It is very normal to get confused about the difference between compostable and biodegradable materials. While all compostable products are biodegradable, not all biodegradable products are compostable. The main differences are related to: their own production materials, how they decompose, and the residual elements after decomposition.
Compostable products are made by organic elements or plants that are able to degrade with time. For example, corn starch, bagasse, PVAL/PVOH, and others. Compostable products produce humus, upon degradation, which is the richest and most important part of all soils. The high level of microbial activity in humus boosts beneficial microbes within your soil which, in turn, assists plants to strengthen their immune systems (Nature’s Path, 2020). Therefore, compostable products do not have any toxic element to the environment after degradation.
It is important to recall that compostable products need a specific compostable environment to degrade which includes warm temperatures, nutrients, moisture and plenty of oxygen.
On the other hand, Biodegradable is mainly used in plastics, where these break down into microplastics faster than regular plastic, in any conditions (compost, landfill, soil). It is possible to find biodegradable products made from plant based materials (like plants, corn oil, or starch) or petroleum-based plastic easier to degrade. Compared with the composting process, biodegradable products can take several months to break down and some recent studies found that some of these products degrade to leave toxic waste behind. This toxic waste is called microplastics, so even if you cannot see it, these micro materials have toxic components for our environment.
The main differences between these materials are that biodegradable products could be referring to any material which breaks down and degrades in the environment, whereas compostable products are only organic elements that degrade in the environment. Compostable products that break down in compostable environments will only leave behind beneficial residual products like fertilizers and others which improve the soil health. On the contrary, biodegradable plastic depends on the element of fabrication which means that some of them can leave micro toxic waste residue behind.
Composition: They are specifically made up of organic matter; like cornstarch, sugarcane, potato starch, and others. Recently, with new technologies, people have discovered a synthetic substance called PVOH or Polyvinyl alcohol that will dissolve in water after reuse, leaving only water and CO2.
Degradation: They are capable of breaking down into natural elements in a compost environment. Because they’re broken down into natural elements, they cause no harm to the environment. Compostable products can be defined 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.
Degradation time: 90% of compostable products degrade in a time period of 180 days specifically in a compost environment.
Benefits over biodegradable plastics: Compostable products use less water, require less energy, and generate fewer greenhouse gas emissions during the manufacturing process. They are environmentally preferable and cause no harm to soil and plants.
Compostable Products Examples
Following are the examples:
Compostable Paper Products: These include uncoated napkins, uncoated paper plates and paper towels (not used with cleaning chemicals).
Compostable Clamshells, Plates or Bowls: These are uncoated paper-like fibre products and are made from sugarcane (“bagasse”), untreated wood, leaves, or other plant pulps.
Compostable Cups and Bowls: These include PLA (i.e. Polylactic Acid, a polymer derived from renewable sources such as corn starch, cane sugar or tapioca) cups used for cold beverages and PLA-lined paper hot cups and bowls. Some are made up of sugarcane too.
Compostable Utensils: These utensils are made up of cornstarch or potato starch.
Compostable films and bags: These are made from biopolymers, such as starch or polylactic acid (PLA). Some water-soluble films are made up of Polyvinyl alcohol (also known as PVOH or PVAL), which is an odourless, compostable, non-toxic and water-soluble synthetic polymer.
Composition: They are made of Poly (Butylene Adipate-Co-Terephthalate) (PBAT), Poly (Butylene Succinate) (PBS), Polylactic Acid (PLA), Polycaprolactone (PCL).
Degradation: They have been created with the ability to slowly break down until they’re able to be consumed on a microscopic level. They undergo degradation resulting from the action of naturally occurring microorganisms such as bacteria, fungi, and algae.
Degradation time: Biodegradable plastics usually take three to six months to decompose. That’s much quicker than regular plastic which takes hundreds of years. This also depends on various factors, such as temperature and the amount of moisture present.
Benefits over Compostable products: Unlike compostable products, they don’t need a specific environment to degrade, just depends on the temperature, moisture present, and time.
Types: The two main types are oxo-biodegradable and hydro-biodegradable.
Australian Standard: Australia has no mandatory standard on biodegradability or degradability. However, the voluntary Australian standard (AS) 4736–2006, Biodegradable plastics—Biodegradable plastics suitable for composting and other microbial treatment has stringent requirements for the time frame in which a product must break down in a commercial composting environment, its toxicity and the amount of organic material it contains.
Biodegradable Product Examples:
Biodegradable plastic bags: These are biodegradable plastic colored t-shirt bags for supermarket’s shopping. These are made up of polyethylene (PE).
Biodegradable Plastic Packaging: This is 100% biodegradable plastic packaging for shopping. It’s made up of a copolyester – PBAT.
Biodegradable Plastic Trays: These are biodegradable food plastic blister trays, made up of recycled polyethylene-PET.
Composition: They are petroleum-based and are made up of Polypropylene (PP), Polyethylene (PE), Polyvinyl chloride (PVC), Polyethylene terephthalate (PET).
Degradation: They usually go into a landfill where they are buried or they get into the water and find a way into the ocean. Although they will not biodegrade, but they will degrade into microplastic after many years. In the process of breaking down, plastic releases bisphenol-A and toxic substances like polystyrene-based (PS) oligomers, which are not found naturally and which make their way into our food and water supply.
Degradation time: Plastic is not degradable till 200 years.
Facts: When in higher climates, plastics can leach different chemicals such as fire-retardants, parabens, artificial dyes, and much more into soil and water systems and bind to different particles, which makes them persistent and lasting in those ecosystems.
|Water-Soluble & Compostable||Polyvinyl alcohol (PVOH, PVAL)||Dissolution: Within 5 minutes in hot (>75°C) or cold water (≥10°C to 25°C)
Compost: 90% in 180 days in composting conditions
Sewage: 60% in 180 days in composting conditions
|If dissolved, H2O+CO2, if not dissolved, H2O, CO2 and biomass||YES, to soil, plants and marine life.
|Compostable||Cornstarch, sugarcane, potato starch etc.||Dissolution: NIL
Compost: 90% in 180 days in composting conditions
|H2O, CO2 and biomass||YES, to soil and plants|
|Biodegradable Plastics||PBAT, PCL, PLA, PBS||Degradable between 3 to 6 months.
|H2O, CO2 and biomass/ in some cases oligomers, bisphenol A||YES, to soil and plants but harmful to marine animals|
|Plastics||Petroleum-based, PP, PE, PVC, PET||Degradable between 200 to 500 years.
|Polystyrene-based (PS) oligomers, bisphenol A||NO|
So, using compostable products has many benefits—reduces waste, lowers greenhouse gas emissions, etc. But at the end of the day, it’s really about one thing: soil. And if you think about it, our future is really about that same thing, our soil. Without healthy soils, we can’t grow the food we need to survive, and countless other organisms depend on it too. Also, marine life will be safer and pollution will be reduced.
We would like to encourage you to be very informed about what type of biodegradable products you are using because not all of them have the same residual elements in landfill. Also, if you prefer compostable products make sure you deliver them in a place where they can be degraded properly. Think about the possibility of building your own compost at home or leave your compostable waste in the compostable bins near your home.