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It’s Not Necessarily Clean

It is a popular misconception that hydrogen is inherently good for the environment. But in fact, hydrogen is no greener than the energy sources used to produce it. As the National Academy panel noted, “It is highly likely that fossil fuels will be the principal sources of hydrogen for several decades.” Any premature push toward hydrogen cars would inevitably mean the hydrogen would come from the cheapest source today, natural gas. Yet, given the constraints on the North American gas supply, we would just be trading imported gas for imported oil.

More important, a fuel-cell car running on hydrogen derived from natural gas offers no significant greenhouse gas savings compared to running advanced hybrid vehicles on oil-as a 2003 MIT study concluded. The best new hybrids have sharply reduced their fuel consumption and hence greenhouse gas emissions. Running on low-sulfur gasoline, the 2004 Prius produces 90 percent less tailpipe emissions than the average new car.

The least expensive hydrogen, however, is dirty. Based on the hydrogen fueling stations Royal Dutch/Shell has proposed to build, the total emissions of nitrogen oxides from a fuel-cell vehicle would be triple that of the best new cars.

Equally important, such a strategy would divert natural gas from a variety of better uses. While vehicles running on natural gas-derived hydrogen won’t provide significant greenhouse gas reductions compared to the best hybrids running on gasoline, a switchover to natural gas can greatly reduce the emissions from electricity generating plants. A coal-fired generator releases more than 1,000 kilograms of carbon dioxide into the air for each megawatt-hour of electricity it produces. The best gas-fired plants, by contrast, release only about 350 kilograms of carbon dioxide per megawatt-hour generated.

Similarly, one megawatt-hour of electricity from renewables, if used to make hydrogen for a fuel-cell vehicle, would save around 230 kilograms of carbon dioxide compared to a Prius running on gasoline. That is some 770 kilograms less than the savings from displacing coal power-and these savings can be achieved without spending hundreds of billions of dollars on fuel-cell vehicles and hydrogen infrastructure. As David Keith of Carnegie Mellon and Alexander Farrell of the University of California, Berkeley, concluded in a July 2003 analysis in Science magazine: “Until CO2 emissions from electricity generation are virtually eliminated, it will be far more cost-effective to use new CO2-neutral electricity (e.g., wind or nuclear) to reduce emissions by substituting for fossil-generated electricity.”

The U.S. Congress, however, won’t pass legislation requiring even 10 percent of electricity in 2020 to be from renewables. This means that hydrogen cars will have no real value as a global warming strategy until after 2030. A 2004 analysis by Pacific Northwest National Laboratory concluded that even with technology breakthroughs and a big push on reducing carbon dioxide emissions, “hydrogen doesn’t penetrate the transportation sector in a major way until after 2035.”

Right now, delivering renewable hydrogen to a car in usable form is prohibitively expensive-equivalent to gasoline at $6 to $10 a gallon. We need a major breakthrough in CO2-neutral hydrogen production, along with significant leaps forward in fuel cells and hydrogen storage, before hydrogen cars will be plausible competitors.

While we’re doing the R&D over the next two decades, we must, if we are to avoid catastrophic global warming, make new CO2-neutral electricity our top priority. A March 2003 analysis by a group of scientists led by Ken Caldeira of the Lawrence Livermore National Laboratory, and published in Science magazine, concluded that “if climate sensitivity is in the middle” of the currently projected range, “even stabilization at 4C warming would require installation of 410 megawatts of carbon emissions-free energy capacity each day”-five times the business-as-usual forecast.

While hydrogen vehicles might have limited value replacing fleets powered by diesels engines in very polluted cities before 2030, fuel-cell cars are unlikely to achieve mass-market success by then. Neither government policy nor business investment should be based on the belief that hydrogen cars will have meaningful commercial success in the near or medium term.

Joseph J. Romm was acting assistant secretary of energy for energy efficiency and renewable energy during the Clinton administration. This article is based on material from his book The Hype about Hydrogen: Fact and Fiction in the Race to Save the Climate, published this month by Island Press. For more information about the book, go to

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