Plastics and Our Mismanaged Environment (Part 1)

Statement of the Problem

It is difficult to know where to begin with this topic. Its scope is enormous because the problem is enormous. We find plastic everywhere. It has been a valuable commodity for our society. Its uses are legion: the preservation and transport of food; in the form of polystyrene, it is important for the protection of objects during shipping; we use items every day that are made of plastic – toothbrushes, dinnerware, drinking cups, numberless toys, others that you can imagine easily yourself. It would be difficult to live without it. 

The major source of plastic is crude oil. A significant part of fossil fuels harvested from the earth is turned into resin pellets, and these are used to manufacture plastics. Stated another way, plastics are a major product of the fracking industry. We have a large and growing plastics industry that produces the raw materials for products for which there are many uses and for which there is a high demand. The situation is a recipe for continued growth both of an industry and of the tremendous problem that we have created.

Petroleum-derived plastics have many desirable characteristics. They are lightweight and have very stable chemical and physical properties, which makes them highly durable. Production methods are well established and very high capacity, resulting in very low cost. Consequently, they have become ubiquitous in the global economy.

The problem is that plastics are basically indestructible. The chemical structure of most plastics renders them resistant to many natural processes of degradation. A little chemistry is in order here to understand the stability of these products and the difficulty of breaking them down to small molecules that can be metabolized by microorganisms, insects, and animals. 

Based on the degradation pathways, which are the important consideration for us, these synthetic plastics can be divided into two groups, plastics with a carbon-carbon backbone and plastics with heteroatoms in the main chain. Those with a backbone built of carbon atoms include PE (polyethylene), PS (polystyrene), PP (polypropylene), and PVC (polyvinyl chloride). Using PE as the example, it is comprised of a linear chain of carbons – a very stable bond structure. It has a semi-crystalline structure and is extremely resistant to biodegradation. Only about 0.1% per year of the carbon that makes up the polymer is converted into CO2 by biodegradation under optimum laboratory conditions. These products probably will outlast humans. 

Polyhydroxyalkanoates (PHAs) have emerged as a sustainable choice due to their putative high biodegradability in different environments, biocompatibility, chemical diversity, their manufacture from renewable carbon resources, and release of non-polluting and non-toxic products. After degradation, they are largely converted into CO2. Polyethylene terephthalate (PET) and polyurethane (PU) plastics have heteroatoms in the main chain. This makes them more susceptible to breakdown by photo-oxidation, hydrolysis, and biodegradation. PU are widely sold and are best known for their uses in adhesives, coats, tires, paints, and fibers. (Mohanan et al., Frontiers in Microbiology, 26 Nov 2020, doi:10.3389/fmicb.2020.580709). The importance of the chemistry is captured best by the Marine Conservancy, which has predicted the decomposition rates of some products: a plastic cup will take 50 years; a plastic beverage holder will take 400 years; fishing line will take 600 years to disintegrate. 

About 380 million tons of plastic were produced annually worldwide from the 1950s to 2018. About 6.3 billion tons. Of this, an estimated 9% has been recycled and another 12% incinerated. The remainder enters the environment. ("The known unknowns of plastic pollution". The Economist. 3 March 2018.) As of 2020, the global mass of produced plastic exceeds the biomass of all land and marine animals combined. (Laville, Sandra (9 December 2020). "Human-made materials now outweigh Earth's entire biomass – study". The Guardian.)

In 2019, a group called Break Free from Plastic organized a large group of volunteers to collect waste. According to Wikipedia, they collected 59,000 plastic bags and 29,000 plastic bottlers.  The most common brands were Coca-Cola, Nestle, and Pepsico. These were primarily single-use containers. Part of the solution is clear: move to reusable containers instead. All three of these companies have responded by increasing the production of reusable containers. At this time, Nestle appears to be well ahead, with 87% of their packaging and 66% of their plastic packaging now reusable. We all are involved in this, however, since we are the people who throw away the materials.

A 2019 study calculated the mismanaged plastic waste. A metric ton is 1000 kilograms (2,204 pounds); these results are in millions of metric tons (Mt) per year: 

·       52 Mt - Asia

·       17 Mt - Africa

·       7.9 Mt - Latin America & Caribbean

·       3.3 Mt - Europe

·       0.3 Mt - US & Canada

·       0.1 Mt - Oceania (Australia, New Zealand, etc.) ·        

Lebreton, Laurent; Andrady, Anthony (2019). "Future scenarios of global plastic waste generation and disposal". Palgrave Communications. Nature. 5(1). doi:10.1057/s41599-018-0212-7. ISSN 2055-1045.

This not reported on a per capita basis and reflects the larger populations in the larger polluted portions of the globe. Despite that, it is clear that the developed countries are making some progress in preventing plastic pollution. The Caribbean islands are the biggest polluters per capita in the world. Of the top thirty polluters, ten are in the Caribbean. For example, Saint Lucia generates more than four times the amount per capita as China. 

These numbers are difficult to comprehend. A metric ton of plastic waste would be a lot, but these are in millions of metric tons. Most of it goes into the oceans.  In 2018, approximately 513 million tons of plastic went into the oceans. There is a large, floating garbage dump in the mid-Pacific Ocean. We will talk about that in the next blog.