Microbiology challenges and opportunities in the circular economy.

Our knowledge and understanding of micro-organisms have led to the development of safe food, clean water, novel foods, antibiotics, vaccines, healthier plants, animals and soils, and more, which feeds into the United Nations Sustainable Development Goals (UN SDGs). The circular economy can contribute to the UN SDGs and micro-organisms are central to circular nutrient cycles. The circular economy as described by the Ellen MacArthur foundation has two halves, i.e. technical and biological. On the technical side, non-biological resources enter manufacturing paths where resource efficiency, renewable energy and design extend the life of materials so that they are more easily reused and recycled. Biological resources exist on the other half of the circular economy. These are used to manufacture products such as bioplastics and paper. The conservation of nature's stocks, resource efficiency and recycling of materials are key facets of the biological half of the circular economy. Microbes play a critical role in both the biological and technical parts of the circular economy. Microbes are key to a functioning circular economy, where natural resources, including biological wastes, are converted by microbes into products of value and use for society, e.g. biogas, bioethanol, bioplastics, building block chemicals and compost for healthy soils. In more recent times, microbes have also been seen as part of the tool kit in the technical side of the circular economy, where microbial enzymes can degrade plastics and microbes can convert those monomers to value-added products.

Plastic waste as a global challenge: are biodegradable plastics the answer to the plastic waste problem?

The strength, flexibility and light weight of traditional oil-derived plastics make them ideal materials for a large number of applications, including packaging, medical devices, building, transportation, etc. However, the majority of produced plastics are single-use plastics, which, coupled with a throw-away culture, leads to the accumulation of plastic waste and pollution, as well as the loss of a valuable resource. In this review we discuss the advances and possibilities in the biotransformation and biodegradation of oil-based plastics. We review bio-based and biodegradable polymers and highlight the importance of end-of-life management of biodegradables. Finally, we discuss the role of a circular economy in reducing plastic waste pollution.