Recycling of Biopolymers!

Currently, about 75 – 85% of the polymeric materials used in various applications such as automotive, household items, construction, etc. are obtained from the non-renewable petroleum source (humans have already consumed about 950 billion barrels of oil till now, leaving about 764 billion barrels in the reserve). Considering the problems of pollution (soil and water) and greenhouse emissions, environmental friendly alternatives are being sought for; increasing the attention towards biopolymers. This has also received policy support from governments of various countries, aiming to decrease the carbon footprint. Automotive companies like Ford Motor Company, have already started using biopolymers for their interior applications.

Biopolymers are polymers produced by or derived from living organisms (renewable sources, plants and / or microbes), which are capable of decomposing (by enzymes) into carbon dioxide, methane water and inorganic compounds, and are predicted to be able to replace 30 to 90% of petroleum based polymers in the future.

Some Formal Definitions of Biopolymers

Certain Characteristic Features of Biopolymers

Various Biopolymers

  • Polyesters such as polyhydroxyalkanoates, polylactic acid etc.
  • Proteins such as silk, collagen, elastin, polyaminoacid, soy, zein, gluten, casein, etc.
  • Polysaccharides, obtained from plant source, such as xanthan, dextran, gellan, cellulose, pollulan, glucans, starch, agar, alginate, carrageenan, pectin etc.
  • Polysaccharides, obtained from animal source, such as chitin, hyaluronic acid etc.
  • Polyphenols such as lignin, tannin etc.
  • Some specialty polymers such as shellac, poly γ-glutamic acid etc.

Broad Application Areas

Biopolymers Market

In 2020, the market of biopolymers was about 10 billion USD, and is expected to grow to about 28 billion by 2025 at a CAGR of approx. 22%; attributed to consumer awareness and governmental legislation; wherein, APAC region is expected to show highest growth; which is largely driven by the packaging industry.

Some of the major players in the biopolymers market are:

  • NatureWorks (Italy)
  • Braskem (Brazil)
  • BASF (Germany)
  • Mitsubishi Chemical Holding Corporation (Japan)
  • Toray Industries (Japan)
  • Arkema (France)
  • Zhejiang Hisun Biomaterials (China).

Why Recycle Biopolymers?

Existing plastic waste disposal options are

  • Landfilling
  • Composting
  • Mechanical recycling
  • Chemical recycling, and
  • Incineration

In the current waste management system, biopolymers have not been methodically integrated. The considerable development in the field of biopolymers dictates recycling of both process and post-consumer biopolymer waste at an early stage. We do know that compositing of biopolymers is very much a studied field; however, it requires maintenance of specific conditions; which may not be possible to provide at times. Thus, in order to have a proper utilization of the benefits of biopolymers; one way of reaping it would be reusing / recycling it till it requires actual disposal; which can be performed finally by compositing.

Some of the recent works dealing with biopolymers recycling are detailed below:

  • Svetlana Metlyaeva et al. from the St Petersburg State University developed a biopolymer from terpenols and borneol; which is capable of both primary and secondary recycling; had been determined to have ability to be re-processed 7 times at moderate temperatures of 120oC without much impact on its other properties.
  • Michael Niaounakis from European Patent Office, Netherlands, in his review published in the European Polymer Journal in 2019, listed various technologies developed for recycling of biopolymers such as biodegradable poly lactic acid, and concluded that mechanical recycling would only be the feasible option for the biopolymer.
  • Zembouai et al. investigated the effect of repeated recycling (6 times) on the performance properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polylactide based blends, and found negligible effect on the same by the reprocessing steps; indicating these biopolymers are not only biodegradable but are also recyclable; thus can decrease burden on the compost facilities. Even researchers at UK universities such as Bath University, and University of Birmingham also developed methods for chemical and mechanical recycling of Poly lactic acid (PLA). Zeus Industrial Products, Inc., headquartered in Orangeburg, SC, USA, announced a new recycling technology for PLA, requiring low temperature and is mild in nature.
  • Miao Hong and Eugene Y.-X. Chen prepared biodegradable aliphatic polyester of γ-butyrolactone by ring opening polymerization under ultra-high reaction pressures. They studied that the polymer can be converted back to the base monomer with very high conversion of about 90%. This obtained monomers can be further polymerized. Thus, making available a recyclable biopolymer.

Thus, it can be observed from above studies that chemical and mechanical recycling for biopolymer recycling could be better methods and can prove superior to that of composting, atleast till proper disposal methods are in place.

Some of the points to be discussed further could be:

  • Detailed study is required for understanding the effect of biopolymer contamination in that of conventional polymers.
  • Can waste biopolymers also contribute to ‘microplastics’?
  • Are developing countries ready composting of biopolymers?

Dear Readers, do go through the above literature and let me know your viewpoints in the Comments section.

Thanks for reading!

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