Previously published in Plastics Engineering and posted with permission from the Society of Plastics Engineers.
A New Study Points to Plastics
Something odd happened to our garbage a couple decades ago. We started creating less of it.
According to a new study by researchers at the Earth Engineering Center at City College of New York, sometime around the late 1990s we began to see a decrease in the rate at which we generate waste compared to economic growth. Typically, as Gross Domestic Product (GDP) increases, the amount of trash increases along with it, at about the same rate. The authors note that both GDP and waste generation tracked each other from 1960 on, as expected… until the late 1990’s. Then, as GDP continued to climb, waste generation began to climb more slowly. We were getting richer… but we were creating less waste.
Why? The study’s authors have just one word for you: plastics.
Let’s recall what happened during this time frame. Despite occasional downturns in the economy, since 1960 the U.S. standard of living, GDP, and personal consumption have climbed relentlessly. Along with our production of trash. In the late 1980s, concerns over our ever-growing garbage boiled over when a barge full of trash from New York wondered all the way to Belize looking for a home for its stinky cargo. (Named Mobro and nicknamed the “Gar-barge,” it finally returned to New York where the trash was incinerated.) The wayward barge received national media attention and stoked fears of dwindling landfill space and a “garbage crisis.”
During this same time frame, a new-ish material—plastics—was displacing traditional paper, metals, and glass. Conventional wisdom at the time said that our garbage crisis was being caused in large part due to the rapid growth of plastics, particularly plastic packaging and “over-packaging.” The conventional wisdom, still assumed today, is that plastics create more waste than alternatives and result in a glut of new and unnecessary waste. In other words, plastics caused our garbage crisis and continue to exacerbate the problem today.
Right? Not according to the study’s authors. In fact, their conclusion is just the opposite.
As noted, the researchers look at economic growth and consumption and compare them to the growth in trash. They use data from studies that measure waste generation slightly differently to account for variations in methodologies. Then they plot the findings on charts, where GDP shows its inexorable march higher… but waste doesn’t keep pace. In fact, the charts show that the waste generation rate has flattened. It’s no longer growing as the economy continues to increase its output.
Then the researchers look for reasons why. They examine the make up of “municipal solid waste” (MSW) from 1960 to the mid-2010s. As a percentage of MSW, every traditional material declined over this time while plastics increased. At first this may seem to correspond with conventional wisdom. “See… plastics are causing our garbage crisis!” But remember: economic growth is far outpacing waste generation, which is a very positive trend for our environment. Something must be “decoupling” the growth in GDP from the growth in waste, leading to less stress on the environment.
The answer lies in the nature of plastics: lightweight yet strong. We may be making more products and packaging year after year, but the products and packaging typically are lighter and use less material. Less material results in less waste in the first place, which leads to a slowdown in waste generated. As plastics replaced heavier materials, we were able produce more stuff without producing the same amount of waste.
The authors provide numerous examples. For example, they note that plastics used in containers and packaging weigh a quarter of the materials they replaced. That’s incredible. While still delivering the same goods, plastics reduce material use by four times!
They also develop scenarios in which plastics have not replaced traditional materials over time to see what impact that would have on waste generation.
“To understand the impact of plastics on MSW, this study quantitatively analyzed hypothetical scenarios in which plastic was removed from the waste stream and was substituted with glass, metal and other materials in its product applications. For US packaging, the combined weight of alternative packaging that would be needed to substitute US plastic packaging is about 4.5 times more than the weight of the plastic packaging that is replaced. For all other product applications, the plastics material substitution ratio is 3.2, meaning that it would require 3.2 times more material by mass for the same product if plastic was replaced… This analysis demonstrates that if glass, metal and other materials were not substituted by plastics… MSW generation would remain coupled to (personal consumption) growth.”
This obviously runs counter to conventional wisdom.
And what about the environmental impacts of increased plastics use, beyond waste? Surely plastics have greater impacts than alternatives? Again, conventional wisdom is turned on its head, based on the authors’ review of previously published studies.
- Replacing conventional materials used for common containers and packaging with plastics “resulted in an 80% reduced energy demand and a 130% reduced global warming potential impact.”
- “… plastic substitution in automobiles reduces the overall weight up to 30% leading to a commensurate reduction in fuel consumption and emissions.”
- “Plastic packaging also conserves energy and natural resources compared to its alternatives. Specifically it would require 1.5 times more aluminum, 4 times more steel, and 20 times more glass than plastic to carry the same volume of a beverage.”
- “… plastic use in building and construction materials saved more than 467 trillion BTUs in a year compared to alternative materials, which is equivalent to the average annual energy demand of 4.6 million households in the US.” (See study for references.)
And it’s likely that these numbers will continue to improve as advances in plastics continue, in particular the ongoing reduction in the weight of plastics needed for certain applications. For example, the authors note that in 2000 the thickness of plastic packaging averaged about one third the weight of alternatives. That thickness has “continuously decreased by about 3% per year, further reducing the weight exchanged until the ratio reached one quarter of the… weight.” In other words, while plastics use increases, the amount of plastics needed in many applications decreases. “Even with this significant increase in plastics, the total MSW generation did not increase significantly…”
These findings do not mean that creating plastic waste is environmentally benign. As the authors note: “Plastics pose environmental challenges for end-of life disposal…” For example, poor or non-existent waste disposal in some parts of the world results in significant amounts of plastics being released into our waterways and oceans, causing serious problems. Multinational efforts are underway to reverse this alarming trend. The authors suggest that “… recycling and thermal conversion technologies [converting plastics into raw materials] can reduce the overall pollution and carbon footprint of plastics.”
This study builds on previous studies that have found that plastics help reduce our environmental footprint, in particular by enabling us to do more with less material in the first place. The findings demonstrate that as our economy grows, we don’t need to trade improved living standards (that plastics help deliver) for increased environmental degradation and waste.