[Paleopsych] Michael Behar: How Earth-Scale Engineering Can Save the Planet
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Fri Jul 15 19:35:41 UTC 2005
Michael Behar: How Earth-Scale Engineering Can Save the Planet
Popular Science, 5.8
Maybe we can have our fossil fuels and burn 'em too. These
scientists have come up with a plan to end global warming. One idea:
A 600,000-square-mile space mirror
David Keith never expected to get a summons from the White House.
But in September 2001, officials with the President's Climate Change
Technology Program invited him and more than two dozen other
scientists to participate in a roundtable discussion
called "Response Options to Rapid or Severe Climate Change." While
administration officials were insisting in public that there was no
firm proof that the planet was warming, they were quietly exploring
potential ways to turn down the heat.
Most of the world's industrialized nations had already vowed to
combat global warming by reining in their emissions of carbon
dioxide, the chief "greenhouse gas" blamed for trapping heat in
Earth's atmosphere. But in March 2001 President George W. Bush had
withdrawn U.S. support for the Kyoto Protocol, the international
treaty mandating limits on CO2 emissions, and asked his
administration to begin studying other options.
Keith, a physicist and economist in the chemical and petroleum
engineering department at the University of Calgary, had for more
than a decade been investigating strategies to curtail global
warming. He and the other scientists at the meeting?including
physicists from Lawrence Livermore National Laboratory who had spent
a chunk of their careers designing nuclear weapons?had come up with
some ideas for "geoengineering" Earth's climate. What they proposed
was tinkering on a global scale. "We already are inadvertently
changing the climate, so why not advertently try to counterbalance
it?" asks retired Lawrence Livermore physicist Michael MacCracken, a
former senior scientist at the U.S. Global Change Research Program
who helped organize the meeting.
"If they had broadcast that meeting live to people in Europe, there
would have been riots," Keith says. "Here were the bomb guys from
Livermore talking about stuff that strikes most greens as being
completely wrong and off-the-wall." But today, a growing number of
physicists, oceanographers and climatologists around the world are
seriously considering technologies for the deliberate manipulation
of Earth's climate. Some advocate planetary air-conditioning devices
such as orbiting space mirrors that deflect sunlight away from
Earth, or ships that intensify cloud cover to block the sun's rays.
Others are suggesting that we capture carbon dioxide?from the air,
from cars and power plants?and stash it underground or react it with
chemicals that turn it to stone.
Carbon dioxide wasn't always public enemy number one. For the past
400,000 years, the concentration of CO2 in the atmosphere has
fluctuated between about 180 and 280 ppm (parts per million, the
number of CO2 molecules per million molecules of air). But in the
late 1800s, when humans set about burning fossil fuels in earnest,
atmospheric CO2 began to increase with alarming speed?from about 280
ppm to the current level of almost 380 ppm, in a scant 100 years.
Experts predict that CO2 could climb as high as 500 ppm by 2050 and
possibly twice that by the end of the century. As CO2 levels
continue to rise, the planet will get hotter. "The question now,"
says Ken Caldeira, an atmospheric scientist at Lawrence Livermore
and one of the world's leading authorities on climate change, "is
what can we actually do about it?" Here are some of the
geoengineering schemes under consideration.
1. Store CO2 Underground
In the southeastern corner of Saskatchewan, just outside the town of
Weyburn?the "Opportunity City"?a steel pipeline descends 4,000 feet
below the prairie at the edge of a 70-square-mile oil field. Into
this subterranean cavern, petroleum engineers are pumping 5,000 tons
of pressurized, liquefied carbon dioxide every day. The aim is
twofold: Use high-pressure CO2 to drive oil from the porous rock in
the reservoir to the surface, and trap the carbon dioxide
Welcome to the world's largest carbon-sequestering operation. Dubbed
the Weyburn Project, it began in July 2000 as a partnership between
EnCana, a Canadian oil and gas company, and Canada's Petroleum
Technology Research Centre. With $13 million in funding from more
than a dozen sponsors, including the U.S. Department of Energy,
engineers have already socked away six million tons of carbon
dioxide, roughly the amount produced by burning half a billion
gallons of gasoline.
Unlike other geoengineering schemes, this one is already happening,
with more than half a dozen major projects under way. The problem,
says Howard Herzog, a principal research engineer at MIT's
Laboratory for Energy and the Environment, is that concentrated CO2
is in short supply. There's too much of the gas floating around in
the air, but actually capturing, compressing, and transporting it
costs money. In the U.S. and most other nations, there are no laws
requiring fossil-fuel-burning power plants?the primary source of CO2
emissions?to capture a single molecule of the gas.
By 2033, the Weyburn Project will store 25 million tons of carbon
dioxide. "That's like taking 6.8 million cars off the road for one
year," says project manager Mike Monea, "and this is just a pilot
test in a small oil reservoir." Saline aquifers, giant pools of
saltwater that have been trapped underground for millions of years,
could hold even more CO2. Humans dump about 28 gigatons of CO2 into
the atmosphere every year. Geologists estimate that underground
reservoirs and saline aquifers could store as much as 200,000
Before CO2 is injected into the ground, it's compressed into what's
called a supercritical state?it's extremely dense and viscous, and
behaves more like a liquid than a gas. In this form, CO2 should
remain trapped underground for thousands of years, if not
indefinitely. The danger is if engineers accidentally "depressurize"
an aquifer while probing for oil or natural gas. There's also a risk
that carbon dioxide could escape slowly through natural fissures in
subterranean rock and pool up in basements or cellars. "If you
walked down into a basement [full of CO2]," Keith says, "you
wouldn't smell it or see it, but it would kill you."
2. Filter CO2 from the air
Klaus Lackner is accustomed to skeptics. They've doubted him since
he first presented his idea for extracting carbon dioxide from
ambient air in March 1999, at an international symposium on coal and
fuel technology. "The reaction from everyone there was utter
disbelief," recalls Lackner, a physicist with the Earth Engineering
Center at Columbia University.
He called for the construction of giant filters that would act like
flypaper, trapping CO2 molecules as they drifted past in the wind.
Sodium hydroxide or calcium hydroxide?chemicals that bind with
carbon dioxide?would be pumped through the porous filters much the
way antifreeze is circulated through a car's radiator. A secondary
process would strip the CO2 from the binding chemical. The chemical
would recirculate through the filter, while the CO2 would be set
aside for disposal.
Lackner is collaborating with engineer Allen Wright, who founded
Global Research Technologies in Tucson, Arizona. Wright is
developing a wind-scrubber prototype but remains tight-lipped about
the project. He estimates that a completed system is at least two
Wind scrubbers can be placed wherever it's convenient to capture
carbon dioxide, so there's no need to transport it. Lackner
calculates that a wind scrubber designed to retain 25 tons of CO2
per year?the average amount each American adds to the atmosphere
annually?would require a device about the size of a large plasma-
screen television. A single industrial-size wind scrubber about 200
feet high and 165 feet wide would snag about 90,000 tons of CO2 a
Some experts are dubious about the ease of separating carbon dioxide
from the binding chemical, a process that in itself would require
energy from fossil fuels. "CO2 is so dilute in the air that to try
to scrub from it, you have to pay too much for energy use," Herzog
says. And to capture all the carbon dioxide being added to the
atmosphere by humans, you'd need to blanket an area at least the
size of Arizona with scrubber towers.
3.Fertilize the ocean
On January 5, 2002, Revelle, a research vessel operated by the
Scripps Institution of Oceanography, left New Zealand for the
Southern Ocean?a belt of frigid, stormy seas that separates
Antarctica from the rest of the world. There the scientists dumped
almost 6,000 pounds of iron powder overboard and unleashed an armada
of instruments to gauge the results.
The intent was to test a hypothesis put forth by oceanographer John
Martin. At a lecture more than a decade ago, Martin declared: "Give
me a half-tanker of iron, and I will give you an ice age." He was
alluding to the fact that the Southern Ocean is packed with minerals
and nutrients but strangely devoid of sea life. Martin had concluded
that the ocean was anemic?containing very little iron, an essential
nutrient for plankton growth. Adding iron, Martin believed, would
cool the planet by triggering blooms of CO2-consuming plankton.
Oceanographer Kenneth Coale, who directs the Moss Landing Marine
Laboratories near Monterey, California, was a chief scientist on the
Southern Ocean cruise. He says the project was a success, proving
that relatively small quantities of iron could spawn colossal blooms
Scientists are wary, saying that too little is known about the deep-
ocean environment to endorse further large-scale experiments. In
October, Coale and other scientists will gather in New Zealand for a
weeklong meeting sponsored by the National Science Foundation, New
Zealand's National Institute for Water and Atmosphere, and the
International Geosphere-Biosphere Programme to decide how to proceed.
Iron fertilization is by far the cheapest and easiest way to
mitigate carbon dioxide. Coale estimates that just one pound of iron
could conceivably hatch enough plankton to sequester 100,000 pounds
of CO2. "Even if the process is only 1 percent efficient, you just
sequestered half a ton of carbon for a dime."
"What is still a mystery," Coale says, "is the ripple effect on the
rest of the ocean and the food chain." One fear is that huge
plankton blooms, in addition to gorging on CO2, will devour other
nutrients. Deep currents carry nutrient-rich water from the Southern
Ocean northward to regions where fish rely on the nutrients to
survive. Says Coale, "A fertilization event to take care of
atmospheric CO2 could have the unintended consequence of turning the
oceans sterile. Oops."
4. Turn CO2 to Stone
The Grand Canyon is one of the largest carbon dioxide repositories
on Earth. Hundreds of millions of years ago, a vast sea covered the
land there. The water, rich in carbon dioxide, slowly reacted with
other chemicals to create calcium carbonate, or limestone?the
pinkish bands striping the canyon walls today.
Nature's method for turning CO2 to stone is achingly slow, but
researchers at the Goldwater Materials Science Laboratory at Arizona
State University are working on a way to speed up the process.
Michael McKelvy and Andrew Chizmeshya use serpentine or olivine,
widely available and inexpensive minerals, as feedstock to fuel a
chemical reaction that transforms CO2 into magnesium carbonate, a
cousin of limestone. To initiate the reaction?known as "mineral
carbonation"?the CO2 is compressed, heated, and mixed with feedstock
and a catalyst, such as sodium bicarbonate (baking soda).
Scaling up the process to handle millions of tons of CO2 would
require huge quantities of serpentine or olivine. A single mineral-
carbonation plant would carve out a mountain, but, McKelvy
says, "You could carbonate [the CO2] and put it right back where the
feedstock came from."
Mineral carbonation is simply an accelerated version of a benign
natural process. The limestone in the Grand Canyon is 500 feet
thick, McKelvy says, "and it has been sitting there not bothering
anybody for millennia."
It costs roughly $70 to eliminate one ton of CO2, a price that
McKelvy says is too high. Also, the feedstock and CO2 must be heated
to high temperatures. "You wind up having to burn fossil fuels in
order to provide the energy to activate the mineral to put away the
CO2," he says.
5. Enhance Clouds to Reflect Sunlight
Some proposed solutions to global warming don't involve capturing
carbon dioxide. Instead they focus on turning down the heat by
deflecting or filtering incoming sunlight.
On any given day, marine stratocumulus clouds blanket about one
third of the world's oceans, mostly around the tropics. Clouds form
when water vapor clings to dust or other particles, creating
droplets. Seeding clouds with tiny salt particles would enable more
droplets to form?making the clouds whiter and therefore more
reflective. According to physicist John Latham, a senior research
associate at the National Center for Atmospheric Research in
Boulder, Colorado, boosting reflectivity, or albedo, in just 3
percent of marine stratocumulus clouds would reflect enough sunlight
to curb global warming. "It would be like a mirror for incoming
solar radiation," Latham explains.
Latham is collaborating with Stephen Salter, an emeritus professor
of engineering design at the University of Edinburgh, who is making
sketches for GPS-steered wind- powered boats that would cruise the
tropical latitudes, churning up salt spray. "I am planning a
flotilla of unmanned yachts sailing backward and forward across the
wind," Salter says. "They would drag propellers through the water to
generate electricity, which we'd use to make the spray."
Salter wants to outfit each boat with four 60-foot-tall Flettner
rotors, which look like smokestacks but act like sails. An electric
motor starts each rotor spinning, which, along with the wind,
creates a pressure differential (less pressure in front of the
rotor, more in back), generating forward thrust. From the top of the
rotor, an impeller would blast a fine saltwater mist into the air.
Until the concept is tested, Salter isn't sure exactly how many
ships would be needed to mitigate global warming. "Maybe between
5,000 and 30,000," he says. That may sound like a lot, but Salter
notes that for World War II, the U.S. built nearly 100,000 aircraft
in 1944 alone.
Latham initially raised the notion in a 1990 paper. "The article
went down like a lead balloon," he says. But early last year in
England, at a geoengineering conference hosted by MIT and the
Tyndall Centre for Climate Change Research, he presented the concept
again. "The consensus was that a number of ideas originally thought
to be outlandish were deemed sufficiently plausible to be supported
further. Our work fell into that category." Latham needs a few
million dollars to test his idea. "On the scale of the damage that
will be caused by global warming, that is utterly peanuts."
What's nice about this idea is that it can easily be fine-tuned. "If
we tried it and there was some deleterious effect, we could switch
it off, and within four or five days all evidence would have
disappeared," Latham says.
One worry is that although the tiny salt particles released by
evaporating sea mist are perfect for marine stratocumulus-cloud
formation, they are too small to create rain clouds. "You might make
it harder for rain to form," Salter says. "Therefore, you would not
want to do this upwind of a place where there is a bad drought."
6. Deflect Sunlight With A Mirror
One of the most ambitious schemes is a giant space "mirror"
positioned between the Earth and sun to intercept sunlight. To build
the mirror, physicist Lowell Wood, a senior staff scientist at
Lawrence Livermore, proposes using a mesh of aluminum threads that
are only a millionth of an inch in diameter and a thousandth of an
inch apart. "It would be like a window screen made of exceedingly
fine metal wire," he explains. The screen wouldn't actually block
the light but would simply filter it so that some of the incoming
infrared radiation wouldn't reach Earth's atmosphere.
Wood, who has been researching the mirror idea for more than a
decade, says it should be considered only as a safety net if all
other means of reversing global warming "fail or fall grossly short
over the next few decades."
Once in place, the mirror would cost almost nothing to operate. From
Earth, it would look like a tiny black spot on the sun. "People
really wouldn't see it," says Michael MacCracken. And plant
photosynthesis isn't expected to be affected by the slight reduction
Wood calculates that deflecting 1 percent of incoming solar
radiation would stabilize the climate, but doing so would require a
mirror spanning roughly 600,000 square miles?or several smaller
ones. Putting something that size in orbit would be a massive
challenge, not to mention exorbitantly expensive.
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