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By Margaret Kriz, National Journal
© National Journal Group Inc.
Friday, Aug. 4, 2006

Sometime in early 2008, the British energy giant known as BP will decide whether to build the first fossil-fuel-burning commercial power plant in the United States designed not to contribute to global warming. The California electric facility on BP's drawing board would emit almost no carbon dioxide or other "greenhouse gases." It is one of a handful of state-of-the-art projects raising hopes that the world can satisfy growing energy demands without accelerating the damage being done to the climate.

There is no silver bullet that will magically halt or reverse global warming, energy experts say. In its absence, they call for improving existing technologies and developing new ones that will more cleanly and economically power the refrigerators, computers, cars, and trucks of tomorrow. Energy efficiency, nuclear power, "clean" coal, hybrid vehicles, wind power, biofuels, and carbon dioxide "sequestration" (locking the gas underground) all come up frequently when experts discuss a combination of aggressive steps to put the brakes on climate change.

Some experts see BP's proposed $1 billion power plant as a promising component of this technology-focused approach to ameliorating climate change. The facility, which would be built at the company's Carson oil refinery near Los Angeles, would generate electricity by burning petroleum coke, a bottom-of-the-barrel material left over after oil is refined. Petroleum coke is basically synthetic coal, according to Gardiner Hill, director of technology for BP's carbon dioxide capture-and-storage program.

The power plant would convert the fuel into hydrogen and CO2. The hydrogen would produce electricity by driving turbines, and the CO2 would be injected into an oil well to squeeze hard-to-reach petroleum toward the surface. Once empty, the well would be sealed, forever trapping the CO2 and keeping it from harming the Earth's atmosphere. Coal-burning power plants could, in theory, use the same process to capture and store their CO2. "We believe this technology has a potential to play an important role to combat climate change," Hill said.

BP, formerly British Petroleum, is already using the CO2 disposal process, known as carbon sequestration, at an experimental plant in Algeria. And at least some other energy corporations see tremendous promise in the technology. American Electric Power, which is based in Columbus, Ohio, hopes to use carbon sequestration at coal-fired plants it is planning to build in Ohio and West Virginia. AEP said it eventually would capture the CO2 created by incineration and store it in underground reservoirs. The company won't use the process in the plants' first years, however, because it has no financial incentive to do so.

AEP President and CEO Michael Morris said he will build cleaner, coal-burning power plants because he's certain that the federal government will eventually regulate carbon dioxide and thus make sequestration financially sensible. "We decided that we were going to build new coal [plants]," Morris said. "And we were convinced from talking with political officials, as well as environmental officials, that over the life of the generating plant -- which is typically 30 to 40 years -- we as a nation will have to take a very appropriate step of addressing the issue of global warming."

The vast majority of scientists who study Earth's climate agree that the planet is warming, and they blame the greenhouse gases that accumulate in the atmosphere and prevent heat from escaping. Since the dawn of the Industrial Age, carbon dioxide levels in the atmosphere have soared because people have burned ever-increasing quantities of fossil fuels -- coal, oil, and natural gas. The International Energy Agency predicts that unless the world adopts greener technologies, the global demand for energy will surge at least 50 percent by 2030. Fossil fuels will remain the dominate source of energy, IEA predicts, and will provide more than 80 percent of the additional power needed to keep up with the growing demand.

Carbon dioxide levels in the atmosphere rose from 280 parts per million before the preindustrial era to 380 ppm today. Two-thirds of that increase has occurred in the past 50 years. Today, human activity pumps 7 billion tons of carbon into the atmosphere every year. That's more than triple the amount spewed into the air in 1955. Many scientists fear that as the world's population increases and economic development spreads, carbon dioxide levels will skyrocket. A report [PDF] by the U.N. Intergovernmental Panel on Climate Change predicted that concentrations could jump to between 540 and 970 ppm by 2100, depending on what countermeasures are taken.

As atmospheric levels of CO2 climbed over the past century, the Earth's surface temperature rose about 1 degree Fahrenheit. The U.N. panel warns of a possible 5-degree increase by the end of this century.

In June, the National Research Council, which is part of the National Academy of Sciences, reported that the final decades of the 20th century were warmer than any comparable period in the past 400 years, and possibly in the past millennium. The warmer temperatures are causing ice sheets to melt in Antarctica and permafrost to thaw in parts of the Arctic Circle. Scientists blame global warming for a worldwide loss of glaciers. And some studies have connected global warming to fiercer hurricanes and unusually extreme droughts, heat waves, and floods.

Scientists worried about global warming argue that national governments should take immediate steps to slash emissions of greenhouse gases. "We should be aiming for the lowest possible level [of greenhouse-gas emissions] that we can get," warned Robert Socolow, co-director of Princeton University's Carbon Mitigation Initiative. "There are no safe thresholds" for increased emissions, he said.

But to halt or slow global warming, the world would have to change the way it generates electricity and the types of vehicles that people drive. "Right now we're rethinking transportation," noted Jae Edmonds, a scientist at the Pacific Northwest National Laboratory and an adjunct professor at the University of Maryland (College Park). "We haven't been in that position in 100 years."

Many scientists, environmentalists, and even some business leaders say that the only way to persuade companies to produce cleaner electricity and to make dramatically more-energy-efficient cars is to regulate carbon dioxide emissions. They argue that the United States should harness the ingenuity of its private sector by charging companies a fee for each ton of carbon dioxide they discharge into the atmosphere.

"There's a real critical wave of investment that's hanging in the balance right now," said Daniel Lashof, science director for the Natural Resources Defense Council's climate center. "Companies are making billion-dollar bets about what kind of power plant to build in an atmosphere of total uncertainty about what the CO2 regulations are going to look like."

Bush administration officials agree that industry executives should ponder the future cost of emitting carbon dioxide. "If I'm a utility executive thinking about a [power] plant that's going to start operating in 2012, I must be asking myself what carbon is going to cost," said David Garman, undersecretary for energy, science, and environment at the Energy Department. "It doesn't cost anything today, but what's it going to cost then?"

The White House has no plans to propose any sort of carbon regulation, Garman said. "For now, the administration has made the point that it is premature for us to do that," he said. Instead, the federal government is spending billions of research dollars on a wide variety of energy technologies. "Our goal is to bring the cost down for all of the low- or no-carbon power-generating options," Garman said.

The following are the most promising technologies under development -- with or without government help -- to reduce the emissions of carbon dioxide and other pollutants that cause global warming.

Energy Efficiency
The best way to reduce U.S. emissions of global-warming pollutants is to make cars, power plants, buildings, and home and business equipment more efficient. "Everything from the [electricity] generation down to the end use -- there are huge gains to be made with efficiency," said Daniel Schrag, director of the Harvard University Center for the Environment.

Industry scientists agree. "You can use energy efficiency to displace the need for new [electric] plant generation in some instances," said Steve Gehl, director of strategic technologies for the Electric Power Research Institute, an industry-funded, nonprofit research group. "We're looking at data that suggests that 15 percent, possibly more, of your overall generation load could be met by energy efficiency," he said. "Things like lighting programs and appliance standards. There are a whole series of technologies, stuff that already exists and is available commercially but we haven't taken advantage of to the degree that we can."

Last year's Energy Policy Act took a step toward making that happen by requiring the Energy Department to adopt new efficiency standards for 15 large commercial or home appliances, including washers, refrigerators, freezers, air conditioners, and ice makers. Almost half of the states have funds dedicated to promoting and subsidizing energy-efficiency and renewable-energy projects. The money comes from surcharges on customers' electric bills or from utility companies.

Many Americans don't realize that products already in the stores can significantly cut energy bills and limit greenhouse-gas pollution. Since 1992, the Energy Department and the Environmental Protection Agency have operated a program that allows manufacturers to stick an Energy Star label on products that are more efficient than the government's minimum standards. The program also educates consumers about steps they can take to save money and curb global warming. The Energy Star Web site asserts, for example, that if all Americans switched their five most-used lighting fixtures to Energy Star-certified bulbs, we would save a total of $6 billion a year and about 800 billion kilowatt hours of electricity. The switch would also reduce greenhouse gases by 1 trillion pounds a year.

The construction industry is going through an environmental revolution as efficient "green" buildings gain popularity, partly because they cut energy costs. For example, the new 12-story headquarters of the biotechnology firm Genzyme uses 42 percent less energy than a comparable conventional building, according to company estimates. The Genzyme building, in Cambridge, Mass., gets high marks from the U.S. Green Building Council, a coalition of industry officials that rates new buildings based on site development, water savings, energy efficiency, construction materials, and indoor environmental quality.

The group also awarded a top rating to the Bank of America's new $1 billion Manhattan headquarters, scheduled to open in 2008. Designed to use half as much energy as a conventional building, it is the first high-rise to earn the council's platinum rating.

Leaders in some of the nation's most energy-intensive manufacturing industries are also working to cut their energy use and reduce their emissions of greenhouse gases. Last year, chemical giant DuPont announced that in 2004 it had reduced its emissions by 72 percent from 1990 levels and kept its energy use flat.

Likewise, the aluminum industry has made progress in lowering electricity consumption and curbing emissions. "People tend to refer to aluminum as solid electricity," said Jonathan Pershing, director of the World Resources Institute's climate and energy program and former director of the State Department's Office of Global Change. "But they've had significant success. A lot of companies are seeing that efficiency is the lowest-cost deal."

'Clean' Coal
Much of the world's global-warming problem can be blamed on a four-letter word: coal. And coal will continue to fire a large portion of the world's economy for the foreseeable future.

In the United States, about half of all electricity comes from coal-burning power plants. Electricity generation creates 40 percent of U.S. CO2 emissions, yet with 275 billion tons of recoverable coal, this country is unlikely to break its coal habit any time soon.

China and India, meanwhile, are fueling their development with their equally impressive coal reserves. Some experts estimate that China is building an average of one coal-fired plant every week to power its booming economy.

So it's not surprising that breakthrough technologies that promise to clean up coal -- by slashing the pollution that even state-of-the-art coal-fired power plants create or by preventing a key pollutant from escaping into the atmosphere -- are widely considered the most important victories so far in the battle to curb global warming.

American Electric Power decided to invest in the cleanest-burning coal-fired power plants after its shareholders urged company executives to take a long, hard look at how to prepare for the regulation of carbon dioxide. The utility is proposing to build two plants that incinerate coal through a process called integrated gasification combined cycle, or IGCC, which would convert coal into a gaseous fuel before igniting it. This method makes it easier to eliminate conventional air pollutants, such as sulfur dioxide, nitrogen oxides, and mercury, and it will give the company the option of eventually separating CO2 emissions for capture and storage.

AEP's Morris said he hopes to begin operating the Ohio plant by 2010 or 2011 and the West Virginia facility somewhat later. But first, the company is asking regulators for permission to pass the plants' costs -- an estimated 15 to 20 percent higher than for traditional plants -- on to customers.

As AEP, BP, and several other power companies move toward building advanced-technology coal plants, the Energy Department is underwriting a $1 billion public-private partnership to design, build, and operate a similar electric facility. The Bush administration's FutureGen will use IGCC technology to produce hydrogen fuel and will store the plant's CO2 emissions in underground reservoirs. The partnership is scheduled to select a site in September 2007 and hopes to begin operation by 2013.

Environmentalists, and some scientists, argue that the Energy Department should distribute that money differently. "Rather than build a single gold-plated plant that is going to take years to get off the ground, I'd say it would be much more productive for DOE to promote more commercial applications" of advanced-coal technologies by commercial utilities, said Lashof of the Natural Resources Defense Council.

So many power plants are under construction and will soon be operating that the electric industry would have to cut its greenhouse-gas discharges by two-thirds just to stabilize the world's carbon dioxide emissions, says Jay Apt, executive director of Carnegie Mellon's Electricity Industry Center. "The sooner you start [to build cleaner power plants], the better it's going to be in terms of cost and dislocation," he said. "What you don't want to do is build a whole lot of new plants that are just the same old technology."

But that's just what most U.S. electric companies are proposing to do, according to a June report [PDF] from the Energy Department's National Energy Technology Laboratory. The report said that 154 coal plants are on the drawing board for construction by 2030 (although many may never be built). Of that 154, only 24 propose to use today's most advanced coal-burning technologies.

Why are most electric companies sticking with the traditional technology that emits more carbon dioxide? "Because it's the low-cost option -- maybe not the life-cycle cost, but for the [start-up]," said Gehl of the Electric Power Research Institute. "And because it's a well-known, highly reliable technology."

If the federal government does begin to regulate carbon dioxide, though, the utilities that own those conventional coal-fired plants may have to install expensive new pollution controls.

Carbon Sequestration
Coal-gasification technology would not be the darling of the foes of global warming if it were not for carbon sequestration. Sequestering carbon dioxide is much like filling and corking a bottle, at least in theory. Power plants that can separate CO2 from the rest of the fuel will be able to pipe it into deep natural holding tanks, such as saline aquifers, depleted oil patches, or coal beds too far underground to be mined. Once filled, a CO2 repository would be overlaid with impermeable caprock.

Some scientists think that the Earth has a huge number of mammoth underground pockets capable of permanently holding CO2. "We've got space for 10,000 billion tons globally," Apt said. "It's about five times the amount of storage you'd need by 2050." Eventually, however, the world's expanding use of coal could fill available reservoirs.

The idea of carbon sequestration isn't new. For the past decade, Norway's state oil company, Statoil, has been injecting CO2 from its North Sea natural-gas fields into an offshore aquifer. Oil companies have long pumped CO2 into declining oil wells to push out more petroleum but have made no attempt to keep the CO2 from escaping.

Sequestration could also be used to capture and store greenhouse gases from natural-gas plants, steel and cement manufacturing facilities, and other industrial processes. The most important question about the technology is whether it is possible to lock the gas away forever. "The worry there is whether the CO2 will escape," Harvard's Schrag said. "Probably, it won't. The problem is, we don't know."

An April report [PDF] by the Global Energy Technology Strategy Program called for more study to guarantee the long-term success of carbon sequestration. Broad use of sequestration "will depend in part on developing a much more robust and accurate suite of measuring, monitoring, and verification technologies," the report concluded. The research group is made up of scientists from the science and technology institute Battelle, the Pacific Northwest National Laboratory, and the University of Maryland.

The federal government is funding research into sequestration. "We hope that by the time we leave [office in 2009], our carbon-sequestration regional partnerships will have completed on the order of 25 small-scale geologic sequestration field programs in 14 or so states," DOE's Garman said.

Even if sequestration is proven to work almost perfectly, utility companies won't begin using it unless the process becomes less expensive. DOE estimates that sequestration could cost $100 to $300 for every ton of carbon dioxide stored underground. The department hopes that new methods will slash that to $10 or less per ton by 2015. But even that would cost $70 million a year for a typical 1,000-megawatt coal plant operating at full power, according to the Electric Power Research Institute.

Nuclear Power
"You're not serious about greenhouse gases if you're not serious about nuclear," argues James Connaughton, head of the White House Council on Environmental Quality. He asserts that nuclear power is the only source of electricity that can deliver the massive quantities of energy demanded by the world's growing economies without producing CO2 emissions.

The United States has 104 commercial nuclear power plants; a total of 440 are operating worldwide. Britain recently gave the green light to expanding its reliance on nuclear power as a way of meeting its ambitious goal of reducing domestic CO2 emissions 60 percent by 2050. No new nuclear plants have been ordered in this country since a 1979 accident at Pennsylvania's Three Mile Island facility nearly caused one reactor to melt down. At about the same time, Wall Street lost faith in nuclear power because of massive overruns in construction costs.

But the fears of the late 20th century have faded, and a growing number of scientists, politicians, and business executives see nuclear power as the solution to the world's global-warming problems. At least two dozen nuclear power plants are in the planning stages in the United States, according to the Nuclear Energy Institute, an industry trade group. That frenzy of activity was sparked in part by last year's Energy Policy Act, which included a basket of incentives for nuclear plant construction.

The first few companies that build the next generation of nuclear reactors will receive a special tax credit for their initial eight years of operation, as well as insurance protection against licensing delays and litigation. The plants will also be eligible for a federal loan guarantee program designed to encourage technologies that reduce greenhouse-gas emissions.

Those sweeteners may be enough to persuade utility executives to order a nuclear power plant, according to Andrew Kadak, a former utility-industry executive who is an engineering professor at the Massachusetts Institute of Technology. "My sense right now is that utilities are ready, after many, many years of saying, 'No, I don't want to talk about nuclear because I'll lose my job,' " Kadak said. "Now they're saying, 'Nuclear is in our plan.' But they're taking baby steps to putting this order in."

DOE's Garman agreed that additional nuclear power plants are on the U.S. horizon. "It's our view that licenses will be filed and that long lead-time orders will be placed by the time that we're done here" in 2009.

Industry supporters say the next generation of nuclear plants will be safer and more efficient than today's facilities. But they will also be more expensive. According to the Electric Power Research Institute, a nuclear power plant will cost about as much to build as a coal-gasification plant. But utility-industry executives anticipate that the federal government will begin to regulate CO2 emissions within a few years, making coal-fired plants more costly and nuclear power more competitive.

"Part of the reason some of the companies are looking at this is they believe the carbon costs are coming, and this is part of a hedging strategy," said Pershing of the World Resources Institute.

Nuclear power's champions continue to fight an uphill battle with some of their traditional opponents. NRDC's Lashof said his group doesn't support new reactors even though nuclear power creates no greenhouse gases. "Our view is not that it's off the table, but that it's just not among the most promising options," he said. But he added, "If we have a cap [on CO2 emissions] in place, everything is on the table."

In June, Wall Street once again heard dire warnings about nuclear power. In a presentation [PDF] to the New York Society of Security Analysts, two energy experts charged that nuclear power is too expensive, that new plants are likely to suffer serious cost overruns, and that the utility industry has vastly underestimated the cost of decommissioning and dismantling nuclear plants at the end of their lifetimes. The analysis came from Peter Bradford, who served on the Nuclear Regulatory Commission and as chairman of the public utilities commissions in New York and Maine, and David Schlissel, a senior consultant with Synapse Energy Economics, a Cambridge, Mass., consulting firm. Bradford and Schlissel noted that the Energy Department still isn't ready to take control of the radioactive waste that has accumulated at commercial nuclear power plants.

In July, DOE tried to put those concerns to rest by announcing that in 2008 it will formally ask the Nuclear Regulatory Commission for a permit to build a permanent nuclear-waste repository inside Nevada's Yucca Mountain. Until then, the department plans to continue to test whether the site can safely serve as a dump for spent nuclear fuel. By 2017, the department hopes to complete construction at Yucca and gain final approval from the NRC to begin accepting waste.

Wind Power
In February, President Bush set a goal of generating 20 percent of America's electric power from wind energy. Even though Bush spelled out no timetable, that's an ambitious proposal, considering that windmills now provide less than 1 percent of U.S. power. But wind is one of the nation's fastest-growing sources of electricity.

Investors like wind for two reasons. First, wind power enjoys a production tax credit that has helped to offset its expensive generating costs. The 2005 energy legislation extended that credit for another two years. Analysts suggest that wind's continued popularity depends on that credit.

Second, 22 states and the District of Columbia require electricity providers to generate some of their power from renewable sources. Those standards have "been very helpful," said Randy Swisher, executive director of the American Wind Energy Association. The government mandates have "taught a sometimes-conservative, slow-to-embrace-new-technology utility industry how economical wind can be," he said.

Electricity-producing wind turbines are popping up at a record pace, with each windmill producing from 750 kilowatts to 1.5 megawatts of power. More than 9,000 megawatts of wind power is now available in the United States. That's the equivalent of the output from nine standard-sized nuclear reactors. Another 3,000 megawatts of wind power is due to come online by the end of this year, Swisher said. Texas has harnessed the most wind power, with California a close second.

Worldwide, wind power produces almost 60,000 megawatts of electricity, meeting 1 percent of electricity demand, according to the World Wind Energy Association. The turbines produce electricity only when the wind is blowing, but Swisher said that utilities are adapting to wind's unreliability by pairing wind turbines with another source of electricity or with energy-storage technologies.

A bigger barrier to expansion of wind power in the United States is the limited reach of the nation's high-power electric lines. "The most significant obstacle to getting to 20 percent," Swisher pointed out, "is the need for transmission to connect the wind resource areas in the Great Plains with the major population centers on the coasts, where the energy would be used."

The Energy Policy Act boosted other forms of renewable energy technology as well. The law offers tax credits to companies that generate electricity from vegetation (or "biomass"), geothermal energy, landfill gas, and trash combustion. The measure also established a federal tax credit for solar-power systems for residential or business use.

While wind power is at the cusp of commercial viability, solar technology is still decades away from providing a significant portion of U.S. electricity. "Maybe in 50 years," said Princeton's Socolow. "It doesn't play a big role in the next 20 years."

The problem? Solar power is too expensive. At a July 19 energy forum sponsored by the U.S. Chamber of Commerce, Howard Berke, the CEO of Konarka Technologies, which makes solar materials, said that solar needs a major technological breakthrough to become competitive.

Biofuels
In the race to slow global warming, transportation may be the trickiest problem. Americans own 136 million passenger cars and 92 million light trucks, a category that includes SUVs. Every gallon of gasoline burned in the average American vehicle sends 20 pounds of carbon dioxide out the tailpipe, according to the Environmental Protection Agency.

Transportation accounts for 33 percent of CO2 emissions in the U.S., and 24 percent worldwide. With China and other developing countries putting cars on the road at a record pace, that global percentage is sure to climb. Socolow estimates that by 2055, 2 billion cars, triple today's number, will be operating.

The only way to reduce vehicles' greenhouse-gas emissions is to make them dramatically more efficient or change their source of power. In this country, according to EPA, passenger vehicles are no more efficient than they were in the early 1990s, and they're less efficient than they were in the late 1980s. America's fleet of "light-duty" vehicles, which includes cars, SUVs, vans, and small pickups, averages 21 miles per gallon. In 1987 and 1988, the average was more than 22 mpg.

David Friedman, research director of the Union of Concerned Scientists' clean-vehicles program, said that carmakers already know how to make the average car or SUV go farther on a tank of gas. "With conventional technology, we can look at cutting global-warming pollution by 40 percent," he said, "just by using boring, ho-hum things like more-efficient engines, better transmissions, high-strength steel and aluminum, and something called an integrated starter generator, which allows engines to shut off when you're at a stoplight or in stop-and-go traffic."

Today's most popular alternative to gasoline is ethanol. In the U.S., ethanol is made almost exclusively from corn. Some economists worry that the popularity of corn-based ethanol could drive up the price of corn, slowing imports and raising the cost of food. Farm groups call that fear unfounded.

Today's cars and SUVs can tolerate a gasoline blend that includes 10 percent ethanol. In some parts of the country, producers have long added small amounts of ethanol to gas to reduce emissions of smog-causing pollutants. The United States now has 100 ethanol refineries, which produce a total of 4.7 billion gallons a year, according to the Renewable Fuels Association. Construction is under way on 32 plants, which together will produce another 2 billion gallons.

Detroit is making flexible-fuel vehicles that can run on a blend of 85 percent ethanol and 15 percent gasoline or use conventional gasoline when the ethanol blend, called E85, isn't available. An estimated 3.8 million flexible-fuel cars are on U.S. highways today, according to the Alliance for Automobile Manufacturers. But only about 700 gas stations nationwide offer E85. So the vast majority of flexible-fuel cars are using conventional gasoline.

So why do automakers produce the flexible-fuel cars? The federal government gives automakers a credit of up to 1.2 mpg for each flexible-fuel car or truck they sell. That credit helps the car companies meet federal corporate average fuel economy standards, which are based on the total number of cars and light trucks each firm sells. Each company's car fleet must average 27.5 mpg; light trucks, including SUVs, must average 21.6 mpg.

Still another bump in the ethanol road is that corn-based ethanol reduces the CO2 emissions that a given vehicle is responsible for by only about 10 percent, once you factor in the petroleum used in the farm equipment and the fertilizer used to grow and harvest the corn. Making ethanol from other plants or from agricultural waste, called cellulosic ethanol, can more significantly reduce greenhouse-gas emissions.

Cellulosic ethanol is made from high-fiber plant materials -- from cornstalks and agricultural plant wastes to crops grown specifically for ethanol production, such as woody plants. Friedman of the Union of Concerned Scientists said that cellulosic ethanol produces 80 to 90 percent fewer greenhouse-gas emissions than gasoline. "But we need some breakthroughs in terms of the efficiency of making ethanol from those materials," he said. DOE's Garman said that cellulosic ethanol now costs $2 to $2.50 per gallon to make, while corn-based ethanol costs about $1 a gallon.

The president has taken up the call for cellulosic ethanol.

In his 2006 State of the Union address, Bush promised to make the fuel commercially competitive within six years. According to the White House, cellulosic ethanol can replace up to 30 percent of the gasoline used by U.S. drivers.

Energy Department officials are even more optimistic. Garman said a 2005 study [PDF] conducted by DOE and the Agriculture Department found that the U.S. produces 1 billion tons of plant waste. "That could produce enough biofuels to displace 60 billion gallons of gasoline," he said. "Today we use about 135 billion gallons [a year], so 60 is a lot. That's why you saw the president excited about cellulosic ethanol and its potential worldwide."

Scientists in government and corporate laboratories are focused on developing crops that can generate more ethanol per acre. They're also seeking easier ways to turn woody material, such as switchgrass, into commercial ethanol. "In a climate-constrained world, you'd actually grow crops for their energy content alone," said Edmonds of the Pacific Northwest National Laboratory. "You can use biotechnology to develop bulk fuels and designer enzymes targeted at breaking down a particular plant and its cell structure."

For farmers, switching from corn to cellulosic plants might be quite profitable. "Maybe a decade from now, we might be making ethanol on a broad scale from cellulosic," said Dave Miller, director of research and commodity services at the Iowa Farm Bureau. "I'm told the yield of ethanol per acre may make it advantageous to jump from corn to woody pulp plants," he said. "Hey, if that's the case, we may be growing fast-growing poplars in Iowa."

Hybrid Vehicles
Americans have purchased almost a half a million hybrid vehicles since the Honda Insight debuted in the U.S. market in 1999, according to Hybridcars.com. Today's hybrids are powered by a rechargeable battery and by gasoline, and they often combine other energy-efficient technologies to stretch each gallon of gas. Although many hybrids have small engines, the batteries provide extra acceleration power. When hybrids stop, the gasoline motor shuts off and the car runs on the batteries. The batteries recharge when the vehicle is decelerating or coasting.

Hybrids' gas mileage varies greatly, depending on the added amenities. The most-efficient cars can travel 55 to 60 miles on a gallon of gasoline. But instead of mileage benefits, some hybrids offer bells and whistles. GM's hybrid pickup truck comes with a pair of 110-volt electrical outlets.

An updated technology is in the lab: Plug-in hybrids will allow drivers to recharge the batteries by plugging an extension cord into almost any outlet. The plug-in car will have more battery power and so will be able to travel longer distances on electricity. Plug-in proponents say the vehicles could travel at least 40 miles by drawing power from the battery alone.

"Most Americans drive less than 30 miles per day," said the White House's Connaughton. "So for the lion's share of the people who take short trips, they can get an all-electric experience. Then they would plug it in at night when electricity is cheap" to recharge the batteries, he said.

Energy experts say the major hurdle facing commercialization of plug-in vehicles is that the current batteries are large, heavy, and take hours to recharge.

Research to improve hybrids' batteries will help advance other transportation technologies that depend on batteries -- such as electric cars and hydrogen-powered fuel-cell cars that produce no tailpipe pollution.

The Bush administration has set a goal of developing and commercializing hydrogen-powered fuel cells for cars by 2020. Most scientists predict, however, that fuel-cell cars will not be available to the public until decades later. The technology faces daunting problems: The tanks needed to transport the hydrogen fuel are bulky and heavy, and refueling would require construction of a national infrastructure of hydrogen filling stations. In addition, although scientists have made progress on fuel-cell technology, it remains prohibitively expensive.

"Hydrogen systems have potential, if breakthroughs come through," said Edmonds. "It could be a really powerful system because it's a great way to reduce the emissions in the transportation sector." But Socolow of Princeton sees hydrogen fuel cells as a distant option. "I tend to see this developing in the second half of the century," he said.

Global-warming specialists say the planet has no time to wait for breakthroughs.

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