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What Are Compostable Bags Made Of? is It Eco-Friendly?

Have you ever seen compostable bags for sale? Chances are you have as they are common in stores like Wal-Mart alongside conventional trash bags. The question is, what are compostable bags made of and does this affect their use?

What is the definition of compostable?

When a material carries a label that says “Certified Compostable” it means that, in an industrial facility with controlled conditions, it will break down the same that an orange peel would break down if you threw it into your backyard. In reality what this means is that the material can break down, but only in very specific conditions.

A recent study has shown that if you toss a “compostable bag” into landfill, even after 3 years it will still be strong enough to use as everyday conditions do not cause it to break down.

What Are Compostable Bags Made Of?

So what are compostable bags made of if they can exist for years without breaking down but then breakdown to compost in the right conditions?

Typically, it is «corn starch» which has featured for years in bags and plastic substitutes.

It is a durable material but lots of manufacturers mix it with other plastic chemicals to make it stronger or more hard-wearing. What these extra chemicals are is usually kept a secret as manufacturers compete for better products.

In most cases, though analysis has shown that the “secret ingredients” tend to be biodegradable polyester and vegetable oil. fairly low tech, but still a secret ingredient.

Bags like this are a prime example of an everyday compostable bag. This one has the advantage of having the BPI stamp which stands for “Biodegradable Plastics Institute” who have certified that his bags meet the criteria required to call itself compostable. This is important but is not a sure-fire guarantee of quality as we will talk about later.

One other stamp to look out for is “European OK Compost Home” which means that these bags can decompose in backyard composting.

This typically means they are less strong but better for the environment. Generally speaking, European regulations are tougher than US ones and anything with an EU stamp is likely to be more rigorously tested. These bags are a good example of a product with a good range of certifications.

What are compostable bags made of

Compostable bags pros and cons


🟢 Certified to be compostable
🟢 Strong enough for regular use
🟢 Fits into standard-sized trash cans
🟢 Breaks down well with right circumstances
🟢 Made from renewable plant resources


🟠 Can begin to give off moisture into your trash can if not removed in a timely manner
🟠 Can disintegrate inside your trash can if too many moist or wet items are placed inside it at once
🟠 Might cost more than other types of bags
🟠 Not all bags compost in the same way and many need specialist facilities
🟠 Incorrectly recycled bags can still exist for several years

Are compostable bags eco-friendly?

Yes, they are. 

A genuinely compostable bag is an eco-friendly purchase and is definitely worth switching to. Even if you don’t have recycling, some can go in your backyard and at the very least what compostable bags are made of is usually plant-based which is still an improvement over crude oil used in plastic bags.

What is the difference between compostable and biodegradable?

The main issue is the misuse of labels with many people mixing up compostable with biodegradable. Compostable is a term with some regulations, not foolproof but with some set standards and criteria. Biodegradable is a bit of a confusing term with manufacturers often using it as a selling point to make people feel good about their purchase.

Read next: What are the problems with biodegradable plastics?

Biodegradable simply means that the product will break down over time into smaller pieces. This could be days or decades and even if it does break into small bits of plastic, it still isn’t good for the environment.

What biodegradable bags are made of is usually very different from what compostable bags are made of and so the two cannot be used interchangeably.

Read the full article: Degradable or biodegradable trash bags | Which is greener?

What are compostable bags made of


What are compostable bags made of? A plant-based substance, typically a form of starch. Compostable bags are a good idea but consumers have to be wary about what compostable bags are made of.

It is always worth checking the labels to see who has certified them. Ensure as well that you are disposing of them in the right way. It is a tricky area and some companies have taken advantage of the confusion and forced poor products with falsified claims onto the market.

Over time this will improve but products such as these are a good choice. Do check as well whether you need bags or whether you can empty rubbish lose into your waste bin as some authorities allow this which saves the need for a bag at all.

In summary, be vigilant but switch to a compostable bag as soon as you can.

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