Biobased, biodegradable and degradable plastics (as a solution for littering)

Biobased plastics and biodegradable plastics have valuable uses in particular instances. For example, aqueous-soluble plastics are useful for the delivery of laundry loads into washing machines at industrial scale (e.g. in hotels), as well as for the delivery of controlled detergent doses in the home. Complex, multilayer items that would otherwise be unrecyclable but can be kept separate from other recycling streams would also be a suitable application for biodegradable polymers. Home composting bags, clearly labelled, provide another opportunity.[1] Below, we do not look at the merits of biobased and biodegradable polymers, but examine them in the context of the open environment and potential impacts on recycling.

Biobased Plastics

‘Biobased plastics’ describe a large category of different types of plastics made wholly or partially from biomass. A clear distinction needs to be made between the various types of bioplastics. The way a plastic is designed to function, as well as what material it is made from, affects how it can be used and what management options are viable for it at the end of its life. Biobased plastics are made using polymers derived from biomass such as starch, cellulose, or lignin. Biobased plastics can be engineered to be biodegradable or they can be made to function exactly like conventional fossil-based plastic (i.e. to have the same durability and recyclability). However, not all bioplastics can be made biodegradable and not all biodegradable plastics can be made recyclable. 

Biodegradable Plastics

Compostable Plastics

Compostable materials are a subset of biodegradable plastics that break down into water, biomass and carbon dioxide under controlled composting conditions using industrial composters or home composting.[3] Materials that are designed to safely break down in industrial composters may not break down under home composting conditions (e.g. some compostable materials need a temperature trigger to break down). Therefore, compostable polymers should also not be discarded in the environment.

Oxo-degradable Plastics

Oxo-degradable plastics are made from traditional fossil feedstocks and are treated with additives that cause the breakdown of the polymer through oxidative degradation. 

Oxo-degradable plastics have been subject to a market restriction prohibiting them being placed on the market under the Single Use Plastics Directive of 2018 of the European Commission. In the UK, Scotland and Wales have proposed a similar restriction.

Impacts on the mechanical recycling stream

The industry is concerned about the impact that some of these materials can have on the established recycling stream. The materials should only be used in areas where they will be prevented from entering the recycling stream, such as established collection schemes for compostable plastics. Biodegradable or compostable items cannot easily be identified and separated from conventional plastics and therefore need to remain separate. The presence of some of these materials in the recycling stream can adversely affect the quality and marketability of the resulting recyclate and its use in products, particularly those with a long life such as damp-proof membranes.

In conclusion...

Biobased and biodegradable plastics are material types that may resonate with some people but they do not provide a viable solution to reducing the amount of plastic waste that wrongly ends up in the natural environment. While some of these might offer sustainability benefits over conventional plastics, the large differences between how these are engineered to function, the feedstocks and their related sustainability as well as the end of life management options need to be carefully considered.

Compostable materials should only be used in applications where there is a clear benefit in using them. Applications include compostable plant pots, liners for food caddies, coffee capsules, food service type items, and packaging that is highly contaminated by food and currently poses significant challenges to recycle economically, or in applications that prevent conventional plastics contaminating the composting stream such as fruit labels. 

The use of bioplastic products should always be accompanied by lifecycle analysis to determine whether or not they are the best environmental choice. Any bio-based or biodegradable product entering the market needs to be accompanied by adequate certification against recognised standards and clear labelling indicating the most appropriate end of life option to ensure there are no false claims and that the products perform in the way expected.

The use of biodegradable products should be discouraged unless they meet recognised standards and certification. Identifying the right application for the right material is key to ensuring that environmental benefits are realised in line with the waste hierarchy, as well as the principles of the circular economy.

Biodegradable plastics should only be used for specific applications where the potential environmental benefits are clear, e.g. applications where collection from the environment is not feasible or where separation of plastic from other waste presents a challenge, and not as a solution to inappropriate waste management or littering. The waste management hierarchy gives priority to reduction, reuse and recycling over the biodegradability of plastics, in line with the principles of the circular economy. Products should also comply with relevant standards and certification schemes. 

 

Sources and further information

1. For further guidance on compostable packaging see: wrap.org.uk/resources/guide/compostable-plastic-packaging-guidance 
2. The impact of the use of oxo-degradable plastic, including oxo-degradable plastic carrier bags, on the environment (2018), Page 1, European Commission
3. For further guidance on compostable packaging see: wrap.org.uk/resources/guide/compostable-plastic-packaging-guidance 

 

Originally published June 2019

Last reviewed and updated July 2024