A new report from BB-REG-NET examines the breakdown of biodegradable plastics in the environment. Based on case studies in composting, agriculture and forestry, it concludes that certified biodegradable plastics break down at similar rates to their rate of entry into environment, preventing long-term accumulation.
Scenarios considered include direct placement of plastics, in applications such as agricultural mulch films and tree guards; and indirect placement, e.g. via organics recycling. Environments include soil and marine. Issues in distinguishing between conventional and biodegradable microplastics are discussed, and the point is made that while biodegradable plastics may fragment into microplastics, their persistence in short-term and field studies suggests an equilibrium is reached between the rate of addition and degradation, with rates of mineralisation depending on exposure conditions.
This is a useful and timely report, and EBNet’s only minor regret is that while it references a number of studies on composting, there is very little on bioplastics degradation in anaerobic digestion: a notable omission given the growing body of work on this topic, including some carried out by EBNet members and staff on behalf of the National Non-Food Crops Centre.
Of course, both digestate and compost are often used in contact with soils or other applications where biodegradation can continue:Â so the report makes welcome reading from this point of view.
Addressing Persistent Plastic Pollution: the case for biodegradable solutions can be downloaded from BB-REG-NET HERE.
On assessing the breakdown of biodegradable plastics in AD, see the following papers – as well as many other studies that have come after or refer to them, and several axcellent reviews:
Degradation of some EN13432 compliant plastics in simulated mesophilic anaerobic digestion of food waste. Zhang, W., Heaven, S. and Banks, C.J., 2018. Polymer degradation and stability, 147, pp.76-88.
Data related to anaerobic digestion of bioplastics: Images and properties of digested bioplastics and digestate, synthetic food waste recipe and packaging information. Zhang, W., Torrella, F., Banks, C.J. and Heaven, S., 2019. Data in brief, 25, p.103990.