It takes hundreds of years for polystyrene to be degraded in the natural environment. But in a solution of orange peel extract, it dissolves almost instantly – without the aid of external heat, pressure or acid. The extract is obtained by simply squeezing the orange peels.
A group of researchers from the Indian Institute of Technology (IIT) Hyderabad, has demonstrated a cheaper, low-energy, and green way of recycling polystyrene and low density styrofoam, which is a popular form of expanded polystyrene, using orange peel extract. They have a working prototype, and a pilot-scale machine to recycle polystyrene is under construction. Recycling thermocol will convert a large-volume waste into smaller volume, making it easier for final disposal.
Currently, only about 12% of polystyrene waste gets recycled, and nearly a third is dumped in landfills. Worldwide, about 31 million tonnes of citrus fruits are produced annually, and about 50% of it is waste in terms of citrus peel. Large quantities of citrus peel waste are generated in fruit juice industry.
Limonene, which is one of components of the extract, is capable of dissolving polystyrene but is not used for this purpose. “Compared with limonene, the whole extract can dissolve polystyrene five times more,” says Prof. Chandra Shekhar Sharma from the Department of Chemical Engineering at IIT Hyderabad, who has incubated a start-up company (Restyro Technologies Privated Limited) at the IIT Hyderabad Technology Incubation Centre. A patent has also been filed.
The project has received financial support of Rs.37 lakhs from the Technology Development Board, Department of Science and Technology (DST) under the Waste Management Programme. The innovation also won a gold medal in the recently concluded World Invention and Innovation Forum (WIIF) 2017 in Guangdong, China.
The process basically involves dissolving polystyrene in the citrus extract and drawing it into fibres using wet/solution spinning. The fibre is then turned into a non-woven fabric of 1 sq. foot size. Since the fabric made of recycled polystyrene is naturally oil-loving, it can be used for day-to-day household cleaning in kitchens. It can also be used for large-scale removal of oil-spills.
Once the fabric absorbs oil, the oil can be removed by squeezing it and the fabric can be reused up to five times. The used fabric can also be dissolved in orange peel extract and a new fabric prepared but the quality will be inferior due to the presence oil trace.
“Using the orange peel extract to dissolve polystyrene will not change the chemical composition and so will not make polystyrene into a biodegradable product. What this process does is to extend the use and life cycle of polystyrene waste material,” says Prof. Sharma.