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What are Biodegradable Plastics?

Biodegradable plastics are plastics that can be broken down into water, biomass, and gases such as carbon dioxide and methane. Biodegradability depends on environmental conditions such as temperature, humidity, the microorganisms present, and oxygen. Compostable materials are a subset of biodegradable plastics that break down safely into water, biomass, and gases under favourable conditions. Industrial composting conditions are the most optimal: temperatures of 55–70℃, high humidity, and oxygen. Materials that break down in industrial composters may not break down under home composting conditions.

Bio-based plastics are made using polymers derived from plant-based sources such as starch, cellulose, or lignin. Bio-based plastics can be engineered to become biodegradable; equally, they can be made to function like conventional fossil-based plastics, which are believed to last much longer.

Not all bio-based plastics are biodegradable, and not all biodegradable plastics are bio-based. The first bio-based and biodegradable plastic was discovered in the late-19th century, although it has only come into popular use recently. This is due to the high costs to make it, and relative difficulty of manufacturing it relative to fossil-based plastics.

A reason for the increased popularity of bio-based and biodegradable plastics is an increased awareness of our environment. Bio-based plastics offer a potentially sustainable and renewable alternative to fossil-based plastics. Biodegradable plastic offers the potential to reduce the high level of plastic waste in the environment.

The UK is currently developing its waste management infrastructure for biodegradable plastics. While anaerobic digestion and industrial composting are being adapted to support these materials, government and industry leaders are questioning whether to also include home composting as part of this infrastructure.

Currently more information is needed to understand how biodegradable plastics work in home composting environments to determine if their disposal at home is a viable alternative to other waste streams such as recycling or landfill.