Most plastics continue to be made from fossil fuels in a process that contributes to increased greenhouse gas emissions along their value chain. Indeed, plastics pollute throughout their life cycle from production, to use, and finally through their disposal.
Recycling rates of plastic are low, and plastics leak into the environment through littering, improper waste management, and wear and tear of products. They can persist in nature for many years and potentially enter the food chain. Contamination with plastic particles poses a particular challenge in maintaining the cleanliness of compost made from separately collected bio-waste (EEA, 2020).
Biodegradable, compostable, and bio-based plastics are increasingly promoted as a solution to some of these challenges. More and more consumer products, such as plastic bags, packaging, and single-use cups, are labelled as 'compostable', 'biodegradable', or 'bio-based'. But what exactly do these terms mean? To what extent can biodegradable, compostable, and bio-based plastics help address the sustainability issues posed by conventional plastics? And do they create new challenges?
Biodegradable and compostable materials can be broken down by microorganisms into water, carbon dioxide, mineral salts, and new biomass within a defined period. The rate and extent of biodegradation or composting of plastic items depend significantly on the disposal conditions, including temperature, duration, the presence of microorganisms, nutrients, oxygen, and moisture (De Wilde et al., 2013; van den Oever et al., 2017).
Different types of biodegradable and compostable plastics are designed to degrade under specified conditions (Box 1). In other environments, they might degrade slowly or not at all and could even fragment into microplastics.
Biodegradable plastics are designed to biodegrade in specific mediums (water, soil, compost) under certain conditions and in varying periods of time.
Industrially compostable plastics are designed to biodegrade under the controlled conditions of industrial composting or anaerobic digestion plants with subsequent composting.
Home compostable plastics are designed to biodegrade in well-managed home composters at lower temperatures compared to industrial composting plants. Most of them also biodegrade in industrial composting plants.
Bio-based plastics are fully or partly made from biological raw materials instead of fossil raw materials like oil, used in conventional plastics.
Non-biodegradable plastics have a long life span and can disintegrate into microplastics, accumulating in the environment.
Oxo-degradable plastics include additives that, through oxidation, lead to fragmentation into microplastics or chemical decomposition.
Biodegradable or compostable plastics can be produced from either bio-based or fossil raw materials (feedstock). They can have functionalities similar to or the same as conventional plastics (WRAP, 2020). The sustainability of bio-based materials, like fossil-based plastics, depends on production practices, product lifetime, and end-of-life treatments (EEA, 2018). The term "bioplastics" is sometimes used for plastics that are either bio-based or biodegradable, or both (European Bioplastics e.V., 2020c). Given their diverse properties, consumers might misunderstand the broad term 'bioplastics'.
Source: ETC/WMGE and EEA.
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