Milk Packet Waste Recycling Iisc Plastic Building Material

To most Indian households, sealed packets of milk are some of the most common grocery items that pass through their doors. But their ubiquity also means thousands of tonnes of plastic waste are generated across the country. A new breakthrough at Bengaluru’s Indian Institute of Science (IISc), however, could mean that these packets, usually made of polyethylene, could soon find a new life as material in the creation of benches and similar goods, instead of being part of a mounting garbage problem.

This discovery was made by a team from IISc’s Department of Materials Engineering, with a research paper on the topic also being published in March. The Indian Express had previously reported on another study, which had found that about 100-120 million single-use milk packets are used every day, amounting to nearly half the packaging material for all the milk in the country.

Why were milk packets chosen as a material?

According to IISc’s Professor Suryasarathi Bose, part of the team, one of the reasons that milk packets were selected for the study is that they are a form of waste that often ends up in public bins or on roadsides for extended periods of time. Other waste items such as plastic bottles are picked up much faster, as they are more valuable to ragpickers and others.

At the recycling stage as well, dark coloured plastics — often used in milk packets as part of an inner layer to block out ultraviolet and visible light to extend shelf life — are not desired by recycling companies.

Bose said, “They might be ending up in landfills eventually, but there is a longer gestation period on the roadside and in dustbins as they don’t get picked up. Oil containers, etc. are picked up by ragpickers… but unless there is a drive, there is no incentive to pick up these packets.”

During recycling, the polyethylene in these milk packets are combined with recycled components of another material, polypropylene, which is used to contain oil and shampoo, etc. However, as these are not similar at the molecular level, molecules known as “vitrimers” aid in using these two materials to form a new recycled material.

“We thought: why not blend these milk pouches that are weaker in terms of properties, and get a material that is structurally very strong and can be used outdoors. We were able to 3D-print podiums which are used in auditoriums…. One such podium is now given to IISc to test it,” said Bose, who is also a founder at VOiLA, a startup specialising in 3D printing recycled waste material.

Podiums are not the only thing that can be printed from the new material — other outdoor furniture such as benches can be made as well.

Another material that is not easily recycled are multi-layer plastics. They are often used in food packaging of the sort that chips and snacks are stored, and known for their ability to preserve a sealed environment and keep perishables fresh. Since they are made of multiple layers, recycling is often impractical as it would require the layers to be peeled apart.

One Bengaluru-based company, Unified Intelligence, is using these plastics to create durable building materials — including interior walls at Bengaluru Airport’s Terminal 1. These plastics are gathered en masse and cleaned before being shredded. They then go through a process called thermofusion to create panels, which can then be used to create walls by creating a honeycomb-like structure between them.

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On the recycled material’s durability, the company’s managing director Paul Koshy said, “At four inches, it is slightly thinner than a brick wall, but it is multiple times stronger. Even if you hammer it, it will bend and then come back to its own shape.”

He added that while it was slightly more expensive to use these recycled materials to build a house per square foot, the advantage came in terms of building speed and water used in construction — regular brick-and-mortar construction can use up tens of thousands of litres of water. As he puts it, the daily plastic waste output of a city like Bengaluru would be about 100 tonnes, which could be converted into a 10,000 square foot building.

Some of the challenges that companies in this field are facing is that the basic standards are written for materials like concrete, brick, and mortar. Unusual building materials will have to rely on direct lab test certificates demonstrating properties such as fire resistance and mechanical stress.

Another aspect is the psychological element: there might be some resistance towards the idea of reusing waste for a building. This is something the Archbishop of Karnataka is hoping to tackle, having placed an order with Unified Intelligence to construct a church in Attibele on the outskirts of Bengaluru.