Microplastics and their potential environmental and health impacts have become increasingly concerning in recent years. Everything in nature, including natural materials, will eventually wear down or decompose. This applies to plants that become humus as much as to mountains and rocks, which gradually break down into grains of sand over centuries. The same is true for all man-made materials, including synthetic polymers and plastics. The difference is that these are not easily reintegrated into the natural cycle, which means they remain in the environment for much longer.
As microplastics can harm the environment and human health, biodegradable plastics and polymers are gaining importance as a possible solution. Although biodegradable plastics also produce small particles through abrasion, these are not as persistent as those from conventional, non-biodegradable materials, as they break down biologically.
A Better Understanding of Microplastic Formation and Impact is Necessary
The Initiative for Natural Circular Economy (INAK) supports all efforts to gain a better understanding of the origins and formation of microplastics, as well as their impact on the environment, in order to minimise environmental pollution. A number of scientific studies are investigating whether biodegradable materials could be a solution to reducing the accumulation of microplastics. This requires gathering data on the residence time of materials in nature, which must then be factored into risk and life cycle assessments. Biodegradable polymers have the advantage of not breaking down into permanent secondary microplastic particles, as most natural environments host microorganisms capable of degrading these polymers. As a result, the residence time of biodegradable polymers is significantly shorter than that of conventional plastic materials.
Industrially compostable plastics reduce the amount of persistent, non-biodegradable microplastic in compost, thereby preventing it from entering soils. Compost produced from separately collected organic waste is increasingly contaminated with (micro)plastics from conventional plastics that were mistakenly disposed of with organic waste. Industrially compostable plastics help to collect more organic waste separately and divert larger amounts of organic waste into organic recycling. At the same time, they help reduce contamination of organic waste with conventional plastics, ultimately reducing microplastics in compost.
Certified industrially compostable plastic products are fully biodegradable under the conditions of industrial organic waste treatment, meaning they are converted into CO2, H2O, and biomass, decomposing within 12 weeks in accordance with the European standard EN 13432. In this context, decomposition is a necessary part of the overall biodegradation process and results in smaller particles that should not be confused with persistent microplastics. Even under suboptimal composting conditions, the biodegradation of these smaller particles continues in the soil.
Biodegradable plastics in soil are especially beneficial in applications close to nature, such as agriculture, forestry, horticulture, or landscaping, or in cases where they enter the environment through abrasion. These offer a practical solution for reducing the release of microplastics into the environment. The “BioSinn” study conducted by the renowned nova-Institute in Hürth (2021, funded by the BMEL) examined the potential uses of biodegradable materials and identified several applications, including mulch films, binding twine, growth sleeves, plant clips, controlled-release fertiliser films, and bristles for street sweepers. Read the full study here.
For example, biodegradable mulch films help reduce the release and accumulation of persistent microplastics in agricultural soils. The European standard EN 17033 sets out the requirements for the biodegradability of mulch films used in agriculture and horticulture. These include decomposition within less than two years, comprehensive ecotoxicological testing, and clear usage guidelines. Unlike conventional PE mulch films, which can lead to a build-up of plastic particles in the soil, biodegradable films do not cause this accumulation.
Biodegradable polymers also offer a solution in applications where microparticles must be deliberately added, such as in certain cosmetic products, where microplastics are used as fillers, exfoliating particles, or emulsifiers. More and more countries around the world are banning the use of deliberately added microplastics made from non-biodegradable materials, and many cosmetic companies are already switching to biodegradable alternatives.
Biodegradability should be tested under the environmental conditions to which the products or microparticles are likely to be exposed, such as soil, marine environments, or freshwater. There are already several standards for testing degradation behaviour, and biodegradable plastic particles should meet these test methods within an acceptable timeframe, which is determined using natural microparticles as a reference. In addition, comprehensive ecotoxicological tests must be part of the assessment to avoid risks to flora and fauna from harmful substances.
Further information on this topic is available from the European association European Bioplastics.
September 2024.