Biodegradable vs Compostable Plastic Bags: What’s the difference?

As we know the earth has a serious problem with the huge amounts of plastic being used and produced. Each year the problem only gets worse. Plastic bags are a major driving force in this problem, with over 5 trillion plastic bags being used yearly and almost all of those being discarded after a single use.

Reducing plastic bag usage has been at the forefront of the agenda for many environmental groups and government organizations. These groups and private companies have been looking for alternatives and so far two alternative forms of plastic bags have been designed and produced. These two alternatives are biodegradable plastic bags and compostable plastic bags. 

Now to really understand the difference between the two we have to look at the meaning of biodegradable and compostable:

As you can see the big difference is what their final products are. A biodegradable object doesn’t have set products, while the compostable one does [1].

Biodegradable plastic bags

Biodegradable plastic bags have become more popular over the last decade. In theory “biodegradable” sounds like an excellent solution to all of the pollution caused by plastic bags. One would think that biodegradable plastic bags are an environmentally friendly alternative to the plastic bags we are used to. 

In some ways this is true, but in other ways they might actually be worse for the environment. To really see the pros and cons to this type of plastic bag we have to look at how they compare to normal plastic bags on a few of their biggest environmental issues: how they are made and what happens to them after we finish using them.

What are biodegradable plastic bags made from?

Biodegradable plastic bags come in a few different forms. What is often referred to as “biodegradable plastic” is actually still made from petroleum, like normal plastic bags. 

“Biodegradable plastic” bags are made in a similar way as normal plastic bags, except they have additional compounds added that help break apart the carbon chains that hold plastic polymers together [2].

How long does it take for biodegradable plastic bags to decompose?

Biodegradable plastics decompose at different rates depending on many different factors including:

• temperature

• amount of moisture

• what the bag is made of

• amount of light

• amount of oxygen 

And the list goes on and on. 

Even with these many factors a general average is considered to be between 3 and 6 months, which is a huge improvement over the many hundreds of years required by standard plastic bags [5]. 

Biodegradable plastic bags are able to decompose faster because compounds that are added during their production break the plastic polymers into small pieces. This allows microorganisms in soil and landfills to break them apart into smaller molecules. 

Can you put biodegradable bags in compost?

The short answer is no, you cannot put biodegradable plastic bags in the compost. 

Now the long answer is usually you can’t compost them, unless they specifically say so. Most biodegradable bags require specific conditions for them to even begin to decompose and even when those conditions are met it is very dependent upon what type of bag it is.

Labeling on biodegradable plastics is not always clear, so the best option is to not try to compost them unless they are sold as “compostable” plastic bags [3].

Compostable plastic bags

Compostable plastic bags are typically the better alternative between biodegradable and normal plastic bags. They look similar to normal plastic bags and are just as strong. They have slowly become more and more common and the same technology has begun to be used for other products, like compostable utensils.

What are compostable plastic bags made of?

Compostable plastic bags are much more environmentally friendly than biodegradable bags, as they are made with natural fibers from plants, like corn or wheat. 

These bags can be produced using much less energy than normal plastic bags and are generally considered to be carbon neutral. The plant fibers used in these bags can even be taken from plant byproducts left after being used to produce other products.

How long does it take for compostable plastic bags to decompose?

The tricky part about compostable plastic bags is how they decompose. 

Generally, with the right conditions, they break down into carbon dioxide and water. This seems very beneficial considering no toxins or carcinogens are being produced. 

The issue arises in the fact that most of these bags actually require specific composting facilities to decompose and can’t be composted at home. 

They require precise conditions that can’t be maintained in a normal household composting system. Composting facilities have to maintain the required conditions by using energy to create a constant temperature and humidity, increasing their carbon footprint. 

That being said there are a few compostable plastic bags that can decompose in household composts, but they are typically more expensive. 

If compostable plastic bags have the correct conditions they will decompose in 1 to 6 months [4]. Just like with petroleum based biodegradable bags make sure to read the labeling and if you are unsure send the bag to a composting facility.

What are the environmental problems with biodegradable and compostable plastic bags?

These bags decrease many of the problems caused with normal plastic bags, like: reducing energy for production, reducing decomposition time, and decomposing into more environmentally friendly particles. Yet even with these improvements they do not completely remove the issues associated with using non-reusable bags. 

There are many environmental issues with these bags, but below are a few examples:

• Many biodegradable bags require oxygen and sunlight to fully degrade. Landfills actively try to reduce the amount of oxygen, water, and sunlight present, which means sometimes these bags cannot degrade, even though they are capable of doing so. This means they will build up in landfills, taking up a lot of space, just like normal plastic bags [2]. Furthermore, plastics in the ocean do not always get enough sunlight or oxygen to break down.

• Petroleum based biodegradable bags can sometimes leave chemicals after they degrade. These chemicals leach into streams and groundwater supplies, leading to animals consuming them [2].

• Biodegradable plastic bags cannot be recycled with normal plastics. This means if they are recycled it requires extra energy (normally produced with fossil fuels) to separate them out and recycle them on their own [2,3].

• They create a feeling with people that it is okay to use more plastic bags because they are biodegradable or compostable. Most people do not know the amount of energy, work, or requirements for their bags to degrade.

Even though these bags are often a better alternative to common plastic bags, there are still much more environmentally friendly alternatives available.

Environmentally-friendly alternatives to plastic bags

The most environmentally conscious alternatives to using plastic bags are not using bags at all or using a reusable bag. Most large grocery stores, local shops, and government agencies now sell reusable bags specifically designed for grocery stopping. If you don’t have one of these bags you use any bag you have: a gym bag, beach tote, backpack, it doesn’t matter.

Being environmentally conscious, sustainable, and helping reduce plastic bag usage comes down to a having a specific mindset. If you try to reduce your personal environmental impact you will make a difference and if the idea keeps spreading the world will see a shift towards a healthier future.

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