In the world of recycling, there are several terms that can be difficult to break down (much like certain types of plastic).
Two of the most commonly used phrases are biodegradable and compostable, but many people don't understand the fundamental differences between the two.
This confusion surrounding biodegradable vs compostable products can make it difficult to figure out whether to throw used plastic products in the recycling bin or the trash can.
In short, the difference between the two terms is that biodegradable products deteriorate naturally over time, while compostable items require a specific environment to become compost, but break down more quickly and can often be recycled and reused.
What Does Biodegradable Mean?
Biodegradable materials are defined by the American Society for Testing and Materials (ASTM) as anything that degrades from the action of naturally occurring microorganisms, such as bacteria, fungi and algae. Usually, products derived from plants, animals, or natural minerals are biodegradable.
Objects defined as biodegradable extend far beyond plants and food, however. Items like paper and cardboard boxes can also be classified as biodegradable products, even though they'll take much longer to break down to a microscopic level.
Plastic could even be argued to be biodegradable because it eventually breaks down, but this process can take centuries. These substances will eventually decompose into carbon dioxide, water and other forms of organic material.
An apple, on the other hand, is something everyone can agree on. That process would most likely take a few months.
Whether it takes a month or a millennium, everything manufactured will ultimately disintegrate into dust and return to the natural elements. When defining which of these substances are biodegradable, scientists and public health officials often ask a few main questions:
- Did the object come from nature?
- Has it undergone an excessive level of artificial modification or processing?
- What are the conditions necessary for deterioration to occur in a reasonable amount of time? Does the object have a positive or neutral impact on an ecosystem?
What Does Compostable Mean?
Composting is a form of biodegradability that transforms organic waste, such as food scraps and fallen leaves, into humus, a dark brown material that can supply soil with valuable nutrients. Unlike many biodegradable materials, compostable products are useful to the environment, and composting can even be done at home.
Homeowners can utilize their own backyard compost pile and recycle organic waste to create a soil conditioner. The resulting compost improves the structure of soil, helping it retain water and nutrients, adding up to a world that is more sustainable for everyone.
The specification ASTM D6400 refers to compostable products that can be processed in municipal or industrial composting facilities, drawing the line between products that can be broken down or composted and those that are simply biodegraded. ASTM D6400 was specifically made to identify plastics that comply with these standards.
According to this ASTM certification, biodegradable materials should disintegrate within 12 weeks and biodegrade at least 90% within 180 days in a composting facility. Approximately 10% of solid material should be left at the end of the six-month-long process, either as compost or biomass and water.
Here's what scientists and public health officials ask when defining compostable materials:
- Can the material transform into organic waste that is useful for the environment?
- Is the compostable material a type of food or organic substance to start with?
- How long will it take for the material to decompose, and can it compost in a timely manner?
Biodegradable vs Compostable Plastics: What's the Difference?
When trying to distinguish between biodegradable vs compostable products, think of biodegradable as an umbrella term and compostable as a term underneath it.
There are certain types of plastic products that are both biodegradable and compostable. For example, compostable plastic waste bags are made using hydrolyzable polymers, chemical compounds that degrade over a period of time when they come into contact with water, a key ingredient in composting.
Unlike other types of plastics, they break down into elements the soil can absorb, and the process takes less than 180 days, not more than 1,000 years.
Composting facilities and industrial companies recycle these plastics by enveloping piles of compost under tarps at temperatures of more than 50 degrees Celsius (roughly 122 degrees Fahrenheit). After about 150 days it becomes useable. Depending on the type of product, facilities sometimes add warm water with a nutrient mixture to accelerate the decomposition process.
Home composting of these plastics isn't recommended. It's much easier to donate them to the proper facilities.
It's also worth mentioning the difference between bioplastics, biodegradable plastics and oxo-degradable plastics.
Bioplastics are made from non-toxic organic materials like corn starch, and will typically break down in a few weeks without releasing toxins into the soil or water. However, bioplastics shouldn't be left to break down in a landfill, as this waste yields methane gas during the biodegradation process. Instead, these plant-based materials should be taken to a commercial composting facility to biodegrade properly.
Biodegradable plastic is chemically different from bioplastics, since it's petroleum-based and mixed with an additive that speeds up the biodegradation process. The two plastic types are sometimes conflated with one another, but the distinction is important.
Finally, there are plastics classified as oxo-degradable, which mimic biodegradation but actually remain in the environment indefinitely. Oxo-degradables are made from a conventional plastic mixed with an additive that causes the plastic to fragment into microplastics. However, the degradable products do not break down at a molecular level, leaving microplastic waste behind until it fully breaks down.
Biodegradable vs Compostable Products: The Different Labels to Look Out For
Food and similar organic substances are inherently compostable, but the situation is not so simple for other products.
The Compostable Label
The Federal Trade Commission [FTC] allows brands to label their products compostable if "all the materials in the product or package will break down into, or otherwise become a part of, usable compost (e.g., soil conditioning material, mulch) in a safe and timely manner in an appropriate composting program or facility, or in a home compost pile or device." In this case "timely manner" means at the rate of the surrounding materials in the compost pile.
The Biodegradable Label
When it comes to claims of biodegradability, the FTC stated that products should fully decompose within one year of disposal. Some of these products are compostable, even if they don't carry that claim.
Companies that want to further substantiate the claim that they carry compostable products can seek certification from the Biodegradable Products Institute [BPI]. The BPI certification rules were written for people in the industry, not consumers, but there's a code with a requirement that's relatively easy for everyone to understand: 90% of carbon in an item needs to disintegrate within 180 days.
Biodegradable products may not be compostable, but they're still valuable to the environment. They may not give as much back to the earth, but at least they take up less space in landfills.
Your Knowledge Can Make the World More Sustainable
Reducing the amount of waste that rots for decades in a landfill starts with buying eco-friendly goods and products that are biodegradable, and preferably compostable, too. Public Goods products such as the Ayate Bath Strip, Ayate Washcloth, Reusable Bamboo Straws, and Wool Dryer Balls are completely biodegradable and compostable, including the packaging.
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