There's a Problem With Plastic:
Are Bioplastics the Solution?
By Sarah (Steve) Mosko
Bioplastics are simply defined as plastics derived from renewable biomass
sources, like plants and microorganisms, whereas conventional plastics are
synthesized from non-renewable fossil fuels, either petroleum, or natural gas.
However, there is a common misconception that a bioplastic necessarily breaks
down better in the environment than conventional plastics. Bioplastics are
marketed as being better for the environment than regular, petroleum-based
plastics, but how do they really compare?
The Problems with Petroleum-Based Plastics
The push to develop bioplastics emerges from alarming realities starting
with the staggering quantity of plastics being manufactured. Globally, over
four hundred and fifty billion pounds of plastic were consumed in 2011
alone. That averages out to about sixty-five pounds per person, al- though
consumption varies great- ly by region, with North America consuming the
most and Africa the least.
Conventional plastics do not biodegrade within any
meaningful human timescale – they just break apart into smaller plastic
fragments. Also, the overall recycling rates for plastics remain fairly low
– eight percent in the United States and twenty-four percent in the European
Union in 2010, for example – in large part because plastic products contain
unique proprietary blends of additives that prevent recycling of mixed
batches of products back into the original products.
So, unlike glass and aluminum, which can be recycled in a closed loop, most plastics recycling is
considered “down-cycling” into lower quality, hybrid-plastic end-products,
like lumber or clothing, which aren’t recycled again. This means that,
except for the fraction of plastic that is combusted for energy production,
all plastics eventually end up as trash, either in landfills or as litter.
Petroleum and natural gas are actually organic substances, but why plastics
synthesized from them do not biodegrade is straightforward: The
exceptionally strong carbon-carbon bonds created to form the backbone of
plastic polymers do not occur naturally in Nature so are foreign to
microorganisms which readily eat up other organic materials.
Molecules of conventional plastic are also gigantic, making them extra
difficult to digest. Each is composed of literally thousands of repeating
units called “monomers” so that the weight of a finished polymer molecule is
typically over ten thousand (for comparison, the weight of a single water
molecule is eighteen). The simplest is polyethylene (e.g., grocery bags,
ketchup and shampoo bottles), which is just an enormous string of carbon
atoms with attached hydrogen atoms.
In the so-called “North Pacific Garbage Patch” between California and Japan,
an ocean area twice the size of the United States, the ratio of the weight
of plastic debris to zooplankton has risen to thirty-six to one, a six-fold
increase in a single decade. This area is the most studied of the world’s
five major oceanic gyres, which are massive, slowly rotating whirlpool
currents that sweep up and accumulate plastic debris.
The non-profit Algalita Marine Research Institute in California has been
measuring how plastics are collecting in the North Pacific gyre since the
late 1990s. Less is yet known about the amassing of plastics in the other
major gyres – located in the South Pacific, North and South Atlantic, and
Indian Oceans – although there is little reason to suspect that the picture
would be much rosier elsewhere.
This buildup of plastics in the marine environment is worrisome. Creatures
as varied as sandworms, barnacles, krill, jellyfish, birds, turtles, and
whales are known to ingest plastic debris, which can block digestive tracts,
while many forms of sea life die instead from entanglement.
Furthermore, ingested plastics are a vehicle for transfer of toxins in
seawater into the food web. We know from Japanese researchers that the oily
nature of plastics allows them to concentrate oily toxins (like
polychlorinated biphenyls, nonylphenols, and derivatives of DDT) from
seawater onto their surfaces. Food web contamination from potentially risky
chemicals added to plastics during their manufacture is a parallel concern
(e.g. Bisphenol-A, phthalates, and nonylphenols).
Nevertheless, international standards have been established by two
bodies: ASTM International (formerly American Society for Testing and
Materials) and the Switzerland-based International Organization for
Standardization (ISO). Despite the confusion this fragmentation generates,
there is consensus on the distinctions among the key terms degradable,
biodegradable, and compostable.
Degradable simply means that chemical changes takes place, maybe from
sunlight or heat, that alter a plastic’s structure and properties, such as
clouding or fragmenting. Biodegradable more narrowly denotes that the
degradation results from naturally-occurring microorganisms (bacteria,
fungi, or algae) but makes no guarantee that the degradation products are
non-toxic or make good compost. Compostable goes a step further: ASTM’s
definition, for example, specifies that the microorganisms’ breakdown
products must yield “CO2, water, inorganic compounds, and biomass at a rate
consistent with other known compostable materials and leave no visible,
distinguishable, or toxic residue,” such as heavy metals.
Plastics can potentially be designed to meet any standard(s) set by ASTM
or ISO for breakdown in either aerobic environments, like water or soil, or
in anaerobic ones (lacking oxygen) like enclosed wastewater treatment
systems. The sealed-off environment within conventional landfills, however,
is not amenable to biodegradation of any materials, so there is little
interest in developing analogous standards for landfills.
Plastics manufacturers submit finished products to independent testing
organizations, which then certify whether they meet standards for
biodegradable or compostable in given environments.
The Biodegradable Products Institute in New York (BPI) offers a single
certification, guaranteeing compostability (as defined by ASTM) in an
industrial composter where conditions like temperature and humidity are
tightly controlled. However, the significance of this certification is
diminished in countries like the United States which have very few
industrial composting facilities nationwide.
In Europe, where development of an infrastructure for composting is
further along, the organization Vinçotte offers not only certification for
industrial compostable but also for home compostable, biodegradable in
agricultural soil, and biodegradable in fresh water.
There is currently only one established standard for biodegradation of
plastics in the marine environment. Basically, it requires that, within six
months, the plastic must be disintegrated into bits smaller than two
millimeters and that biodegra- dation must have progressed so that at least
thirty percent of the carbon has been converted by microorganisms into
carbon dioxide (ASTM D7081).
Neither BPI nor Vinçotte yet offer certification for this, so any company
making this claim would be basing it on their own testing.
Bioplastics on the Market Today
The following compares the certifications and other environmental merits
of some contemporary bioplastics grouped according to the source material
(i.e. feedstock). Although starch and cellulose are actually biopolymers
found in the natural world that can be converted into plastics (like packing
peanuts that dissolve in water), I’ll limit the following discussion to
biopolymers synthesized by microorganisms in industrial settings because
they represent the frontier of bioplastics and can be processed on the same
equipment as conventional plastics.
Be mindful that you can’t rely on the internationally-recognized numbered
chasing arrows system to identify bioplastics. Nearly all bioplastics fall
under the “#7 OTHER” label which is a catchall for plastics not made of the
conventional resin types, which are labeled #1 through #6.
Corn: Just one company worldwide claims to make bioplastics that meet
ASTM’s marine biodegradable standard, and that’s Metabolix, based in
Massachusetts. Polyhydroxyalkanoates (PHAs) are biodegradable monomers, naturally made by
bacteria during fermentation of sugar, which can be combined to make high
molecular weight polymers suitable for plastics. Metabolix is using bacteria genetically altered to produce high yields of PHAs from
the sugar in corn kernels. The resulting biopolymer, called Mirel™, is pure
PHAs except for proprietary additives mixed in to impart desired properties.
According to company spokesperson Lynne Brum, the additives do not include
Bisphenol-A, phthalates, or nonylphenols, which have been linked to health
problems in lab animals and humans.
Various Mirel™ resins are available for fashioning into many typically
disposable items, such as eating utensils, food storage tubs, jars, and
lids. All are certified for industrial composting, and some are also
certified for home composting and/or biodegradation in agricultural soil or
However, only the thinnest film grades of Mirel™, appropriate for making
carryout bags, yard waste/kitchen compost bags, and agricultural film,
supposedly meet marine biodegradable standards because greater material
thickness would impede biodegradation.
As is true of conventional plastics and organic materials in general, Mirel™
will not biodegrade in landfills. Brum stated that although closed-loop
recycling of Mirel™ is certainly possible, the company’s focus thus far has
been on biodegradation as an end-of-life option.
Polylactic acid (PLA) is a different biopolymer derived from corn through
fermentation by bacteria that naturally produce lactic acid, which is then
tweaked to form polymers. The primary U.S. manufacturer, NatureWorks LLC,
advertises that its PLA resin family, Ingeo™, relies on no
genetically-modified materials, and uses fifty percent less energy and
produces sixty percent fewer greenhouse gases than petroleum-based polymers.
The range of possible applications is very wide, including clothing, durable
goods like mobile phone casings, credit cards, drink bottles, and all sorts
of food packaging and food service items.
Although Ingeo™ does not biodegrade in any water or soil environments, it
has received certifications for industrial composting. NatureWorks claims
that used Ingeo™ is being recycled in a closed loop into new Ingeo™, but
recycling on a large scale is not yet feasible because Ingeo products lack a
unique identification code and they have to be shipped to the sole recycler
An Italian company, Novamont, is manufacturing a family of biodegradable
resins under the label MATER-BI,® which do not necessarily qualify fully as
bioplastics because unspecified “monomers” derived from “fossil fuels” can
be used in the proprietary blends of ingredients which include cornstarch
plus other renewables, like vegetable oils. Nevertheless, MATER-BI® resins
are certified for industrial composting, and the company claims the
feedstock does not rely on genetically modified crops or deforestation.
MATER-BI® can be made into a myriad of products including doggie poop bags,
mulching film, shopping bags, bubble wrap, pens, and rulers.
Sugarcane: Polyethylene (PE), the most ubiquitous plastic, is made by
polymerizing ethylene synthesized from ethanol derived conventionally from
petroleum, although synthesis of ethanol from plant sources is also
possible. In Brazil, where sugarcane grows abundantly, a company named Braskem is manufacturing ethylene instead from ethanol made from fermented
sugarcane. Braskem touts that its Green Ethylene is one hundred percent
renewable source-based and the resulting “Green PE” resins are at least
eighty-four percent renewable content.
Because Green PE is identical to that produced from petroleum, it can be
made into the very same products and recycled together with conventional PE.
However, this also means it is no more biodegradable than conventional PE in
any environment and poses the same risks to the ocean food web.
Nevertheless, Braskem asserts that Green PE merits its green label on other
grounds, like the fact that growing sugarcane draws carbon dioxide out of
the atmosphere. For every kilogram of Green PE produced, two-and-a-half
kilograms of carbon dioxide are supposedly sequestered in the resin. Also,
fifty percent more ethanol can be fermented from sugarcane than from corn.
Are Plastics Really Convenient?
Single-use, disposable plastics were a direct outgrowth of industries
developed during World War II and quickly became symbolic of the convenience
of modern day living. The supply of fossil fuels felt endless at the time,
and the fact that plastics could be made into just about anything and were
so long-lasting seemed a good thing.
Nowadays, the prospect of mass conversion from conventional plastics to
ones made from renewable sources is raising concerns typically stemming from
the fact that arable land would be diverted to growing feedstock for
bioplastics. These concerns include deforestation, monocultures, fresh water
supplies, soil erosion, food supplies, and food prices.
Bioplastics manufacturers like to point to the fact that the fraction of
global food crops or farm acreage currently used to make bioplastics is
minuscule, sidestepping the obvious question of what the realistic impacts
would be if bioplastics were ever to replace conventional ones on a large
scale. Consider that ethanol gas, for example, is already in competition
with the food supply for available corn.
A research institute in Rotorua, New Zealand called Scion is
experimenting with sewage sludge as an alternative renewable feedstock. The
idea is that, by cooking sewage sludge, reusable substances can be recovered
and converted into bioplastics as well as fertilizers and biofuels. However,
the first pilot plant began operations just a year ago, so it will be a long
while before the feasibility of making any plastics from sewage is known.
Even if the feedstock issues can be resolved, what to do with plastics at
the end of their useful life looms as the far more daunting problem. Plastic
industry experts expect demand for plastics to rise exponentially in the
very near future as emerging markets expand, especially in the Asia-Pacific
region, including in China and India.
As soon as 2015, global plastics consumption will reach almost six hundred
billion pounds, according to a leading market research firm (Global Industry
Analysts, Inc.). Without a drastic reduction in per capita consumption, it’s
virtually impossible to conceptualize the volume of additional plastic waste
there will have been created by mid century when the world’s population is
expected to top nine billion.
Bioplastics designed to biodegrade in industrial composters are no doubt
an important step in reducing the burden placed on landfills, although
widespread municipal composting in less developed countries is, at best, a
pipedream at this point. Furthermore, making plastics compostable does
nothing to prevent the continuing buildup of plastics in the marine
environment. Ocean plastics derive primarily from land-based sources, like
street litter carried via storm drains that empty into rivers flowing into
While the development of marine biodegradable plastics should be
encouraged, it is wishful thinking to assume they will ultimately be the
solution. Marine biodegradable plastics do not just dissolve in seawater.
ASTM’s marine biodegradable standard allows that decomposing plastics can
linger in seawater for many months, ample time to endanger sea life by
ingestion or entanglement. Furthermore, we know nothing yet about how
bioplastics compare to conventional ones as vehicles for transferring oily
toxins in seawater into the food chain.
It’s even conceivable that wide availability of marine biodegradable
plastics would add to the volume of ocean plastics because labeling as
marine biodegradable might encourage dumping at sea, even though any ocean
dumping of plastics has been illegal by international treaty since 1988
(MARPOL Annex V).
Halting the flow of all types of plastics into the ocean is the most
rational solution to the crisis of plastic ocean debris. On a local level,
this simply entails placing secure lids on trash receptacles and
well-designed grates across all storm drains and river mouths that outflow
to the sea. On a societal level, however, this means a deliberate shift away
from the throwaway culture that led to the exponential rise in the
production of plastics in the first place.
After more than a half century of profligate consumption of plastics, we
are face-to-face with the reality that there is nothing convenient about
getting rid of it all and preventing it from trashing our oceans and
contaminating the marine food web.
Sarah (Steve) Mosko is licensed psychologist and sleep
disorders specialist living in Southern California. A background in
neurobiology and medical research enables her to delve into and explain
current scientific research findings which show how our materialistic
society is endangering human health and the environment. Her hope is that
her writings will help empower people to make changes in their personal
lifestyles and in the society at large which are critical to preserving the
environment for future generations of humans and all life forms. A
compendium of her environmental articles is available at