The Blue Food Revolution

Reinventing the Leaf

ScientificAmerican.com How Much is Left?

Special for Earth Day ™ Scientific American, Inc. in brief Meat consumption is rising worldwide, but production in­ volves vast amounts of energy, water and emissions. At the same time, wild fisheries are declining. Aquaculture could become the most sustainable source of protein for humans. Fish farming already accounts for half of global seafood pro­ duction. Most of it is done along coastlines, which creates sub­ stantial water pollution. Large, offshore pens that are anchored to the sea­floor are often cleaner. Those farms, other new forms of aquacul­ ture, and practices that clean up coastal operations could ex­ pand aquaculture significantly. Questions remain about how sustainable and cost-effective the approaches can be.

Scientific American, February 2011 Fish raised in offshore pens, such as these yellowtail at Kona Blue Water Farms near Hawaii, could become a more sustain- able source of protein for humans than wild fish or beef.

sustainability The Blue Food Revolution New fish farms out at sea, and cleaner operations along the shore, could provide the world with a rich supply of much needed protein

By Sarah Simpson

February 2011, ScientificAmerican.com Sarah Simpson is a freelance writer and contributing editor for Scientific American.She lives in Riverside, Calif.

eil sims tends his rowdy stock like any de- voted farmer. But rather than saddling a horse like the Australian sheep drovers he grew up with, Sims dons a snorkel and mask to wrangle his herd: 480,000 silver fish corralled half a mile off the Kona coast

of Hawaii’s Big Island. Tucked discretely below the waves, Sims’s farm is one of 20 ever, it must operate in environmentally sound ways—and make

Noperations worldwide that are trying to take advantage of the its benefits better known both to a jaded public and to policy anization; earth’s last great agricultural frontier: the ocean. Their offshore makers with the power to help or retard its spread. Org e ur

locations offer a distinct advantage over the thousands of con- In the past, condemnation might have been apt. When mod- lt cu i

ation ventional fish farms—flotillas of pens that hug the coastline. ern coastal fish farming began about 30 years ago, virtually no ); Too often old-style coastal farms, scorned as eyesores and ocean one was doing things right, either for the environment or for

polluters, exude enough fish excrement and food scraps to the industry’s long-term sustainability. Fish sewage was just r A d m inist preceding pages preceding cloud the calm, shallow waters, triggering harmful algal blooms one of the issues. Shrimp farmers in Southeast Asia and Mexi- ( ations Food and Agr N or snuffing out sea life underneath the pens. At offshore sites co clear-cut coastal mangrove forests to make ponds to grow p he r i c m os t such as Kona Blue Water Farms, pollution is not an issue, Sims their shrimp. In the salmon farms of Europe and the Americas, A explains. The seven submerged paddocks, each one as big as a animals were often too densely packed, helping disease and es: United CoolWaterPhoto.com CoolWaterPhoto.com high school gymnasium, are anchored within rapid currents parasites sweep through the populations. Fish that escaped urc o S C

that sweep away the waste, which is quickly diluted to harm- farms sometimes spread their diseases to native species. Mak- HI P A

less levels in the open waters. ing matters worse, the aquaculture industry represented (and Ushioda Masa GR and Oc eani c N ational Rather than taking Sims’s word for it, I put swim fins on my feet and a snorkel around my neck, high-step to the edge of his small service boat, and take the plunge. From the water, the feeding the world double-cone-shape cage is aglow like a colossal Chinese lan- tern, with shimmering streams of sunlight and glinting forms Protein Supply: Land or Sea? of darting fish. To the touch, the material that stretches taut around the outside of the cage’s frame feels more like a fence The World Needs More Protein than a net. The solid, Kevlar-esque material would repel hun- gry sharks as effectively as it contains teeming masses ofSerio - WORLD CROP AND GRAZING la rivoliana, a local species of yellowtail that Kona Blue has do- POPULATION areas, at today’s yields, mesticated as an alternative to wild tuna. will increase would have to rise by 50% to 70% to meet Why yellowtail? Many wild tuna fisheries are collapsing, and from 6.9 billion to 9.3 billion 2050 food needs; such sushi-grade yellowtail fetches a high price. Sims and fellow ma- by 2050. land may not exist. rine biologist Dale Sarver founded Kona Blue in 2001 to raise 2010 2050 2010 popular fish sustainably. But the company’s methods could just as well be applied to run-of-the-mill fish—and­ we may need them. The global population of 6.9 billion people is estimated to rise Who Is Poised to Provide It? to 9.3 billion by 2050, and people with higher living standards ASIAN COUNTRIES produce AQUACULTURE also tend to eat more meat and seafood. Yet the global catch the vast majority of aquaculture produces 47% of the from wild fisheries has been stagnant or declining for a decade. fish and shellfish. global seafood people Raising cows, pigs, chickens and other animals consumes vast consume. It could amounts of land, freshwater, fossil fuels that pollute the air and sustainably provide 30 fertilizers that run off and choke rivers and oceans. Americas (4.6%) 62% of the world’s Where will all the needed protein for people come from? The Asia (88.9%) total protein by 2050 20 Europe (4.4%) answer could well be new offshore farms, if they can function ef- if it continues to grow Other at its current annual ficiently, and coastal farms, if they can be cleaned up. Africa (1.8%) rate of 7.4% and 10 Oceania (0.3%) agriculture continues Cleaner Is Better its 2.0% growth rate. to some scientists, feeding the world calls for transferring the 0 production of our animal protein to the seas. If a blue food rev- 1970 1980 1990 2000 olution is to fill such an exalted plate at the dinner table, how-

Scientific American, February 2011 Graphics by Jen Christiansen still does) a net drain on fish mass; wild forage fish—small, gression within a predictable current that traverses the Carib- cheap species that humans do not prefer but that bigger, wild bean Sea every nine months. fish eat—are captured in large quantities and ground into feed for the bigger, tastier, more expensive farmed fish folks favor. Feeding Frenzy Clearly, such ills were not good for business, and the indus- the aspect of marine (saltwater) aquaculture that has been try has devised innovative solutions. Kona Blue’s strategy of sit- hardest to fix is the need to use small, wild fish as food for the uating the farm within rapid offshore currents is one example. large, farmed varieties. (The small fish are not farmed, because Other farmers are beginning to raise seaweed and filter-feeding a mature industry already exists that catches and grinds them animals such as mollusks near the fish pens to gobble up waste. into fish meal and oil.) The feed issue comes into pungent focus Throughout the industry, including freshwater pens, improve- for me when Sims and I climb aboard an old U.S. Navy trans- ments in animal husbandry and feed formulations are reduc- port ship cleverly transformed into a feeding barge. The sea ing disease and helping fish grow faster, with less forage fish in swell pitches me sideways as I make my way to the bow, calling their diets. It may still be a long time before environmental to mind a bumpy pickup truck ride I took long ago, across a groups remove farmed fish from “don’t buy” lists, however. semifrozen Missouri pasture to deliver hay to my cousin’s Here- Some cutting-edge thinkers are experimenting with an even fords. The memory of sweet-smelling dried grass vanishes bolder move. Nations exercise sole rights to manage waters out when I grab a handful of oily brown feed from a 2,000-pound to 200 nautical miles from their shores—a vast frontier un- sack propped open on the deck. The pellets look like kibble for tapped for domesticated food production. Around the U.S., that a small terrier but reek of an empty anchovy tin. frontier measures 3.4 million square nautical miles. Submerged The odor is no surprise; 30 percent of Kona Blue’s feed is fish pens, steered by large propellers, could ride in stable ocean ground up Peruvian anchovy. Yellowtail could survive on a veg- currents, returning months later to their starting points or a etarian diet, but they wouldn’t taste as good, Sims explains. Nor distant destination to deliver fresh fish for market. would their flesh include all the fatty acids and amino acids Ocean engineer Clifford Goudey tested the world’s first self- that make them healthy to eat. Those ingredients come from propelled, submersible fish pen off the coast of Puerto Rico in fish meal and fish oil, and that is the issue. “We are often pillo- late 2008. A geodesic sphere 62 feet in diameter, the cage ried because we’re killing fish to grow fish,” Sims says. Salmon proved surprisingly maneuverable when outfitted with a pair farming, done in coastal pens, draws the same ire. of eight-foot propellers, says Goudey, former director of M.I.T. Detractors worry that rising demand from fish farms will Sea Grant’s Offshore Aquaculture Engineering Center. Goudey wipe out wild anchovies, sardines and other forage fish. Before imagines launching dozens of mobile farms in a steady pro- modern fish farming began, most fish meal was fed to pigs and

The U.S. Has Vast Potential Fish farms near shore and farther out into the ocean could expand greatly in federal waters. Animal aRCtiC OCEan Fish

Vegetable Alaska FISH supply only 7% 2050 of the world’s protein.

World Fishery Food Supply Projected annual U.S. Midway atlantiC (pounds per capita) growth: 7.4% Islands Northern Hawaiian OCEan Mariana Wake Islands Puerto Rico, Islands Island Virgin Islands 30 Aquaculture PaCiFiC OCEan Johnston Navassa Atoll Island Guam Kingman Reef, 20 Howland Island, Palmyra Atoll Fisheries Baker Island equator Jarvis Island 10 A country’s “exclusive economic zone” extends up to American 200 nautical miles from its coast. The U.S. zone (blue) Samoa 0 is the world’s largest, covering 3.4 million square 1970 1980 1990 2000 nautical miles—more than its land area.

Map by XNR Productions February 2011, ScientificAmerican.com how it works chickens, but today aquaculture consumes 68 percent of the fish meal. Consumption has lessened under advanced feed for- mulas, however. When Kona Blue started raising yellowtail in Five Ways to 2005, its feed pellets were 80 percent anchovy. By early 2008 the company had reduced the share to 30 percent—without Raise Seafood sacrificing taste or health benefit, Sims says—by increasing the Most farmed marine fish are raised in on- concentration of soybean meal and adding chicken oil, a by- shore tanks or coastal pens, but cages product of poultry processing. The compound feed pellets are a are increasingly being anchored farther big improvement over the egregious practice of dumping whole offshore. At least one mobile, prototype sardines into the fish cages. Unfortunately, this wasteful habit en­closure, submerged and steered by remains the norm among less responsible farmers. prop­ellers, has been tried way out in the A goal for the more enlightened proprietors is a break-even open ocean. Entrepreneurs are also grow- ratio, in which the amount of fish in feed equals the weight of ing seaweed and mussels on lines placed fish produced for market. Farmers of freshwater tilapia and next to coastal pens and might do the catfish have attained this magic ratio, but marine farmers have same around offshore wind turbines. not. Because 70 percent of Kona Blue’s feed is agricultural pro- tein and oil, it now needs only 1.6 to 2.0 pounds of anchovies to produce one pound of yellowtail. The average for the farmed salmon industry is around 3.0. To achieve no net loss of marine protein, the industry would have to reduce that ratio. Still, farmed fish take a far smaller bite than their wild equivalents Antenna do: over its lifetime, a wild tuna may consume as much as 100 pounds of food per pound of its own weight, all of it fish. Surface buoy The pressure to reduce sardine and anchovy catches will in- crease as the number of fish farms grows. Aquaculture is the fastest-growing food production sector in the world, expanding at 7.5 percent a year since 1994. At that pace, fish meal and fish oil resources could be exhausted by 2040. An overarching goal, Support lines therefore, is to eliminate wild fish products from feed altogether, within a decade or so, asserts marine ecologist ­Carlos M. Duarte, who directs the International Laboratory for Global Change at Thruster the Spanish Council for Scientific Research in Majorca. One breakthrough that could help is coaxing the coveted omega-3 fatty acid DHA out of microscopic algae, which could replace some of the forage fish content in feed. Advanced Bio­ Nutrition­ in Columbia, Md., is testing feed that contains the same algae-derived DHA that enhances infant formula, milk and juice now sold in stores. Recently researchers at Australia’s Commonwealth Scientific and Industrial Research Organiza- Open Ocean Cages tion coaxed DHA out of land plants for the first time. Duarte In the future, a series of suggests that fierce competition for agricultural land and fresh- mobile, submerged pens, water means that fish farmers should eventually eliminate soy, each steered by propellers or thrusters, could ride chicken oil and other terrestrial products as well, instead feed- in predictable currents, ing their flocks on zooplankton and seaweed, which is easy to arriv­ing at a distant grow. (Seaweed already accounts for nearly one quarter of all des­­tination months later marine aquaculture value.) when fish are mature. Despite improvements in marine fish farming, prominent en- Machinery would vironmentalists and academics still shoot it down. Marine ecol- dispense feed stored ogist Jeremy Jackson of the Scripps Institution of Oceanography in the central spar. says he is “violently opposed” to aquaculture of predatory fish and shrimp—basically, any fish people like to eat sashimi-style. He calls the practice “environmentally catastrophic” in the pres- sure it puts on wild fish supplies and insists it should be “illegal.” Offshore Cages Young fish are placed in an anchored cage the size of Smarter Than Beef a gymnasium. Flooding the central spar submerges the pen jackson’s point, echoed by other critics, is that the risk of col- until the fish grow mature. A boat or barge sends food inside lapsing forage fisheries, which are already overexploited, is too through tubes, and natural currents sweep away excrement. great to justify serving up a luxury food most of the world will The pen is raised for harvesting and cleaning. never taste. Far better would be to eat the herbivorous sardines and anchovies directly instead of farmed, top-end predators.

Scientific American, February 2011 Turbine Collars Onshore Tanks Mussels and seaweed readily cling to synthetic All marine fish are hatched in tanks on land. Many are lines and grow naturally. The lines could be moved to pens at sea when old enough (fingerlings), but strung around or between turbines in offshore some innovators are also raising fish to harvestable size wind farms to enhance investment and to help in onshore tanks, where pollutants, disease and escaped reduce competition for offshore space. fish can be controlled.

Circulation system

Automated feeder

Collar

Mussels

Seaweed

Mussels

Feeding Coastal Pens Zipper entry tube Heavy mesh pens are relatively for divers easy to anchor and maintain. Automated feeders can minimize food waste by turning off when infrared sensors on the seafloor detect falling pellets. Seaweed and mussels that feed on fish waste can, if raised immediately “down­ stream,” reduce pollution and add revenue. Trays of waste-­munching organisms, such as red sea urchins, can also be placed below the pens.

Spar (holds air and water for buoyancy)

Illustration by Don Foley February 2011, ScientificAmerican.com Farmed yellowtail grow more efficiently than wild fish, which expend much energy hunting and evading predators.

Sims agrees that we should fishlower on the food web but says the environmental impacts of all the various protein produc- that does not mean we need to eat lower. “Let’s get real. I eat an- tion systems, so that society can “focus its energies on efficient- chovies on my pizza, but I can’t get anyone else in my family to do ly solving the most demanding problems,” writes Kenneth M. it,” he says. “If you can get a pound of farmed sushi for every pound Brooks, an independent aquatic environmental consultant in of anchovy, why not give people the thing they want to eat?” Port Townsend, Wash. Brooks estimates that raising Angus beef Certain people scoff at fish consumption—whether wild- requires 4,400 times more high-quality pasture land than sea­ caught or farm-raised—on the premise that the planet and its floor needed for the equivalent weight of farmed Atlantic salm- human inhabitants would be healthier if people ate more on filets. What is more, the ecosystem below a salmon farm can plants. But society is not rushing to become vegetarian. More recover in less than a decade, instead of the centuries it would people are eating more meat, particularly as populations in the take for a cattle pasture to revert to mature forest. developing world become wealthier, more urban and more An even more compelling reason to raise protein in the sea Western. The World Health Organization predicts a 25 percent may be to reduce humanity’s drain on freshwater. As Duarte increase in per capita meat consumption by 2050. Even if con- points out, animal meat products represent only 3.5 percent of sumption held steady, crop and grazing areas would have to in- food production but consume 45 percent of the water used in crease by 50 to 70 percent, at current yields, to produce the food agriculture. By shifting most protein production to the ocean, required in 2050. he says, “land agriculture could grow considerably without ex- That reality begs for a comparison rarely made: fish farming ceeding current levels of water use.” versus terrestrial farming. Done right, fish farming could pro- Of course, collecting and transporting soybean meal and vide much needed protein for the world while minimizing the chicken oil and feeding fish flocks all consume energy and cre- expansion of land-based farming and the attendant environ- ate emissions, too. Fuel consumption and emissions are greater mental costs. for farms that are farther from shore, but both types of farming Land-based farmers have already transformed 40 percent of rate better than most fishing fleets. The only way offshore farm- the earth’s terrestrial surface. And after 10,000 years to work ers can be profitable right now is to raise high-priced fish, but out the kinks, major problems still abound. Cattle eat tremen- costs can come down: a few experimental farms are already dous amounts of heavily fertilized crops, and pig and chicken raising cost-competitive mussels in the ocean. farms are notorious polluters. The dead zones underneath coastal fish farms pale in comparison to the huge dead zones Environmental Distinctions

that fertilizer run-off triggers in the Gulf of Mexico, Black Sea if providing more fish to consumers is an answer to meeting CoolWaterPhoto.com and elsewhere and to the harmful algal blooms that pig farm global demands for protein, why not just catch more fish di- effluent has caused in Chesapeake Bay. rectly? Many wild fisheries are maxed out, right at a time when

A growing number of scientists are beginning to compare global population, as well as per capita demand for fish, is boom- Ushioda Masa

Scientific American, February 2011 ing. North Americans, for example, are heeding health experts’ an operation,” Goudey asserts. All U.S. farms exist inside the advice to eat fish to help reduce the risk of heart attacks and im- three-mile-wide strip of water that states control, and only a prove brain function. few states, such as Hawaii, allow them. California has yet to What is more, fishing fleets consume vast amounts of fuel grant permits, despite government estimates that a sustainable and emit volumes of greenhouse gases and pollutants. Widely offshore fish-farming industry in less than 1 percent ofthe used, indiscriminate fishing methods, such as trawling and state’s waters could bring in up to $1 billion a year. dredging, kill millions of animals; studies indicate that at least half the sea life fishers haul in this way is discarded as too small, Protein Policy overquota or the wrong species. All too often this so-called by- to grow, and do so sustainably, the fish-farming industry will catch is dead by the time it is tossed overboard. Aquaculture need appropriate policies and a fairer playing field. At the mo- eliminates this waste altogether: “Farmers only harvest the fish ment, robust government fuel subsidies keep trawling and dredg- in their pens,” Sims notes. ing fleets alive, despite their well-known destruction of the sea­ Goudey points out another often overlooked reality: you can floor and the terrible volume of dead by-catch. Farm subsidies grow fish more efficiently than you can catch them. Farmed fish help to keep beef, pork and poultry production profitable. And convert food into flesh much more effectively than their wild powerful farm lobbies continue to block attempts to curtail the brethren, which expend enormous amounts of energy as they flow of nitrogen-rich fertilizer down the Mississippi River. “Al- hunt for food and evade predators, seek a mate and reproduce. most none of these more traditional ways of producing food Farmed fish have it easy by comparison, so most of their diet have received the scrutiny that aquaculture has,” Brooks says. goes into growth. The public has accepted domestication of the land but main- Kona Blue’s yellowtail and most farmed salmon are between tains that the ocean is a wild frontier to be left alone, even one and three years old at harvest, one-third the age of the though this imbalance may not be the most sustainable plan large, wild tuna targeted for sushi. The younger age also means for feeding the world. farmed fish have less opportunity to accumulate mercury and Policy shifts at the federal and regional levels may soon open other persistent pollutants that can make mature tuna and up U.S. federal waters. In January 2009 the Gulf of Mexico Fish- sword­fish a potential health threat. ery Management Council voted in favor of an unprecedented Indeed, fish farming already accounts for 47 percent of the plan for permitting offshore aquaculture within its jurisdiction, seafood people consume worldwide, up from only 9 percent in pending approval from higher levels within the U.S. National 1980. Experts predict the share could rise to 62 percent of the to- Oceanic and Atmospheric Administration. NOAA will evaluate tal protein supply by 2050. “Clearly, aquaculture is the plan only after it finalizes its new national aqua- big, and it is here to stay. People who are against it re- see a slide show culture policy, which addresses all forms of the indus- ally aren’t getting it,” says Jose Villalon, aquaculture of fish farms try and will probably include guidance for the devel- director at the World Wildlife Fund. Looking only at ScientificAmerican.com/ opment of a consistent, nationwide framework for feb2011/simpson the ills of aquaculture is misleading if they are not regulating commercial activities. “We don’t want the compared with the ills of other forms of food production. Aqua- blue revolution to repeat the mistakes of the green revolution,” culture affects the earth, and no number of improvements will says NOAA director Jane Lubchenco. “It’s too important to get it eliminate all problems. But every food production system taxes wrong, and there are so many ways to get it wrong.” the environment, and wild fish, beef, pork and poultry produc- Given relentlessly rising demand, society has to make hard ers impose some of the greatest burdens. choices about where greater protein production should occur. To encourage good practices and help distinguish clean fish “One of my goals has been to get us to a position where, when farms from the worst offenders, the World Wildlife Fund has co- people say food security, they don’t just mean grains and live- founded the Aquaculture Stewardship Council to set global stan- stock but also fisheries and aquaculture,” Lubchenco says. dards for responsible practices and to use independent auditors ­Duarte suggests we take some pressure off the land and turn to to certify compliant farms. The council’s first set of standards is the seas, where we have the opportunity to do aquaculture expected early this year. The council believes certification could right, rather than looking back 40 years from now wishing we have the greatest effect by motivating the world’s 100 to 200 big had done so. seafood retailers to buy fish from certified farms, rather than As for Neil Sims’s part of the blue food revolution, he is trying to crack down directly on thousands of producers. courting technology companies for upgrades. Tools such as ro- The Ocean Conservancy’s aquaculture­ director George Leon­ botic net cleaners, automated feeders and satellite-controlled ard agrees that this kind of farm-to-plate certification program video cameras to monitor fish health and cage damage would is an important way to encourage fish farmers to pursue better help Kona Blue’s crew manage its offshore farms remotely. “Not sustainability practices. As in any global industry, he says, just so we can grow more fish in the ocean,” Sims says. “So we cheap, unscrupulous providers will always exist. Setting a regu- can grow more fishbetter. ” latory “floor” could require U.S. farmers to behave responsibly more to explore “without making it impossible for them to compete.” That point is key. Only five of the world’s 20 offshore instal- The State of World Fisheries and Aquaculture 2008. FAO, 2009. lations are in U.S. waters. Goudey thinks more aquaculture en- Will the Oceans Help Feed Humanity? Carlos M. Duarte et al. in BioScience, Vol. 59, No. 11, trepreneurs would dive in if the U.S. put a licensing system into pages 967–976; December 2009. Sustainability and Global Seafood. Martin D. Smith et al. in Science, Vol. 327, pages784–786; place for federal waters, from three nautical miles offshore to February 12, 2010. the 200-mile boundary. “No investor is going to back a U.S. op- Will Farmed Fish Feed the World? An analysis from the Worldwatch Institute. eration when there are no statutes granting rights of tenancy to www.worldwatch.org/node/588 3

February 2011, ScientificAmerican.com xxxxxxxx

Photograph/Illustration by Artist Name October 2010, ScientificAmerican.com 87 © 2010 Scientific American Antonio Regalado is a science and technology reporter and the Latin America contributor to Science magazine. He lives in São Paulo, Brazil, where he writes about energy topics, including renewables.

ENERGY Reinventing the Leaf The ultimate fuel may come not from corn or algae but directly from the sun itself

By Antonio Regalado

ike a fire-and-brimstone preacher, nathan s. as we do oil or natural gas, to power cars, create heat or generate Lewis has been giving a lecture on the energy electricity, and we can store the fuel for use when the sun is down. crisis that is both terrifying and exhilarating. Lewis’s lab is one of several that are crafting prototype leaves, To avoid potentially debilitating global warm- not much larger than computer chips, designed to produce ing, the chemist from the California Institute hydrogen fuel from water, rather than the glucose fuel that nat- of Technology says civilization must be able to ural leaves create. Unlike fossil fuels, hydrogen burns clean. generate more than 10 trillion watts of clean, Other researchers are working on competing ideas for captur- carbon-free energy by 2050. That level is three times the U.S.’s ing the sun’s energy, such as algae that has been genetically Laverage energy demand of 3.2 trillion watts. Damming up every altered to pump out biofuels, or on new biological organisms lake, stream and river on the planet, Lewis notes, would provide engineered to excrete oil. All these approaches are intended to only five trillion watts of hydroelectricity. Nuclear power could turn sunlight into chemical energy that can be stored, shipped manage the feat, but the world would have to build a new reac- and easily consumed. Lewis argues, however, that the man- tor every two days for the next 50 years. made leaf option is the most likely to scale up to the industrial Before Lewis’s crowds get too depressed, he tells them there is levels needed to power civilization. one source of salvation: the sun pours more energy onto the earth every hour than humankind uses in a year. But to be saved, Lewis Fuel from Photons says, humankind needs a radical breakthrough in solar-fuel tech- although a few lab prototypes have produced small amounts of nology: artificial leaves that will capture solar rays and churn out direct solar fuel—or electrofuel, as the chemicals are sometimes chemical fuel on the spot, much as plants do. We can burn the fuel, called—the technology has to be improved so the fuel can be

in brief

Natural energy: Plants produce their Man-made leaf: Researchers are devis- cars, create heat or generate electricity, made cheaply in thin, flexible sheets, per- own chemical fuel—sugar—from sun- ing artificial leaves that could similarly ending dependence on fossil fuels. haps from silicon nanowires, and use in- light, air and water, without producing convert sunlight and water into hydro- Nano solution: To be practical, this so- expensive catalysts that help to generate harmful emissions. gen fuel, which could be burned to power lar-fuel technology would have to be hydrogen efficiently.

Artificial leaves could use sunlight to produce hydrogen fuel for cars and power plants.

Scientific American, October 2010 Illustrations by Cherie Sinnen manufactured on a massive scale, very inexpensively. To power ing the water-splitting reaction, but it costs $1,500 an ounce. the U.S., Lewis estimates the country would need to manufac­ That means Honda’s solar-hydrogen station will never power ture thin, flexible solar-fuel films, instead of discrete chiplike the world. Lewis calculates that to meet global energy demand, devices, that roll off high-speed production lines the way news- future solar-fuel devices would have to cost less than $1 per print does. The films would have to be as cheap as wall-to-wall square foot of sun-collecting surface and be able to convert 10 carpeting and eventually cover an area the size of South Carolina. percent of that light energy into chemical fuel. Fundamentally Far from being a wild dream, direct solar-fuel technology has new, massively scalable technology such as films or carpets made been advancing in fits and starts ever since President Jimmy from inexpensive materials are needed. As Lewis’s Caltech col- Carter’s push for alternative energy sources during the 1970s oil league Harry A. Atwater, Jr., puts it, “We need to think potato shocks. Now, with a new energy and climate crunch looming, chips, not silicon chips.” solar fuel is suddenly gaining attention. Researcher Stenbjörn Styring of Uppsala University in Sweden, who is developing artifi- Finding a Catalyst cial systems that mimic photosynthesis, says the number of con- the search for such technology remains at an early stage, sortiums working on the challenge has ballooned from just two despite several decades of on-again, off-again work. One pioneer- in 2001 to 29 today. “There are so many we may not be counting ing experiment shows why. In 1998 John Turner of the National correctly,” he adds. Renewable Energy Laboratory in Golden, Colo., built a device In July the Department of Energy awarded $122 million about the size of a matchbook that when placed in water and over five years to a team of scientists at several labs, ledby exposed to sunlight kicked out hydrogen and oxygen at a prodi- Lewis, to develop solar-fuel technology, one of the agency’s three gious rate and was 12 times as efficient as a leaf. But Turner’s cre- new energy research priorities. Solar fuels “would solve the two ation depended on rare and expensive materials, including plati- big problems, energy security and num as the catalyst. By one estimate, Turner’s solar-fuel cell cost carbon emissions,” says Steven E. $10,000 per square centimeter. That might do for military or sat- Koonin, the top science ad­­min­is­ If we want to ellite applications, but not to power civilization. trat­or at the doe. Koonin thinks save the planet, Noble metals, often the best catalysts, are in short supply. sun-to-fuel schemes face “formi- “That’s the big catch in this game,” Styring says. “If we want to save dable” practical hurdles but says we have to get the planet, we have to get rid of all those noble metals and work the tech­­nology is worth invest- rid of all those with cheap minerals like iron, cobalt or manganese.” Another ing in be­­cause “the prize is great difficulty is that the water-splitting reaction is highly corrosive. enough.” noble metals Plants handle that by constantly rebuilding their photosynthetic In photosynthesis, green leaves and work machinery. Turner’s solar-fuel cell lasted just 20 hours. use the energy in sunlight to rear- with cheap Today Turner’s research is consumed with devising succes- range the chemical bonds of water sive generations of catalysts that each are a bit cheaper and of and carbon dioxide, producing minerals like solar collectors that each last a little longer. At times the search and storing fuel in the form of iron to catalyze is agonizingly hit or miss. “I am wandering through the forest sugars. “We want to make some- looking for a material that does what I want,” Turner says. “Prog- thing as close to a leaf as possi- reactions. ress has been minimal.” ble,” Lewis says, meaning devices Other teams are also chasing catalysts, including one led by that work as simply, albeit producing a different chemical out- Daniel G. Nocera of the Massachusetts Institute of Technology. In put. The artificial leaf Lewis is designing requires two principal 2008 Nocera and a colleague hit on an inexpensive combination elements: a collector that converts solar energy (photons) into of phosphate and cobalt that can catalyze the production of oxy- electrical energy (electrons) and an electrolyzer that uses the gen—one necessary part of the water-splitting reaction. electron energy to split water into oxygen and hydrogen. A cata- Even though the prototype device was just a piece of the lyst—a chemical or metal—is added to help achieve the splitting. puzzle—the researchers did not find a better catalyst for creat- Existing photovoltaic cells already create electricity from sun- ing hy­dro­gen, the actual fuel—M.I.T. touted it as a “major leap” light, and electrolyzers are used in various commercial processes, toward “artificial photosynthesis.” Nocera began predicting so the trick is marrying the two into cheap, efficient solar films. that Americans would soon be cooking up hydrogen for their Bulky prototypes have been developed just to demonstrate cars using affordable backyard equipment. Those bold claims how the marriage would work. Engineers at Japanese automaker have not sat well with some solar-fuel experts, who maintain Honda, for example, have built a box that stands taller than a that research has decades to go. Others are more bullish: the refrigerator and is covered with photovoltaic cells. An electro- doe and the venture capital firm Polaris Venture Partners are lyzer, inside, uses the solar electricity to break water molecules. supporting Nocera’s ongoing work at Sun Catalytix, a company The box releases the resulting oxygen to the ambient air and he created in Cambridge, Mass. compresses and stores the remaining hydrogen, which Honda At Caltech, meanwhile, Lewis has been working on a way to would like to use to recharge fuel-cell cars. collect and convert the sun’s photons—the first step in any solar- In principle, the scheme could solve global warming: only fuel device—that is much cheaper than conventional, crystalline sunlight and water are needed to create energy, the by-product is silicon solar cells. He has designed and fabricated a collector oxygen, and the exhaust from burning the hydrogen later in a made of silicon nanowires embedded in a transparent plastic film fuel cell is water. The problem is that commercial solar cells con- that, when made larger, could be “rolled and unrolled like a blan- tain expensive silicon crystals. And electrolyzers are packed with ket,” he says [see box on opposite page]. His nanowires can con- the noble metal platinum, to date the best material for catalyz- vert light into electric energy with 7 percent efficiency. That

Scientific American, October 2010 how it works Solar Nanowires Mimic Nature Plants harness the sun’s energy to convert carbon dioxide and water molecules, creating hydrogen fuel. Nathan Lewis’s group at the Cali­ into glucose—chemical fuel that can be used or stored (left). Research- fornia Institute of Technology is designing a small leaf with arrays of ers are devising artificial leaves that use sunlight to split water silicon nanowires that could produce hydrogen (right).

Natural Leaf Artificial Leaf

Energy in. Solar photons are absorbed by a photoactive material: in plants, thylakoids inside a Semiconductor chloroplast; in artificial water-splitting nanowire Chloroplast arrays, semiconductor nanowires. Photon Oxidation catalyst

Oxidation. Absorbed photon H O energy knocks electrons from 2 water molecules in the chloroplast or array, which splits the molecules Thylakoid into hydrogen ions (H+) and oxygen.

e– H+

O2

Stroma Reduction. In plants, H+ ions combine with electrons and carbon dioxide to form glucose in the stroma. In the array, H+ ions move through a membrane and CO2 combine with electrons to form hydrogen molecules.

Reduction catalyst

Semiconductor Fuel out. Both processes create a H storable, trans­portable fuel: glucose 2 nanowire Hydrogen in plants; hydrogen in arrays. Glucose

pales in comparison to commercial solar cells, which are up to area,” Lewis says. But he is worried that society—including policy 20 percent efficient. But if the material could be made inexpen- makers, government funding agencies and even scientists—still sively enough—those sheets rolling off a press like newsprint— has not grasped the size of the energy problem or why revolution- lower efficiency could be acceptable. ary solutions are needed. That is why he spends so much time on Researchers also debate whether hydrogen is the best choice the lecture circuit, preaching solar salvation: “We are not yet for solar fuel. Teams working with biological organisms that treating this problem like one where we can’t afford to fail.” produce liquid biofuels say these fuels are easier to store and transport than hydrogen. But hydrogen gas is flexible, too: it can more to explore be used in fuel-cell cars, burned in power plants to generate electricity, and even serve as a feedstock in producing synthetic Powering the Planet: Chemical Challenges in Solar Energy Utilization. Nathan S. Lewis and diesel. Nevertheless, “the key is to make an energy-dense chemi- Daniel G. Nocera in Proceedings of the National Academy of Sciences USA, Vol. 103, No. 43, pages cal fuel,” with minimal carbon emissions, Lewis says. “Let’s not 15729–15735; October 24, 2006. In Situ Formation of an Oxygen-Evolving Catalyst in Neutral Water Containing Phosphate get hung up on which one.” and Co2+. Matthew W. Kanan and Daniel G. Nocera in Science, Vol. 321, pages 1072–1075; August Real-life leaves prove that sunlight can be converted into­ fuel 22, 2008. using only common elements. Can humankind imitate this pro- Powering the Planet with Solar Fuel. Harry B. Gray in Nature Chemistry, Vol. 1, No. 7; April 2009. cess to rescue the planet from global warming? The prognosis is Energy-Conversion Properties of Vapor-Liquid-Solid-Grown Silicon Wire-Array Photocathodes. Shannon W. Boettcher et al. in Science, Vol. 327, pages 185–187; January 8, 2010. not clear. “The fact that we can’t solve the problem with off-the- shelf components is why it’s an exciting time to be working in this interactive version at www.ScientificAmerican.com/interactive

October 2010, ScientificAmerican.com 2010 2020

World production rate World Cumulative production [ environment ] Million barrels per day trillion barrels

Peak 80 2.00 production

70 1.75

60 1.50

50 1.25 how much 40 1.00

30 0.75 is 20 0.50 10 0.25

0 0.00 left 1940 1980 20 14 2060 2100 1940 1980 2020 2060 2100 A graphical accounting of the limits to what one planet can provide

<< By michael moyer >> ? with reporting by carina storrs

if the 20th century was an expansive reeling from two centuries’ worth of green- era seemingly without boundaries—a time house gas emissions. Even life itself seems of jet planes, space travel and the Inter- to be running out, as biologists warn that net—the early years of the 21st have we are in the midst of a global extinction showed us the limits of our small world. event comparable to the last throes of Regional blackouts remind us that the flow the dinosaurs. of energy we used to take for granted may The constraints on our resources and be in tight supply. The once mighty Colo- environment—compounded by the rise of rado River, tapped by thirsty metropolises the middle class in nations such as China of the desert West, no longer reaches the and India—will shape the rest of this cen- annual Change ocean. Oil is so hard to find that new wells tury and beyond. Here is a visual account- in Glacier thickness extend many kilometers underneath the ing of what we have left to work with, a Gain seafloor. The boundless atmosphere is now map of our resources plotted against time. Loss

e n Up to 0.25 m More than 0.25 m no data 1976–1985 1986–1995 1996–2005 n Christians e n

Experience an interactive version of this article at www.ScientificAmerican.com/interactive J

Scientific American September 2010 2010 2020

[ fossil fuels ] World production rate World Cumulative production Million barrels per day 2014 >> the peak of oil trillion barrels Peak The most common answer to “how much oil is 80 2.00 production left” is “depends on how hard you want to look.” As easy-to-reach fields run dry, new 70 1.75 technologies allow oil companies to tap harder- to-reach places (such as 5,500 meters under 60 1.50 the Gulf of Mexico). Traditional statistical models of oil supply do not account for these 50 1.25 advances, but a new approach to production forecasting explicitly incorporates multiple 40 1.00 waves of technological improvement. 30 Though still controversial, this multi­ 0.75 cyclic approach predicts that global 20 0.50 oil production is set to peak in four years and that by the 2050s we 10 0.25 will have pulled all but 10 percent of the world's oil 0 0.00 from the ground. 1940 1980 20 14 2060 2100 1940 1980 2020 2060 2100

[ water ] 1976–2005 >> glacier melt accelerates Glaciers have been losing their mass at an accelerating rate in recent decades. In some regions such as Europe and the Americas, glaciers now lose more than half a meter each year. annual Change in Glacier thickness Gain

Loss Up to 0.25 m More than 0.25 m no data 1976–1985 1986–1995 1996–2005

www.ScientificAmerican.com SCIENTIFIC AMERICAN 75 [ minerals ] 2030 2028 >> indium Indium is a silvery metal that sits next permian–triassic extinction to platinum on the periodic table and Duration: 720,000 to 1.2 million years shares many of its properties such as species lost: 80%–96% its color and density. Indium tin oxide rate of species loss (arrow angle): is a thin-film conductor used in flat- panel televisions. At current pro­ 8.0%–9.6% per millennium duction levels, known indium reserves contain an 18-year world supply. Cretaceous–tertiary extinction Duration: less than 10,000 years species lost: 75%

rate of species loss: 15% per millennium

Current 11,000 years ago to the present and beyond species lost: to be determined ? rate of species loss Prehuman: 0.01%–0.1% per millennium 1900–2000: 1%–10% per millennium 2000–2100 (projected): 2%–20% per millennium

[ water ] drYinG out 2025 >> total renewable Water per Capita Cubic meters per person per year battle over water 2008 2025 [ minerals ] In many parts of the world, one major river Ethiopia supplies water to multiple countries. Climate 1,500 2029 >> silver change, pollution and population growth are Because silver naturally kills microbes, putting a significant strain on supplies.I n some it is increasingly used in bandages and areas renewable water reserves are in danger of as coatings for consumer products. At dropping below the 500 cubic current production levels, about 19 asia meters per person per year  years’ worth of silver remains in the north Africa considered a minimum for  Ukraine ground, but recycling should extend  Middle East a functioning society. india that supply by decades.  Europe 1,000 potential hot spots

EGYPT: A coalition of countries led by Ethiopia is challenging old agreements [ food ] that allow Egypt to use more than 50 percent of the Nile’s flow. Without the >> fewer fish river, all of Egypt would be desert. netherlands Fish are our last truly wild food, but the rise in Uzbekistan demand for seafood has pushed many species Eastern europe: Decades of pollution hungary have fouled the Danube, leaving down- to the brink of extinction. Here are five of the stream countries, such as Hungary and oman 500 most vulnerable. the Republic of Moldova, scrambling to find new sources of water.

middle east: The Jordan River, racked syrian arab republic by drought and diverted by Israeli, Syrian Pakistan and Jordanian dams, has lost 95 percent republic of Moldova of its former flow. singapore Former Soviet Union: The Aral Sea, Jordan at one time the world’s fourth-largest israel ) inland sea, has lost 75 percent of its saudi arabia fish Egypt hammerhead sharks (

water because of agricultural diversion ee 0 have declined by 89 percent since 1986. programs begun in the 1960s. 2008 2025 The animals are sought for their fins, which

are a delicacy in soup. Jason L

Scientific American September 2010 2030

[ biodiversity ] permian–triassic extinction Duration: 720,000 to 1.2 million years >> Our mass extinction species lost: 80%–96% Biologists warn that we are living in the midst of a mass extinction on par with the other five great rate of species loss (arrow angle): events in Earth’s history, including the Permian- 8.0%–9.6% per millennium Triassic extinction (also known as the Great Dying; it knocked out up to 96 percent of all life on Earth) Cretaceous–tertiary extinction and the Cretaceous-Tertiary extinction that killed Duration: less than 10,000 years the dinosaurs. The cause of our troubles? Us. species lost: 75% Human mastery over the planet has pushed many species out of their native habitats; rate of species loss: others have succumbed to hunting or 15% per millennium environmental pollutants. Here we compare our current extinction with Current its predecessors using the latest 11,000 years ago to the present and beyond estimates of species loss per species lost: to be determined year. If trends continue—and ? rate of species loss unfortunately, species loss is Prehuman: accelerating—the world 0.01%–0.1% per millennium will soon be a far less diverse place. 1900–2000: 1%–10% per millennium 2000–2100 (projected): 2%–20% per millennium drYinG out total renewable Water per Capita Cubic meters per person per year 2008 2025 Ethiopia 1,500

[ minerals ] Ukraine 2030 >> gold india The global financial crisis has boosted demand for gold, which is seen by 1,000 many as a tangible (and therefore lower-risk) investment. According to Julian Phillips, editor of the Gold Forecaster newsletter, probably about 20 years are left of gold that can be netherlands easily mined. Uzbekistan hungary oman 500 syrian arab republic Pakistan republic of Moldova singapore Jordan israel saudi arabia european eel orange roughy Egypt russian sturgeon populations have declined by off the coast of New Zealand 0 have lost spawning grounds because Yellowmouth grouper 80 percent since 1968; because have declined by 80 percent since 2008 2025 of exploitation for caviar. Numbers may exist only in pockets of its the fish reproduces late in life, the 1970s because of overfishing are down 90 percent since 1965. former range, from Florida to Brazil. recovery could take 200 years. by huge bottom trawlers.

www.ScientificAmerican.com SCIENTIFIC AMERICAN 2040 2050

[ food ] the effects of Global Warming on Agriculture daily per Capita Calorie Availability Food prices (U.s. dollars per metric ton) Percent change in production for the world's eight largest growers (by the 2080s) 2000 2050 >> feeding 400 2050 no climate change a warming world argentina 2.2% 2050 With climate change Researchers have recently started to 3,000 australia –15.6% untangle the complex ways rising temperatures will affect global Brazil –4.4% 300 agriculture. They expect climate change to lead to longer growing China 6.8% seasons in some countries; in others india –28.8% 2,000 the heat will increase the frequency of extreme weather events or the Mexico –25.7% 200 prevalence of pests. In the U.S., russia 6.2% productivity is expected to rise in the Plains states but fall further in the U.s. 8% 1,000 already struggling Southwest. Russia 100 and China will gain; India and Mexico Pacific northwest 26% will lose. In general, developing rockies and Plains 47% nations will take the biggest hits. By 2050 counteracting the ill effects southeast –18% of climate change on nutrition will 0 0 southwest Plains –25% Developed Developing rice Wheat Maize cost more than $7 billion a year. countries countries

[ minerals ] 2044 >> copper Copper is in just about everything in infrastructure, from pipes to electrical equipment. Known reserves currently stand at 540 million metric tons, but recent geologic work in South America indicates there may be an additional 1.3 billion metric tons of copper hidden in the Andes Mountains.

[ biodiversity ] mammals 18 percent endangered >> mortal threats The Iberian lynx feeds on rabbits,

As the total number of species declines, some have a prey in short supply in the lynx’s ) fared worse than others [see “Our Mass Extinction,” on habitat ever since a pediatrician species preceding page]. Here, at the right, are five life-forms, introduced the disease myxo­ ( matosis from Australia to France ee the estimated percentage of species thought to be in 1952 to kill the rabbits in

endangered, and an example of the threats they face. his garden. Jason L

Scientific American September 2010 2040 2050

the effects of Global Warming on Agriculture daily per Capita Calorie Availability Food prices (U.s. dollars per metric ton) Percent change in production for the world's eight largest growers (by the 2080s) 2000 400 2050 no climate change argentina 2.2% 2050 With climate change 3,000 australia –15.6%

Brazil –4.4% 300 China 6.8% india –28.8% 2,000

Mexico –25.7% 200 russia 6.2%

U.s. 8% 1,000 100 Pacific northwest 26%

rockies and Plains 47%

southeast –18% 0 0 southwest Plains –25% Developed Developing rice Wheat Maize countries countries

plants 8 percent endangered The St. Helena redwood is native to the island in the South Atlantic where Napoleon lived his last years. Its excellent timber led to exploi­ birds tation; by the 20th 10 percent century only one endangered remained in lizards The black-necked amphibianS the wild. 20 percent endangered crane suffers 30 percent endangered The blue spiny lizard must retreat from habitat Archey’s frog has from the sun before it overheats; loss in the wetlands been devastated by higher temperatures have cut down on of the Tibetan a fungal disease in its the time it can forage for food. plateau. native New Zealand.

SCIENTIFIC AMERICAN 2060 2070

[ fossil fuels ] Annual production (u.K.) Cumulative production (u.K.) projected Cumulative production Millions of metric tons Billions of metric tons Billions of metric tons 2072 >> limits of coal 300 Peak 30 Unlike oil, coal is widely thought to be virtually production 90% inexhaustible. Not so, says David Rutledge of the 600 90% d California Institute of Technology. Governments rl o routinely overestimate their reserves by a factor of W four or more on the assumption that hard-to-reach seams will one day open up to new technology. 200 20 Mature coal mines show that this has not been the 400 case. The U.K.—the birthplace of coal mining— offers an example. Production grew through the 19th and early 20th centuries, then fell as supplies were depleted. Cumulative production curves 100 10 in the U.K. and other mature regions have 200 followed a predictable S shape. By extra­ 90% 90% China polating to the rest of the world’s coal fields, Rutledge concludes that the u.S. world will extract 90 percent of available coal by 2072. 0 0 1820 1920 2020 1820 1870 1920 1984 2020 1850 1900 1950 2000 2050 2072 2100 2150

[ water ] 2060 >> changing the course of a river Climate change will shift weather patterns, leading to big changes in the amount of rain that falls in any given region, as well as the amount of water flowing through streams and rivers. Scientists at the U.S. Geological Survey averaged the results of 12 climate models to predict how streamflow will alter over the next 50 years. While East Africa, Argentina and other regions benefit from more water, southern Europe and the western U.S. will suffer.

predicted streamflow Percent change in 2041–2060

(compared with 1970–2000) ) map

–40% 0 40% ( upp i a h a c ssi je

Scientific American September 2010 2060 2070

Annual production (u.K.) Cumulative production (u.K.) projected Cumulative production Millions of metric tons Billions of metric tons Billions of metric tons 300 Peak 30 production 90% 600 90% d rl o W

200 20 400

100 10 200 90% 90% China

u.S.

0 0 1820 1920 2020 1820 1870 1920 1984 2020 1850 1900 1950 2000 2050 2072 2100 2150

[ water ] 2100 >> The Alps Parts of the Alps are warming so [ water ] quickly that the Rhone Glacier is expected to have disappeared by 2070 >> himalayan ice the end of the century. Snow melt from the Himalayas is a prime source of water for Asia’s major river valleys, including the [ minerals ] Yellow, Yangtze, Mekong and Ganges. By 2070 ice-covered landmass in the Himalayas could 2560 >> lithium decrease by 43 percent. Because lithium is an essential component of the batteries in electric cars, many industry analysts have [ sources ] worried publicly that supplies won’t WATER Global Glacier Changes: Facts and Figures. U.N. Envi­ron­ Geology, 2010. MINERALS Mineral Commodity Summaries 2010. keep up with growing demand for the ment Program/World Glacier Monitoring Service, 2008; AQUASTAT U.S. Geological Survey. BIODIVERSITY “Consequences metal. Still, known lithium reserves Database, U.N. Food and Agriculture Organization; “Global Pattern of Changing Biodiversity,” by F. Stuart Chapin III et al., in Nature. are big enough to keep us supplied of Trends in Streamflow and WaterA vailability in a Changing Vol. 405; May 11, 2000; “Quantifying the Extent of North American Climate,” by P.C.D. Milly et al., in Nature, Vol. 438; Nov. 17, 2005. Mammal Extinction Relative to the Pre-Anthropogenic Baseline,” by for more than five centuries, even FOOD Climate Change: Impact on Agriculture and Costs of Adapt­ Marc A. Carrasco et al., in PLoS ONE. Vol. 4, No. 12; Dec. 16, 2009; ignoring the vast supply of lithium ation, by Gerald C. Nelson et al. International Food Policy Research “Re-assessing Current Extinction Rates,” by Nigel E. Stork, in Institute, Washington, D.C., 2009; Global Warming and Agriculture: Biodiversity Conservation, Vol. 19, No. 2; Feb. 2010; “The Future in seawater. Impact Estimates by Country, by William R. Cline. Center for Global of Biodiversity,” by Stuart L. Pimm et al., in Science, Vol. 269; July 21, Development, Washington, D.C., 2007. OIL “Forecasting World 1995; “Are We in the Midst of the Sixth Mass Extinction? A View Crude Oil Production Using Multicyclic Hubbert Model,” by Ibrahim from the World of Amphibians,” by David B. Wake and Vance T. Sami Nashawi et al., in Energy Fuels, Vol. 24, No. 3; March 18, 2010. Vredenburg, in Proceedings of the National Academy of Sciences COAL David Rutledge, submission to International Journal of Coal USA, Vol. 105, Supplement 1; Aug. 12, 2008.

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