Biodegradable and compostable are two words which are often used interchangeably when talking about recycling. But there’s a world of difference between these two terms. We often see the word ‘biodegradable’ on some products that we buy, such as soap and shampoo. But what does it actually mean? Anything biodegradable will break down quickly and safely into mostly harmless compounds. But what makes a substance biodegradable? Anything that is plant-based, animal-based or natural mineral-based products is usually biodegradable. However, they will break down at different rates depending on the original material it’s made out of and how much it has been processed. According to the American Society for Testing and Materials (ASTM) biodegradables are anything that undergoes degradation resulting from the action of naturally occurring microorganisms such as bacteria, fungi, and algae. Although quickly is not defined, biodegradable products are broken in way less time than non-biodegradable products like plastic, for instance. Biodegradable objects can be much more than plants, as most people assume. It can be papers, boxes, bags, and other items that have all been created with the ability to slowly break down until they’re able to be consumed on a microscopic level.
Compostable means that a product is capable of breaking down into natural elements in a compost environment. Because it’s broken down into its natural elements it causes no harm to the environment. The breakdown process usually takes about 90 days. The ASTM defines compostables as anything that undergoes degradation by biological processes during composting to yield CO2, water, inorganic compounds and biomass at a rate consistent with other compostable materials and leaves no visible, distinguishable or toxic residue.
Looking at the definitions of both terms it’s pretty understandable why they are so easily confused but there’s a difference. While all compostable material is biodegradable, not all biodegradable material is compostable. Although biodegradable materials return to nature and can disappear completely they sometimes leave behind metal residue, on the other hand, compostable materials create something called humus that is full of nutrients and great for plants. In summary, compostable products are biodegradable, but with an added benefit. That is, when they break down, they release valuable nutrients into the soil, aiding the growth of trees and plants.
While biodegradable items refer to just any material which breaks down and decomposes in the environment, compostable goods are specifically organic matter which breaks down, the end product having many beneficial uses which include fertilising and improving soil health. Most importantly compostable items don’t leave toxic residue behind because it’s already organic. Unlike compostable, certain biodegradable products can take several years to break down and in some cases even leave toxic waste behind. Plant-based plastics for instance are often labelled as biodegradable. While they are meant to break down more easily than regular plastic and be safer for the environment, if the right environmental factors are not present it might take just as long as regular plastics.
While biodegrading is totally dependent on the products being exposed to the right amount of moisture and temperature compostable products will break down easily despite external environmental factors. When it comes to recycling, the terms biodegradable and compostable dominate in popularity and can cause confusion. Concern raised by the compost industry, which was faced with materials that claimed to be biodegradable or compostable, led to the development of the European Standard EN 13432 which lays down criteria for what can or cannot be described as compostable and what can be called biodegradable. The US Standard ASTM D6400-99 also sets out similar standards. Many items that are labelled as “biodegradable” are not accepted by composting facilities because they take too long to break down and/or will not decompose entirely, disrupting the composting cycle. However, materials that meet either the European or US Standard will break down effectively in virtually all composting systems.
Australia Calling for Standardisation
Waste industry experts have warned that “Massive amounts” of plastic contamination are entering food and garden waste through user error and misleading “biodegradable” labelling. Leading figures at some of Australia’s largest waste companies are calling for the government to standardise certification of compostable products, as many bin liners, compostable coffee cups and other materials labelled “compostable” or “biodegradable” do not break down into organic matter.
The warnings come as states across the country are introducing food and organic waste collection programs in households in an attempt to halve the amount of food waste that ends up in landfill by 2030. In NSW, councils will be required to collect food and organic waste from all households by 2030.
“[There is a] massive amount of plastic that ends up in Fogo [food organics and garden organics] bins … [and] non-biodegradable items that wrongly claim to be compostable,” said Richard Kirkman, CEO and managing director of Veolia ANZ. “These materials aren’t organic and don’t naturally decompose into the ground. Instead, they just contaminate what would otherwise be high-quality compost from genuine Fogo.” Much of the food and garden waste processed in Australia’s waste sector is turned into compost to be used in agriculture.
Confusion among consumers about the labelling of different products complicated the matter, said Kirkman. According to the Australian Standards for commercial composting, “compostable” products must disintegrate after 12 weeks and completely biodegrade after six months in a dedicated composting facility.
“Biodegradable” products are able to break down into elements found in nature, but not in a specified timeframe, which means the biodegradation process could take years. “Not all liners on the market meet these standards,” said Kirkman. “Australians want to do the right thing, but it is virtually impossible to tell which caddy liners should be used. In fact, some liners remain fully intact after 16 weeks of accelerated composting and we have no option but to remove them by hand.”
Kirkman called the “contamination caused by ‘compostable’ bags and kitchen liners” used in Fogo bins “a nightmare for the industry”. Ash Turner, state manager for resource recovery at Cleanaway, says that many of the kitchen liners sold at the supermarket are not compostable and will break down into microplastics that are then ploughed into the soil along with the compost. “So they’ll say ‘biodegradable compost liner’ … but they’re not necessarily biodegradable,” he says. They do break down, he says, but adds: “Do they compost and break down into an organic? No, they don’t.”
Research by Veolia from earlier this year found that 72% of those surveyed thought compostable single-use coffee cups could be recycled in the yellow bin and 58% thought biodegradable plastic bags could be recycled, when Veolia advises that both items should only be placed in red bins and should end up in landfill. On top of this, there were challenges around misleading labelling.
In 2023, researchers from the Institute for Sustainable Futures analysed 26 bioplastic products sold in Australia and produced by 14 companies, including plastic bags, coffee pods, postage backs and balloons. The research found that nearly one-third of sustainability claims about the products were potentially misleading, including that not all that claimed to be compostable were certified to the Australian Standards. Others used the term “biodegradable” for products that are not compostable and may take many years to biodegrade.
Both Kirkman and Turner have said they would like to see the Environment Protection Agency take steps to make it easier for consumers to buy bags they can be confident will compost, and enable those working in the plants to pull non-compostable bags out of the processing lines.
“We’re working with the EPA,” said Turner. “We’ve asked … that compostable bags be certified in some ridiculous colour … so if you want to make a compostable bag, you have to get certified and you’ve got to make it that colour, so either the guys on the line or our optical sorting equipment can be sure [it is compostable] and everything else comes out.”
Kirkman said: “If Australia was to go down the route of a single, easily identifiable caddy liner, that was certified, council-issued and built to a single national standard, that would be world-beating.” But Gayle Sloan, CEO of Waste Management Resource Recovery Australia, goes further, advocating for no bin liners at all, saying the simplest solution is to have people put food waste into their kitchen caddy and take that straight to their kerbside bin each day. “Bags complicate it,” she said. “It’s complicated for the consumer because you’re not sure if the bag is what it says it is … We’re creating waste with the liner. It’s one less piece of material that we have to use.”
Effective plastic labelling is a critical tool in reducing plastic waste and contamination in recycling systems. Countries around the world are recognising the importance of clear, standardised, and truthful labelling to empower consumers, support recycling infrastructure, and drive sustainable behaviours.
While challenges remain, initiatives like the EU’s harmonised labels, Australia’s ARL, and Canada’s EPR programs demonstrate that progress is possible when governments, industries, and consumers work together. By adopting global standards, improving education, and leveraging technology, the world can take a significant step toward stopping plastic pollution and creating a more sustainable future.
