Current plastic recycling methods are able to replace no more than 15-20% of the fossil raw material needed to meet society's demand for plastic. The advanced methods proposed by the researchers are based on thermochemical technologies and involve the waste being heated to 600-800 degrees Celsius. The waste then turns into a gas, which after the addition of hydrogen can replace the building blocks of plastics. Using this recycling method could decouple new plastic products from the supply of new fossil raw materials.
The researchers behind the study are developing a thermochemical recycling method that produces a gas which then can be used as a raw material in the same factories in which plastic products are currently being made from fossil oil or gas. Different types of waste, such as old plastic products and paper cups, with or without food residues, are put into the reactors at the Chalmers Power Central. "The key to more extensive recycling is to look at residual waste in a whole new way: as a raw material full of useful carbon atoms. The waste then acquires value, and you can create economic structures to collect and use the material as a raw material worldwide," says Henrik Thunman.
The principle of the process is inspired by the natural carbon cycle. Plants are broken down into carbon dioxide when they wither, and carbon dioxide, using the sun as an energy source and photosynthesis, then creates new plants."However, our technology differs from the way it works in nature because we don't have to take the detour via the atmosphere to circulate the carbon in the form of carbon dioxide. All the carbon atoms we need for our plastic production can be found in our waste, and can be recycled using heat and electricity," says Henrik Thunman. The researchers' calculations show that the energy to power such processes can be taken from renewable sources such as solar, wind or hydro power or by burning biomass, and they will be more energy-efficient than the systems in use today. It is also possible to extract excess heat from recycling processes, which in a circular system would compensate for the heat production currently derived from waste incineration, while eliminating the carbon dioxide emissions associated with energy recovery.