Biodegradable Trash Bags vs Compostable Trash Bags: Your Questions Answered

What are the main differences between biodegradable and compostable trash bags? 

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The terms compostable and biodegradable are commonly used interchangeably, but this is not factually accurate. There are many differences between the two and despite popular opinion, they are not the same.

In order for a trash bag to be certified as compostable, it must meet a government-approved industry standard. This is shown on the packaging as BPI certified (Biodegradable Products Institute). The use of this term is heavily regulated across the United States and Europe. 

What does biodegradable mean?

When a plastic bag is biodegradable, this means that it can be broken down and decomposed by living organisms such as bacteria. This does not mean that the plastics are made of natural and non-toxic materials, but the term can be used in this way.

Biodegradable plastic bags will break down faster than non-biodegradable plastics, but they will not necessarily release beneficial compounds into the environment. The term biodegradable is not regulated. 

Biodegradable trash bags are made from petroleum-based plastics. This is what gives them a similar appearance, texture, and quality to traditional plastic trash bags. The bacteria break the larger plastic chains into smaller ones.

This can be achieved by incorporating heavy metals into the composition of the plastic. This is because some bacteria respire using metals instead of oxygen. These bacteria see the metal in the biodegradable plastic as food and will break them down to grow. 

Some biodegradable bags will be covered in a layer of film known as a biodegradable additive. This is said to help them decompose completely, but there is minimal evidence to support this claim. It is such a disputed claim that it has even been challenged through the court system. It is a biodegradable product.

What does compostable mean?

A compostable trash bag tends to be made from natural materials such as corn or potato starch. These have been reformed into bioplastics, chains of short-term carbons. These materials can break down completely in the right circumstances, meaning that overall waste is reduced. 

The micro-organisms contained within the soil and within compost piles will break down the starch with ease. The bags will compost like any other plant matter. This will not produce toxic byproducts and contaminate the soil, unlike other plastics. Many non-compostable plastics will leech heavy metals and petroleum into the soil, which can be very harmful to the natural wildlife and soil balance. It is made of compostable material.

How long do biodegradable trash bags take to decompose?

Biodegradable trash bags will only decompose in the presence of moisture, oxygen, and light. Under these conditions, it will likely take a few months for the plastic bags to decompose. 

Many biodegradable trash bags will end up in landfills. The conditions of a landfill are not ideal for the breakdown of biodegradable plastic. In this instance, the biodegradable bags will break down no faster than the regular plastic bags. This can be anywhere from decades to centuries to fully decompose.

Biodegradable trash bags force the garbage inside to decompose much more slowly than if the garbage is exposed to air, moisture, and light. This means that an increased level of methane gas is released into the atmosphere.

Methane is much worse than carbon dioxide in terms of global warming. It is estimated to contribute up to 20 times more to the greenhouse effect than carbon dioxide over 100 years. 

How long do compostable trash bags take to decompose? 

Compostable trash bags are designed to decompose optimally in commercial or industrial composting facilities. This does not mean that they will not decompose on your home compost pile, but the process may take longer to complete. 

A plastic that has been advertised as compostable should break down in 90 to 180 days. This time frame is applicable under ‘compost conditions’. You would be forgiven for assuming that this means on your home compost pile, but it actually refers to the conditions inside a high-temperature industrial compost facility. There are some compostable bags that are labeled suitable for home use. These will break down in your home compost pile. 

In order to be classified as compostable, the plastic must break down into natural elements and cannot leave toxic byproducts in the soil. While in theory, the bags will break down in under 6 months, many users notice that they are still intact after several months more.

Some studies have noticed compostable trash bags that are still intact up to 3 years after being thrown onto a landfill pile. This is likely due to a variance in the pH levels, moisture content, and heat of the compost pile. The bags will break down faster in the presence of a lower pH, and higher moisture and heat levels. 

Most plastic eventually enters the water system, commonly through the ocean. Compostable trash bags will dissolve very quickly in the water into non-toxic bioplastics. The plastics will break down into carbon dioxide rather than methane, which will cause less environmental damage.

Common misconceptions about trash bag alternatives

Most biodegradable trash bags do not end up in appropriate areas for decomposition to occur. Instead, they tend to get thrown into landfills where they do not biodegrade. The EPA (Environmental Protection Agency) states that landfills should block out moisture, sunlight, and air. These three elements are absolutely vital for biodegradation to occur, so even biodegradable trash bags will not break down.

Biodegradable trash bags will release methane gas into the atmosphere as they break down. This is exacerbated when the decomposition process takes place on a landfill, as the process takes a lot longer. 

Compostable and biodegradable trash bags cannot be recycled. They should be disposed of in your home compost or general waste bins, respectively. 

They are not actually much better for the environment than standard plastic trash bags. They will break down faster leading to less of a waste build-up, but this is about it. They break down into thousands of tiny plastic molecules, known as microplastics.

These can find their way into the water system. This can cause harm to humans and animals alike and is a contributor to plastic pollution. Before the bags decompose, animals may stumble across them and consume fragments. This is highly detrimental to their health. 

Are compostable and biodegradable trash bags worth it?

The price point for more environmentally friendly alternatives to traditional plastic trash bags is considerably higher. They can cost up to 5 times more than a standard trash bag, so you would be expecting a considerable level of quality. 

There are many issues with the functionality of ‘green’ trash bags. Compostable bags tend to be relatively weak and cannot handle being filled to the brim. They also do not contain liquids well, which is something else to take into consideration. Biodegradable bags will perform better, but when you consider the empty environmental promises they make, the price does not match up. 

What are the recycling codes, and what do they mean?

Many biodegradable trash bags are not recyclable. Printed on the bag, you will see a small triangle made of arrows with a number inside. This is the recycling code. There are 7 different numbers and each refers to a different type of plastic and disposal method.

You cannot put a number 7 plastic in the recycling bag with numbers 1 or 2. When they are melted down the number 7 would contaminate the entire recycling load, making it all unusable. 

1: PET (polyethylene terephthalate)

This is the plastic that is most commonly used for single-use items, such as water bottles. It is easy to recycle and is accepted by most curbside recycling programs. You should take care to ensure that all recycled plastics are washed and emptied before placing them out for collection. 

2: HDPE (high-density polyethylene)

This plastic is commonly used for more robust packaging, such as milk jugs, household cleaners, and shampoo bottles. This is commonly accepted in curbside recycling programs although we recommend checking with your local recycling company first. 

3: PVC (polyvinyl chloride)

This is a tough and weatherproof plastic that is often used for external piping and siding. When burnt, the plastic releases chlorine fumes which are very toxic. This is not often recycled, but some plastic manufacturing companies may recycle them for you. 

4: LDPE (low-density polyethylene)

This has traditionally not been accepted by recycling companies, but this is changing as the years go on. It is a very flexible type of plastic and is found in squeezy bottles, shopping bags, and toothpaste tubes. LDPE shopping bags can often be returned to the store that you got them from to be recycled. 

5: PP (polypropylene)

This is a type of plastic with a very high melting point and is commonly used for containers holding hot liquids. Most recycling companies will accept this kind of plastic, provided it has been emptied and cleaned. 

6: PS (polystyrene)

This is commonly seen in the form of foam (styrofoam). It is unlikely to be recycled as it is 98% air. The styrene monomer is a possible carcinogen and can escape into foods during decomposition. 

7: Miscellaneous

There are a lot of plastic types that do not fit into one of the aforementioned categories. PLA (polylactic acid) and polycarbonate are 2 common types of this miscellaneous group. These plastics tend to be used for DVDs, bullet-proof materials, and sunglasses. They do not tend to be recycled.

How can you reduce the trash that you produce?

An easy way to reduce your trash is to start cooking more of your meals at home. On the go meals are very convenient, but they produce a lot of trash and the packaging is single-use. There tends to be a large quantity of packaging when compared to the number of servings you receive.

This means that way more waste is produced for the same caloric amount. Instead, try to meal prep for the week and transport all of your food in reusable containers. You would be surprised by how much this decreases your trash. 

As well as this, we recommend starting a compost pile in your backyard. This will allow you to dispose of your food scraps in a natural way, without adding to the size of landfills. Alternatively, some neighborhoods will organize curbside pickup of food waste. 

You should always take reusable bags with you when you visit the grocery store. This applies to the bags you use to take your shopping home, but also those you use to purchase loose produce. There are many cotton and mesh bags available on the market designed with this specific purpose in mind. 

Purchasing in bulk where possible will also help to cut down on your household’s garbage production. Try a health food store or Whole Foods, as these will commonly have large containers of dried goods. You can simply portion out the quantity you desire into a reusable container for purchase.

This also tends to work out as a cheaper alternative to purchasing smaller quantities of goods. Many companies have also started offering recycling programs. These commonly allow you to return empty and cleaned containers to the manufacturer for refilling or recycling. 

Another great way to improve your shopping experience is to visit farmer’s markets for fresh produce. The foods here are sold without packaging so there is no trash involved. As well as this, the crops and foods will all be locally sourced. This further reduces your environmental impact as there are fewer carbon emissions involved in the production and supply process. 

When making purchasing choices, try to opt for products in cardboard, glass, metal, or paper packaging. These are all much more easily recycled than plastic is, although they do still need to be cleaned and emptied. If your paper or cardboard packaging gets wet or dirty, you can throw it on the compost pile and allow it to decompose naturally. 

Terracycle is a recycling program that encourages consumers to recycle products that are traditionally a lot harder to recycle. The company runs this initiative across 21 countries and appears to be expanding further. There are many different programs under the company’s umbrella for a huge variety of materials. 

You can also consider creating an eco brick. These are large, empty plastic bottles that you fill with clean, dry, unrecyclable plastics. You will use this bottle as a bin for all of your non-recyclable materials and condense it down until it is completely solid.

This can then be repurposed and used as a building block in a sustainable building project. In developing countries, these are used to make buildings and furniture. In the UK they have been used to construct children’s playgrounds. This prevents plastic waste from being thrown into landfill sites and eventually making its way into the ocean. 

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Cassie brings decades of experience to the Kitchen Community. She is a noted chef and avid gardener. Her new book "Healthy Eating Through the Garden" will be released shortly. When not writing or speaking about food and gardens Cassie can be found puttering around farmer's markets and greenhouses looking for the next great idea.
Cassie Marshall
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