24 Scientific American, December 2019VENTURES
THE BUSINESS OF INNOVATIONWade Roush is the host and producer of Soonish, a podcast
about technology, culture, curiosity and the future. He
is a co-founder of the podcast collective Hub & Spoke and
a freelance reporter for print, online and radio outlets,
such as MIT Technology Review, Xconomy, WBUR and WHYY.Illustration by Jay BendtLearning to
Love Plastic
In some ways, it can actually be good
for the environmentBy Wade Roush“Biodegradable” plastic doesn’t do what you think it does. Your
paper or metal straw takes only a tiny sip at the problem of plas-
tic pollution. And your supposedly eco-conscious cloth grocery
bag is more damaging to the environment than conventional
plastic bags—unless you reuse it literally thousands of times. In
other words, many of our ideas about plastic and the environ-
ment are confused. And that may be getting in the way of the
fight against global warming.
Take the ruckus over single-use plastic bags and straws, which
the conservative British magazine The Spectator predictably but
correctly pegged as a “moral panic.” The hullabaloo has spurred
restaurateurs to roll out cups and utensils made from biodegrad-
able materials such as polylactic acid (PLA), a polyester derived
from starchy plants, including corn and sugarcane. The popular
myth is that you can safely toss such items onto the forest floor
or into the ocean, and microbes will break them down into raw
materials that will magically be reborn as daisies or seahorses.
Not so much. In America and Europe, the technical standards
for biodegradability are mostly about industrial composting. Put
a plastic bag or bottle into a composting vessel, throw in some
microorganisms and turn up the temperature to between 50 and
60 degrees Celsius (122 and 140 degrees Fahrenheit). If 90 per-
cent of the material is released as carbon dioxide within 180 days,
then you get to call the item “biodegradable” or “compostable.”
In other words, a biodegradable material is one deliberately
designed to dump its carbon into the atmosphere at the end of its
life cycle. Even worse, if biodegradable plastic ends up in an oxy-
gen-deprived landfill rather than a composting facility, anaerobic
decomposition will turn it into methane, a gas that warms the
planet from 34 to 86 times as much as carbon dioxide. And if you
dump biodegradables into the ocean, they break up into tiny bits
that choke marine animals long before they degrade appreciably.
Globally, we produce an eye-popping amount of plastic—some
380 million tons a year, virtually all of it from fossil-fuel feedstocks.
So it’s understandable why consumers would cling to the comfort-
ing 1980s-era idea that plastic can be engineered to disappear
back into the environment. But the reality is that 60 percent of all
the plastic ever produced is accumulating in landfills or as litter.
And from a climate scientist’s point of view, that may actual-
ly be a good thing. Of course, it’s a crime that so much plastic
waste gets into terrestrial and aquatic ecosystems. But we won’t
outgrow our need for plastic anytime soon: for one thing, it sub-
stitutes for heavier materials in cars and planes, which saves fuel.
On top of that—and this is my main point—plastic can function
as an artificial carbon sink. If we’re going to extract carbon from
the ground at all, far better that it ends up in a soda bottle that
will last 400 years than in the combustion chamber of your car.
If we want to save Earth, we should stop obsessing over biode-
gradability and invest instead in plastics that are bio- based.
Plants use photosynthesis to convert water and CO 2 from the
atmosphere into sugars, starch and cellulose, all of which can be
processed to make plastics. PLA is one of those, but it’s designed
to be composted, which makes it carbon-neutral at best. The most
exciting work in this area focuses on nonbiodegradable plastics
such as polyethylene terephthalate (PET), which Coca-Cola uses
in its Plant Bottle. The current version, introduced in 2009, uses
PET that is 30 percent plant-based. Both Coca-Cola and Pepsi
have announced bottles made from 100 percent plant-derived
PET, although neither has a market-ready version yet.
The United Nations Intergovernmental Panel on Climate
Change points out that to limit global warming to 1.5 degrees C
above preindustrial levels, we may need to remove tens to hun-
dreds of gigatons of CO 2 from the atmosphere, ideally by 2050.
If the world fully converted to nonbiodegradable bioplastics
starting in 2020, the carbon sequestered over the next 30 years
could amount to more than 10 gigatons—which would be a good
start. When it comes to plastic, it’s time to think more flexibly.JOIN THE CONVERSATION ONLINE
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