Compostable & Biodegradable Guide

In today’s pursuit of a more sustainable economy, Compostable and Biodegradable have become buzz words, but the true meaning of these words tends to not be fully understood. The purpose of this guide is to clarify these terms and give you a better understanding of what they mean and why they are different.

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    Simply put biodegradable means that an item will be broken back down to its natural components by bacteria. For instance, food scraps will biodegrade into water, carbon dioxide and a biomass. Whereas many plastics do not fully biodegrade, but rather degrade (breakdown) into smaller fragments of plastic. The important consideration here is that all the term biodegradable tells you is that an item will break down, but the term does not tell you how long this will take, nor does it tell you what environment the item needs to be in for biodegradation to occur.

    If a biodegradable item ends up in a landfill site it can take many more years to breakdown than in other environments due to the typical lack of; bacteria, light, water and oxygen, which are required to aid the process of biodegradation. This consideration means that the term biodegradable tends to lack real meaning in the context of understanding the end of life of an item. This consideration is revisited at the end of this guide.

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    In simple terms composting is introducing an item into an environment which aids in the biodegradation process.

    There are two broad types of composting;

    • Home Composting: you can put this item in a home compost bin.
    • Industrial Composting: These items need to go into your food waste collection bins. This is because industrial composting facilities reach higher temperatures and have a controlled environment which accelerates the composting process.

    If you put something meant for industrial composting in your home compost bin, expect it to sit there for a while!


Certification Standards

In this section we will be discussing 5 standards which relate to composting and biodegradability. These are; Industrial composting, Home composting, Biodegradable (soil), Biodegradable (water) and Biodegradable (marine).

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    Industrial Compostable

    The European standard EN 13432 states that for an item to be certified as Industrial compostable it must meet the following criteria;

    • Test Conditions: The waste sample is mixed with organic waste and kept at a temp of 58 °C
    • Disintegration: After 12 weeks at least 90% of the waste sample must be able to pass through a sieve with 2mm holes.
    • Biodegradability: After 6 months the amount of carbon dioxide produced by the control sample is recorded. For the test sample to pass it must have produced at least 90% of the volume of carbon dioxide produced by the control sample. The control sample is a variable factor but in principle the substance used is one which biodegrades within 6 months.
    • Eco toxicity: No constituents which appear of the Substances of Very High Concern or REACH are accepted.
    • Chemical Analysis: Low levels of heavy metals (Potentially Toxic Elements) and no adverse effect of the quality of compost produced. There are 11 chemicals which have defined upper limits and the compost is tested against these.
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    Home Compostable

    (TUV Certification programme) – Follows the same as the above except;

    • Test Conditions: The waste sample is mixed with organic waste and test is performed at ambient temperature (20 – 30 °C) rather than 58°C.
    • Disintegration: The time frame for the test is 26 weeks rather than 12 weeks.
    • Biodegradability: The time frame is 1 year rather than 6 months


Biodegradable Testing

The next 3 standards relate to biodegradability. All three conform to the European standard EN 13432 industrial composting standard unless stated otherwise. The testing environments for all three of these tests are different and are designed to replicate the three real-life environments.

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    Biodegradable (Soil)

    • Testing environment: Based on ISO 17556
    • Test Conditions: Placed in a soil environment in the dark or in diffused sunlight and kept at a temperature of 20°C-25°C
    • Disintegration: There is no specification set.
    • Biodegradability: the time frame is 2 years rather than 6 months.
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    Biodegradable (Marine)

    • Testing environment: Based on American standard ASTM D 6691
    • Test Conditions: Test is performed in a mixture of salt water and natural sea water which contains a pre-grown population of at least ten aerobic marine microorganisms. The solution is kept at a temperature of 30 °C (+/- 2°C).
    • Eco Toxicity: Must have no negative influence on marine aquatic organisms
    • Chemical Analysis: Cobalt added to the list of heavy metals.
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    Biodegradable (Water)

    • Testing environment: Based on ISO 14851/ISO 14852
    • Test Conditions: Tested in an aqueous medium mixed with sludge/compost/soil at 20°C-25°C
    • Disintegration: There is no specification set.
    • Biodegradability: The time frame is 8 weeks.

    As discussed at the beginning of this guide, the word biodegradable tends to lack any real definition. The above tests help remedy this and we will only use the word ‘biodegradable’ if the yarn used holds one of the above accreditations. This ensures we can always clarify what we mean and ensure our customers understand the context in which we use the term.


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