Biodegradable Plastic Blends Create New Possibilities for End-of-Life Management of Plastics but They Are Not a Panacea for Plastic Pollution

Abstract

Plastic waste pollution is a global environmental problem which could be addressed by biodegradable plastics. The latter are blended together to achieve commercially functional properties, but the environmental fate of these blends is unknown. We have tested neat polymers, polylactic acid (PLA), polyhydroxybutyrate, polyhydroxyoctanoate, poly(butylene succinate), thermoplastic starch, polycaprolactone (PCL), and blends thereof for biodegradation across seven managed and unmanaged environments. PLA is one of the world's best-selling biodegradable plastics, but it is not home compostable. We show here that PLA when blended with PCL becomes home compostable. We also demonstrate that the majority of the tested bioplastics and their blends degrade by thermophilic anaerobic digestion with high biogas output, but degradation times are 3-6 times longer than the retention times in commercial plants. While some polymers and their blends showed good biodegradation in soil and water, the majority of polymers and their blends tested in this study failed to achieve ISO and ASTM biodegradation standards, and some failed to show any biodegradation. Thus, biodegradable plastic blends need careful postconsumer management, and further design to allow more rapid biodegradation in multiple environments is needed as their release into the environment can cause plastic pollution.

Recent Advances in Bioplastics: Application and Biodegradation

“…Blending of polymers with the aim of improving mechanical properties could have a positive/synergistic effect on their biodegradation capacity, but it could also decrease the biodegradation potentials of individual components. For example, blending of PLA with oil-based, but biodegradable polycaprolactone (PCL) resulted in improved mechanical properties and biodegradability of PLA under home composting conditions [1]. Similar to this, blends of PHB and PCL, and PCL and TPS showed higher degradation in anaerobic digestion, while the same blends exhibited antagonism during biodegradation tests in aquatic environments.…”

“…PLA reaches international standards for biodegradation in industrial composting and anaerobic digestion conditions, but shows a very slow rate of degradation in soil and water, with estimates being that it would take decades or longer to completely degrade depending on the environment [1]. TPS and PHB were the only bioplastics that satisfied the criteria for biodegradation proposed by international standards across various environments representing managed (industrial composting, home composting, and anaerobic digestion) and unmanaged environments (soil, fresh, and sea water) [1]. Blending of polymers with the aim of improving mechanical properties could have a positive/synergistic effect on their biodegradation capacity, but it could also decrease the biodegradation potentials of individual components.…”

“…Plastics are a large family of polymers, traditionally derived from fossil resources that are characterised as having a broad range of properties and characteristics [1]. Approximately 90% of plastics produced are derived from fossil feedstocks [2].…”

“…The plastic industry is important for employment, given the reported over 1.6 million people employed in the industry across the EU, and the €360 billion turnover in 2018 [8]. [1,35]. Table 1.…”

Computational redesign of a PETase for plastic biodegradation by the GRAPE strategy

“…Accumulated marine and terrestrial pollution problems, as well as the negative impacts of microplastic exposure on human health, have caused escalating public and governmental concerns 3,4 . With the excessive use of plastics and increasing pressure on the capacity for plastic waste disposal, the demand for eco-friendly waste management has assumed dramatically importance in the last few years 5,6 .…”