Biotechnology to decompose a sea of wastes

Current recycling technologies are limited for plastic polymers, resulting in either poor quality recycling or high processing costs. But enzymes now offer a glimmer of hope since the discovery in Japan a few years ago of the "plastic-eating" enzyme "Ideonella sakaiensis" bacteria. Working with common plastic PET, a French company is trying to prove that biotechnological approaches can close the loop in the life cycle of the material. They hope to soon be able to recycle plastic infinitely and at an affordable price.

 

APlastics are excellent materials, says Martin Stephan, "They are cheap and easy to make, and they can have many different properties. Of course, the CEO of the French biotech green chemistry company Carbios SA is also very aware that there is a downside to all practicalities - an almost indestructible litter. "We've neglected the end-of-life of plastics for too long." he adds.

 

In a recent study published in ScienceAmerican researchers Jeanette Garcia and Megan Robertson have found that  "Although there are significant incentives for recycling plastics, in practice end-of-life treatment options are quite limited. They estimate that the energy equivalent of 3.5 billion barrels of oil - with a present value of about US$176 billion - could be saved if we recycled all of the world's solid plastic waste. The most pressing problem is plastic packaging materials, which account for nearly 60% of the mountain of plastic waste generated each year in Europe. Only 14 % of polymer-based packaging waste is collected for recycling worldwide. Europe manages around 30-40%.

 

There are several reasons why recycling is not more widespread. Sorting waste is expensive and time-consuming, and recycling is energy-intensive. The available recycling technologies also only work for a few different polymers. Most importantly, the quality of recycled materials is often worse than the original bio- or oil-based materials. This is where Carbios intervenes. The French team of 19 people claims to have developed a new technology for recycling polyethylene terephthalate (PET) that is truly circular. Martin Stephan explains that the method addresses the problem of quality loss, and believes that Carbios can "bring a lot of value to the PET value chain".

 

About half of all solid plastics produced annually are used once before being thrown in the garbage. That's 150 million tons wasted. PET is one of the most common and important plastics. It is mainly used for synthetic fibres and bottles. "Western Europe consumes around 4.3 million tonnes of PET per year". explains Stephan. "It is estimated that about 2.7 million tonnes are not recycled but end up in landfills or are incinerated. We believe we are tapping into a huge source of unused raw materials. » He is quick to point out that Carbios does not compete with other recycling technologies currently available:  "It's just another solution, but this approach is the only one that opens the way to infinite recycling."

 

What makes the Carbios process unique at this stage is that it is based on enzymes. "I think we are the first to create a new space for the use of enzymes, namely the plastics industry. We have the ambition to do this on a commercial scale, said Stephan. "I think we're the most advanced with our technology. And there is no doubt that we are the only company whose process is adapted to the market. »

 

Enzymes throughout the recycling industry are not a new idea. The Danish companies Novozymes and Ørsted have developed a plant for the conversion and recycling of waste into biogas based on enzymes that liquefy organic compounds in mixed household waste. "There are no details on the enzyme mixture because it is commercially sensitive information, said Hannes Reuter, Head of New Bio Solutions at Ørsted in European Biotechnology.

 

Enzyme "Ideonella sakaiensis"

 

The largest plant called Renescience, which can process 15 tonnes of waste per hour, is about to open in Northwich (UK).

Several other companies are working on biotechnologybased strategies to recover metals from electronic scrap or isolate carbon fibres from discarded composite materials.

But enzymes that could break down plastics on a scale that would tackle the current torrent of waste? Most in the industry would just shake their heads, because petroleum-based plastics are highly resistant to enzymatic degradation. It's true that some newly developed bio-plastics have been designed to be biodegradable, but the scales of production and use of these materials are still extremely limited. In Europe, more than 80% of the plastics sold today are petroleum-based: polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyurethane (PEU) and of course PET. Among them, there are polymers that contain a pure carbon skeleton (PE, PP, PS, PVC), which are particularly difficult to obtain.

 

 

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