Unexpected application for hemp

Hemp field in Côtes-d’Armor, Brittany, France. Credit: Barbetorte, Creative Commons

Hemp has been banned from US in the last century (better know as marijuana...) but in the last few years several States have abolished the prohibition. Now, a team of Canadian researchers has reported to the American Chemical Society a useful application of hemp to increase the energy density of super-capacitors.

Super-capacitors have very short recharging (and discharging, if needed) time. You can recharge a super-capacitor in seconds, rather than in hours as required by a normal battery.

The problem is the energy density contained in a super capacitor, too little to be useful. Super-capacitors would be ideal to power electrical cars, since you would be able to recharge the car in a shorter time that you need today to fill her up of gasoline. But the super-capacitor low energy density would require you to fill the whole trunk and still you would be able to run the car for just few km.

A solution is to use graphene. Its one layer atom thick structure allows packing a tremendous amount of surface in the space of a normal battery (in the millions of sq m) thus increasing the energy density. The problem with graphed, today, is the cost to manufacture large quantities (and that is one of the goal of the European Flagship 10 years initiative on graphene).

Waiting for graphene to become cheap scientists have been looking to other materials. And this is where this news from the American Chemical Society fits.

By using hemp researchers have been able to create carbon electrodes able to increase the energy density several times (although not to the level of graphene) making super capacitors a bit more compact and powerful.

To do this they heat the hemp at about 150 degrees for 24 hours and then they blast it with a high heat wave that produces an exfoliation of carbon sheets. These are collected and aggregated to form the electrodes.

The process is cheap and can be managed at industrial level. According to the researchers they are just a few months away from a commercial product.

Who would have thought that hemp was good beyond smoke?

Author - Roberto Saracco

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