Hydrogen just can't get a break.
Once touted as the clean wonder fuel of the future, hydrogen fuel cells for cars or homes are now routinely panned as inefficient and impractical, particularly when compared to technologies like electric cars or solar thermal water heaters.
Joseph Romm, a physicist, author of, among other books, Hell and High Water: Global Warming--the Solution and the Politics--or Hydrogen and editor of the respected ClimateProgress, also points out that the gas can be worse for the atmosphere than regular gas, depending on the circumstances.
Hydrogen burns clean out of the car's tailpipe, but producing hydrogen at a factory generates significant amount of CO2. The standard hydrogen process involves mixing methane with water at 815 degrees Celsius.
It takes about a megawatt-hour worth of electricity to produce enough hydrogen to drive a fuel cell car 1,000 miles. If the electricity came from a coal-burning power plant, it would generate about 2,100 pounds of carbon dioxide, according to Romm's calculations.
By contrast, a gas-powered car that gets about 40 miles per gallon would produce 485 pounds of CO2, or less than a quarter. (The MIT Technology Review does an extended analysis of the book..)
Of course, different variable will impact the results, but none really upend his argument. Here are some hypothetical options. You could get electric power from a plant running on hydroelectric or solar power. Coal fired plants, however, produce a substantial amount of the electricity in the U.S. ( Coal produces 23 percent of the total energy consumed in the U.S.--it's bested only by oil at 40 percent, according to stats from the National Renewable Energy Lab.). Therefore, on average, a hydrogen car would likely result in more CO2 than a standard car.
Hydrogen can also be produced at nuclear power plants or through biological or chemical reactions. These methods would short-circuit coal, but neither are considered practical or economical alternatives for mass production at the moment. Similarly, solar-powered stations for splitting water into hydrogen and water via electroalysis wouldn't pollute, but they also don't exist.
To top it off, the conventional hydrogen generating techniques produce lots of CO2 independent of the CO2 produced by the coal: for every kilogram of hydrogen, 9.3 kilograms of CO2 are produced.
Hydrogen backers, though, assert that many of these problems can be ameliorated through better, non-coal-burning electrical plants. Unlike gas cars, hydrogen cars belch out their CO2 at the factory, so the gas could be stored underground someday. Sequestration experiments are just getting underway.
So it's not completely dead, but the arguments against it are getting stronger. Municipalities are tinkering with the idea of deploying hydrogen cars as fleet cars, which never have to travel too far from a central filling station. These trials could become a big indicator if hydrogen has much of a chance in the coming decades.
Of course, this doesn't mean other alt fuel vehicles won't make it. There's a lot of work going on in biofuels and batteries and even hydrogen hybrids.