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Towards biodegradable graphene-based "super batteries"?

Capacitors are everywhere in our electronic devices - but recycling them is a real headache. A single layer of carbon atoms in the form of graphene sheets could make them biodegradable.

Graphene is a crystallized form of carbon discovered in 2004. In sheets it forms the basis of the nanotubes in biodegradable capacitors.

Electronic devices have invaded every aspect of our lives. From the refrigerator to the smartphone, the computer to the car, the objects that surround us every day all contain electronic components. The planned obsolescence of most of these objects comes with a major problem: that of recycling WEEE, waste electrical and electronic equipment, which contains heavy metals, organic chlorine compounds (PCBs) and gas.

Going further to recycle electrical and electronic equipment

According to a United Nations report dated April 2015 (unu.edu/news/ewaste-2014-unu-report.html et unu.edu/media-relations/releases/discarded-kitchen-laundry-bathroom-equipment-comprises-over-half-of-world-e-waste-unu-report.html#info), the volume of e-waste was 41.8 million tonnes worldwide in 2014 - and could reach almost 50 million tonnes by 2018.

In France today, nearly 80% of WEEE is recycled, for example on the Veolia Angers site. But some of this waste is beyond this virtuous recycling loop – capacitors for example.

These basic electronic components are present in motherboards, circuit boards, plasma and LCD screens, satellite tuners, hi-fi systems, etc. They consist of two conducting plates, or electrodes, separated by an insulator. They are used to stabilize a power supply, process and filter signals, separate the alternating current from the direct current, and for storing energy. In this case they are called super-capacitors. There are electrolytic, ceramic or chemical capacitors.

Recycling capacitors is a real headache so they usually end up in incineration or landfill, because they contain toxic heavy metals, gases, organic chlorine compounds (the PCBs) and even cyanide. But a discovery in 2004, crowned with a Nobel Prize in 2010, could perhaps change all that.

Carbon, a 100% biodegradable solution?

Two physicists at the University of Manchester, in England, Andre Geim and Konstantin Novoselov, isolated graphene - an ultra-fine carbon crystal different from its graphite and diamond form. Two other researchers, Californian this time, Maher El Kady and Richard Kaner, then tested this new carbon molecule, producing high-quality sheets.

Result: supple and flexible, graphene exhibits increased electrical conductivity and mechanical strength making it possible for capacitors to leverage their energy storage capacity. Just a few seconds to charge a telephone or a few minutes for an electric car!

What’s more, the composition of graphene makes it 100% biodegradable since carbon is a natural material!

Thus carbon-based capacitors could perhaps simply end up in the garden compost with all the plant waste instead of polluting the environment! A crazy project is even being developed to use a mixed composition of graphene sheets and a natural pigment extracted from Sencha tea leaves. E-green tea from Japan would indeed make capacitors more biodegradable! Green tea – the miracle recipe?

Main picture: Getty Images

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