To degrade or not to degrade, that is only half the question

Biodegradable, oxo biodegradable, compostable, home compostable are all words used to describe the ‘green’ credentials of packaging materials. No wonder consumers are confused about biodegradability says Dr Matthew Aylott from the NNFCC. The packaging industry must come together, put greenwash to one side and simply and clearly communicate just what biodegradability means. A lack of clear definitions is damaging the industry and could result in consumers making choices based on incorrect information.

Biodegradable
The term ‘biodegradable’ simply means the ability of a material to be broken down by bacteria or another biological means. It puts no conditions or time frame on this process and neither does it make the product environmentally friendly or sustainable. In fact, it can be very dangerous to assume that something is sustainable simply because it biodegrades.

Plastics made from oil can be biodegradable and likewise plastics made from plants – known bioplastics – can be designed so they don’t biodegrade for thousands of years, meaning they can be recycled as you would with a normal plastic.

Oxo biodegradable
Oxo biodegradables additives allow plastics to degrade in the presence of oxygen and sunlight thanks to the addition of small amounts of catalysts. This sounds like an ideal solution to having bags blowing around in the wind but as they break down these materials release fossil-based carbon dioxide into the atmosphere.

In addition, degradability depends on where and under what conditions the material ends up after use. For example, in landfill oxo biodegradable materials don’t degrade because there is no light or oxygen. They are also difficult to recycle so the stored energy within the bag, box or bottle is lost. But what if we could capture the carbon of a material as it breaks down? This is where composting and anaerobic digestion could be important in turning waste into a valuable commodity.

Compostable
Composting is where organisms break down a biodegradable material in the presence of air to make water, carbon dioxide and a valuable fertiliser. In contrast, within an anaerobic digester this air is taken away and microorganisms break down the material into a high-quality fertiliser, which can be spread on the land, and a methane rich gas, which can be burned to make energy and money. Both processes prevent waste being sent to landfill and reduce our reliance on fossil-based fertilisers, which have risen 50 per cent in price over the past year and can now cost in excess of £1,000 per tonne for speciality blends.

To ensure degradable bioplastics break down homogenously, the NNFCC worked in collaboration with other expert groups to develop and promote a European standard for compostability, EN13432, and its associated logo. This clearly and simply identifies biodegradable packaging, allowing easier segregation from non-biodegradables. EN13432 requires a material to break down to 10 per cent of its original mass within 90 days under controlled conditions. But what happens to these same materials in a home compost heap can be very different.

Home compostable
The UK is a nation of home composters, every year we compost half a million tonnes of garden and kitchen waste, which helps avoid the costs associated with waste collection and disposal. But adding plastics – even if they are made from plants – to the compost heap is a foreign concept to many and only some plastics are suitable.

Owing to the smaller volume of waste involved, the temperature in a garden compost heap is much lower and less constant than in an industrial composter. This is why composting at home is a slower, more difficult process. Home compostable plastics need a different standard to ensure compatibility with home composting and the NNFCC, along with the Association for Organics Recycling and other organisations, are working towards a new home compostable standard and logo for the bioplastics in the UK.

Future
We need to develop and promote a transparent industry, which is based on clear definitions and standards that cannot be misinterpreted and are universal across the UK and beyond. This will serve to better inform consumers, while promoting more sustainable and affordable plastics and end-of-life options.

Dr Matthew Aylott is science and technology writer for the NNFCC (The UK’s National Centre for Biorenewable Energy, Fuels and Materials).

For more information visit www.packagingnews.co.uk.