materials Review Review on the Biological Degradation of Polymers in Various Environments Silvia Kliem * , Marc Kreutzbruck and Christian Bonten Institut für Kunststofftechnik, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany;
[email protected] (M.K.);
[email protected] (C.B.) * Correspondence:
[email protected]; Tel.: +49-711-685-62831 Received: 10 September 2020; Accepted: 12 October 2020; Published: 15 October 2020 Abstract: Biodegradable plastics can make an important contribution to the struggle against increasing environmental pollution through plastics. However, biodegradability is a material property that is influenced by many factors. This review provides an overview of the main environmental conditions in which biodegradation takes place and then presents the degradability of numerous polymers. Polylactide (PLA), which is already available on an industrial scale, and the polyhydroxyalkanoates polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV), which are among the few plastics that have been proven to degrade in seawater, will be discussed in detail, followed by a summary of the degradability of further petroleum-, cellulose-, starch-, protein- and CO2-based biopolymers and some naturally occurring polymers. Keywords: biodegradable polymers; environmental pollution; end of life scenario; plastics in the environment 1. Introduction Plastics have become an indispensable part of everyday life. The various strengths of plastics come into their own in a wide variety of applications—packaging, clothing, car tires and much more. At the same time, however, the often-desired resistance to environmental influences and other stresses represents a major challenge. Plastic waste is increasingly found in the oceans, in rivers and in the ground, mostly as a result of human misconduct.