It’s easy to assume that just because a product—or its packaging—is labelled as biodegradable, it’s a sustainable option. But that’s not always the case, and in fact, it’s an area ripe for greenwashing. Here, we explain the difference between biodegradable and compostable, and how that can help you when you’re shopping.
Defining biodegradable and compostable
Before understanding the difference between these two prominent sustainability terms, you need to know clearly what each one means.
Biodegradable describes something that can be decomposed by microorganisms like bacteria, fungi or microbes, and in natural conditions. Everything will biodegrade at some point, but the time frame for some materials to break down could even be centuries or millennia. And it’s also important to note that biodegradability doesn’t necessarily mean that the product or material will return to nature safely—some could release toxic chemicals, gases and microplastics into the environment.
Compostable materials, meanwhile, disintegrate in specific, human-controlled conditions into biomass, organic and inorganic compounds, CO2, and water—which are all natural, non-toxic elements. Microorganisms, oxygen (aerobic conditions), humidity, and heat are key to making the composting process happen.
Composting takes place either at home or in an industrial facility, and these conditions dictate how much and how quickly something will break down—industrial composting often happens at much higher temperatures, for instance. Importantly, composting can’t happen in landfills. Becca Willcox, ratings analyst at Good On You explains why: “In landfills, organic matter that could have been composted is instead broken down under anaerobic conditions due to the lack of oxygen, which means it generates methane—a powerful greenhouse gas.”
Willcox continues, “So composting reduces methane emissions compared to the landfill route. Some other positives of composting are that it might reduce the need for nitrogen fertilisers, as well as improving water conservation in soil, and preventing erosion.” And while composting is a brilliant sustainability solution, Willcox cautions that we should keep in mind that the broken down material isn’t always nutrient-rich, and that too much composting can be harmful to soil and plants.
If something’s biodegradable, does that mean it’s compostable, too?
Not always. Everything that is compostable is biodegradable, but not everything that is biodegradable can be composted.
In consumer labelling, compostability is defined by certifications and standards that denote how quickly and in what conditions a product should break down. In contrast, biodegradability isn’t subject to the same scrutiny, and can therefore be used on a product label without needing evidence to show how quickly it’ll break down and how that will impact the environment. That’s where it gets cloudy, and there’s a risk of greenwashing from brands keen to signal they’re doing something to improve their impact—but more on that later.
It’s perfectly understandable if all this takes a while to get your head around. In fact, studies have shown that many people find it difficult to comprehend the difference between industrially compostable, home compostable, biodegradable, and bio-based materials. And consumers aren’t the only ones finding things challenging: “In my experience, the standards for compostable products are not always used or labelled correctly, and another issue is that few facilities take textile waste for composting because they’re often only set up for packaging and food,” Willcox says.
Are any plastics biodegradable or compostable?
Things can get even more confusing when it comes to plastic, especially because there are so many different kinds. The European Environment Agency explains: “If and how quickly a plastic item biodegrades depends on: (1) if it is designed for biodegradation or composting and (2) the conditions it is exposed to after use and for how long.”
A note on bio-based plastics
Bio-based plastics (also called bioplastics) are made using biological materials instead of fossil fuels, and unsurprisingly, that leads some people to assume they’re compostable or biodegradable. But that’s not always the case, and the European Environment Agency’s explanation applies here too—whether or not a bioplastic can biodegrade depends on how it has been designed and the conditions it’s exposed to.
The term bioplastics can also be cause for confusion, as the European Environment Agency explains: “‘Bioplastics’ is sometimes used for plastics that are either bio-based or biodegradable, or both (European Bioplastics e.V., 2020c). Given that these have very different properties, consumers could misunderstand the rather vague term ‘bioplastics’.”
How are brands approaching compostable and biodegradable products?
The risk of greenwashing is high in product labelling for biodegradability. According to the Biodegradable Products Institute, the term biodegradable “is often used to describe non-compostable products intentionally made to look similar to certified compostable products. These products are commonly referred to as ‘lookalikes’ and are a leading cause of contamination at compost facilities.” That’s why it’s really important for consumers to understand the difference and be aware of what they’re buying and eventually disposing of.
Another key issue is the labelling of products made from 100% natural fibres—like linen or cotton—as compostable, which may not always be true if the chemicals, dyes, and treatment used in the fabric’s processing, and components like synthetic stitching, buttons and zips, are not also deemed compostable.
Some brands are doing a great job of producing and labelling compostable items, though, and KENT is an example of that. The brand makes plant-based underwear that’s designed to be composted at home or at its partner farm in California. Its Compost Club has clear descriptions of the process, including how long home composting takes (roughly 90 days depending on conditions); a video on how to compost at home (aptly titled Plant Your Pants); and details of how underwear sent to the farm is sorted and processed for composting. Anya Hindmarch’s online information for its Return to Nature compostable leather is similarly detailed, with photos of the material’s decomposition process, timelines, and links to the test results for biodegradability.
Elsewhere, H&M’s Cradle to Cradle Certified-Gold compostable baby clothes are another example of products that have been created using only fabrics, chemicals and components that are confirmed to be compostable to ensure that everything can be broken down.
So the next time you see something marketed as compostable or biodegradable, check whether it’s accompanied by any standards, certifications, or descriptions of the conditions and time required for the item to break down. Have a look at the components, too, and if you’re in doubt, reach out to the brand in question to get some clarity.
