence decreasing the overall cost of construction. A government order in November 2015 made it mandatory for all road developers in the country to use waste plastic, along with bituminous mixes, for road construction. This is to help overcome the growing problem of plastic waste disposal in India.
The technology for this was first developed in India by the ‘Plastic Man of India’, Prof. R Vasudevan of Chemical Engineering, Thiagarajar College of Engineering, Madurai, TN. The plastic waste items that can be used for road construction are various items like plastic carry bags, plastic cups, plastic packaging for potato, chips, biscuits, chocolates etc. The whole process is very simple. The plastic waste material is first shredded to a particular size using a shredding machine. The stone aggregate mix is heated at 165 0C and transferred to the mixing chamber and the bitumen is then heated to 160 0C to result in good binding. It is important to monitor the temperature during heating. The molten semi-liquid shredded plastic is then added to the stone aggregate. Its gets coated uniformly over the heated stones within 30 to 60 seconds giving an oily look. The plastic waste coated stone aggregate is mixed with hot bitumen and the resulting mix is used for road construction. The mix laying temperature for road construction is between 110 0C and 1200C. The roller used shall be of 8 tonnes.
The advantages of using waste plastics road construction are many. The process is easy and hardly needed any new machinery. For every kilo of stone, 50 gm of bitumen is used and 1/10th of this is plastic waste. This reduces the cost of bitumen being used. Plastic increases the strength of stone aggregates and improves the quality of road pavements. Wear and tear of the road will be decreased to a large extent. Thus plastic waste helps increase the strength of the road reducing road fatigue failure. These roads have better resistance towards rain water and cold weather too. A large amount of plastic waste is required for a small stretch of road. Apart from its uses in road pavement, waste plastic has various other uses in making different other construction materials like paver blocks, tiles, window frames (sliding or nonsliding types), recycled plastic corrugated roof sheet etc. Also, these processes will generate an additional job for the rag pickers.
If we adopt these construction processes mandatorily in our vicinity, the amount of waste plastic scattered around will be reduced drastically and subsequently, making a cleaner and greener environment for our future. For these to be materialized active participation from all the stakeholders in this regard are very much needed.