Plastics: Science is Winning

By Kip Hansen — Re-Blogged From WUWT

Science is beginning to win in the long battle over misinformed anti-plastic advocacy.  It has been a long time coming.  The most recent paper on the subject of pelagic plastic (plastic floating in the oceans) is from a scientific team at the Woods Hole Oceanographic Institution on Cape Cod, Mass., and the Massachusetts Institute of Technology.

The study is “Sunlight Converts Polystyrene to Carbon Dioxide and Dissolved Organic Carbon” by Collin P. Ward, Cassia J. Armstrong, Anna N. Walsh, Julia H. Jackson and Christopher M. Reddy.   It is good basic science.


styrene_cupsWe are all familiar with polystyrene — it is prevalent in modern packaging, both as a solid,  such as yoghurt cups, or in expanded form used for disposable foam drink cups.  Much of the plastic flotsam found on the worlds beaches and floating  in rivers is this ubiquitous plastic, particularly the expanded foam.

The new abstract of the new study starts with this:

“ABSTRACT:   Numerous international governmental agencies that steer policy assume that polystyrene persists in the environment for millennia.  Here, we show that polystyrene is completely photochemically oxidized to carbon dioxide and partially photochemically oxidized to dissolved organic carbon. Lifetimes of complete and partial photochemical oxidation are estimated to occur on centennial and decadal time scales, respectively. These lifetimes are orders of magnitude faster than biological respiration of polystyrene and thus challenge the prevailing assumption that polystyrene persists in the environment for millennia.”   [ bolding mine — kh ]

It is about time that someone scientifically challenged the activist position held and promulgated by many environmental, anti-plastics and anti-corporate groups that “Plastic is Forever”.

Plastic is not forever.  Glass, both natural and man-made,  is forever, but not plastic.

What are plastics?

 Plastics are hydrocarbons.    That is, plastics are primarily made of hydrogen and carbon combined into various configurations.   And, when Nature adds oxygen and nitrogen, we get the substance of all living things (that we know of).  People, plants, animals, microbes, petroleum, natural gas, dead leaves, peat bogs — basically everything that was once alive (and some that weren’t) are made of hydrogen and carbon and oxygen and nitrogen strung together, with little bits of other elements.

Hydrocarbons, strictly, contain only hydrogen and carbon.  Many of the building blocks of plants are hydrocarbons — like cellulose.  Cellulose, the material that makes up the structural part of most plants,  was the basic ingredient that was used to make the first synthetic plastics in the mid-1800s.

The thing that makes plastics plastic [plasticity — the ability to deform without breaking] is that its basic building blocks — carbon atoms with hydrogen atoms attached — are combined into long chains  — often twirled into spirals with other elements tacked in, looking like this:


Here we see the common plastic, polyethylene,  made up of  a string of H-C-H bits strung together to make the typical long plastic chain.

Why review all this chemistry? 

 Plastics are, at heart, very simple natural structures — carbon atoms bonded with hydrogen atoms.  They are not Frankensteinian monstrosities made by chemical madmen through arcane alchemy.

And, as we will see, because they are quite natural, they are not indestructible but susceptible to the normal paths of entropy in the natural world.

Plastics are Food

Not food for you and I, but food for the tiniest of plants and animals.  Because plastics are hydrocarbons,  they make good food for living things, which oxidize hydrocarbons for energy and use them for the building blocks of their bodies.

With the oil in the Deepwater Horizon incident in 2010, it was found that “Naturally occurring microbes at this depth are highly specialized in growing by using specific components of the oil for their food source.”   Microbes ate a great deal of the 4.1 million barrels of crude oil that poured into the Gulf of Mexico.

disappearing_bitsWith pelagic plastics (plastics floating in the open oceans) it has also been found that as the plastic items  become  degraded by the sun, they break into smaller and smaller pieces through the action of the wind and the waves. The illustration shows what they found  when sieving the ocean for floating plastic    Intuitively, the number of pieces at various sizes should continue to increase as items breaking into smaller and smaller pieces but  instead  they found numbers to begin decreasing at about 5 mm and drop off dramatically when items become smaller than 1 mm — approaching zero at less than 0.5 mm.   This is not for lack of trying, the sieves are very fine.  In the real world, when the pieces get down below the 1 millimeter size they rapidly disappear altogether.

microbesWhat happens to these little pieces?  Microbes eat them up entirely.

Of course, the plastic-eating microbes have been eating away at the surfaces of the floating plastic all along, but when the pieces get very small, the surface area to volume ratio factor allows the microbes to win out and consume the entire little piece, like a tiny ice chip that rapidly disappears in a glass of water (whereas a larger ice cube persists).

( see my fuller explanation here )

This interesting news is not unique, another paper confirms that microbes are eating the plastic film that ends up in the oceans, stating:  “…tailored marine consortia have the ability to thrive in the presence of mixtures of plastics and participate in their degradation.”

Last year, scientists in Japan discovered bacteria that was eating PET plastic — the plastic that those clear soda and water bottles are made of — and another group discovered an enzyme that breaks down PET.  Of course, “ Waxworm caterpillars have been found to break down plastic in a matter of hours, and mealworms possess gut microbes that eat through polystyrene. Beckham [Gregg Beckham, a researcher at the U.S. Department of Energy’s National Renewable Energy Laboratory] thinks, given how ubiquitous environmental pollution has become, “it is likely that microbes are evolving faster and better strategies to break down man-made plastics. It seems that nature is evolving solutions.”

It is not just bacteria and ocean-dwelling critters that are eating plastic:

 “In 2017, Khan and a team of other scientists collected a sample of a previously undiscovered strain of fungus on top of a garbage dump in Islamabad, Pakistan. When they took it back to China to study in the laboratory, the species of fungus, a previously undiscovered strain of the species Aspergillus tubingensis, was able to break down polyurethane—common in industrial settings and used in refrigerators, fake leather, and many other applications—in just weeks instead of decades. The fungus secretes enzymes that break down the plastic’s chemical bonds and uses its mycelia—filaments fungi grow that are much like a plant’s roots—to break apart the plastic further.”

Back to the latest study….

Anyone who has participated in a roadside cleanup (a popular volunteer activity in the United States) or helped to collect trash off the beaches knows that foam drink cups left in the sun for any length of time break down and literally fall apart when one tries to pick them up.

cups_to_CO2This is precisely what the new study found.  More importantly, it is not just that the structure of the foam breaks down, the substance of the foam “is completely photo-chemically oxidized to carbon dioxide and partially photo-chemically oxidized to dissolved organic carbon.”  In essence, the hydrocarbon-based plastic simply breaks back down into CO2 and organic carbon dissolved in water.  How long does it take?  This study estimates time scales of a decade to centuries.

sieved_plasticIn my personal experience, I have found foam drink cups to degrade to the point of “breaking to pieces when touched” in a single summer in the direct sun.  As for pelagic Starbucks cups, I have never found a foam drink cup floating on the open sea (whereas I have found plenty on the shores of islands without proper garbage collection and disposal).  The absence of floating foam cups indicate that they break down much faster than a decade when in the sea under the full sun under the combined forces for the wind, the waves and the Sun.  Little bit of polystyrene foam are not found in the plastic sieved from the oceans surface.

Science vs. Advocacy

As readily admitted in the abstract of the latest study, the anti-plastics activists are pushing the false belief that “Plastics Are Forever” — that they will never naturally degrade or break down in the sea or in landfills.  Science, however, is finding that plastics are degraded, decomposed, eaten and photochemically oxidized back into their essential elements – carbon and hydrogen — or used as food by various microbes and fungi.  Most of the plastic waste that enters the oceans disappears altogether.

hdpeThere plastics that are intentionally engineered to withstand exposure to sunlight  and chemicals without  degrading.  Among them are various types of  HDPE (High-density polyethylene) , which is used in the manufacture of thousands of items, including potable water pipes, surgical implants,  landfill liners, pyrotechnic mortars and fuel cans.  Another personal note:  If you are buying jerry cans for marine use, or fuel cans for outboard motors, buy only those marked HDPE with the symbol shown here.  Many consumer gas cans are meant to be stored in garages and breakdown rapidly if left exposed to sunlight.  HDPE fuel cans are intended to be exposed and last a very long time.

Bottom Lines:

—   Plastics fall under Kindergarten Rules — Clean up your own messes — Pick up after yourself.  Put your trash in the proper trash bin – recyclables go  in the Recycle Bin.

—  Trash does not belong in the natural environment — regardless of what it is made of.  Nations, states, counties and cities should take great care to see that the waste and trash of human civilization is properly and sensibly collected and disposed of.

—  Plastics are hydrocarbons — like petroleum.  Thus should be recycled into useable building material, such as plastic boards for patios and decks or used as fuel to produce electrical power in modern clean-burn power plants.

—  Thin film plastic shopping bags, like those being banned all across the world, should be replaced with re-engineered materials to be more easily degradable and deployed in common useMany types are already commercially available, albeit at some added cost.

—  Most of the plastic that has been allowed to escape into the environment will be disposed of by natural processes in reasonable amounts of time.  This fact should not be used as an excuse to fail in our responsibility to take care of our own messes.

—  Landfilled plastics will take longer to degrade — but will do so under attack by microbes and fungi.  Some plastics will have a very long lifetime in landfills — this is what landfills are for.  Other human products, such as glass jars and ceramics, will be there for future interstellar archaeologists to find.


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