Biodegradable / Oxo-degradable / Compostable

The terms biodegradable and compostable are often mistakenly thought of as interchangeable, but they do not mean the same thing.

Other terms are also used, such as degradable, oxo-degradable, or bioplastic, leading to confusion as few people understand the differences.

These terms all sound good, but what do they actually mean? Understanding that there’s a huge difference between these terms is crucial in order to make educated and positive choices. In additional, a lot of companies are ‘green-washing’ their products, meaning they advertise that it is eco-friendly when in fact, it is not.

A lot of companies are ‘green-washing’ their products, meaning they advertise that it is eco-friendly when in fact, it is not.

It is imperative for the consumer to have knowledge of the materials they are buying and to be conscious of the fact that no matter what type of material/product, it must be subject to appropriate disposal and recovery processes. However, this is all very confusing and there isn’t enough information on products to educate the consumer, so we’ve done some research to help you out! 

Biodegradable

If something is biodegradable it is capable of decomposing back into natural elements, through a process called biodegradation. Biodegradation is a slow process, in which materials are metabolised to CO2, water, and biomass (compost), with the help of microorganisms, such as bacteria, fungi and algae, that are available in the environment. However, this does not necessarily imply that the product can be converted into good quality compost because some biodegradable plastics are not biobased and don't always break down into harmless substances: sometimes they leave behind a toxic residue.

On its own the term biodegradable is, to a degree, obsolete as most materials will biodegrade given time. There are no defined time limits for biodegradable materials to break down, thus the use of this word can be potentially confusing to the consumer, both in terms of where to dispose of it, and what happens to it once discarded.

The process of biodegradation depends on conditions such as location, temperature, humidity, and presence of microorganisms. 

The process of biodegradation depends on conditions such as location, temperature, humidity, and presence of microorganisms. It also depends on the material itself, and the specific environment, such as an industrial compost plant or home compost. For example, plastics that are biodegradable in an industrial composting plant (the most aggressive atmosphere regime) are not usually biodegradable in water, soil, or even in your home compost bin. Consequently, the process of biodegradation and its outcome can vary considerably.

As each environment has different conditions, the speed of the biodegradation process may vary from one place to another, but it usually takes a really long time in nature - perhaps decades or even centuries, and is completely dependent on the temperature and the amount of moisture present. As such, biodegradable materials should always be sent to an industrial composting facility as they need very specific conditions to break down. For example, most councils (in the UK) have industrial composting systems for food waste that are designed to allow the necessary micro-organisms needed to break down biodegradable materials, to thrive. Although biodegradable materials would eventually break down in a home compost, it would take a really long time. It is better to send them to industrial compost facilities, where biodegradable materials will break down in approximately 12 weeks.

Biodegradable materials should always be sent to an industrial composting facility as they need very specific conditions to break down. 

Biodegradable plastics are often regarded as a possible solution to the plastic pollution problem. However, this is not a viable answer, as biodegradable materials need very specific conditions to break down, such as those in an industrial composting facility, and so will not break down in nature. For example, in the oceans, the water is usually too cold to break down biodegradable plastics, so they either float forever on the surface (just like conventional plastics) or break down into microplastic fragments that are harmful to marine life. It is also important to remember that biodegradable does not necessarily mean biobased, there are some biodegradable fossil-fuel based plastics. These biodegradable plastics are currently still made in petrochemical production processes, so it would be better to avoid using these materials in favour of bioplastic alternatives.

There are international standards that specify what properties a material must have in order to be labelled ‘biodegradable.’ This includes factors such as the timeframe and the level of biodegradation, and the required surrounding conditions that allow this process to happen. The EN 13432 standard defines that the product is suitable for industrial composting and the conditions of a composting plants, but not for those outside in nature. Anything with these labels must be send to an industrial composting facility.

Oxo-biodegradable / Oxo-degradable / Degradable

The terms degradable or oxo-degradable describe a type of fossil-fuel based plastic that has been treated with additives, usually consisting of calcium carbonate and heavy metals, which causes the material to mimic biodegradation and disintegrate over a number of years. Degradable bags do not 'compost' when composting, and will contaminate the end compost reducing its value or limiting its use. Degradable bags will also contaminate any recyclable plastics feedstock, causing great damage to a material which should be able to be recycled over and over again.

The additives that are added to the plastic do not enable it to fully break down, or degrade. Instead, the main effect of oxidation is fragmentation of the material into smaller particles, often referred to as microplastics, that remain in the environment. This process would be more accurately described by the term “oxo-fragmentation,” rather than the obviously misleading term “oxo-degradable.” Oxo-biodegradable materials do not fulfill the requirements of EN 13432 on industrial compostability, like biodegradable plastics do, and are therefore unable to be disposed of in this way.

In 2017, over 150 organisations worldwide, including EUBP and many of its members, endorsed a statement by the New Plastics Economy initiative of the Ellen MacArthur Foundation that proposes banning oxo-degradable plastic packaging worldwide.

Compostable

All compostable material is biodegradable. Compostability is a characteristic of a material that allows it to biodegrade under certain conditions (e.g. time frame, temperature), and break down completely without harming the environment. If something is considered a compostable material, it is capable of decomposing back into natural elements within a matter of months, as long as the specific conditions are present. The exact time something takes to fully decompose depends on the material and the composting conditions.

The specific properties of a material required to be labelled as ‘compostable’ are described in standards, such as the European standard on industrial composting (EN 13432 - for packaging or EN 14995 - for plastic materials in general). Wherever possible, check that the product you are buying has these environmental certifications to back up their claims of being a green product.

Composting can reduce the volume of organic waste quite significantly, while the compost produced can be used for agricultural and horticultural purposes. About 50% of all domestic waste comprises organic material, a percentage that is set to grow in the future owing to the growing popularity of compostable products.

Some products that are labelled ‘compostable’ must be sent to an industrial composting facility, but others can be composted in your home compost bin. 

Some products that are labelled ‘compostable’ must be sent to an industrial composting facility, but others can be composted in your home compost bin. Composting at home is a more difficult, slower-paced process. This is because the comparatively smaller volume of waste involved means that the temperature in a garden compost heap is lower and less constant, than in an industrial composting environment. Products that are certified as ‘OK-compost’ will only compost in industrial facilities at temperatures between 55 to 60°C so should not go into a home compost. Products that are certified as ‘OK-compost-HOME’ will compost at lower temperatures, so they can go into the compost heap at home, or to industrial facilities.

Products that are certified as ‘OK-compost’ will only compost in industrial facilities and should not go into a home compost.

Products that are certified as ‘OK-compost-HOME’ can go into a home compost, or to industrial facilities.

Compostable plastics that are certified according to the European standard for industrial composting EN 13432 are required to disintegrate after 12 weeks and completely biodegrade after 6 months. That means that 90 percent or more of the plastic material will have been converted to CO2. The remaining share is converted into water and biomass, which no longer contains any plastic. EN 13432 also includes test on ecotoxicity and heavy metal contents to ensure that no harmful substances are left behind.

Whilst both compostable and biodegradable materials return to nature and can disappear completely, compostable materials are specifically organic matter and do not leave behind any toxic residue. Instead, compostable materials create something called humus that is full of nutrients and great for plants. Compostable materials are basically biodegradable materials, but with the added benefit of releasing valuable nutrients as they break down, fertilising and improving soil health.

Compostable materials are specifically organic matter and do not leave behind any toxic residue, they are basically biodegradable, but with the added benefit of releasing valuable nutrients as they break down.

Unlike biodegradables, where specific conditions, such as temperature and moisture levels, must be met in order to facilitate biodegradation, compostable materials will break down more easily despite external environmental factors.

A biodegradable material is not necessarily compostable.

A compostable material is always biodegradable.

I am just a tattoo artist, not a scientist, and this is written from my own research. I hope you found it helpful!