Short explainer: What is the real difference between compostable and biodegradable?

Compostable versus biodegradable. Do you know the difference? Let's take a closer look at the meaning of these two important terms.

November 8, 2022

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The terms biodegradable and compostable are often used interchangeably. But there are important differences between them. Understanding these differences can help ensure you are disposing of household items in the most sustainable way possible.  Let’s take a closer look.

What does biodegradable mean?

Biodegradable simply refers to the organic breaking down of an item into its natural components, carbon dioxide and water vapour, by organisms like bacteria and fungi, without any scientific or chemical treatment.  

Most materials are biodegradable to some extent and will eventually break down. It is just a question of how long it will take. 

While some materials can take only a matter of months to break down, others can take hundreds to thousands of years. Thankfully, to earn the biodegradable label, products must quickly decompose into their natural elements, a period often restricted to six months.

What does compostable mean?

Compostable materials break down into environmentally friendly, non-toxic components. BUT, only in a compost setting. These non-toxic components might be water, carbon dioxide, or biomass, organic material that comes from living organisms like plants and animals. 

Different materials decompose at different rates and depend on their environment to determine this rate. Compost requires food, water, and air. In the right environment, when an item decomposes these organisms break it down and return it to the earth in a non-harmful way.

Industrial composting vs home composting

If you’re like most city dwellers, you may not have access to a home compost. That’s where industrial composting steps in providing a viable alternative. 

In industrially managed compost facilities, key factors are monitored to ensure complete biodegradation. For example, pH, carbon, nitrogen ratios, as well temperature and moisture levels, are controlled maximising efficiency and ensuring the quality of the resulting compost mix.

Access to industrial composting services may not be available where you live, but is worth investigating as an alternative to home composting. 

What materials can you compost?

Kitchen scraps are probably the first thing that comes to mind when we think about composting. But there are plenty of other items you may not have realised are compostable.

Compostable versus biodegradable? Always check the label.

Clothing made from natural fibres is also suitable for composting. Garments made from materials such as organic cotton, linen, wool, bamboo, and silk can all be added to your compost bin. 

However, before throwing your old clothes into the compost pile, you’ll need to check for non-compostable elements. Zips, buttons, and synthetic fabrics must be removed as these materials are not compostable and can damage the environment.

This said, clothing items made from a combination of materials, such as organic cotton mixes with polyester, are not suitable for composting as the additional synthetic fibres will not break down. Instead, these fibres heat up under the sun releasing toxic fumes that will destroy your compost environment.

Certain items like bioplastics must be approved for composting by accreditation bodies. In Europe, the most widely recognised is TUV Austria, offering the OK compost INDUSTRIAL certification. In the US, the most well known certification body is the Biodegradable Products Institute (BPI), which is the equivalent to the OK compost certification. On packaging, look for the ASTM D6400, EN 13432, BPI, and TUV Industrial logos to determine whether the product is suitable for the compost route. 

What is compostable packaging made of?

Compostable packaging is made from plant-based raw materials such as sugar cane and corn. They are a more sustainable alternative to petroleum based products like traditional plastic bags and food packaging. 

Their compostability allows the waste product to become an incredible resource – a valuable fertiliser that can enrich soil and plants. But what happens to compostable packaging that doesn’t make it into the compost bin?

Why you should compost

You might be wondering why you should compost at all. After all, won’t compostable materials just biodegrade in a landfill anyway?

First off, composting can significantly reduce organic waste and the resulting compost can be used for agricultural and horticultural purposes. Around 50% of domestic waste contains organic material, a percentage that is likely to increase as more and more biodegradable products (packaging, disposable cups, etc.) are introduced.

Materials such as food waste and natural clothing fibres can naturally biodegrade, whereas bioplastics such as takeaway coffee cups and mailer bags do not properly decompose in landfill sites and may take just as long as biodegradable alternatives. 

The lack of an appropriate compost environment means that a potentially valuable resource is turned into yet another waste product.

The key difference between biodegradable and compostable

The breakdown processes of biodegradable and compostable materials are quite similar. Both involve  the breaking down of organic fibres into smaller components. But, there is one key distinction: while all compostable items are biodegradable, not all biodegradable items are compostable.

In a specific environment, compostable fibres return to the earth and enrich the environment. But what happens when these compostable waste products don’t make it into the compost bin? 

Sadly, if they end up in landfill, they will not be composted and will continue to exist in the landfill for a very long time. Compostable materials require moisture, oxygen, and bacteria in order to biodegrade and landfills are often kept dry to minimise the amount of methane released.

Nonetheless, we would argue it is still better to use compostable products in place of petroleum-based plastics, even if they do end up in a landfill. Overall, the environmental impact is certainly less.

On the other hand, biodegradable materials will break down naturally in any type of external environment, even landfill, but they don’t always benefit the environment. 

When dumped into landfills, biodegradable materials often get buried. This can cause a lack of oxygen required by the beneficial bacteria to do its job. The result is the production of methane. Definitely not a desired by-product!

While the precise difference between both biodegradable and compostable is often unclear, there is good news. This confusion has led to the development of a European Standard (EN 13432) which sets out criteria for what is biodegradable and what is compostable. The US Standard (ASTM D6400-99) contains similar criteria.

If you’re unsure about whether a product is compostable or biodegradable, look for the ETL, TUV, and UL labels.

Final Thoughts

As with so many eco-friendly practices, knowledge is the key to success. If you wish to be more sustainable, always check the composition of a product and packaging before making a purchase. 

Compostable packaging can be a more eco-friendly option but only If you have access to an industrial composting facility. The most sustainable choice is to opt for a reusable product and cut down on the additional waste entirely.

Looking for more ways to reduce your waste? You might be interested in these posts:

5 Easy Ways You Can Reduce Your Fashion Waste

Turning Old Garments Into New Pieces of Clothing – The Art of Mending

The Ultimate Guide to Sustainable Living