Plastic Bag Degradation – What You Should Know
One trillion plastic bags are used and disposed of annually worldwide. Most of these bags are made from petroleum. In the United States alone, it is estimated that 12 million barrels of oil are used annually to make plastic bags . The manufacturing of plastic bags adds many tons of carbon and toxic chemicals into the atmosphere as well .
Of the one trillion bags used, less than five percent are recycled . The rest end up in landfills or are lost to the environment where they contaminate soil and waterways, endangering bird and marine life and entering the food chain when these animals ingest them [4,5].
Ingesting plastic can cause serious adverse health effects. Stressed plastic, even the low-level toxicity type required for use in plastic bags by grocers, releases chemicals that seriously alter the structure and function of human cells .
Do plastic bags ever decompose?
Plastic bags do not decompose.
Decomposition is a biological process where microorganisms fed on organic matter and eventually transform it into humus, a rich soil.
Most of the one trillion plastic bags disposed of annually worldwide are not made of organic matter, but are made from a petroleum byproduct which microorganisms do not recognize as food. Accordingly, they never decompose .
Given the right conditions and in some cases, a thousand years, plastic bags can photodegrade. This is not the same as decomposing. It simply means that the plastic will break into smaller and smaller pieces. It does not reabsorb or transform into the natural elements like carbon, hydrogen and oxygen that make up life on our planet [8,9].
These conditions do not exist in a landfill where many plastic bags end up. The plastic bags in a landfill will neither decompose or biodegrade. As far as we know, they will remain intact as plastic bags through eternity.
The process of photodegradation
Photodegradation happens when the sun’s ultraviolet rays strike plastic, over time making it brittle, breaking the binds holding its molecular chain together . The plastic breaks into smaller and smaller pieces.
These small pieces easily enter the food chain when animals accidentally ingest them. You have probably heard of the Great Pacific Garbage Patch, one of five huge whirlpool currents of garbage in our oceans. Read our article about how plastic in the ocean is endangering sea turtles or watch this “mockumentary” narrated by Jeremy Irons.
What can we do? – The solution to the plastic bag environmental crisis
An alternative that has arisen in recent years is a “compostable” or bioplastic bag made from biodegradable materials such as starch, soy protein cellulose or lactic acid .
It sounds like a perfect eco-solution: plastic from plants, not petroleum. But this is not the perfect solution! As crop production demands new cropland, often clearing trees that would otherwise absorb carbon. And crop production at the industrial level is one of our largest environmental problems contributing to global warming as well as fertilizer and pesticide runoff in the water supply.
Furthermore, this solution is proving infeasible as the decomposition requires very specific conditions of high temperature over an extended period of time at an industrial composting facility and this is simply not cost-efficient for the facilities that technically do not have this capacity .
As an example, the box for biobag food scrap bags offered for sale for home use by Wal-Mart, one of the largest retailers in the United States contains the following caveat: “Compostable – For use in municipal facilities where applicable .
Few municipal facilities are collecting compostable bags and the ones that end up in landfills emit an inordinate amount of methane in the natural decomposition process .
What about the bags that end up along the roads, in the parks, in the ocean? Will they biodegrade?
It’s well-intentioned but wrong. A lot of plastics labelled biodegradable, like shopping bags, will only break down in temperatures of 50 degrees Celsius (122 degrees Fahrenheit) and that is not the ocean. They are also not buoyant, so they’re going to sink, so they’re not going to be exposed to UV and break down.Jacqueline McGlade, chief scientist at the UN Environment Program
How do paper bags compare?
Paper bags are not a good alternative. Although paper would completely biodegrade in a compost pile, it does not in a landfill, which lacks the requisite microorganisms for decomposing and lack the water, light and oxygen required for biodegradation.
Furthermore, the production of a paper bag requires four times as much energy as it takes to manufacture a plastic bag and generates 70 percent more air pollutants and 50 times more water pollutants than plastic bags .
If you do use a paper bag, recycle it. Paper recycling is a widely available alternative.
What about using and re-using a tote?
This is probably the best solution today and is being embraced by governments and conscientious consumers alike. Totes are used widely in Europe and are beginning to be encouraged by grocers in the United States. Kroger, the largest retail grocer in the United States now has signs in its parking lots reminding shoppers: “Did you remember your reusable bag?”
Surprisingly, this option has been attacked using a study showing that the manufacture of totes and their commensurate life span have a larger carbon footprint than using plastic bags .
This report measuring the impact on global warming considers production through disposal and concludes that a cotton bag would have to be re-used 171 times to emit a similar level of global warming potential to re-using a plastic bag once. Considering that many people shop a few times a week and that totes can be re-used for years, the number is hardly as astronomical as it initially sounds.
This same report cautions too that a cotton bag is not as hygienic as it can be a breeding ground for harmful microorganisms. Cotton is probably the least taxing tote material on the environment as it is not manufactured of man-made materials and can decompose at the end of its life. The solution is simple. Keep it clean and dry. If kept washed and re-used for years, it is a good option.
Re-using totes is now a practice encouraged by many governments around the globe either through outright banning the use of plastic bags or imposing a tax upon their use.
If you are in a situation where you do not have a backpack or tote and absolutely must use plastic bags, recycle them. Many businesses reclaim post-consumer plastics and in the United States most stores that offer plastic bags have a recycling bin for their return.