Trials at the Hohenstein Institute in Germany suggest that biotechnology can be used to open up entirely new ways of recycling carbon fibre composites.
Researchers in the team led by Christin Glöckner are using microbiological systems to bring about the controlled breakdown of the synthetic matrix.
Even though carbon composites are very expensive, at a cost of €25-30 per kilo, every year about 3,000 tonnes of carbon waste is generated in Europe alone, but recycling carbon fibres is not easy.
The recycling process mainly used at present – a multi-stage pyrolytic process – is extremely energy-intensive and only short-staple carbon fibres can be recovered. The chemical and mechanical recycling methods known today meanwhile, are very labour-intensive.
In pursuing an alternative solution based on biotechnological recycling, the Hohenstein researchers are expoliting the ability of certain microorganisms to metabolise chemical substances, such as polyether resin.
They have now managed to break down the epoxy resin of carbon composites and returned it to the materials cycle as a metabolite. At the same time, the carbon fibres can be extracted without damaging them.
It is apparent that, in future, quality standards will have to be defined for recycled fibres, so that companies can preserve the value of recycled carbon composite materials and react more effectively to the needs of the industries that re-use them. One sustainable approach could possibly be this recycling method using biotechnology.
At the first Composites Recycling conference held earlier this year in Stuttgart, Germany, leading composites producers, manufacturers and recyclers new ideas and solutions were presented and aspects of eco-balancing – energy efficiency, reduced emissions, costs – were discussed. It was agreed that in future there will be more and more end-of-life products which should go on to be recycled, but the search for alternative and sustainable solutions is not yet over.
Following on from recycling, new options for using recycled fibres were also presented at the conference, such as the wet laid process used in carbon fibre paper manufacture and the extrusion of short-staple fibres in a polyamide filament matrix.
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