As we move towards a more environmentally aware society, we keep making efforts to introduce more eco-friendly products into the mainstream. One important factor we consider before classifying a product as eco-friendly is its material composition. When trying to understand biodegradable vs compostable - what's the difference?
Biodegradable materials can go out of existence completely without causing harm to the environment. Biodegradable materials are designed to decompose through the action of living organisms. We should use them for products which we cannot recycle. This lessens their impact on the environment.
Compost refers to organic matter that has been decomposed through intentional efforts using a process called composting. We use composts as fertilizers, an inexpensive source of soil nutrients. It goes without saying that for a substance to be compostable, it has to biodegrade. Biodegradation is the process that allows composting to be possible.
The diversity in biodegradable substances' properties makes it impossible to assume that because they all eventually break down, they are all compostable.
According to the EPA, the US generates around 300m tons of municipal solid waste annually, of which only 30% is composted or recycled. With growing environmental concerns, numerous products, from biodegradable garbage bags to compostable poop bags, purport to reduce to virtually nothing. So what's the difference?
It is possible to assume both terms mean the same thing because they have so much in common. In truth, compostable materials are a subset of biodegradable materials. Biodegradable products break down fully or partially with or without oxygen.
Microorganisms break biodegradable materials down within a specified amount of time, converting them into carbon dioxide, methane, water, and biomass.
All biodegradable materials do not decompose at the same rate. Some take as long as a hundred years.
On the other hand, compostable materials break down into natural elements like carbon dioxide, water, biomass, and inorganic compounds within 12 weeks2. The primary criterion for distinguishing compostable products from other biodegradable materials is the speed of decomposition.
While biodegradation happens naturally via biological processes, composting is a deliberate process with an end purpose in mind. Composting is the controlled conversion of biodegradable material with the aid of microorganisms into organic and inorganic by-products. As such composting food waste and other biodegradable items provide a means of recycling organic waste into something useful - soil-enriching compost.
Uncontrolled biodegradation, such as the kind that occurs in landfills, poses a threat to the environment. Lack of oxygen in the degradation process will cause high methane production and encourage the growth of harmful microbes. When appropriately done, compost releases carbon dioxide, good microbes, along with nutrients into the soil.
To answer the question above, we need to identify what is compostable and what is not. For a material to be compostable, it has to be biodegradable. The time factor in the degradation rate makes one material biodegradable and another suitable for compost.
We make compost from organic waste, which can be ready within five weeks to a year. Things like leather, wool socks, plywood, and bones may take as long as five years to decompose and are, therefore, not suitable for home composting.
You can process most compostable items, such as vegetable scraps, food scraps, bread, rice, and so on in your backyard aerobically or anaerobically. However, aerobic composting is best as it eliminates the chances that the compost heap will generate methane.
Aerobic composting requires that you turn the heap over or stir it regularly, perhaps once a week. This gets the heap aerated and allows oxygen to enter into the biodegrading process.
On the other hand, Anaerobic composting requires no extra activity beyond the initial heaping of the compost inputs. It is slower than aerobic composting and may not receive enough oxygen. Therefore it has the probability of producing negligible amounts of methane.
A home composting facility is relatively inexpensive and straightforward to operate. Using a hole in the ground or a compost bin, you can make compost using several methods, including vessel composting, windrow composting, static composting, and sheet composting, amongst others.
Vermicomposting is a composting method that uses the deliberate introduction of earthworms to hasten the composting process.
You can use compostable material, including wood chips, yard waste, food waste, pet droppings, agricultural waste, and compostable plastics for backyard compost. You can use the end compost product for gardening, landscaping, weed control, erosion control, or simply enriching the yard soil4.
With growing moves to sustainable living, you can also find ways to compost in an urban setting. If you find no use for the compost, then you can sell it to your more agriculturally inclined neighbors.
A large-scale industrial composting facility works with more sophisticated equipment and processes. This allows a broader range of commercially compostable products, including biodegradable plastic products that are not backyard compostable, to enter the commercial composting system.
As a watch out for consumers, a number of compostable goods on the market, such as compostable cups, cutlery, takeout containers, and so on, actually require an industrial facility with the right conditions to break down into compost. The only answer here to properly dispose of such goods is to read the fine print to assess if they are only industrially compostable or suitable for home composting.
Around the world, many consider composting to be an appropriate form of organic material recovery. Biodegradable products do not reach their full value if, after use, they do not end up in a waste management system that uses up its benefits.
An example is the compost system, which generates carbon and nutrient-rich material added to the soil.
If composting becomes more widely practiced and perhaps even commercialized, there will be a marked reduction in the waste volume that goes to the landfills. About 300 industrial composting sites in the UK collectively compost around 2 million tonnes of compostable waste annually. We should compost easily biodegradable waste instead of sending it to landfill.
Researchers have found newspapers that are still easily readable despite being in a landfill for over 40 years. So also 10-year-old carrots that are brown on the outside but retain their bright orange color on the inside.
For the average person, this fact may be hard to believe. After all, we consider paper and food as organic waste and, therefore, easily biodegradable. Some sources say that paper waste should be completely decomposed and unrecognizable within 2 - 5 months. Vegetables and fruits should decompose within a month.
How then is that after decades in landfills, some organic materials have still not decomposed? Without an enabling environment, biodegradable products may never biodegrade.
In landfills, they solidly pack dirt to maximize space. This makes the degradation system anaerobic. Because of the anaerobic system, oxygen can not penetrate the waste, making microbes unable to act on it. Therefore decomposition does not occur, and when decomposition does occur, it happens very slowly.
The absence of oxygen causes the waste to produce a greenhouse gas called methane. Methane has 23-71 times greater heat-trapping capacity than carbon dioxide.
This gas is harmful to the planet as it contributes to global warming. To prevent uncontrolled biodegradation in modern landfills, we keep the dirt dry and airtight. But this is an unsustainable practice because if the waste never degrades, the landfills will soon run out of space.
Plastic is infamous for its inability to biodegrade. It remains in its processed form for years. Degradable plastics were initially thought to be the answer to plastic pollution, especially oxo-degradable plastics.
Oxo-degradable plastics are conventional plastics to which chemicals that speed up oxidation and fragmentation under sunlight are added. Research has shown that plastics, even oxo-degradable plastic, simply break into microscopic particles due to photodegradation1.
These microplastics are harmful to our health and environment. Clearly, conventional plastic made from petro-chemicals is not sustainable. This is why researchers continuously make innovative efforts to make plastic biodegradable.
Bioplastics are made from polymers that are the same as those that microbes encounter in nature. These microbes, fungi, bacteria, and algae recognize these polymers as food and have enzymes to digest them5. Based on their sources, bio-plastics may be classified as bio-based or petro-chemical based. Manufacturers typically make bioplastics from starch or cellulose.
You will be wrong to assume that simply because a type of plastic is classified as bio-based, it will automatically biodegrade or that every plastic that degrades is bio-based. Sometimes they make bioplastic using a substance that requires specific industrial chemical processes to biodegrade. And since no single substance can be composted in isolation, they are therefore unsuitable for compost.
Compostable plastic can undergo full decomposition as part of a compost heap. Their speed of decomposition is consistent with other compostable substances like paper and vegetable waste.
In commercial level research conducted in 2001 by Kassel3 introduced biodegradable packaging to households. And participating householders were instructed to trash it with organic waste while collecting compost inputs. The research results showed that the compost generated had the same quality compared to conventional compost consisting solely of green waste.
A study on biodegradable polymers categorizes a subset of biodegradable plastic as compostable. Another study differentiates between bioplastics that can be composted at home and those that require industrial composting facilities to undergo proper and full biodegradation.
It is important to remember that oxo-degradable plastics are not classified as compostable products as they only break down into microplastic.
All compostable substances are biodegradable, but not all biodegradable substances are compostable. With many biodegradable and compostable products now on the market, it's important to understand the difference and avoid greenwashing.
Biodegradation will occur naturally, but composting requires deliberate effort. We can process most compostable products at home, but some can only biodegrade in an advanced composting facility.
In the case of biodegradable vs. compostable, it is clear that biodegradation is simply the process by which organic substances break down in nature with or without oxygen with microorganisms' help. While composting is a means of waste management that allows biodegradable substances to decompose in the most beneficial way to the environment.
|1||New plastics economy. oxo-degradable plastic packaging is not a solution to plastic pollution, and it does not fit in a circular economy|
|2||Song JH, Murphy RJ, Narayan R, Davies GB. Biodegradable and compostable alternatives to conventional plastics. Philos Trans R Soc Lond B Biol Sci. 2009 Jul 27;364(1526):2127-39. doi: 10.1098/rstb.2008.0289. PMID: 19528060; PMCID: PMC2873018.|
|3||Song JH, Murphy RJ, Narayan R, Davies GB. Biodegradable and compostable alternatives to conventional plastics. Philos Trans R Soc Lond B Biol Sci. 2009 Jul 27;364(1526):2127-39. doi: 10.1098/rstb.2008.0289. PMID: 19528060; PMCID: PMC2873018.|
|4||Ayilara, Modupe & Olanrewaju, Oluwaseyi & Babalola, Olubukola & Odeyemi, Olu. (2020). Waste Management through Composting: Challenges and Potentials. Sustainability. 12. 4456. 10.3390/su12114456.|
DeBruyn, Jennifer & Bandopadhyay, Sreejata & Hayes, Doug & Inglis, Debra & Miles, Carol. (2018). Biodegradation-Putting Biology to Work.
Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.
Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.