It’s crazy how something as cheap as a plastic lawn chair will appear new for decades. As long as it doesn’t break, we’re grateful for its durability. The problem comes when we have to throw away our plastic objects: old plastic toys, kitchen gadgets and old shampoo bottles. Once plastic gets released into nature, it never quite fades from memory, as we wish it would. That plastic chair could still remain intact thousands of years from now.
That’s because plastic doesn’t biodegrade like organic material. Apart from a few rare findings of organisms that can break down select types of plastic, most plastic keeps its molecular form indefinitely. And while some plastics degrade into smaller and smaller particles in sunlight, others like polypropylene (number five plastic) can stay intact for millennia.
Not to mention, we throw away a huge volume of plastic. By 2050, the total volume of plastic in the ocean will surpass that of fish. And plastic in the environment serves no nutritional purpose, yet it organisms often mistake it for food. Scientists estimate that by 2050, 99 percent of seabirds will have ingested plastic. Yet, researchers still don’t fully understand its biological impacts.
One thing scientists do know is that humans consume microplastics, too. A recent study found that humans consume roughly 50,000 particles of plastic per year and inhale a similar amount. That means roughly 100,000 particles of plastic enter our bodies each year.
These alarming facts should make us think twice about the longevity of plastic. In spite of plastic’s low cost and abundance, we can’t dismiss it as easily as organic waste, precisely because it’s not going away any time soon.
What does biodegradable mean?
The word “biodegradable” describes any material that living things such as microbes, fungi and bacteria can decompose. For instance, paper and food scraps made of organic matter quickly decompose in nature. However, materials such as glass may break into smaller pieces, but their molecular composition does not change. This means they are “non-biodegradable.”
Is plastic biodegradable?
Many plastics are classified as non-biodegradable. For instance, plastics made with propylene (number five plastic), are linked monomers connected by strong carbon-carbon bonds. Organisms don’t have the capability to break down these strong bonds.
Each type of plastic is made of different molecular compounds. The plastic numbering classification system labels the most common plastics with the numbers one through six. Number seven is reserved for miscellaneous types of plastic, including biodegradable plastic.
Recently, scientists have identified several organisms that can digest certain types of plastic. For example, fungi found in the coastal mangrove forests of India are capable of digesting polyethylene (PE), which is used in numbers one, two and four type plastic and accounts for sixty-four percent of plastic waste. Another Amazonian fungus can digest polyurethane, which is used for applications as diverse as fake leather, credit card machine rollers, shoe soles and bedding material.
So, a few organisms are capable of biologically breaking down specific types of plastic. However, the rate of decomposition in these cases is still quite slow compared to the rate we produce plastic.
How plastic breaks down over time
One of the ways that plastic breaks down in nature is by a process called photodegradation. Plastic hit by the sun’s UV rays gets broken into particles the size of one molecule. Though these plastic particles are incredibly small, their chemical compound makeup remains intact.
Microplastics pose risks to wildlife. In marine environments like the oceans, where large gyres of plastic waste have accumulated, microplastics attract toxins to their surface. These toxins can harm organisms at the bottom of the food chain, like zooplankton, when they ingest plastic particles.
What makes biodegradable plastic different?
A variety of biodegradable and compostable plastics are now being manufactured and marketed as bioplastic. Yet, these plastics require special facilities capable of providing the right conditions to break them into natural compounds. In the absence of these processing facilities, bioplastic remains intact for long periods, much like regular plastic. It can also emit methane, a potent greenhouse gas that contributes to climate change.
How long does it take for plastic bags, straws, bottles, etc. to decompose?
Many plastics we use are designed to be used just once before throwing them away. This modern day paradox means we design with one of the world’s longest lasting materials to create items used for the shortest amount of time. Take a look at these time frames for familiar plastic objects to dissolve into microplastic dust or soup.
- Plastic grocery bags: 10 to 20 years
- Plastic sandwich bags: up to 1000 years
- Plastic straws: 100-500 years
- Plastic bottles: 450 years
- Plastic diapers: 450 years
- Plastic sanitary pads: 450 to 1000 years
- Plastic coffee pods: 150 to 500 years
- Styrofoam cups: 50 years
It’s important to remember that no challenge poses a greater risk than a lack of awareness. Share your knowledge and inspire your friends, families and communities to take action on reducing plastic pollution.
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