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Cheese comes in wedges. So do pie and pizza. But a wedge of carbon?
That’s the unit of measurement being used at the Carbon Mitigation
Initiative (CMI), a joint project of Princeton University, BP, and the
Ford Motor Co. In recent articles in Science
and Scientific
American, CMI’s co-directors Stephen Pacala and Robert Socolow
introduced the wedge concept to focus discussion on one of the most
important global problems facing humanity today—the rising greenhouse-gas
emissions that are leading to global climate change.
The authors project that, if we continue on our current course for the
next 50 years, atmospheric carbon dioxide (CO2 ) will reach a level that’s double the
pre-industrial level. Although scientists are still working out the exact
implications of a doubling—from warmer average temperatures and
increasingly severe weather patterns to rising sea levels and shrinking
ecosystems—the evidence is mounting that the changes could be both
dramatic and disastrous. For an introduction to the issues, I recommend
that you watch Al Gore’s 2006 documentary, An Inconvenient Truth.
Can we prevent this doubling? What will it take in terms of new
technology and economic restructuring? In terms of lifestyle changes and
shifts in public opinion? In terms of international cooperation and
political will? These are huge and complex questions, and the
all-too-human temptation is to postpone action, while pointing
optimistically to a revolutionary solution in the distant future.
The Pacala and Socolow articles, however,
offer an alternative, arguing that “a portfolio of technologies now
exists to meet the world’s energy needs over the next 50 years and limit
atmospheric carbon dioxide to a trajectory that avoids a doubling of the pre-industrial
concentration.” As summarized in their graphs we can prevent this
doubling, beginning right now, by implementing mitigation technologies
that will keep carbon out of the atmosphere.
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What’s a “Wedge”?
To represent the cumulative impact of these mitigation technologies,
the authors introduce the concept of a “stabilization triangle” with
seven “stabilization wedges.” According to their definition, “a wedge
represents an activity that reduces emissions to the atmosphere that
starts at zero today and increases linearly until it accounts for 1
GtC/year [gigaton of carbon per year] of reduced carbon emissions in 50
years. It thus represents a cumulative total of 25 GtC of reduced emissions
over 50 years.”
According to Sally Benson, the carbon sequestration program leader at
Lawrence Berkeley National Laboratory, the Pacala–Socolow approach
provides an “extraordinarily useful framework.” Benson says, “Up until
the time that it was published, lots of people viewed that there were
going to be one or two technologies that would really make the big
difference. The very valuable thing that they did was say, ‘No, it’s
going to be a whole suite of things, and every one of them is going to be
challenging. Therefore, we’d better make sure that we’re investing and
keeping open the possibilities across the board.’”
Follow the Carbon Atom
If a whole portfolio of technologies will be required to mitigate the
carbon-emission problem, will chemistry and chemists play a role in any
of those technologies? “Frankly, I can’t imagine a discipline that’s more
central to this problem than chemistry,” says Socolow. “For me, the way
to think about this problem is to follow the carbon atom. Wasn’t it Deep
Throat in All the President’s Men who told Woodward and
Bernstein to ‘follow the money’? Well, if you’re following the carbon
atom, you’re doing chemistry, whether it’s geochemistry or other kinds of
chemistry.”
To calibrate the objectivity of this statement about the critical role
of chemistry, it’s helpful to know that Socolow is not a chemist. He
received his Ph.D. in theoretical high-energy physics at Harvard, and his
faculty position at Princeton is in the department of mechanical and
aerospace engineering.
The Pacala–Socolow approach lists 15 technologies that could each
provide at least one of the seven stabilization wedges. Examples include
(among others): solar electricity; nuclear electricity; biofuels; carbon
capture and storage; and increased energy efficiency in the areas of
transportation, heating, or electricity. The CMI Web site provides details about
each of the 15 technologies.
All these technologies bring with them a series of technological
challenges, economic implications, social changes, and political issues.
Choosing among the alternatives to find a set of seven technologies,
while balancing all these factors, will involve every sector of our
society, not just scientists and engineers. To illustrate the sort of
public debate that will be necessary, the CMI Web site offers materials
for a team-based “stabilization wedge game” that drives home the scale of
the carbon mitigation challenge and the tradeoffs involved in planning
climate policy.
Show Me the Chemistry
Looking through the list of potential mitigation technologies, a
chemist can easily see that chemistry is indeed the central science for
this issue. Many of the most active areas of chemistry research and
development today are, in fact, addressing these needs.
Here are just three examples of how chemistry can help solve the
greenhouse-gas problem:
- Green chemistry. Although “green
chemistry” isn’t listed as one of the mitigation technologies, it’s
an enabling science and technology for many of the listed
technologies. Through its 12 guiding principles (see http://chemistry.org/greenchemistryinstitute),
green chemistry emphasizes atom economy, energy efficiency, and
renewable feedstocks. Its environmental and economic benefits often
include reduced emissions of greenhouse gases such as organic
solvents and CO2
.
- Biofuels. As discussed in the Winter
2007 issue of Chemistry, biodiesel and cellulosic ethanol from
biomass can offer significant mitigation of CO2 emissions. It’s important
to note that today’s most common biofuel—alcohol derived from corn
grain—doesn’t offer as large a reduction of greenhouse-gas emissions
as will newer technologies under development.
- Carbon capture and
storage.
Also called “carbon sequestration,” this approach involves capturing
CO2 while generating energy
at coal–electric or natural-gas power plants and then injecting and
storing it permanently underground. Benson says, “The level of
interest and engagement in this area has increased dramatically over
the past five years. You go to a conference now, and you see that
half of the people there are new to the community.” In 2003, the
U.S. Department of Energy established seven regional
carbon-sequestration partnerships to foster cooperation among industry,
academe, and the Federal government. The goal of the partnerships is
to determine the most suitable technologies, regulations, and
infrastructure needs for carbon capture and storage in different
areas of the country.
The Invisible Wedge—Educating the Public
Although an increasing number of chemists will be directly involved in
research and innovation for carbon-mitigation technologies, most will
continue working in other important areas of chemical research, from
biotechnology to nanotechnology, from the chemistry classroom to the
pharmaceutical laboratory. Does this mean that most chemists don’t really
have a role to play in carbon mitigation?
Absolutely not! One of the most important needs today is for an
improved public understanding of basic chemistry concepts. Although
“public understanding” is not directly listed by Pacala and Socolow as a
carbon-mitigation technology, none of the listed technologies can succeed
without it.
Benson points out that the general public is hearing and reading more
and more every day about global warming and greenhouse gases. However,
she says, “I think there’s still a long way to go to increase general
knowledge about the basic scientific issues and what we’ll need to do to
remedy the situation.” For example, how many members of the general
public know what it means to be “carbon-neutral” or understand the
difference between carbon and CO2
?
Socolow, who has extensive interactions with journalists and the public,
says, “One of the problems with this field is that some people are
talking about costs per ton of carbon and others are talking about costs
per ton of CO2 . It’s the
most common mistake that journalists make.”
If the distinction between these units isn’t understood, the
calculations and estimates quickly become confusing. “The conversation
becomes hopeless in about five minutes,” says Socolow. “This is a job for
high school and college chemistry teachers.”
The subject of carbon mitigation offers a wealth of good examples for
teaching chemistry at all levels, from middle school to graduate school.
Examples include pH and buffering (the interaction of CO2 , carbonic acid, the ocean, and
the global carbon cycle), spectroscopy (the interaction of various
greenhouse gases and infrared radiation), and states of matter (CO2 injected and stored underground is
“supercritical”).
Chemistry—the Central Science
Near the end of An Inconvenient Truth, after he presents the
evidence that global warming is indeed occurring, Gore says, “If we
accept that this problem is real, maybe it’s just too big to do anything
about. There are a lot of people who go straight from denial to despair,
without pausing on the intermediate step of doing something about the
problem.” At this point in the film, Gore introduces the Pacala–Socolow
strategy, saying, “We already know everything we need to know to
effectively address this problem. We’ve got to do a lot of things, not
just one.”
Gore’s words are directed at an audience of the general public, but
his words are especially relevant for us chemists. We occupy a central
place in the sciences, and we can also occupy a central place in that
space “between denial and despair.” We have the knowledge to do something
about the problem, either by working directly on carbon-mitigation
technologies or by helping the public understand the underlying
chemistry.
So, what are you waiting for? Pick a wedge and get to work.
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