Compostable / Biodegradable / Oxo-degradable
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 and oxo-degradable, 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 that are inline with out values.
One of the reasons it's really important to understand these terms is that a lot of companies are ‘green-washing’ their products. This means that something is advertised as being eco-friendly when in fact, it is not.
It is imperative for the consumer to have knowledge of the products they are buying and to be conscious of the fact that no matter what type of material, it must be subject to appropriate disposal and recovery processes. However, this is all very confusing and there often isn’t enough information on products to educate the consumer, so we’ve written this guide to help you out!
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.
Composting is the process of breaking down organic waste by microbial digestion to create compost. To go through a composting process, organic waste requires the right level of heat, water, and oxygen. In a pile of organic waste, there are millions of tiny microbes that consume the waste, transforming the organic materials into compost.
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.
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. Composting at home is a more difficult, slower-paced process 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.
There are international standards that specify what properties a material must have in order to be labelled ‘compostable.’ This includes factors such as the timeframe, the level of biodegradation, and the required surrounding conditions that allow this process to happen. Wherever possible, check that the product you are buying carries these environmental certifications to back up their claims of being a green product.
The EN13432 certification is the European standard that guarantees the compostability of a material. The standard details that under the correct conditions, materials 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. The EN13432 standard also includes tests on ecotoxicity and heavy metal contents to ensure that no harmful substances are left behind.
There are two types of EN 13432 compostability certification - one for industrial composting and one for home composting.
Products that are certified as ‘OK-compost’ will only compost in industrial facilities at temperatures between 55-60°C and 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 a home compost, or to industrial facilities.
All of our products and packaging carry the European EN13432 compostability certification, as well as the equivalent certification from other governing bodies around the world including;
EN13432 (Europe), ASTM6400 (USA), AS4736 (Australia), GreenPLA (Japan)
Unlike biodegradables where specific conditions must be met in order to facilitate biodegradation, compostable materials will break down more easily despite external environmental factors. And when they break down, 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 biodegrade, fertilising and improving soil health.
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.
If something is biodegradable it is capable of decomposing back into natural elements through a process called biodegradation. However, unlike compostable materials, some biodegradable materials are not entirely biobased and don't always break down into harmless substances, sometimes they leave behind a toxic residue.
The definition of biodegradable is that a material is capable of undergoing biological anaerobic or aerobic degradation leading to the production of CO2, H2O, methane, biomass, and mineral salts, depending on the environmental conditions of the process.
Biodegradation is a slow process in which materials are metabolised with the help of microorganisms that are available in the environment, such as bacteria, fungi and algae. However, this does not necessarily imply that the product can be converted into good quality compost.
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 landfill. 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.
Although biodegradable materials would eventually break down in a home compost, it would take a really long time, so it’s better to send them to industrial composting facilities where biodegradable materials will break down in approximately 12 weeks. Industrial composting systems are designed to allow the micro-organisms needed to break down biodegradable materials to thrive.
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, will not break down easily in nature, and many are even damaging to the environment when they do eventually break down.
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 important to remember that biodegradable does not necessarily mean biobased, there are some biodegradable fossil-fuel based plastics.
Some biodegradable plastics are not entirely biobased and many still contain fossil-fuels. These biodegradable plastics are currently still made in petrochemical production processes, so it would be better to avoid using these materials in favour of 100% plant-based and compostable alternatives.
To a degree, the term biodegradable is 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.
A biodegradable material is not necessarily compostable.
A compostable material is always biodegradable.
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 main effect of oxidation is fragmentation of the material into smaller particles, often referred to as microplastics, that remain in the environment. The additives that are added to the plastic do not enable it to fully break down, or degrade. This process would be more accurately described by the term “oxo-fragmentation,” rather than the obviously misleading term “oxo-degradable.” Additionally, oxo-biodegradable materials do not fulfill the compostability requirements of the EN 13432 certification, 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.
I am a tattoo artist, not a scientist, and this is written from my own research. I hope you found it helpful!