Fuels for the Future

The good news is that automakers and other researchers have been working on a variety of alternatives to conventional gasoline-fueled, internal-combustion engines. But the reality is that only hybrids and upcoming "clean diesels" promise to be practical alternatives in the near future.

The petroleum problem

Some analysts see the recent spike in gasoline prices as a sign of things to come. Experts argue that it's only a matter of time before increasing worldwide demand and tightening supplies of this declining resource drive pump prices still higher, especially because the U.S. is increasingly dependent on oil imports from politically unstable parts of the world.

Predictions about when this will happen range from a decade or two to more than a century. For example, Colin Campbell, a petroleum geologist and former consultant to oil companies, has stated that petroleum will run short worldwide in about 20 years, by which time the U.S. will be importing 90 percent of its oil. In contrast, Michael C. Lynch, president of the consultant group Strategic Energy and Economic Research, says, "The pessimists underestimate how much oil will come on-line in the next few years. We'll still be using oil a hundred years from now, but a lot less of it. We'll see a gradual shift away from oil as nonemitting alternatives become more feasible."

Aside from pricing and supply issues, burning fossil fuels creates pollution-related health hazards and acid rain, and adds billions of tons of carbon dioxide (CO₂) to the atmosphere annually. CO₂ is thought to be a major contributor to global warming.

Searching for solutions

Technology can help, but as John Steele Gordon, a finance historian, has argued, a new technology replaces an older one only when it's cheaper, better, or both. So far, that's proved a stumbling block to many "green" vehicles that haven't been able to match the balance of price, convenience, performance, and driving range that conventional gasoline vehicles provide.

All-electric cars have failed to become commercially viable because of limited range and long recharge times. Alternative fuels have generated only niche markets. The clean-running hydrogen-powered cars are still in their infancy. And while diesels show promise, excessive emissions have remained an obstacle.

The alternative that has gained the most acceptance so far is the gas-electric hybrid, an innovative technology that meets conventional cars halfway.

Biodiesel: A promising blend

Another renewable fuel that is getting a lot of attention is biodiesel, a fuel made from vegetable oil that can be used to power diesel engines. Biodiesel is renewable, nontoxic, nonexplosive, and biodegradable, and it burns more cleanly than petroleum diesel.

Biodiesel is fuel made commercially from vegetable oil treated with lye to make it more viscous, and with other substances to make it last longer in storage. Mostly it is used in blends with petroleum diesel, in mixes such as B5 (5 percent biodiesel to 95 percent petroleum diesel), B10 (10 percent biodiesel), and B20.

Currently, 100 percent biodiesel, called B100, costs about $3 a gallon compared with about $2.60 a gallon for regular diesel.

A gallon of B20 can operate most diesel engines with no modification. It costs about 15 to 25 cents more than a gallon of petroleum diesel, but it uses 20 percent less petroleum and burns cleaner.

Most biodiesel outlets are located in the Midwest. To see where to buy biodiesel, visit the Web site of the National Biodiesel Board.

Most makers of diesel cars will not honor warranties on cars that burn biodiesel in higher concentrations than B5 because it can eat away at seals in the fuel system.

According to statistics published by the U.S. Department of Energy's National Renewable Energy Laboratory, the U.S. will soon have the capacity to produce about 900 million gallons a year, or enough to supplant less than 1 percent of the gasoline used in this country.

In Consumer Reports' own tests, a car running on biodiesel produced slightly less pollution than the same car running on conventional diesel but achieved slightly fewer mpg.

A variation on biodiesel is straight vegetable oil (SVO), which can also burn in diesel engines without modification. Cars running on SVO, however, need a separate fuel tank for the veggie oil and a preheating system to keep it from congealing. Conversion kits to add the fuel tank and other hardware to existing diesels cost about $800, and the components reduce a vehicle's cargo space.

In our tests, the car running on vegetable oil posted almost the same acceleration and similar emissions as it did on petroleum diesel. Many people who go this route get free recycled fryer oil from restaurant kitchens. But it has to be filtered thoroughly before being put in the tank.

Diesels: Cleaning up their act

Pros Good fuel economy, typically lower fuel prices, lower CO₂emissions.

Cons Higher NOx and particulate emissions, noisy, usually slower acceleration.

Diesel engines are up to 30 percent more efficient than gasoline engines. But drawbacks have kept them from gaining general acceptance in the U.S. Historically, they've suffered from slow acceleration, a loud clatter, smoky exhaust, and an oily smell. Compared with gasoline engines, diesels also emit higher levels of two hard-to-manage pollutants: oxides of nitrogen (NOx), which forms smog and contributes to acid rain, and particulates (soot), which have been linked to respiratory problems. Because of this, emissions laws in five states—California, Maine, Massachusetts, New York, and Vermont—effectively ban the sale of diesel cars. (Trucks such as pickups and SUVs are allowed.)

That's beginning to change, however. With turbocharging, ultra-precise, high-pressure "common rail" fuel injection and better exhaust-system catalysts, modern diesel cars are quicker, quieter, and much cleaner than their predecessors.

Most important in the resurgence of diesels, the federal government has mandated a switch to low-sulfur fuel, which is supposed to go on sale in October 2006. This will allow automakers to lower NOx emissions by using special catalytic converters, which now would be easily contaminated by sulfur. According to the latest EPA regulations, this would likely allow diesels to be sold in all states. The de-sulfurizing process is estimated to add about five to seven cents per gallon to the cost of diesel fuel.

In March 2006, the Environmental Protection Agency loosened proposed diesel emissions regulations to allow more diesels to be sold. Honda, Nissan, Subaru, Toyota, and others are developing diesel models to join those offered by Mercedes-Benz and Volkswagen.

Chet France, lab director at the EPA's Office of Transportation and Air Quality, predicts that "the new-generation diesels will be more than 90 percent cleaner than current models."

Unlike hybrids, which achieve fuel mileage gains mainly in stop-and-go city traffic, diesels are more efficient on the highway.

Some environmentalists, however, claim that the efficiency advantage of diesel is overstated because more oil goes into refining diesel than gasoline.

Hydrogen: A long wait

Pros Low or virtually no harmful emissions.

Cons Fuel-supply problems, expensive fuel-cell technology, onboard fuel storage, range, cold-temperature driveability.

At first glance, hydrogen-powered electric cars using fuel cells seem like the ideal solution to pollution woes and dependence on imported oil. They don't use combustion but rather an electro-chemical reaction whose only major byproduct is water. Fuel cells have been used for years to power spacecraft, and hydrogen is the most abundant element in the universe.

Many automakers are testing working prototypes, including the DaimlerChrysler F-Cell, Ford Focus FCV, General Motors HydroGen3, Honda FCX, Hyundai Santa Fe FCEV, Toyota FCHV, and Volkswagen HyMotion. And the federal government has committed hundreds of millions of dollars to do research on fuel cells and hydrogen issues. But daunting technical and infrastructure challenges make it unlikely that fuel-cell cars will get beyond the prototype stage for decades to come. General Motors is committed to selling hydrogen fuel cell cars commercially by 2010. But don't expect that you'll be able to put one in your driveway that soon. Most alternative fuel vehicles are tested in fleets for years.

Of several fuel-cell designs, the one favored for vehicles—because of its compactness and high energy-to-weight ratio—is the PEM (proton exchange membrane) system. When hydrogen gas is applied to one side of the sheet-plastic cell, it combines with atmospheric oxygen and produces electricity and water—something like the reverse of electrolysis.

Manufacturing costs are now about a hundred times that of an equivalent gasoline car, however, and reliability and life-span issues are still unknown. Honda's little FCX city car is the first fuel-cell vehicle able to start at subzero temperatures, but a Honda spokesman told us they didn't expect to produce a mass-market fuel-cell vehicle for at least 20 years.

More pressing is the problem of where to get the hydrogen and how to get it to the vehicle. While hydrogen is abundant, it's almost always bound up in minerals, hydrocarbons, or water. The cheapest way to obtain hydrogen gas is by extracting it from natural gas. But if one of the goals of moving to hydrogen cars is to get away from fossil fuels, then taking hydrogen from natural gas is self-defeating.

An alternative is taking electricity from a nonpolluting source like solar, wind, or hydro power and using it to split water into its hydrogen and oxygen components. The problem here is that it takes more electricity to make the hydrogen than the hydrogen can generate in a fuel cell. Even if hydrogen fuel is relatively expensive, it could be the best alternative for making pollution-free vehicles.

Another problem is that hydrogen gas carries very little energy per cubic foot. So automakers are developing different ways of storing sufficient amounts of it in a car. One method is to compress hydrogen to very high pressures (5,000 to 10,000 psi). Another is to compress it into liquid form at temperatures near absolute zero (minus 459 degrees F), but that process consumes a lot of energy. Some automakers are developing ways to store hydrogen in a solid form, but this is heavy and expensive.

Building a hydrogen distribution network also faces a major chicken-and-egg problem. Without the ability to refill them, people won't buy the cars, and without masses of cars to service, businesses won't spend the billions of dollars it would take to build the infrastructure. California is constructing a small network of hydrogen filling stations, which will increase the range of the tiny fleet of fuel-cell cars undergoing tests there. Those stations have electric-powered reformers that electrolyze water to make hydrogen on-site. Similar initiatives have been proposed in Canada.

A simpler solution is to burn hydrogen in a regular internal combustion engine, as BMW has demonstrated with a hydrogen-powered 7 Series sedan.

A hydrogen-burning engine creates no carbon dioxide (CO₂), is relatively inexpensive to produce, and doesn't need the ultra-pure hydrogen a fuel cell demands. On the other hand, it still requires a hydrogen-fueling system and needs a catalytic converter to reduce NOx emissions.

Ethanol: Growing renewable fuels

Pros Low emissions, made from renewable resources, less dependent on petroleum supplies.

Cons Currently low production volume, lower fuel economy.

Several alternative fuels that can power an internal-combustion engine are readily available, including compressed natural gas, propane, and alcohols such as methanol and ethanol. Ethanol, or ethyl alcohol, is the most promising renewable, not-from-petroleum gasoline substitute. It has long been used in motor fuel, usually as an oxygenate additive or blend with gasoline, because ethanol burns cleaner than gasoline.

In Brazil, 75 percent of the new cars sold can run on either gasoline or ethanol. It is also used in South Africa and Sweden.

Most ethanol fuel in the U.S. is made from corn and sold at service stations in the Midwest, near where it's made. The standard ethanol fuel is called E85, which is 85 percent ethanol and 15 percent gasoline. The gasoline is needed to give the fuel enough volatility to start the engine readily.

Ethanol contains less energy per gallon than gasoline, so E85 gets roughly 30 percent fewer miles per tankful. Factoring in that loss, corn-based ethanol sells for about $4.09 for the energy equivalent of a gallon of gasoline, making it more expensive than gasoline at today's prices.

Ethanol's lower fuel economy also results in more carbon dioxide (CO₂) emissions than a similar gasoline vehicle, although ethanol advocates say there is no net gain; the plants used to grow crops for the fuel absorb as much CO₂ as the cars burning it emit.

Millions of "flex-fuel" vehicles, which can run on either E85 or gasoline, are already on the road in the U.S. For those models, check out this list. Some are only available to commercial fleets.

An incentive for automakers to produce vehicles that run on E85 is that they are credited to the automaker's Corporate Average Fuel Economy ratings as if they operate 50% of the time on the alternative fuel and 50% of the time on conventional fuel. A National Highway Traffic Safety Administration document details an example "for a dual-fuel model that achieves 15 miles per gallon operating on alcohol fuel and 25 mpg on the conventional fuel, the resulting CAFE [calculation] would be…40 miles per gallon." This offsets the production of vehicles, such as large SUVs and trucks, which get poor fuel economy.

While most ethanol today is made from corn, cellulose is more promising. Cellulose ethanol can be made from corn stalks after harvesting, limbs left from logging operations, and from growing switchgrass. Sweden is moving toward greater dependence on ethanol from wood-based cellulose. And Iogen, a biotechnology firm, is building a plant in Canada to distill ethanol from cellulose.

Since switchgrass and agricultural byproducts aren't food sources, they can replace a much larger portion of our energy needs—up to 30 percent of transportation fuel—according to a 2003 Energy Department study.

So far, cellulosic ethanol costs about 50 percent more than corn-based ethanol—about $6.04 per gallon of gasoline equivalent. Even corn ethanol sells with a 51 cents per gallon tax break for producers, so ethanol has a long way to go before becoming cost effective in the U.S.

Summary

• A number of promising alternatives to the conventional, gasoline-powered car are being developed.
• Hybrid vehicles, using gas-electric or diesel-electric powertrains, are likely to continue generating consumer interest if gasoline prices remain high.
• Cleaner diesel engines are expected to become available when low-sulfur fuel is introduced in 2006.
• Renewable fuels made from farm crops will help, but they cannot yet replace more than a small percentage of U.S. petroleum needs.
• Hydrogen fuel-cell cars, which are ultraclean and use no petroleum, are still at least a decade away from being a practical alternative.
• Over the next 10 to 20 years, we are likely to see incremental improvements in a number of areas, which will help improve fuel economy, stretch petroleum supplies, and reduce pollution.

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