Why Is Plastic So Nondegradable—It's All Natural?

From your phone battery to the Empire State Building, every single thing we as a species have created was made from things we found in nature. This includes, of course, plastics.

Turtle eating plastic
Stock image: turtle encountering plastic gloves floating in the ocean. iStock / Getty Images Plus

A recent Reddit thread posed a very pertinent question to the public jury of the internet: How did we make plastic that isn't biodegradable out of materials only found on Earth?

Plastics are made from crude oil buried deep underground. Jaewook Myung, an assistant professor of civil and environmental engineering at the Korea Advanced Institute of Science & Technology, tells Newsweek this oil is made from remains of very old living organisms, such as algae, bacteria and plants that have been buried for more than thousands and millions of years. Over time, the unique environment underground—high pressure, high temperature—gradually turns these remains into petroleum.

Plastic is made by speeding up what would eventually happen to that oil in the ground, just at an incredibly slow rate. "Petroleum contains lots of so-called propylene. A long chain of propylene is polypropylene, which is one of the most common forms of plastics. Chemists use a catalyst (a substance that speeds up chemical reactions) along with a mixture of propylene to synthesize plastics at a fast rate. This process takes thousands of years below ground without this catalyst," Myung tells Newsweek.

Unfortunately, plastics take a very long time to break down. A disposable coffee cup will take 30 years to decompose, while a plastic toothbrush can take up to 500 years.

Hydrocarbon bonds created in plastic manufacturing aren't able to be broken down by many microorganisms, since they didn't have to evolve the mechanism at any point before now.

"There are natural enzymes that can break down plastics and digest the polymers in them. The final product of this breakdown is carbon dioxide and water. However, in nature, these natural enzymes are not commonly found, however, and the speed of the breakdown process is not so fast, " he told Newsweek.

Plastic beach
Stock image: Plastic littering a tropical beach. iStock / Getty Images Plus

Around 8 million tons of plastic waste is released into the oceans from coastal nations each year, resulting in the deaths of millions of marine animals. Even after these plastics have been partially broken down into small particles known as microplastics, they continue to be toxic to marine life, which bioaccumulates up the food chain to be toxic to the things who eat marine life—including us.

There is hope yet. Scientists are actively investigating methods to make plastics in a way that the enzymes can "better attack" the plastic particles. As Myung tells Newsweek, by modifying the surface of the plastics, the natural enzymes can better adhere to the surface, which speeds up the biodegradation process. Additionally, many species of bacteria are naturally evolving new enzymes with the ability to break down plastics in the oceans, and scientists are developing mutant enzymes that can break down plastics in record times.

One option in the future could be to breed bacteria that produce this enzyme on a large scale.

"If we can breed the bacteria that are capable of excreting lots of plastic-degrading enzymes, we can break down the hydrocarbons in plastics. However, breeding bacteria is not as easy as one might think because we need to provide enough food for these organisms to grow, which is often costly. Also, the temperature of the oceans is usually too cold for these microorganisms to break down microplastics at a fast rate," Myung told Newsweek.

While there may be hurdles to face in the future, so long as we don't keep dumping plastic into the seas, our scientists might just be able to make plastic more biodegradable than ever thought possible. Life, as they say, finds a way.