What is Compostable Plastic? A Quick Explanation

What it is, how it is recycled and what are the differences with biodegradable plastic

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By Max Bender

compostable plastic

In recent years, there has been a growing popularity of compostable plastic, with its usage extending to the production of everyday items like fruit and vegetable bags, shopping bags, as well as disposable cups and napkins.

This article aims to provide a comprehensive understanding of compostable plastic, including its definition, appropriate disposal methods, and the crucial importance of responsible disposal in fostering a circular economy.

What is compostable plastic

Compostable plastic, composed of natural elements like corn, may look similar to biodegradable plastic or even traditional plastic. When introduced into a compost system, compostable plastic undergoes nearly complete decomposition (90%) within three months. This rapid breakdown contrasts with the six-month decomposition time typically associated with biodegradable plastics.

Compostable plastic is designed to break down into natural, non-toxic elements, and they typically decompose into water, carbon dioxide, and organic matter.

To be considered compostable, a material must meet specific standards, such as those outlined in standards like ASTM D6400 or EN 13432. Compostable plastics usually require specific conditions, such as high temperatures and microbial activity found in industrial composting facilities, to break down efficiently.

What do you get from the decomposition of compostable plastic? The end result of the composting process is nutrient-rich compost that can be used to improve soil quality.

What’s the difference between compostable plastic and bioplastic

There is a common misconception that “biodegradable” and “compostable” are synonymous terms, but in reality, they represent distinct concepts. Let’s clarify this distinction.

Biodegradable plastics are designed to break down (typically into water, carbon dioxide, and sometimes residual fragments of the original material) through natural processes, but the term is broad and doesn’t specify the time frame or the end products.

The time it takes for biodegradable plastics to break down can vary significantly, from a few months to several years, depending on the material and environmental conditions.

Biodegradable plastics may break down in various environments, including landfills, oceans, or composting facilities. However, the conditions required for biodegradation can vary widely, and there are currently no universal standards for biodegradability.

compostable plastic

On the other hand, compostable plastics usually require specific conditions, such as high temperatures and microbial activity found in industrial composting facilities, to break down efficiently. And -most important- the end product of compostable plastic is compost, that can be used in agriculture.

Last, compostable plastics often have specific certification standards, ensuring that they break down within a defined timeframe and leave no harmful residues. Biodegradable plastics lack consistent and universally accepted standards.

Which materials are used to make compostable items?

Polylactic Acid (PLA) is a biopolymer derived from corn starch, compostable according to the European standard EN13432.

This material is utilized in the production of cups, spoons, and single servings for finger food. With an appearance closely resembling plastic, this material is transparent and can withstand temperatures of up to 35°C.

How to recognize it? Just search for this symbol on the package:

PLA compostable plastic

How to recognize compostable plastic in the U.S.A

Another certification label worth noting is the “compostable” certification from the U.S. Composting Council and Biodegradable Products Institute. Various versions of this label exist, each signifying that the plastics utilized adhere to ASTM specifications D6400 or D6868 for USCC-BPI compostable products.

These have been tested and certified by ASTM International, a recognized standards organization.

compostable plastic

How to recognize compostable plastic in Europe

To verify the compostability of a plastic bag or container, it is essential to refer to the declaration of conformity for EN 13432:2002. To confirm that the material aligns with this standard, seek the statement “Biodegradable and compostable product complying with EU standard EN 13432.” This wording is usually found on the front or side of the item.

In addition to the conformity statement of the EN 13432:2002 standard, compostable plastic can be identified through marks certifying biodegradability. For instance, labels such as “Compostable” and “OK Compost” are indicative. Alongside these logos, there should also be a code, followed by a number, referencing the manufacturing company responsible for ensuring traceability.

compostable plastic
Compostable plastic? When in doubt, always read the labels.

Disposal of Compostable Plastic

Typically, plastic packaging features a recycling symbol that guides you to the appropriate bin for discarding that particular waste.

For items crafted from compostable plastics, the presence of the descriptor “compostable” means they should be disposed of in the wet organic waste bin. This ensures that they can undergo proper processing in dedicated composting facilities.

Recycling Compostable Plastic

Compostable plastic, breaking down in a matter of weeks, undergoes recycling in composting plants alongside organic waste. Consequently, items like bags and containers made from this material can be appropriately disposed of in the wet waste bin.

In many countries organic waste recycling plants form a qualified and efficient supply chain in the management of compostable plastic packaging.

In practice, organic waste is transformed into compost, a product rich in humus, active microbial flora, and microelements, fostering soil fertilization and combatting depletion.

However, there could be an issue related to the significant presence of conventional plastics within organic waste. When data show over 5 percent of non-compostable materials in organic waste, the production of high-quality compost is generally jeopardized.

To prevent contamination, non-compostable plastics are separated from the rest of the waste before entering the plant. Yet, this pre-sorting process involves rigorous actions on multiple fronts, posing the risk of inadvertently removing portions of wet waste and compostable plastics that could otherwise be safely recycled.

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