Indian scientists turn plastic bags into car fuel

In their approach, the team heats the plastic waste to between 400 and 500 degrees Celsius over a kaolin catalyst.

This causes the plastic's long chain polymer chains to break apart in a process known as thermo-catalytic degradation.

This releases large quantities of much smaller, carbon-rich molecules.

The team used the analytical technique of gas chromatography coupled mass spectrometry to characterise these product molecules and found the components of their liquid fuel to be mainly paraffins and olefins 10 to 16 carbon atoms long.

This, they explain, makes the liquid fuel very similar chemically to conventional petrochemical fuels.

In terms of the catalyst, Kaolin is a clay mineral - containing aluminium and silicon. It acts as a catalyst by providing a large reactive surface on which the polymer molecules can sit and so be exposed to high temperature inside the batch reactor, which breaks them apart.

The team optimised the reaction at 450 degrees Celsius a temperature with the lowest amount of kaolin at which more than 70 per cent of the liquid fuel is produced.

In other words, for every kilogram of waste plastic they could produce 700 grams of liquid fuel. The by-products were combustible gases and wax.

They could boost the yield to almost 80 per cent and minimise reaction times, but this required a lot more catalyst one kg of kaolin for every 2 kg of plastic.