State-of-the-art technologies created from brewing residues

Called quantum dots, these crystals are actually nanocrystals that measure only a few billionths of a meter (one nanometer is one billionth of a meter).

Normally produced from heavy metals and pollutants such as cadmium and lead, these quantum dots could instead be produced from spent grains, this cereal residue from breweries which, in recent years, has been reused in animal feed.

Quantum dots are used, among other things, in the emission and absorption of light, for example as sensors in biomedicine or as LEDs in next-generation displays. South Korean giant Samsung, in particular, is devoting vast resources to synthesizing quantum dots for use in its phones.

It could also be used for applications that are a little less technologically and commercially mature, such as solar technologies, i.e. absorbing light to convert it into another form of energyexplained Professor Federico Rosei, of INRS.

It could be electricity, where it can be used to break up water molecules and separate hydrogen from oxygen. And then hydrogen can be used as a clean fuel.

Already used in the manufacture of feed for livestock, brewing residues possess hitherto unsuspected technological attributes.

Photo: Shutterstock / BLACKDAY

Professor Rosei and his colleagues showed this spring, in an article published in the journal RSC Advances of the Royal Society of Chemistry, that it is possible to produce carbon quantum dots with the means at hand.

They used a home microwave oven to carbonize the spent grains, creating a black powder which was then mixed with distilled water and returned to the microwave. A passage through the centrifuge and advanced filtration steps made it possible to obtain the quantum dots.

The finished product is able to detect and quantify heavy metals, as well as other contaminants that affect water, the environment and health.

We can modulate the properties of quantum dots by changing their size, morphology and compositionsaid Professor Rosei.

Eliminate heavy metals

The quantum dots that have the best performance, he continues, unfortunately contain heavy metals whose use is far from desirable from an environmental point of view. We therefore sought to replace them with non-toxic and, ideally, very abundant elements.

The draff contains elements such as carbon, nitrogen and phosphorus, which will contribute to the efficiency of the quantum dots obtained. Previous work had shown that quantum dots obtained from carbon are interesting for capturing sunlight and transforming it into another form of energy.

This project was completed thanks to the collaboration of the microbrewery Brasseur de Montréal, which provided its cereal residues. The researchers are not now ruling out contacting a larger brewery that might be interested in this technological breakthrough.

The basic principle is to try to recover wastesaid Professor Rosei.

But hey, from there to concluding that the more beer you drink, the more you will help our hospitals to equip themselves with the cutting-edge equipment they need, there is certainly a step that you must not take.

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