Biological plastic recycling

Categories: Circular economy in the plastics industry, Developments and trends in plastics recycling

What is biological recycling?

Biological recycling refers to all the processes of plastic waste transformation that implicate the action of microorganisms or molecules produced by those in useable resources as compost or biogas.

The fact of employing microorganisms in order to resolve or help to resolve environmental problems can sound dangerous for public health, and even more so in the times of Covid-19. However, far from reality microorganisms have been used for decades in order to resolve environmental problems, as an example in wastewater treatment plants or in some industries use microbial-based technologies to treat volatile organic compounds or eliminate odours.

Classification of biological recycling processes in plastic materials

Is a process in which organic substance is degraded and stabilised in the presence of oxygen through different microorganisms, obtaining as a final product compost. Of the plastic materials composed they convert this compost that can be employed as an organic amendment of the soil for supporting necessary nutrients that improve the development and growth of plants. Its main advantage is the ease of process and the acceptation and distribution of technology on a global level. However, the product (compost) itself is of low economic value so it is difficult to obtain economic return and neither represents a recovery neither energy nor material.

It is a process in which the organic substance is degraded in anaerobic conditions, that is to say in the absence of oxygen, for different microorganisms that cooperate with each other to carry out complete degradation of organic matter and plastics. In this case, the main product obtained is biogas, a gas with a high methane content that can be employed as a source of heat and/or energy. Therefore, due to the anaerobic degradation of plastic materials we obtained energy and/or heat.

One of the big advantages of this method is that it produces a valuable product in the market as a biogas that allows an economic valorization of waste, and furthermore is easily implemented in the industry. However, this process prior did not allow the material valorization valorization of plastic waste but was more a energetic valorization . In order to be a valuation material, it would require transforming methane posteriorly in other chemical substances, processes that currently have a low performance.

It is a process in which plastic materials are partially degraded by the action of different enzymes produced principally by fungus and bacteria. The final product of this treatment are monomers and oligomers that make up the polymer. Later, these monomers can be purified by the means of diverse techniques for repolymerising them and obtaining new plastic materials. The advantage of this method of recycling resides, mainly, in the quality of recycled material, because the new recycled materials present the same characteristics and properties than virgin materials. On the contrary, its main inconvenience is the elevated cost of enzymes and its “distance” to the market because this technology is still in development. Therefore, it is a technology still immature but promising.

Plastics susceptible to being biologically recycled

One of the main inconveniences that we find in general when we speak about biological plastic recycling is that not all the types of plastic materials or polymers are susceptible to being recycled by means of this technology. In general, those polymers that are considered biodegradable or present an elevated biodegradability could be biologically recycled.

This is because processes of biological recycling are based on the biodegradation of polymers or the cleavage of its chains. Therefore, those polymers that are more inert and present a high stability source of biodegradation would be less indicated to be recycled through these methods. Despite this, currently a big force is being carried out from the scientific community in order to obtain microorganisms with high capacities in order to degrade these materials, and for the part of the plastic industry to obtain and produce more materials with biodegradable characteristics. Furthermore, also the possibility of improving the capacities of these treatments by the means of application of different pre-treatments to reduce the molecular size of materials and/or add target groups of hydrolytic enzymes is being considered and studied in order to favour and ease the enzymatic and microbial degradation. An example of these studies is a European project BiolCEP.

AIMPLAS Services

At AIMPLAS we offer services and solutions in all lines of biological plastic recycling, from more classic services such as the determination of biodegradability of a material in different environments (soil, compost, marine, anaerobic) up to more modern solutions such as the use of enzymes in order to obtain the monomers of a polymer and the obtention and preparation of inoculums “on demand” with higher capacity to biodegrade different polymers. Furthermore, we also offer combined services as preparation of specific inoculums for its addition to a traditional compost process that allows the acceleration of the process, and in this way, biodegrade the plastic material in less time, that is adjusted at the request for the market.

Do not hesitate to get in contact with us should you want to know more about these services.

Pablo Ferrero. Chemical Recycling researcher at AIMPLAS

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