Which bin liner is the most sustainable?

Your recycling initiative is up and running, and now it's time to pick your bin liner. Biodegradable, degradable, compostable, clear, or black - what's the difference?

Be wary of misleading words

In 2013 a disposable bag company received a $60,000 fine (NZD) for misleading customers about the eco-friendliness of their plastic products.

Cases like this illustrate that if you are wanting to go down the eco-liner route, we need to decipher the real definitions behind the language.

The sustainability of different liners

Plastic liners:

The classic plastic liner is the most commonly used bin liner, both durable and cost effective. Plastic liners are made from petroleum or natural gas, both non-renewable resources, but can take anywhere from fifteen to a thousand years to degrade.

Degradable liners:

There is no specified timeframe that a liner sold as “degradable” must degrade in. In fact, all plastics could technically be defined as degradable – they all break down eventually. Some plastics have additives that will make the liner break down faster in certain conditions, but this process only transforms large parts of plastic in tiny sized pieces.

Professor Tony Underwood from the University of Sydney described degradable plastic bags as "...not a solution to anything much, unless we are quite happy to shift it all into particle-sized plastics rather than plastic bag-sized plastic."

Micro-plastics are hard to contain in landfill and have recently been under scrutiny for their harsh impact on marine life. They are ingested by microorganisms and make their way up the food chain, ending up in animals and even humans.

Plant based plastics:

Some people opt for plant based plastic liners as an environmentally friendly alternative to classic plastic. As the name suggests, these liners replace non-renewable petroleum with biomass like sugarcane and corn, in a bid to reduce harm to the environment.

Plant based plastics can be broken down further into two categories – non-biodegradable and biodegradable.

Non-biodegradable plant-based plastics are produced in the same fashion as, and are intended to replicate, normal plastics. Plants are manipulated to give the plastic long shelf life and the final product cannot be easily digested by living organisms. This makes them fit for the recycle bin but not for the compost.

Biodegradable liners:

Biodegradable plant-based plastics (the most common variety of biodegradable liners) are called so because they can be attacked and digested by living organisms in the early stages of the degradation process. This means that they complete the natural cycle – they are produced and assimilate smoothly back into nature.

Certification standards have been created to ensure that what we are buying is going to fully biodegrade within a specific timeframe. When looking to buy biodegradable liners it is very important that the product refers to a reliable standard such as Australian Standard AS 4736 or European Standard EN 13432.

Biodegradable liners can be broken down even further into two categories - commercially compostable and home compostable.

Commercially compostable liners:

Many biodegradable liners require a very specific environment to decompose – oxygen, 60-degree temperatures and a perfect heat/moisture ratio found at a commercial composting site to be exact. These are called commercially compostable liners and should only be used if your waste is going to a commercial composting site. If you’re putting commercially compostable liners into landfill, then either a petroleum or a biodegradable liner would realistically be just as suitable and sustainable.

Home compostable liners:

Home compostable liners, your most environmentally-friendly option, can be broken down in your backyard compost bin. You’ll need to check the liners refer to a certification standard for home compost though, such as AS 5810-2010.

We should use home compostable liners for all waste streams, then? Not exactly. Landfills are very dark, non-oxygenated places, meaning that even compostable liners do not have the conditions needed to biodegrade properly. Over time, compostables in landfill produce methane which can be much more harmful to the environment than CO2 itself.

The most sustainable way to use bin liners would be to use the home compostable variety, but to then remove the contents into the bin before waste collection and put your liner in with your home compost. But this isn’t always possible.

Start a conversation with your waste collection providers about what their bin liner policy is

If you wish to keep your waste continuously contained, or it’s not viable for you to go without a liner because of your waste collection provider, we recommend using black liners for landfill, clear liners for recycling streams and home-compostable liners for organics.

This makes it easy for office cleaners and collectors to sort and ensures that compostable liners are not going into landfill, where they’ll most likely struggle to degrade in the conditions or be ripped open.

You can also consider options for plant based, non-biodegradable liners as while they are still plastic, at least they are made from a renewable resource and are much less toxic in their production.

Finding the right bin liner doesn’t need to be complicated

If you do your research, make sure bin liner classifications are backed up by reliable certification standards, and discuss options with your waste removal contractors and cleaners, you’ll be on track towards your sustainability goals.