Is turning plastic waste into green energy the most environmentally friendly option?

3rd October 2018 | Recycling

In the adventure classic Back to the Future, Emmet “Doc” Brown uses energy generated from rubbish to power his DeLorean time machine. But while a time machine may still be some way off, the prospect of using rubbish for fuel isn’t too far from reality. Plastics, in particular, contain mainly carbon and hydrogen, with similar energy content to conventional fuels such as diesel.

Plastics are among the most valuable waste materials – although with the way people discard them, you probably wouldn’t know it. It’s possible to convert all plastics directly into useful forms of energy and chemicals for industry, using a process called “cold plasma pyrolysis.”

Cold plasma pyrolysis

Pyrolysis is a method of heating, which decomposes organic materials at temperatures between 400C and 650C, in an environment with limited oxygen. Pyrolysis is normally used to generate energy in the form of heat, electricity or fuels, but it could be even more beneficial if cold plasma was incorporated into the process, to help recover other chemicals and materials.

Cold plasma pyrolysis makes it possible to convert waste plastics into hydrogen, methane and ethylene. Both hydrogen and methane can be used as clean fuels, since they only produce minimal amounts of harmful compounds such as soot, unburnt hydrocarbons and carbon dioxide (CO2). And ethylene is the basic building block of most plastics used around the world today.

As it stands, 40 per cent of waste plastic products in the US and 31 per cent in the EU are sent to landfill. Plastic waste also makes up 10 per cent to 13 per cent of municipal solid waste. This wastage has huge detrimental impacts on oceans and other ecosystems. Of course, burning plastics to generate energy is normally far better than wasting them. But burning does not recover materials for reuse, and if the conditions are not tightly controlled, it can have detrimental effects on the environment such as air pollution.

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