Bioplastics and biodegradable plastics
by Chris Woodford. Last updated: October 25, 2020.
From cars to food wrap and from planes to pens, you can make
anything and everything from plastics—unquestionably
the world's most versatile materials. But there's a snag. Plastics are
synthetic (artificially created) chemicals that don't belong in our
world and don't mix well with nature. Discarded plastics are
a big cause of pollution, cluttering
rivers, seas, and beaches, killing fish, choking birds, and making our
environment a much less attractive place. Public pressure to clean up
has produced plastics that seem to be more environmentally friendly.
But are they all they're cracked up to be?
Photo: A typical eco-friendly bag made using EPI chemical additives. Added to normal plastics in small quantities (about 2–3 percent), they cause the plastic to break down after exposure to sunlight, heat, or after repeated stresses and strains through regular use.
The global plastics problem
Photo: An oxy-biodegradable fruit and vegetable bag produced by
d2w® for the UK's Co-op chain of grocery stores.
Oxy-biodegradable means it needs only oxygen (not light or anything else) to
break down. d2w® stands for "degrade to water"; after it breaks
down, only oxygen, carbon dioxide, and biomass remain. The Co-op
stopped using these bags in 2010 following growing concerns over oxy-biodegradable plastics.
Plastics are carbon-based polymers (long-chain molecules
that repeat their structures over and over) and we make them mostly
from petroleum. They're incredibly versatile—by definition: the word
plastic, which means flexible, says it all. The trouble is that plastic
is just too good. We use it for mostly disposable, low-value items such
as food-wrap and product packaging, but there's nothing particularly
disposable about most plastics. On average, we use plastic bags for 12
minutes before getting rid of them, yet they can take fully 500 years to
break down in the environment (quite how anyone knows this is a
mystery, since plastics have been around only about a century). 
Getting rid of plastics is extremely difficult. Burning them can
give off toxic chemicals such as dioxins, while collecting and recycling them responsibly is also
difficult, because there are many different kinds and
each has to be recycled by a different process. If we used only tiny amounts of plastics that wouldn't be so
bad, but we use them in astounding quantities. In Britain alone (one
small island in a very big world), people use 8 billion disposable
plastic bags each year.  If you've ever taken part in a beach clean,
you'll know that about 80 percent of the waste that washes up on the
shore is plastic, including bottles, bottle tops, and tiny odd fragments known as
"mermaids' tears." 
We're literally drowning in plastic we cannot get rid of. And we're
making most of it from oil—a non-renewable resource that's becoming
increasingly expensive. It's been estimated that 200,000 barrels of oil
are used each day to make plastic packaging for the United States alone,
though the actual figure may be significantly higher. 
Chart: How long do plastics last in the environment? PE = polyethylene; PP = polypropylene;
PET = polyethylene terephthalate; PVC = polyvinylchloride. Composting typically takes 180–365 days depending
on whether it happens in an industrial composter or a home compost heap. Sources: See note .
Making better plastics
Photo: Plastics can begin to photodegrade quite quickly, but they take a very long
time to break down completely. The old grocery store bag on the left has been exposed to the light for
a few months and has already started to turn yellow (compared to the new bag on the right).
Ironically, plastics are engineered to last. You may have noticed
that some plastics do, gradually, start to go cloudy or yellow after long
exposure to daylight (more specifically, in the ultraviolet light that
sunlight contains). To stop this happening, plastics manufacturers
generally introduce extra stabilizing chemicals to give their products
longer life. With society's ever-increasing focus on protecting the
environment, there's a new emphasis on designing plastics that will
disappear much more quickly.
Broadly speaking, so-called "environmentally friendly" plastics fall into three types:
- Bioplastics made from natural materials such as corn starch
- Biodegradable plastics made from traditional petrochemicals, which are engineered
to break down more quickly
- Eco/recycled plastics, which are simply plastics made from recycled plastic materials rather
than raw petrochemicals.
We'll look at each of these in turn.
Photo: Some bioplastics can be harmlessly composted. Others leave toxic residues or plastic fragments behind, making them unsuitable for composting if your compost is being used to grow food.
The theory behind bioplastics is simple: if we could make plastics
from kinder chemicals to start with, they'd break down more quickly and
easily when we got rid of them. The most familiar bioplastics are made
from natural materials such as corn starch and sold under such names
as EverCorn™ and NatureWorks—with a distinct emphasis on environmental
credentials. Some bioplastics look virtually indistinguishable from
traditional petrochemical plastics. Polylactide acid (PLA)
looks and behaves like polyethylene and polypropylene and is now widely
used for food containers. According to NatureWorks, making PLA saves
two thirds the energy you need to make
traditional plastics. Unlike traditional plastics and biodegradable
plastics, bioplastics generally do not produce a net increase in carbon
dioxide gas when they break down (because the plants that were used to
make them absorbed the same amount of carbon dioxide to begin with).
According to a 2017 study by Daniel Posen et al, if the US switched from traditional
plastics to PLA, it could cut greenhouse emissions
by about a quarter.
Another good thing about bioplastics is that they're generally compostable:
they decay into natural materials that blend harmlessly with soil. Some
bioplastics can break down in a matter of weeks. The
cornstarch molecules they contain slowly absorb water and swell up,
causing them to break apart into small fragments that bacteria can
digest more readily. Unfortunately, not all bioplastics compost easily or completely and some leave toxic residues or
plastic fragments behind. Some will break down only at high temperatures
in industrial-scale, municipal composters or digesters, or in
biologically active landfills (also called
not on ordinary home compost heaps or in conventional landfills.
There are various eco-labeling
standards around the world that spell out the difference between home
and industrial composting and the amount of time in which a plastic
must degrade in order to qualify.
If you're in the habit of reading what supermarkets print on their
plastic bags, you may have noticed a lot of environmentally friendly
statements appearing over the last few years. Some stores now use what
are described as photodegradable, oxydegradable
(also called oxodegradable or PAC, Pro-oxidant Additive Containing, plastic), or just biodegradable bags (in practice, whatever they're called, it often
means the same thing). As the name suggests, these biodegradable
plastics contain additives that cause them to decay more rapidly in the
presence of light and oxygen (moisture and heat help too). Unlike
bioplastics, biodegradable plastics are made of normal (petrochemical)
plastics and don't always break down into harmless substances:
sometimes they leave behind a toxic residue and that makes them
generally (but not always) unsuitable for composting.
Photo: A typical message on a biodegradable bag. This one, made
from Eco Film™, is compostable too.
Biodegradable bags sound great, but they're not without their problems. In 2014, for example, some members
of the European Parliament tried hard to bring about a complete ban on oxydegradable plastics in the EU,
with growing doubts over their environmental benefits. Although that proposal was blocked, it lead to more detailed
studies of oxydegradable plastics, apparently confirming that they can't be effectively composted or anaerobically
digested and don't usually break down in landfills. In the oceans, the water is usually too cold to break down
biodegradable plastics, so they either float forever on the surface (just like conventional plastics) or, if they do break down, produce tiny plastic fragments that are harmful to marine life.
One neat solution to the problem of plastic disposal is to recycle
old plastic materials (like used milk bottles) into new ones (such as
items of clothing). A product called ecoplastic is sold as a
replacement for wood for use in outdoor garden furniture and fence
posts. Made from high-molecular polyethylene, the manufacturers boast
that it's long-lasting, attractive, relatively cheap, and nice to look
Photo: This "wooden" public bench looks much like any other until you look at the grain really closely. Then you can see the wood is actually recycled plastic. The surface texture is convincing, but the giveaway is the ends of the "planks," which don't look anything like the grain of wood.
But there are two problems with recycled plastics. First, plastic that's recycled
is generally not used to make the same items the next time around: old recycled plastic
bottles don't go to make new plastic bottles, but lower-grade items such as
plastic benches and fence posts. Second, you can't automatically assume recycled plastics are better for the
environment unless you know they've been made with a net saving of energy and water, a net reduction in greenhouse gas emissions, or some
other overall benefit to the environment. Keeping waste out of a landfill and turning it into new things is great,
but what if it takes a huge amount of energy to collect and recycle the plastic—more even than making brand new plastic
Are bioplastics good or bad?
Photo: A home-compostable bioplastic bag, made from potato starch, and used for mailing out magazines.
Anything that helps humankind solve the plastics problem has to be a
good thing, right? Unfortunately, environmental issues are never quite
so simple. Actions that seem to help the planet in obvious ways
sometimes have major drawbacks and can do damage in other ways. It's
important to see things in the round to understand whether
"environmentally friendly" things are really doing more harm than good.
Bioplastics and biodegradable plastics have long been
controversial. Manufacturers like to portray them as a magic-bullet
solution to the problem of plastics that won't go away. Bioplastics,
for example, are touted as saving 30–80 percent of the
greenhouse gas emissions you'd
get from normal plastics and they can give food longer shelf-life in
stores. But here are some of the drawbacks:
- When some biodegradable plastics decompose in landfills, they
produce methane gas. This is a very powerful greenhouse gas that adds
to the problem of global warming.
- Biodegradable plastics and bioplastics don't always readily
decompose. Some need exposure to UV (ultraviolet) light or relatively high temperatures and, in some
conditions, can still take many years to break down. Even then, they
may leave behind micro-fragments or toxic residues.
- Bioplastics are made from plants such as corn and maize, so land
that could be used to grow food for the world is being used to "grow
plastic" instead. By 2010, about a quarter of US grain production
had been turned over to biofuels and bioplastics production;
taking more agricultural land out of production could cause a significant rise in food prices
that would hit poorest people hardest.
- Growing crops to make bioplastics comes with the usual
environmental impacts of intensive agriculture, including
greenhouse emissions from the petroleum needed to fuel farm machinery,
and water pollution caused by runoff
from land where fertilizers are used in industrial quantities.
In some cases, these indirect impacts from "growing" bioplastics are
greater than if we simply made plastics from petroleum in the first place.
- Some bioplastics, such as PLA, are made from genetically modified
corn. Some environmentalists
consider GM (genetically modified) crops to be inherently harmful to the environment,
though others disagree.
- Bioplastics and biodegradable plastics cannot be easily recycled.
To most people, PLA looks very similar to PET (polyethylene
terephthalate) but, if the two are mixed up in a recycling bin, the
whole collection becomes impossible to recycle. There are fears that
increasing use of PLA may undermine existing efforts to recycle
- Many people think terms like "bioplastic," "biodegradable," and "compostable" mean
exactly the same thing. But there's a huge difference between a "biodegradable" plastic
(one that might take decades or centuries to break down) and a truly "compostable" material
(something that turns almost entirely into benign waste after a matter of months in a composter),
while "bioplastic," as we've already seen, can also mean different things. Confusing jargon hampers public understanding, which makes it harder for consumers to grasp the issues and make positive choices when they shop.
Given all these problems, it's well worth asking whether there are better ways of reducing the impact of traditional plastics than switching over to bioplastics. The 2017 study by Daniel Posen et al (mentioned above) found that switching all US plastics
to PLA would reduce greenhouse emissions by 25 percent, which sounds great. However, the same study calculated
switching traditional plastics production to using renewable energy would reduce emissions by 50–75 percent,
concluding that was a better short-term strategy.
How to cut down on plastics
Why is life never simple? If you're keen on helping the planet,
complications like this sound completely exasperating. But don't let
that put you off. As many environmental campaigners point out, there
are some very simple solutions to the plastics problem that everyone
can bear in mind to make a real difference. Instead of simply sending
your plastics waste for recycling, remember the saying "Reduce, repair,
reuse, recycle". Recycling, though valuable, is only slightly better
than throwing something away: you still have to use energy and water to
recycle things and you probably create toxic waste products as well.
It's far better to reduce our need for plastics in the first place than
to have to dispose of them afterwards.
Photo: Recycling only works if it's economically viable. You can help create a market for recycled products by actively choosing them over alternatives. This Bic Evolution pencil, for example, is made from 57 percent recycled plastic, which is a mixture of pre-consumer waste (a waste product from another industry) and post-consumer waste (recycled household and office material).
You can make a positive
difference by actively cutting down on the plastics you use. For
- Get a reusable cotton bag and take that with you ever time you go
- Buy your fruit and vegetables loose, avoiding the extra plastic
on pre-packaged items.
- Use long-lasting items (such as razors and refillable pens)
rather than disposable ones. It can work out far cheaper in the long
- If you break something, can you repair it simply and carry on
using it? Do you really have to buy a new one?
- Can you give unwanted plastic items a new lease of life? Ice
cream tubs make great storage containers; vending machine cups can be
turned into plant pots; and you can use old plastic supermarket
bags for holding your litter.
- When you do have to buy new things, why not buy ones made from
recycled materials? By helping to create a market for recycled
products, you encourage more manufacturers to recycle.
One day, we may have perfect plastics that break down in a trice.
Until then, let's be smarter about how we use plastics and how we get
rid of them when we've finished with them.