Learning How Plastic Bags Decompose

Posted on November 6, 2017 | Last Updated On: September 22nd, 2020 by

Plastic pollution is a major environmental concern that affects the entire earth, including most of countries and our vast oceans. It is estimated that 12 million barrels of fuel are used each year in the production of plastics bags to meet the annual demand in the US. When plastic bags are tossed away, they can sit in the environment for many years before they begin to break down, unless they are made from special types of biodegradable plastic.

One of the advances in environmental science in the past decade has been the advances made in biodegradable plastics. Plastic bags can be made from biodegradable plastics that break down much faster than traditional plastic bags.

If you care about the environment and want to learn how biodegradable plastic decomposes, the outline below should provide you with the essential information. Remember, typical plastic bags can take hundreds or thousands of years to decompose.

Below is the process for decomposition of more environmentally, biodegradable plastic bags. Even better are reusable, cloth shopping bags that can last you for years and never end up in a landfill.

Phase 1: Aerobic Phase

The enzymes and chemicals in decomposition are a catalyst to the biofilms that coat the plastic in the bag. During this period, aerobic microbes are established and moisture increases in the plastic bags. Standard absorption for regular plastic bags is small but over many years, molecular spaces are created for microbial growth. This begins a slow degradation process where oxygen is converted to carbon dioxide.

Anaerobic, Non-Methanogenic Phase – When oxygen concentrations have dropped enough, the anaerobic process commences. During this stage, also known as hydrolysis, the microbes slowly eat the particulates. Through various enzymatic processes, the large polymers are reduced into monomers. As time goes by, acidogenesis happens where monomers are converted to fatty acids. Production of carbon dioxide happens faster in this stage.

Phase 2: Anaerobic, Methanogenic Unsteady Phase

Microbe colonies in the plastic continue to grow and eat away at polymer chains to create bigger molecular spaces. During this period, acetogenesis happens, which converts fatty acids to acetic acid, carbon dioxide and hydrogen. Carbon dioxide rates drop and production of hydrogen ceases eventually.

Phase 3: Anaerobic, Methanogenic Steady Phase

Final decomposition involves the process of methanogenesis. As microbe colonies eat away at the remaining polymer surface, acetates are then converted to methane and carbon dioxide, Hydrogen is consumed. This process continues until all that that remains is humus. This is highly nutritional soil that improves the environment for microbes and boosts the final decomposition stage.

How To Recycle Plastic Bags

It is great there are options available to use biodegradable plastic bags that are gentler on the environment. But what about all of the tons of existing conventional plastic bags in the US? There are ways they can be recycled so they do not end up clogging landfills for centuries.

Here’s how plastic bag recycling basically works:

  1. Used plastic bags piled up by the tone are put on a conveyor belt where workers remove any contaminants that cannot be recycled.
  2. Bags are thoroughly washed in flood tanks, where all non metallic contaminants are removed. Magnets may be used to remove any metal from the bags.
  3. Plastic bags are melted to separate any contaminants from the resin. Impurities that are still solid are removed.
  4. Melted plastic compound is dried and cut into tiny pellets.
  5. Pellets are washed in flood tanks and scanned with magnets to remove any metallic and nonmetallic impurities.
  6. Pellets are cut into finer pieces in a consistent size. Oversized ones are removed.

The final recycled pellets are sent to plastic bag manufacturers to be reused in new bags. Even the waste products from the recycling plant, such as cut off plastic pieces, are used for recycling. Experts note the recycling process is easier with bags made from gray or brown colors.

Tips for Recycling

Below are some simple tips to make your home recycling more productive and easier:

  1. Try to reduce waste in the first place. Recycling is great, but it is easier to reduce the amount of trash we produce from the start. When you buy anything, look at the packaging and decide if you really need it. If you can, choose products that have recycled packaging or packaging with minimal plastic.
  2. Make trash into treasure. Many household items that you need no longer can be used for various craft projects. You can convert empty cans, milk bottles, cardboard food boxes and other similar things into gifts or decorations. They also are very useful for kids’ projects.
  3. Remember e-waste. Most people recycle cardboard, newspapers and paper, but what about your electronic garbage and waste? Most e-waste also ends up in a landfill or incinerator or is sent to Asia. You may be able to dump old computers and cell phones at sites in your area.
  4. Don’t put your recyclables in plastic bags. You spent a lot of time sorting your recyclable products, so don’t waste all that effort by putting them in plastic bags.


We hope you gained some knowledge from this article about how bags can decompose, as well as how they can be recycled.


About the Author

Douglas Lober Chief Product Specialist

Doug Lober is Co-Founder and Chief Product Specialist for ReuseThisBag.com. Lober is a passionate environmentalist with roots in the Southern California surf culture. Over the last 15 years, Lober has launched and supported a number of environmental initiatives around the land, sea, and air. Today, he continues to provide and support the use of eco-friendly promotional products for small, medium, and Fortune 500 companies. You can learn more about his extensive background in the industry on Linkedin.com, Quora.com, Instagram.com, Twitter and Alignable.com

You have 0 item(s) in your quote.
Your Quote can have up to 5 items.

Submit Quote Now