“There is a great future in plastics,” Mr. McGuire warmly explains to Dustin Hoffman’s Ben character in the often-quoted scene from the iconic 1969 movie, The Graduate. Who could have foreseen the accuracy of Mr. McGuire’s prediction from a half-century ago? Fast forward to the present. We’ve become a society utterly wrapped in plastic, or more accurately, we’ve become a society wholly dependent on synthetic materials, mostly derived from hydrocarbons (oil and natural gas), of which plastic is the most prevalent.
In 1970, total worldwide petrochemicals demand (consumption) measured approximately fifty million metric tonnes (MMT); today this consumption has grown steadily to almost eight hundred MMT, a sixteen-fold increase in fifty years or a compound annual growth rate of just under 6 percent. Although all synthetic materials are included in this current demand figure of eight hundred MMT, plastics constitute the bulk of synthetic material consumption. The remainder includes synthetic fibers (such as nylon, polyester and related derivatives), solvents, adhesives and direct-use petrochemicals.
The majority of the five hundred twenty-five MMT of annual plastic demand comes in one of five compounds: low density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high density polyethylene (HDPE), polypropylene (PP) and polyvinyl chlorine (PVC).
To put this in perspective, among the primary building materials, plastic demand is now about one-eighth of global concrete demand, one-third of global steel and about half of global wood demand. Given the staggering growth in plastics production over the past fifty years, several fundamental questions naturally arise: why do we use so much plastic, what did plastic replace in our daily lives before the 1960s and what makes plastics so challenging from a disposal and recycling perspective?
What is it about plastics that have made them so ubiquitous in our society and so sought after as a material of construction? The main benefit that plastics bring to the table is a straightforward engineering one: plastics sit in a “Goldilocks Zone” in terms of their strength-to-weight ratio. “Stronger than wood, lighter than metal,” would be the easiest way to explain this sweet spot in non-engineering terms. Furthermore, unlike wood, steel and other metals, plastic is easily tailored to specific end-use requirements, which explains the amazing variety of end-use applications. Think of the intricate parts involved in a child’s (or adult child’s) flying drone toy. Making this device out of wood requires hundreds of hours of a skilled carpenter’s time; made out of metal, this device would be too heavy to fly on battery power alone. The light weight, strength and infinite moldability of plastics solve both of these design challenges simultaneously.
The following list of desirable engineering properties explains the usefulness of plastics and their widespread usage in modern society:
• Strength-to-weight ratio bridges the gap between wood and metals;
• Excellent electrical properties (non-conducting);
• Superior chemical resistance, especially to strong acids and bases;
• Easily tailored cosmetic properties, coloring and moldability;
• Resistant to weathering and UV degradation;
• Highly suitable for mass production;
• Generally non-toxic, inert to human contact and consumption, although this is still a matter of some scientific debate.
These advantages are offset by several disadvantages of plastics and other synthetic materials: production and recycling are energy-intensive; low absolute tensile strength; soft (making them subject to surface scratching); low thermal properties (heat deformation and melting); and the last and most detrimental property, resistance to organic degradation making disposal highly problematic. This last property, plastics’ resistance to environmental degradation, is the main societal concern with plastic usage and the focus of various environmental initiatives to ban or limit the use of plastic, especially plastic bags.
Although pure plastics are generally considered inert and non-toxic for human consumption, there is emerging research indicating that microplastics and certain plastic hardening agents such as bisphenol A [to make the plastic more scratch resistant] are detrimental to human health and development. We’ll discuss these topics in a future article.
HOW PLASTICS ARE PRODUCED
Plastic and other petrochemical production is highly integrated in the oil refining process. The purpose of a petroleum refinery is to produce environmentally compliant transportation fuels, but plastic and petrochemical production fills an economically viable secondary role in providing a use for the molecules contained in the oil barrel that aren’t suitable for blending into transportation fuels.
Most plastics and synthetic rubber are produced from ethane, propane and butane, molecules that are too light or volatile for blending into gasoline or diesel fuel. The other main family of petrochemicals is the aromatics family (named for its sweet cotton-candy-like odor), commonly referred to as BTX molecules (for benzene, toluene and xylene). These molecules are suitable for blending into transportation fuels in that they have low volatility and high octane. However, environmental regulations restrict the amount of these molecules that can be blended into gasoline due to human health concerns and the great equalizer. . . price. BTX molecules typically carry a greater value (and price) as synthetic-fiber building blocks than as an octane booster for gasoline blending.
Today, roughly 7.5 percent of each oil barrel consumed globally is converted into building-block molecules for plastic and synthetic material production—a good use for molecules that have little value for transportation.
HOW PLASTICS ARE CONSUMED
See Figure 1 for a good representation of plastic demand by end use. In the building, construction and automotive sectors, plastics are primarily used as an engineering alternative to wood, concrete and metal, mostly steel.
Plastics use in automobiles is interesting from an environmental and engineering perspective. Plastics help reduce the weight of an automobile, a key requirement for improved fuel efficiency and for reducing the greenhouse gas emissions. Given that these plastics are designed to last the life of the building or automobile, they don’t produce a significant amount of single-usage waste compared to the alternatives. More importantly, they provide a variety of environmentally beneficial properties when compared to other construction materials.
Packaging presents a different challenge altogether and is likely what most of us have in mind when we think about plastic waste and plastic pollution. From the gadgets to the groceries, pretty much everything we buy today comes encased in some form of often frustrating-to-open plastic packaging, and almost all of it is discarded after one or two uses. Nonetheless, much of the global supply chain is dependent on plastic packaging.
The ease of application, durability and compressive flexibility of plastic packaging materials make them key enablers of these global supply chains stretching across the continent and the globe. If all of the electronics purchased from Asia arrived at your doorstep cracked and smashed, it is unlikely that you would continue to buy televisions from Japan and tennis shoes from Vietnam. How often do we care that the packaging that our precious device arrives in looks as though it has been through a trash compacter? It is typically made of cheap materials that are going to be thrown away anyway. They are, by design, discardable.
In food packaging, the benefit of ultra-thin but impermeable plastic packaging has to do with preventing food waste. It so happens that plastic presents an excellent barrier to “oxygen ingress,” the key process that causes food to rot. Consider, for example, a cucumber: wrapping the lonely cucumber in a thin sheet of plastic wrap extends the shelf life from days to weeks. Some studies estimate that plastic packaging reduces the amount of food waste that occurs from the farm to your table by over 25 percent.
A key side effect of our plastic-encased world is the ability to create global food chains that enable us to enjoy seasonal fruits year-round. There’s a reason why your grandparents were not able to enjoy Chilean blueberries in the dead of winter, but you can enjoy these out-of-season treats. Whether or not you personally agree with global food supply chains, the reality is that plastic packaging allows us to move food effectively from locations of surplus to areas of scarcity year-round.
PLASTICS AND THE ENVIRONMENT
Before we demonize the use of plastics, we need to ask what we used for food and gadget packaging in the pre-plastics era. The answer is glass, tin or steel and wood (as paper or cardboard, which are still widely used today). Plastic production may be energy-intensive, but it is only about half as energy-intensive as the readily available alternatives. And since plastic provides the same strength properties at a much lower weight, it substantially reduces the energy cost of moving goods around the world. To put this in analytical terms, see Figure 2, a comparison of plastic to its packaging alternatives by the Danish consulting firm Denkstatt. Plastics, even with no degree of recycling, result in a substantial reduction in greenhouse gas emissions and energy consumption when compared to the current technologically available alternatives.
Another paradox: despite sixty years of population, economic and consumption growth, the amount of landfill waste in the developed world is on the decline. Figure 3, provided by the U.S. Environmental Protection Agency, shows that the combination of recycling and using lighter-weight packaging materials is shrinking our environmental footprint in absolute terms, despite all the other variables that should result in waste being on the rise. The major reason for this is the substitution of plastic for glass, tin, steel and wood.
THE PLASTIC PATCH
In spite of the fact that plastic usage is resulting in less waste both in absolute and per capita terms, there is a constant stream of news articles lamenting the evils of plastic usage and highlighting the “plastic patches” growing in the middle of our oceans.
The main reason we have these plastic patches in the oceans is that the landfilling and recycling efforts are largely concentrated in Western countries and not in the emerging world. Specifically, the majority of plastic pollution in the oceans comes from ten rivers, mostly in Asia, as shown in Figure 4, where open trash dumping is the norm and a large capital investment in point-source sanitation has yet to be made.
A second challenge with cutting plastic waste is that without strong government support, the companies that produce plastic have little economic incentive to favor plastic recycling over virgin plastic production. Core plastic manufacturing is overwhelmingly performed by large oil and refining companies, with very few companies integrated from the point of production (the refinery) to the point of end-use. Asking oil companies to increase their level of waste plastic aggregation and recycling comes at the cost of cannibalizing their core business, namely the conversion of raw crude oil into plastic products. Due to a variety of complex social and political reasons, not the least of which is the lobbying-industrial complex, the current solution of reducing plastic usage is to cut end-use demand by taxing consumers versus the more efficient and point-targeted solutions of improving municipal waste collection, recycling and incentivizing well-capitalized companies to invest in industrial-scale recycling efforts.
This leaves us with a profound problem if we are concerned about plastic pollution globally but realize that local initiatives to ban single-use plastic won’t do much to get rid of those ocean plastic patches. Here’s what we can do:
• Don’t fall for the bait: differentiate between local self-serving political plastic initiatives that do very little to reduce pollution and larger initiatives that address waste at the source.
• Support recycling in all its forms, particularly financial incentives that apply the tax at the point of production versus the point of consumption.
• Support investment in point-source sanitation in the developing world. Prevent the plastic from being dumped in rivers in the first place by subsidizing modern world-scale recycling initiatives.
• If you don’t like the image of single-use plastic, don’t use it, but don’t wait for a ban to take effect. Start reasonable low-effort conservation efforts without the government is involvement. All of us can keep a couple of canvas bags for trips to the store as a matter of lifestyle choice.
• Support initiatives that separate oil companies from their petrochemical operations. Oil companies are in the business of selling oil, and recycling reduces raw oil consumption, particularly around plastics. Remove the perverse barriers that present an economic hurdle for increased investment in plastic recycling.
• Shrink the length of your personal supply chain. Buying food and other consumable goods from local manufacturing shrinks the length of the supply chain, requiring less intensive packaging practices.
• Support research and development efforts in biodegradable plastics, that is, plastics that decompose naturally over time, without sacrificing the material properties of the plastic. Don’t confuse biodegradability with being produced from cash crop plants. Fairly sizeable initiatives from the corn and soy industries to find yet even more outlets for corn and soy components are already underway and are well funded. Try out their version of plastic, see how it compares to the real thing and make your choice based on material performance.
• Last but not least, keep an open mind and consider all of the beneficial properties of our plastic-saturated society before we vilify a construction material that is doing exactly what it’s designed to do.
This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly journal of the Weston A. Price Foundation, Fall 2020