Review
Designing Biobased Recyclable Polymers for Plastics

https://doi.org/10.1016/j.tibtech.2019.04.011Get rights and content

Highlights

  • Rational polymer design is important for desired functionality and recyclability.

  • Increasing the glass transition temperature is an effective strategy for enhancing the performance and recyclability of biobased polymers.

  • Selective polymer depolymerization and repolymerization of monomers offers an important route to plastic recycling.

  • Microbial cells and enzymes constitute important tools for the production as well as recycling of polymers.

  • Feedstock sustainability is a concern and CO2 will become an important alternative to biomass for fossil-free polymers.

Several concurrent developments are shaping the future of plastics. A transition to a sustainable plastics system requires not only a shift to fossil-free feedstock and energy to produce the carbon-neutral building blocks for polymers used in plastics, but also a rational design of the polymers with both desired material properties for functionality and features facilitating their recyclability. Biotechnology has an important role in producing polymer building blocks from renewable feedstocks, and also shows potential for recycling of polymers. Here, we present strategies for improving the performance and recyclability of the polymers, for enhancing degradability to monomers, and for improving chemical recyclability by designing polymers with different chemical functionalities.

Section snippets

The Need of the Hour

At the start of 2018, the European Commission communicated ‘a European Strategy for Plastics in a Circular Economy’, emphasizing improved design and production of plastics and plastic products to facilitate reuse, repair, and recycling. It also noted the need to decouple plastic production from fossil resources and reduce greenhouse gas (GHG) emissions in line with the commitments under the Paris Agreement on Climate Changei. Even though plastics provide economic and environmental benefits

Plastics from Renewable Feedstock

The global production capacity of biobased plastics in 2018 was estimated at 2.11 million tons, of which 1.2 million tons were nonbiodegradable and the remaining biodegradableiii. The biodegradable products currently on the market are thermoplastic starch and several aliphatic polyesters, including poly(lactic acid) (PLA), polyhydroxyalkanoates (PHAs), and poly(butylene succinate) (PBS) (Table 1) [18]. PLA is by far the most commercially developed, having reached an annual production volume of

Industrial Biotechnology: The Key Enabling Technology for Biobased Plastics

Irrespective of the polymers being biodegradable or nonbiodegradable, or the feedstock used, industrial biotechnology is a key enabler for the production of most biobased plastics, starting from providing tools for the first step of biomass deconstruction to simpler entities, to the production of building blocks and also polymers 18, 22, 46, 47, 48, 49. Enormous efforts have gone into the screening and development of enzymes that hydrolyze the different components of the lignocellulosic biomass

Designing Biobased Polymers for Enhanced Performance

High performance biobased polymers with desirable material features that are retained even when subjected to processing and recycling, are in demand. The glass transition temperature (Tg) is one of the most important thermal properties of amorphous plastic materials, determining their physical, mechanical, and rheological properties and, hence, their range of applications, while the melting temperature, Tm, is important for semicrystalline plastics 86, 87. PET, the most widely recycled plastic,

Design for Enhanced Degradation

Although biodegradable plastics appear to be less favored than nonbiodegradable ones, biodegradability is a useful feature for certain applications where recovery of the plastics is difficult or impossible and leakage into the environment is difficult to avoid, such as in agricultural mulch films, fishing nets, or cosmetics. Biodegradability could also be used as a means to enable polymer recycling. However, a major bottleneck when designing degradable polymers is to achieve good properties and

Towards Recyclable Polymers and Monomers

In addition to mechanical recycling, there is increasing attention being paid towards developing technologies for recovering the building blocks from plastics for repolymerization to the original polymer or conversion to another product, in a process referred to as chemical recycling 3, 12, 133 (Box 2). The traditional process of chemical recycling by pyrolysis, in which plastics are subjected to high temperatures in the presence of a catalyst, gives a mixture of smaller molecules that are

Concluding Remarks and Future Perspectives

Plastic materials are crucial to modern life and society, and their continued importance in multiple applications is undisputed. Given the damaging environmental effects of the current linear plastics economy and also the future material demands for the growing global population (estimated to be 9 billion by 2050), a major shift to a sustainable plastics system based on renewable feedstocks and energy, and material recycling is essential [5]. Here, we argue that polymer design should be an

Acknowledgments

The authors are among the academic and industry representatives of a research program ‘Sustainable Plastics and Transition Pathways (STEPS) supported by the Swedish Foundation for Strategic Environmental Research (Mistra) L.J.N. also acknowledges funding from the EU Horizon2020 project REINVENT (No. 730053). Thanks are due to Smita Mankar and Adel Abouhmad for assistance with some tables and figures.

Glossary

Amorphous polymers
polymers with a random structure that do not have a sharp melting point and soften gradually with increases in temperature.
Biobased plastics
plastics comprising, wholly or a significant part thereof, renewable biological raw materials (such as plant, animal, and marine materials), including products and residues from agriculture and forestry.
Biodegradable plastic
a plastic that is broken down by microorganisms in the environment for use as a carbon and energy source.

References (156)

  • J.C. López

    Biogas-based polyhydroxyalkanoates production by Methylocystis hirsute: a step further in anaerobic digestion biorefineries

    Chem. Eng. J.

    (2018)
  • S.M. Cragg

    Lignocellulose degradation mechanisms across the Tree of Life

    Curr. Opin. Chem. Biol.

    (2015)
  • D.G. Olson

    Recent progress in consolidated bioprocessing

    Curr. Opin. Biotechnol.

    (2012)
  • J.W. Lee

    Microbial production of building block chemicals and polymers

    Curr. Opin. Biotechnol.

    (2011)
  • S. Kind

    From zero to hero - production of bio-based nylon from renewable resources using engineered Corynebacterium glutamicum

    Metab. Eng.

    (2014)
  • S. Noda et al.

    Recent advances in microbial production of aromatic chemicals and derivatives

    Trends Biotechnol.

    (2017)
  • K. Sudesh

    Synthesis, structure and properties of polyhydroxyalkanoates: biological polyesters

    Prog. Polym. Sci.

    (2000)
  • M. Koller

    Producing microbial polyhydroxyalkanoate (PHA) biopolyesters in a sustainable manner

    New Biotechnol.

    (2017)
  • J.D. Winkler et al.

    Recent advances in the evolutionary engineering of industrial biocatalysts

    Genomics

    (2014)
  • Y. Chen et al.

    Advances in metabolic pathway and strain engineering paving the way for sustainable production of chemical building blocks

    Curr. Opin. Biotechnol.

    (2013)
  • H. Chung

    Bio-based production of monomers and polymers by metabolically engineered microorganisms

    Curr. Opin. Biotechnol.

    (2015)
  • C.E. Nakamura et al.

    Metabolic engineering for the microbial production of 1,3-propanediol

    Curr. Opin. Biotechnol.

    (2003)
  • N.J. Gallage et al.

    Vanillin – bioconversion and bioengineering of the most popular plant flavor and its de novo biosynthesis in the vanilla orchid

    Mol. Plant

    (2015)
  • N.S. Kruyer et al.

    Metabolic engineering strategies to bio-adipic acid production

    Curr. Opin. Biotechnol.

    (2017)
  • J. Yu

    Bio-based products from solar energy and carbon dioxide

    Trends Biotechnol.

    (2014)
  • A. ElMekawy

    Technological advances in CO2 conversion electro-biorefinery: a step towards commercialization

    Bioresour. Technol.

    (2016)
  • J.-I. Kadokawa et al.

    Polymer synthesis by enzymatic catalysis

    Curr. Opin. Chem. Biol.

    (2010)
  • A. Douka

    A review on enzymatic polymerization to produce polycondensation polymers: the case of aliphatic polyesters, polyamides and polyesteramides

    Prog. Polym. Sci.

    (2018)
  • S. Farah

    Physical and mechanical properties of PLA, and their functions in widespread applications – a comprehensive review

    Adv. Drug Deliv. Rev.

    (2016)
  • P. Wang

    Indole as a new sustainable aromatic unit for high quality biopolyesters

    Polym. Chem.

    (2018)
  • A. Llevot

    Renewable (semi)aromatic polyesters from symmetrical vanillin-based dimers

    Polym. Chem.

    (2015)
  • Ellen MacArthur Foundation

    The New Plastics Economy – Rethinking the Future of Plastics

    (2016)
  • R.C. Thompson

    Plastics, the environment and human health: current consensus and future trends

    Philos. Trans. R. Soc. B Biol. Sci.

    (2009)
  • A. Rahimi et al.

    Chemical recycling of waste plastics for new materials production

    Nat. Rev.

    (2017)
  • K. Regaert

    Mechanical and chemical recycling of solid plastic waste

    Waste Manag.

    (2017)
  • M.A. Hillmyer

    The promise of plastics from plants

    Science

    (2017)
  • J. Candela et al.

    The annual global carbon budget

    (2017)
  • E.J. North et al.

    Plastics and environmental health: the road ahead

    Rev. Environ. Health

    (2013)
  • M. Eriksen

    Plastic pollution in the world′s oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea

    PLoS One

    (2014)
  • M. Hong et al.

    Chemically recyclable polymers: a circular economy approach to sustainability

    Green Chem.

    (2017)
  • UNEP

    Single-Use Plastics: A Roadmap for Sustainability

    (2018)
  • European Commission

    Innovating for Sustainable Growth. A Bioeconomy for Europe

    (2012)
  • M. Carus et al.

    The ‘Circular Bioeconomy’ – Concepts, Opportunities and Limitations

    (2018)
  • T. Mani

    Microplastics profile along the Rhine river

    Sci. Rep.

    (2015)
  • UNEP

    Plastic in Cosmetics. Are We Polluting the Environment with Our Personal Care?

    (2015)
  • T. Debuissy

    Biotic and abiotic synthesis of renewable aliphatic polyesters from short building blocks obtained from biotechnology

    ChemSusChem

    (2018)
  • T. Iwata

    Biodegradable and bio-based polymers: future prospects of eco-friendly plastics

    Angew. Chem. Int. Ed.

    (2015)
  • J. Pagacz

    Bio-polyamides based on renewable raw materials. Glass transition and crystallinity studies

    J. Thermal Anal. Calor.

    (2016)
  • P.F.H. Harmsen

    Green building blocks for bio-based plastics

    Biofuels Bioprod. Biorefin.

    (2014)
  • E. de Jong

    Bio-Based Chemicals. Value Added Products from Biorefineries

    (2012)
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