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Biodegradable versus Compostable

Biodegradable versus Compostable

Understanding Differences in Language, Products, Packaging, and How They Affect the Health of Our Planet




Recognizing Greenwashing


There can be a major language barrier when it comes to trying to live and purchase more sustainably. New terms reflect changes in technology and practice. And current terms are also used in different, and at times, problematic ways.

A 2010 study of 5,300 home and family products found that 95 percent made problematic green claims—what is known as greenwashing.


Words are Just Words


Adjectives like “green” and “eco-friendly” have earned themselves a spot on the Federal Trade Commission’s no-no list. These terms are so broad and all-encompassing that product claims are nearly impossible to substantiate. These claims are meaningless to the conscientious consumer.

When choosing between compostable and biodegradable products, it is crucial to speak (and critique) the language enough to cut through the marketing lingo to the heart of the sustainability issue at hand. After all, you want to make certain you’re putting your effort—and dollars—to good use. 

What Biodegradable Means


The word biodegradable means “capable of being broken down by living organisms.” If you look at the basic roots, the definition is very straight forward. “Bio” means life, “degrade” means to break down or deteriorate, and “able” means the ability to.

Unfortunately, the make-up of the word is where the simplicity stops. Because, under this definition, nearly everything qualifies as biodegradable.

Given enough time (read: millennia), bacteria, fungi, algae and other microorganisms can reduce almost anything—metal, plastic, people, mountains—to basic elements.

To claim something is biodegradable under such a broad definition means almost nothing. If a company says that something is biodegradable, you need to probe deeper to determine in what environment and over what time period.


Technical Definitions


That’s why regulating bodies like the American Society for Testing and Materials and the US Federal Trade Commission have stepped in to provide more clarity when it comes to labeling the products we use and buy.

The US Federal Trade Commission Green Guides define biodegradable products as products that “eventually decompose into elements found in nature, disintegrating or disappearing.” If you just mentally highlighted “eventually” while releasing a skeptical guffaw, good on you. You’re catching on!


Time Matters


To further clarify, the FTC Green Guides note, “Marketers may make an unqualified degradable claim only if they can prove that the ‘entire product or package will completely break down and return to nature within a reasonably short period of time after customary disposal.’” 

For decomposition of solid waste products like biodegradable packaging, that reasonably short time is 365 days. If a full breakdown of the product (disintegration into natural elements) can occur in a calendar year, it is biodegradable without qualification.


Biodegradable Plastics and Other Qualifiers


Of course, if a product can be labeled biodegradable without qualification, that means another product must be labeled biodegradable with a qualification. This is where most biodegradable plastics and bioplastic products come into the picture.


Conventional Plastic with a Kick


Some biodegradable plastics are essentially conventional, petroleum-based plastics, but with additional chemical that cause the plastic to break down more quickly (roughly 2-5 years) than it would on its own. However some definitions of biodegradable reject the inclusion of any synthetic materials and their potential long-term toxicity




Bioplastics, on the other hand, are derived from some form of plant material— flax, sugar cane, corn, wheat, etc. Sugar from the plant material is transformed into polylactic acid (PLA), which replaces the petroleum base of conventional plastic.


The most common use of PLA bioplastic is single-use utensils and food packaging. PHAs (polyhydroxyalkanoates) are derived from microorganisms and most often found in medical devices.


Replacing Oil with Soil


Swapping out the petroleum base for plant biomass allows bioplastics to biodegrade much more quickly than biodegradable plastics with chemical additives. In some cases, biodegradable items may even qualify as compostable (hold on…we’re almost there!), but the quality of the end results are variable.


Many biodegradable products still cause major environmental problems if they become ocean waste rather than breaking down on land. They can also leach toxins in either location.


Global Plastic Production


Still, bioplastic alternatives represent a major area of sustainability research and innovation because of the sheer volume of plastic humanity produces. In 2015, the World Economic Forum reported that 322 million tons of plastic was produced around the world.

Researchers estimate “8300 million metric tons . . . of virgin plastics have been produced to date.” These figures account for an unimaginable amount of oil, energy, carbon, and ultimately, waste. Replacing oil with renewable plant material as the basic building block of these products is generally considered a win.



What’s Not Biodegradable


To return to the FTC’s definition, traditional plastics do not qualify as degradable. Depending on the environmental conditions, conventional plastics like polyethylene, polypropylene, polystyrene, poly(vinyl chloride) and poly(ethylene terephthalate) may never break down, or take hundreds or thousands of years to break down. 


Even if they do “break down,” they tend to facture into micro pieces of plastic and leave behind toxins and chemicals in the soil.


Trash Doesn’t Count


The FTC also prevents items destined for landfills (90% of US plastic), incinerators, or recycling facilities from being categorized as biodegradable without qualification.


The Landfill Tomb


The reason being, a landfill is essentially a less ornate sarcophagus. In a landfill, every new layer of waste added cuts off the previous layer from access to oxygen, preventing its breakdown.



Greenhouse Gas Emissions


The anaerobic (lacking oxygen) environment of the landfill also facilitates the formation of volatile gases. Landfill gas is in the neighborhood of 45-60 percent methane and 40-60 percent carbon dioxide, making landfills major greenhouse gas emitters and climate change contributors.

If a product is destined for the landfill it is not biodegradable, because in a landfill environment, even organic waste and bioplastics won’t break down in a year. Conventional plastics and other synthetic materials don’t stand a chance.


Recap: Biodegradable Means…


While it truly depends on who is defining the term, biodegradable typically means natural organisms (fungi, bacteria, algae, and bugs) must be able to reduce that product to natural elements within a year’s time. 


If the product is destined for the landfill, it doesn’t matter what it’s made of. It won’t breakdown there, so the biodegradable claim falls apart. 



Cut Through the Confusion


Now that you’re privy to the vague lingo that serves as the foundation of greenwashing, you’re going to be considerably harder to fool. To stay even sharper, look for 3rd party certifications for any product claiming to be biodegradable. If a company couldn’t prove their claim to an independent certifying organization, don’t buy the claim (or the product, for that matter).


What Compostable Means


Now it’s time to talk compost.

Handful of soil


Biodegradable Plus+


The term biodegradable is something of an umbrella, and it’s underneath that shady canopy that we find the word compostable. If something is compostable, it is by definition biodegradable—all compostable materials can be broken down by living organisms within a year. However, compostable materials surpass biodegradable materials in two crucial ways: they must be non-toxic and capable of transforming from waste to food.

Compost is defined by the quality of the final product: humus.




Unlike biodegradable products, which are simply capable of falling apart into smaller, natural materials, compostable products, the ASTM notes, must “be scientifically proven to break down into humus (usable compost), carbon dioxide, and water in a safe and timely manner without releasing toxins and unacceptable levels of metals into the soil.”




Humus is the key word here, and even it has a bit of a slippery definition. If you noticed, ASTM defines compost as able “to break down into humus” and then in the same sentence calls humus “usable compost.” We’re stuck on a linguistic merry-go round here!

But in this case, the circular reasoning is actually pretty fair. While we know how  humus is formed (microorganisms reduce plant and animal material to their most basic chemical elements), the chemical composition of humus has been notoriously hard for scientists to pin down.

The best way to describe it is the portion of soil that is not sand, silt, or clay—the extremely stable organic material that microbes can’t break down any further (at least we think).


Soil Fuel


Humus is essentially a “you-know-it-when-you-see-it” kind of thing. Push back the top layer of the forest floor, and you’ll be met by the unmistakable smell (earthy), texture (spongy), and color (dark brown) of humus. When you can’t distinguish the particular elements of your compost pile (banana peel, wood chip, tree leaf), you’re entering the realm of humus.

humus is soil fuel 


Humus is Microorganism Housing


The benefits of this material cannot be overstated. The organic materials that eventually become humus are food and fuel for the soil microorganisms responsible for creating healthy soil (and by extension healthy people).




As a soil element, humus is chock-full of plant-available nutrients. It supports healthy soil structure, preventing compaction and maintaining a good balance of oxygen and water. This in turn increases the soil’s water-holding capacity which can minimize the effects of drought.


Stores Carbon


Pioneer of biological agriculture Graeme Sait notes that, “we have lost two thirds of our humus to the atmosphere following two centuries of extractive agriculture.” Nearly every soil in the world could benefit from more of this product.

Turning waste into humus via the compost process, and returning it to our soil, could go a long way towards storing atmospheric carbon and breathing life back into our agricultural systems.


What is Compostable?


With the end result of soil-saving humus in mind, for a product to qualify as compostable it must be a naturally organic material. 

If it came from a plant or animal, it should be compostable, at least in the ideal conditions of composting facilities. If the product is the result of a synthetic process (forming plastic out of petroleum for example), it’s not.

Food waste is the most basic and easy-to-recognize compostable product, but composting extends beyond your kitchen scraps. An active compost pile will reduce your 100% cotton t-shirt to humus just fine. But your synthetic polypro workout shirt, not so much.


composting food scraps


How Composting Works


In a compost pile, microorganisms break down organic materials with the help of  oxygen.


Heating Up


In the first stage of composting, mesophilic microorganisms (they can live in temperatures from 68-113˚ F) and beneficial bugs and insects go to work on the material, eating, shredding, and decomposing it. As they work, they release heat, a byproduct of the reactions taking place.


Phase 2


As the pile heats up, mesophilic microorganisms are replaced by heat-loving microorganisms, which can survive the increasing temperature. This stage, which can last a few days or a few months depending on the type and amount of material composting, is when the bulk of the work is done. 


It’s crucial to keep the pile aerated and moist during this process. If the temperature gets too high (above 160°F is getting too hot), or the pile gets too dry, the microorganisms can die off before the job is finished.

Without the presence of oxygen (like in the landfill), anaerobic microorganisms take over, producing a smellier product that may not be beneficial to plant life.


Who Does the Work?


Once the hottest stage is complete, the cool-preferring microorganisms repopulate the pile and complete the transition to stable humus. While some 80-90% of the microorganisms involved in compost are bacteria, fungi, like molds and yeasts, also play an important part. 


Oxalic acid excreted by fungi is capable of binding to metal ions like sodium, tying up salts and reducing the salinity of materials like dairy manure, which has huge potential for environmental restoration.


Final Product


In any case, the end result of the composting process is humus. All plant and animal materials, properly managed, will be reduced to the rich, earthy-smelling organic matter that soil needs so badly.


Compostable Certifications


While it’s easy to recognize plant and animal materials as compostable, it can be hard to know what some commercial products are made of.




The Biodegradable Products Institute (BPI) is one of many that certifies compostable products and packaging can be reduced to soil-supporting humus. They also offer a useful search engine for finding certified compostable products.




ASTM also provides testing specifications for compostable products, including bioplastics, foam, and paper products. Most of these certifications are based on the conditions found in commercial composting facilities, not home composting piles.


Commercial Composting


Because they are working with much more material, the temperatures generated in commercial facilities are much higher than those found in backyard piles, and the oxygen and moisture levels are monitored to facilitate microorganism health.

This means that some compostable products, like bioplastics, that will readily break down in a commercial setting may not decompose in a smaller, cooler backyard compost heap.

Commercial Composting


You can find a commercial composting facility near you here.


Home Composting


While some products are best left to the composting professionals, food scraps, yard waste, shredded paper, and similar materials collected in a compost bin are perfect for backyard composting. Managing your own compost also means you get to keep all those nutrients on-site, adding beneficial humus to your own soil.


Carbon-Nitrogen Ratio


There are endless resources on composting dos and don’ts, but the basics are pretty simple. A good compost pile will balance materials high in carbon (“brown” materials like wood shavings, paper, dry leaves and grass clippings) with materials high in nitrogen (“green” materials like food scraps, animal manures, and fresh plant matter).


Smaller is Faster


Larger materials and materials high in carbon will take longer to transform into humus than smaller materials and materials that have a higher ratio of nitrogen. So chicken manure (higher in nitrogen) will break down faster than wood shavings. And wood shavings will break down faster than tree limbs.


Home Composting Systems


There are lots of ways to compost on a home scale. You’ll have to experiment and find what works for you, but here are a few staples to get you thinking:


Home Composting System





Deciphering all the lingo can be confusing. Some of the language surrounding these materials has been purposefully twisted to confuse consumers. Some of the confusion is just the result of a big and complicated world.


Learn the Steps


The best way to guarantee you’re supporting a healthy system is to try and understand the process you’re supporting from start to finish.


Where Did it Come From?


Is the product you’re purchasing derived from natural (plant or animal-based) materials or synthetic, petrochemical products? Have the biodegrability claims been certified by a reliable 3rd party?


Where is it Going?


What is the end result—disintegration or regeneration? Biodegradable products are certainly “less bad” than products that never break down, but compostable products that turn into humus can capture carbon and restore soil.


What Can You Do?

Ultimately, how you engage the system makes a dig difference. Purchasing a compostable product that is eventually transformed to humus in a local composting facility can do great good. But if that same product ends up in a landfill, a breakdown has occurred in the breaking down.