When President Bush announced in his 2003 State of the Union speech that he was committing more than $1 billion to boost research into using hydrogen to power cars to reduce America’s dependence on foreign oil while also improving the environment, many people were rightly pleased. “A single chemical reaction between hydrogen and oxygen generates energy, which can be used to power a car – producing only water, not exhaust fumes. With a new national commitment, our scientists and engineers will overcome obstacles to taking these cars from laboratory to showroom, so that the first car driven by a child born today could be powered by hydrogen, and pollution-free,” the president said last January.

This timetable is overly optimistic, according to a report issued last week by the National Academy of Sciences. The academy found there was potential for replacing gasoline with hydrogen in 50 years, but that even with this slower timeline, many technical barriers that must be overcome. Those barriers include the fact that current fuel cells are 10 to 20 times too expensive to be considered for use in commercial vehicles. Fuel cell lifetimes are also too short for use in cars and trucks. Another challenge to be overcome is the high cost of distributing hydrogen to dispersed locations.

This does not mean the research should not be done. On the contrary, finding alternatives to fossil fuels – which hydrogen currently is not because it is produced least expensively by burning coal or natural gas – is imperative. In the meantime, however, the president and Congress should push for energy conservation while also seeking alternative energy sources that can be brought on line much more quickly than hydrogen.

Over the next 25 years, the effects of hydrogen-powered cars on oil imports and greenhouse gas emissions are “likely to be minor,” according to the NAS report. With this in mind, the academy suggested that further work on battery-power cars and hybrid cars that combine gasoline and electric motors could be a better choice than investing so much in hydrogen now.

Doubts about hydrogen’s potential have also been raised by Joseph Romm, the Energy Department official in charge of conservation and alternative energy in the Clinton administration, whose book “The Myth About Hydrogen” will soon be released.

A major hurdle, according to Mr. Romm, is that the fuels now used to make hydrogen can be better used to produce electricity directly. Most hydrogen produced today is made from natural gas. Using natural gas to create electricity, thereby replacing coal, would provide many more environmental benefits than using the gas to create hydrogen. Americans would get more energy from a cubic foot of natural gas burned in a modern gas-powered electric plant than if it were converted to hydrogen, he told The New York Times last week. “People who want to build ‘hydrogen highways’ and drive a hydrogen car in 10 to 15 years on a mass scale, are just kidding themselves,” Mr. Romm said.

Given these assessments, efforts to reduce pollution by modernizing power plants and reducing fossil fuel consumption by raising the fuel efficiency of passenger cars and trucks must continue. So, too, should projects aimed at creating more energy from the wind and sun.