Biodegradable plastics do not compost, that is, absorb back into the earth with no trace of toxic residue like your kitchen scraps in the compost pile. They simply degrade with the help of biological organisms. They degrade, that is, they break into smaller bits under the right conditions of air and sunlight.
Biodegradable plastics are manufactured so that under the right conditions, air and sunlight will break apart its polymer chains and it will begin to disintegrate from its manufactured form into smaller bits of plastic .
Why do we need biodegradable plastic?
Before biodegradables were discovered, plastics were made primarily from petroleum byproducts. In 2009, approximately 10% of the oil and gas the United States produced and imported was used to make synthetic plastics, and the market was expected to grow at a rate of up to 15% per year.
A positive effect of biodegradable plastic is ostensibly reducing the use of fossil fuels and the commensurate greenhouse effect.
Since the advent of biodegradable plastics, has the difference been measurable? How much oil and gas is still devoted today to the manufacture of plastic?
A current search yields only the following comment from the US Energy Information Administration:
Because the petrochemical industry has a high degree of flexibility in the feedstock [raw materials] it consumes and because EIA does not collect detailed data on this aspect of industrial consumption, it is not possible for EIA to identify the actual amounts and origin of the materials used as inputs by industry to manufacture plastics.— US Energy Information Administration
The petrochemical industry in the United States has no requirements for reporting what raw materials it uses. Go figure.
The petrochemical industry campaign contributions to Congressmen quadrupled in 2012 as a key player in the industry rallied support to defeat Barack Obama, perceived as “the most dangerous man in America” for his perceived sensibilities in environmental protection .
And have risen since then with the movements to defeat GMO labeling, defeat efforts to ban plastic bags, approve fracking operations, approve additional natural gas pipelines and on and on. The coalitions are busy, powerful… and their effects silently omnipresent in American society.
Politics aside, can using biodegradable plastic help the environment?
How does biodegradable plastic help the environment?
The definition of biodegradable plastics are plastics that can be broken down by microorganisms (bacteria or fungi) into water, carbon dioxide and some bio-material.
It is unclear how much difference biodegradable plastic has made ecologically.
In 2005, the US Environmental Protection Agency reported that only 5.7% of the nearly four and a half million tons of synthetic plastics discarded in the US was recovered and recycled . The rest ended up in landfills, along roadsides, in lakes and the oceans. Biodegradable plastic is meant to mitigate this problem.
In addition to aesthetics and overfull landfills, another concern surfacing was that of toxic pollution. Synthetic plastic was found to leach chemicals harmful to humans and other species.
For example, BPA, is a basic building block of common polycarbonate plastics used in bottled water and food packaging. It breaks down under stress and can leach into the product to be consumed, i.e. the water or food. When it becomes trash, it can leach into groundwater. BPA has been recognized since the 1940s as an endocrine disrupting chemical that interferes with normal hormonal function.
President Trump’s Food and Drug Administration recently overrode its additional concerns of “potential effects of BPA on the brain, behavior and prostate gland of fetuses, infants and children”  with a widely-criticized unsubstantiated blanket statement minimizing effects from exposure to BPA .
More acutely, marine and wildlife fatally ingesting plastic bits became a widespread phenomenon, diminishing the numbers of albatross and sea turtles at a staggering pace.
In the 1980s when it became apparent that our landfills and oceans were filling with plastic, intensive research began on how to break plastic down. During this period of experimenting with chemical additives and genetically modified microorganisms to accelerate the decomposition of petroleum-based plastics, it became apparent that a new plastic could also be made from raw renewable resources that could be broken down by bacteria .
Biodegradable plastics can be made from all-natural plant materials. These can include corn oil, orange peels, starch, and plants.
Plant-based biodegradable plastic decomposes naturally in the environment. Microorganisms in the environment metabolize and break down the structure of biodegradable plastic. When they decompose, they do not release toxic chemicals as distinguished from traditional plastic made with chemical fillers that can be harmful to the environment when released.
The more plastic that decomposes the less chance that it can harm marine and wildlife or clog waterways.
How are biodegradable plastics made?
The process of how is biodegradable plastic made differs depending upon the raw materials used.
An example is the bioplastic Mirel. Corn sugar is fed to engineered microbes inside fermentation tanks. The microbes convert the corn sugar into bioplastic polymers within the cells.
The solution can be made into resin pellets which can again be liquefied and poured into molds to make the end product .
Advantages of biodegradable plastics
- Biodegradable plastic makes durable products for food storage, transport, buildings, construction.
- The majority of biodegradable plastics do not contain the environmentally-harmful chemicals that conventional plastics contain.
- Most are not made with petroleum, like conventional plastics are.
- Most are made with all natural components that can safely return to the environment at the end of their life under the right conditions.
Disadvantages of biodegradable plastics
- Biodegradable plastics typically require a higher cost to produce than conventional plastics.
- Biodegradable plastics do not decompose if they are not properly disposed of. They need the correct conditions of moisture, temperature, and humidity that are similar to a composting environment.
- Biodegradable plastics breaking down in an oxygen-free environment, such as in a landfill, can emit methane, a greenhouse gas that is 25 times more potent than CO2.
- There is some concern that biodegradable plastics might contain certain metals that could be released into the environment when the plastics break down. However, research and evidence is not conclusive on this issue.
- Biodegradable plastics do not solve the litter issue, which is the result of irresponsible behavior. The primary focus of the waste stream should be on waste reduction and recycling.
- Not all biodegradable plastics are made from biomaterials. A few types of biodegradable plastics are still made from oil.
What are the problems with biodegradable plastics?
Biodegradable plastic needs air and sunlight to biodegrade. It does not biodegrade in the ocean.
It is estimated that regular plastic bottles take between 450 and 1000 years to decompose .
If the plastic is made from petrochemicals (with compounds added which help it biodegrade), then the problem of toxic residue remaining after the degradation is not solved.
There could well be the perception that using copious amounts of plastic no longer poses a problem.
Furthermore, if the biodegradable plastic ends up in the landfill, it will not have the necessary light and air to biodegrade.
Examples of uses of biodegradable plastic
Biodegradable plastic should be used where it is clearly beneficial. Three examples stand out.
One is using it in the agricultural industry for seed blankets or mulch in lieu of herbicides. Bioplastics could be safely tilled back into the soil and reduce the host of problems agricultural farming poses using fossil fuel and herbicides.
A second is food packaging where the food has spoiled and could then be disposed of along with its contents.
A third is for medical sutures which then do not need to be removed from the body.
If you do decide to purchase products that are made of biodegradable plastic, be sure that you are purchasing a truly biodegradable product, instead of those that just claim to be but aren’t. To ensure that the products are truly biodegradable, look for products with the Biodegradable Products Institute logo, which is earned through a third-party scientifically-based certification process.
At the end of their useful life, biodegradable products should go to a commercial composting facility where they will properly break down. However, not all communities offer such a facility, so be sure to research and find out if your community has one before you purchase such products.
The bottom line remains that we should reduce our dependence on plastics. Use compostable plastic bags when necessary.
Biodegradable plastic is only helpful as a product in specific situations like the three above. Used for plastic bags or packaging, it is only helpful when it is litter and then the adverse effects might be minimized if they degrade before choking an animal or clogging a sewer drain.