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Thursday, Oct 17, 2019

Putting plastic waste to use

Experts say proper waste collection and management is at the core of ensuring more plastics get recycled instead of ending up in landfills and oceans.

india Updated: Oct 11, 2019 04:35 IST
Anonna Dutt
Anonna Dutt
Hindustan Times, New Delhi
The Ghaziabad civic body constructed a road using plastic waste on September 29.
The Ghaziabad civic body constructed a road using plastic waste on September 29. (Sakib Ali/ht photo)
         

India generates at least 25,940 tonnes of plastic waste daily, equivalent to the weight of around 4,300 elephants. Of this, about 60% gets recycled, according to the Union environment ministry. The rest gets dumped in landfills, clogs drains, goes into the ocean as micro-plastics, or is burnt, leading to air pollution.

In the absence of a proper waste management system, the plastics that get recycled are often dirty, which makes the re-cycling process water-intensive and expensive.

“It is the process of cleaning the plastics before recycling that makes it resource intensive. A lot of water is required to wash the collected plastics, especially if it is oily or greasy as it has to be cleaned with a solvent,” said Dr Suneel Pandey, director of environment and waste management, The Energy and Resources Institute (TERI).

Experts say proper waste collection and management is at the core of ensuring more plastics get recycled instead of ending up in landfills and oceans.

“Improper waste management also makes plastics collected for recycling less safe as they pick up environmental toxins, bio-medical waste or very unpleasant bacteria, viruses and fungi at a landfills,” said Dr Anjan Ray, director of Indian Institute of Petroleum (IIP), a laboratory of the Council of Scientific and Industrial Research (CSIR-IIP).

After reaching the recycling facility, food packaging material also presents a unique challenge. They are made of multiple layers of different kinds of plastics that are impossible to separate and hence recycle. Also, all plastics can be recycled only seven to eight times at best.

Wealth out of waste

Researchers from various institutes have come up with innovative ways to utilise the plastic waste that cannot be recycled further or are unrecyclable.

At IIT Delhi, a group of chemical engineers are working on chemically breaking down plastics to its smaller hydrocarbon molecules and then synthesising diesel out of it. The process uses packaging material, Polyethylene terephthalate (PET) bottles, polystyrene, and multi-layer packaging.

“The process is meant for plastics that are at the end of their life. The plastics are basically cleaned out and melted, when the vapours form, they are further cracked or broken down to smaller molecules using a catalyst, a fraction of which is then condensed and collected to be used as fuel,” said Uma Dwivedi, a PhD student working on the project.

The fuel produced can currently be used as a blend in stationary diesel machines like generators and needs further testing and standardisation to be used as commercial diesel in vehicles.

A similar processing method is used by the CSIR - IIP in Dehradun to create commercial grade diesel. “Recycling is definitely important but to my mind, the ultimate solution would be to take the plastic agglomerates and turn them back into its constituents. Plastics are mainly made of carbon and hydrogen and so are fossil fuels. So, at CSIR-IIP we have set up a plant to convert waste plastic to diesel. For every 1,000 kg of plastic, we can make 800 litres of diesel. The balance is mostly LPG, which we use to heat the reactor that makes the diesel,” said Ray.

A German chemical producer called BASF is also working with similar chemical recycling method to create a raw material usually derived from fossil fuels for its products. The challenge with these technologies is the pricing. The marketability of the diesel also depends on the crude price of petroleum and the resulting products in the market.

“Scientists are now looking for ways to close the loop and create a circular economy for plastic, meaning all the plastic produced should be reused and recycled. The few methods that are out there, like what is being done by the German company, the cost of the processing is too high,” said Pandey.

One cost-effective solution was developed by Dr Rajagopalan Vasudevan, professor at Thiagarajar College of Engineering in Madurai. The National Highways Authority of India is currently scaling up his technology to use plastic waste in making roads.

He came up with the idea of mixing plastic waste with Bitumen used for constructing roads in 2001. “That year the Tamil Nadu government had planned to ban plastic and my concern began with the more than 1 lakh people employed by the industry. Since plastic is derived from petroleum just like Bitumen, I thought of using it for road construction. The result, not only plastic waste was getting utilised, the roads were cheaper and steadier,” he said. The plastic waste does not have to be segregated and even multi-layered plastics can be used in the mix. “All we need to do is collect the waste, dry it out and use it,” he said.

The construction of every kilometre of road required nine tonnes of Bitumen and one tonne of plastic waste. This means for every kilometre of road, one-tonne Bitumen is saved, which costs about ₹30,000.

Research needed

These processes are necessary to combat the challenge of existing plastic waste, but researchers say that there is a need to focus on effective alternatives that can help in reducing the use of plastic products.

“To make plastic eco-friendly we must make it more biodegradable. A lot of work is going on in bio-degradable plastics, but petroleum-derived plastics like polyethylene, polypropylene, and polystyrene are cheap and abundant. It is therefore necessary for investment in research to develop better plastics that are more efficiently biodegradable,” said Dr Pandey. Research on ways to degrade plastic that is already in the soil or landfills using microbial solutions is also needed, he said.

First Published: Oct 11, 2019 04:35 IST

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