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But the news isn’t all bad. For the same energy delivered, producing hydrogen from methane dumps about half as much carbon dioxide into the atmosphere as burning fossil fuels does. That’s largely because hydrogen-based fuel cells are more efficient than internal combustion engines. In addition, serious research programs are underway to find a way to sequester carbon dioxide, whether it comes from hydrogen production or any other process that burns fossil fuels. One cheap solution could be to bury it in depleted gas and oil wells. My pessimistic bet, though, is that sequestering will be expensive. Politicians will choose to dump carbon dioxide into the atmosphere, and pay the hidden price of pollution, rather than ask the public to pay an up-front price at the pump.

Still, hydrogen is far from an ideal automobile fuel. Even in its densest form (liquid), hydrogen has only one-third as much energy per liter as gasoline. If stored as compressed gas at 300 atmospheres (a more practical option), it delivers less than one-fifth the energy per volume as gasoline. Such low energy density means that fuel storage would take up lots of room in a hydrogen-powered car-or, alternatively, a modest-sized fuel tank would severely restrict the vehicle’s range between fill-ups. Technology being developed to allow higher pressures would make hydrogen cars more attractive.

The known U.S. reserves of natural gas will be gone in a few decades, or sooner if we start using it for automobiles. The key assumption behind the push for a hydrogen economy appears to be the belief that there exist vast, undiscovered reserves of natural gas in the United States and around the world. But even if that belief proves wrong, we can always go back to making hydrogen from coal; we have enough of that for a century, if we don’t mind open pit mines.

I believe that the hydrogen economy is inevitable. Apparently so do big investors, who are setting up port facilities for future importation of large quantities of liquefied natural gas.

I also believe that the hydrogen will be made by whatever method is cheapest. In the short run, we could revert to electrolysis, powered by electricity from nuclear plants. Right now nuclear energy is expensive, largely, I believe, because of regulations driven by the perceived risk of radioactivity. Yet I think that carbon dioxide in the atmosphere offers a much greater long-term threat to the environment and to health than do nuclear power plants. We experienced the dangers of nuclear power in Chernobyl. For the carbon-based economy, the equivalent of Chernobyl is not just global warming; it is war. We saw that in Iraq. So on balance, I prefer nuclear-produced to methane-produced hydrogen.

When solar-generated electricity becomes cheaper than natural gas or coal, we can leave the fossil fuels in the ground, and have the best of all worlds. Cheap solar is inevitable, and we will not have to plaster the state of California with solar cells to enjoy its benefits. In a square kilometer of sunlight there is are 1,000 megawatts of solar power-the equivalent of a large nuclear power plant. Even if only 10 or 20 percent of the sunlight’s energy is extracted as electricity, the area of the solar cells will not be much larger than what we currently devote to nuclear, gas, or coal plants. Energy can be stored at night (and during cloudy days) in hydrogen. The solar future is coming.

Creating a hydrogen economy is good goal. But in the near term, barring a nuclear-power revival, the transition to hydrogen will probably mean a growing dependence on imported natural gas, and the continued pollution of the atmosphere with carbon dioxide. Despite President Bush’s optimism, the first cars of today’s children are highly unlikely to be powered by hydrogen that was cleanly produced. But maybe the cars of their children will be. And in the long term, our switch to hydrogen could ease the transition to a solar-powered economy.

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