| Dear
EarthTalk: What are the environmental pros
and cons of corn-based plastic as an alternative to conventional
petroleum-based plastic?
-- Laura McInnes, Glasgow, Scotland
| |
A
cup made from PLA, plastic made from cornstarch.
© Bec, courtesy Flickr |
Polylactic
acid (PLA), a plastic substitute made from fermented plant
starch (usually corn) is quickly becoming a popular alternative
to traditional petroleum-based plastics. As more and more
countries and states follow the lead of China, Ireland,
South Africa, Uganda and San Francisco in banning plastic
grocery bags responsible for so much so-called “white
pollution” around the world, PLA is poised to play
a big role as a viable, biodegradable replacement.
Proponents
also tout the use of PLA—which is technically “carbon
neutral” in that it comes from renewable, carbon-absorbing
plants—as yet another way to reduce our emissions
of greenhouse gases in a quickly warming world. PLA also
will not emit toxic fumes when incinerated.
But
critics say that PLA is far from a panacea for dealing with
the world’s plastic waste problem. For one, although
it does biodegrade, it does so very slowly. According to
Elizabeth Royte, writing in Smithsonian, PLA may well break
down into its constituent parts (carbon dioxide and water)
within three months in a “controlled composting environment,”
that is, an industrial composting facility heated to 140
degrees Fahrenheit and fed a steady diet of digestive microbes.
But it will take far longer in a compost bin or in a landfill
packed so tightly that no light and little oxygen are available
to assist in the process. Indeed, analysts estimate that
a PLA bottle could take anywhere from 100 to 1,000 years
to decompose in a landfill.
Another
issue with PLA is that, because it is of different origin
than regular plastic, it must be kept separate when recycled,
lest it contaminate the recycling stream. Being plant-based,
PLA needs to head to a composing facility, not a recycling
facility, per se, when it has out served its usefulness.
And that points to another problem: There are presently
only 113 industrial-grade composting facilities across the
U.S.
Another
downside of PLA is that it is typically made from genetically
modified corn, at least in the U.S. The largest producer
of PLA in the world is NatureWorks, a subsidiary of Cargill,
which is the world’s largest provider of genetically
modified corn seed. With increasing demand for corn to make
ethanol fuel let alone PLA, it’s no wonder that Cargill
and others have been tampering with genes to produce higher
yields. But the future costs to the environment and human
health of genetic modification are still largely unknown
and could be very high.
While
PLA has promise as an alternative to conventional plastic
once the means of disposal are worked out, grocery shoppers
could do well to by simply switch to reusable containers,
from cloth bags, baskets and backpacks for grocery shopping
(most chains now sell canvas bags for less than a dollar
apiece) to safe, reusable (non-plastic) bottles for beverages.
As for other types of PLA items—such as those plastic
“clamshells” that hold cut fruit (and there
is a whole host of industrial and medical products now made
from PLA)—there is no reason to pass them by. But
until the kinks are worked out on the disposal and reprocessing
end, PLA may not be much better than the plain old plastic
it’s designed to make obsolete.
CONTACTS:
Smithsonian’s
“Corn Plastic to the Rescue”; NatureWorks
Dear
EarthTalk: How is it that hydrogen can replace
oil to run our cars? There seems to be a lot of controversy
over whether hydrogen can really be generated and stored
in such a way to be practical?
-- Stephane Kuziora, Thunder Bay, ON
| |
Nissan's
hydrogen-fueled X-TRAIL FCV fuel cell vehicle.
© Donbraco, courtesy Flickr |
The jury is still
out on whether hydrogen will ultimately be our environmental
savior, replacing the fossil fuels responsible for global
warming and various nagging forms of pollution. Two main
hurdles stand in the way of mass production and widespread
consumer adoption of hydrogen “fuel cell” vehicles:
the still high cost of producing fuel cells, and the lack
of a hydrogen refueling network.
Reining in manufacturing
costs of fuel cell vehicles is the first major issue the
automakers are addressing. While several have fuel cell
prototype vehicles on the road—Toyota and Honda are
even leasing them to the public in Japan and California—they
are spending upwards of $1 million to produce each one due
to the advanced technology involved and low production runs.
Toyota hopes to reduce its costs per fuel cell vehicle to
around $50,000 by 2015, which would make such cars economically
viable in the marketplace. On this side of the Pacific,
General Motors plans to sell hydrogen-powered vehicles in
the U.S. by 2010.
Another problem
is the lack of hydrogen refueling stations. Major oil companies
have been loathe to set up hydrogen tanks at existing gas
stations for many reasons ranging from safety to cost to
lack of demand. But obviously the oil companies are also
trying to keep customers interested in their highly profitable
bread-and-butter, gasoline. A more likely scenario is what
is emerging in California, where some 38 independent hydrogen
fuel stations are located around the state as part of a
network created by the non-profit California Fuel Cell Partnership,
a consortium of automakers, state and federal agencies and
other parties interested in furthering hydrogen fuel cell
technologies.
The benefits
of ditching fossil fuels for hydrogen are many, or course.
Burning fossil fuels like coal, natural gas and oil to heat
and cool our buildings and run our vehicles takes a heavy
toll on the environment, contributing significantly to both
local problems like elevated particulate levels and global
ones like a warming climate. The only by-product of running
a hydrogen-powered fuel cell is oxygen and a trickle of
water, neither of which will cause any harm to human health
or the environment.
But right now
95 percent of the hydrogen available in the U.S. is either
extracted from fossil fuels or made using electrolytic processes
powered by fossil fuels, thus negating any real emissions
savings or reduction in fossil fuel usage. Only if renewable
energy sources—solar, wind and others—can be
harnessed to provide the energy to process hydrogen fuel
can the dream of a truly clean hydrogen fuel be realized.
Stanford University
researchers in 2005 assessed the environmental effects of
three different hydrogen sources: coal, natural gas, and
water electrolysis powered by wind. They concluded that
we’d lower greenhouse gas emissions more by driving
gasoline/electric hybrid cars than by driving fuel cell
cars run on hydrogen from coal. Hydrogen made using natural
gas would fare a little bit better in terms of pollution
output, while making it from wind power would a slam-dunk
for the environment.
CONTACT:
California
Fuel Cell Partnership |
