Solving the plastic dilemma: the fungal and bacterial biodegradability of polyurethanes

Abstract

Polyurethane (PU) is a plastic polymer which, due to its various desirable characteristics, has been applied extensively in domestic, industrial and medical fields for the past 50 years. Subsequently, an increasing amount of PU waste is generated annually. PU, like many other plastics, is highly resistant to degradation and is a substantial threat to our environment. Currently PU wastes are handled through conventional disposal techniques such as landfill, incineration and recycling. Due to the many drawbacks of these techniques, a ‘greener’ alternative is necessary, and biodegradation appears to be the most promising option. Biodegradation has the potential to completely mineralise plastic waste or recover the input materials and better enable recycling. There are hurdles to overcome however, primarily the efficiency of the process and the presence of waste plastics with inherently different chemical structures. This review will focus on polyurethanes and their biodegradation, outlining the difficulty of degrading different versions of the same material and strategies for achieving more efficient biodegradation.

Recycling of polyurethanes: where we are and where we are going

“…It is possible to exploit such living microorganisms as bacteria and fungi to biodegrade polyurethane wastes, including post-consumer materials: 29,85–87 because of the interaction with the microorganisms, either under aerobic or anaerobic conditions, the macromolecular chains are shortened, and the molecular weight of the polymer significantly decreases. Further, according to the adopted experimental conditions, it is possible to achieve the full mineralization of the biodegraded polymer.…”

Designing biodegradable alternatives to commodity polymers

“…Polyurethanes are used in a broad range of applications such as adhesives, coatings and personal care products, with increasing demand over the past 50 years leading to a bottleneck as they accumulate in both terrestrial and aquatic environments. 170 Determining the environmental fate of polyurethanes is crucial because of the ability of both the polymer itself, and the additives typically present, to leach hazardous compounds into the environment, leading to the identification of polyurethanes as one of the most toxic classes of polymers. 171 Pfohl et al investigated the biodegradation of polyurethanes in compost to construct a structure-degradation relationship and investigate the mechanism by which fragmentation and subsequent biodegradation is achieved.…”

“…Bhavsar et al have discussed the challenges associated with biodegradation of polyurethanes, and evaluates the potential of employing bacteria and fungi to accelerate biodegradation. 170…”

Aplicação de microrganismos lipolíticos em alimentos e na biodegradação de poliuretanos

“…The rigid segment comprises a wide variety of isocyanate-based components and short-chain extenders, which provide hardness and mechanical strength. The flexible segment mainly consists of the long part of a polyol, such as a polyester or a polyether, which imparts absorption, elasticity, and elongation traits (Bhavsar et al, 2023;Spence and Plehiers, 2022). The flexible segments do not form crystals or have low crystallinity, being the part most susceptible to biodegradation.…”

“…The flexible segments do not form crystals or have low crystallinity, being the part most susceptible to biodegradation. PU polyester is more biodegradable than PU polyether due to the presence of ester groups, which are more prone to attack by microbial enzymes (Bhavsar et al, 2023;Rajan and Vijayalakshmi, 2023).…”