Using ‘selected enzymes and microorganisms’ could help society recycle multi-layer plastic scrap, according to Amiplas. The Spanish technological institute for plastics says the innovation also removes the smell of food from packaging.
Researchers working on the EU-funded ENZPLAST2 have developed a recycling technology that degrades the middle adhesive layers of multilayer materials so that the other layers can be ‘easily classified and recycled’.
The process has two steps: the binding of microorganisms to the polymer surface and growth of these microorganisms using the polymer as a source of carbon, followed by final polymer degradation into CO2 and water under aerobic conditions, and biogas and water under anaerobic conditions.
‘To carry out biodegradation, microorganisms produce and secrete enzymes into the environment that break down the polymer chain into low-molecular-weight fragments,’ the researchers report. The direct use of these specific enzymes is therefore another alternative for breaking down polymers. ‘The monomers obtained as a product of the degradation reaction can be recovered and used to synthesize new products, thus making it a sustainable chemical recycling method,’ the researchers note.
Lab tests has shown that the enzymes can help degrade certain polymers like polyurethane film by up to 70%. It is pointed out that the optimal working temperature of enzymes is 25-95ºC. This is a lot less than the 180-230ºC temperature range conventional methods require, meaning the innovation notably curbs energy consumption.
The work is explained in more detail in a paper prepared for The Plastics Recycling Update. You can read it here.
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