The Hydrogen Solution

If ever a phrase tripped lightly over the tongue, “the hydrogen economy” does. It appeals to the futurist in all of us, and it sounds so simple: We currently have a carbon economy that produces carbon dioxide (CO2), the most prominent of the greenhouse gases that are warming up the world. Fortunately, however, we will eventually be able to power our cars and industries with climate-neutral hydrogen, which produces only water. Well, can we? This issue of Science exposes some of the problems, and they're serious. To convert the U.S. economy in this way will require a lot of hydrogen: about 150 million tons of it in each year. That hydrogen will have to be made by extracting it from water or biomass, and that takes energy. So, at least at first, we will have to burn fossil fuels to make the hydrogen, which means that we will have to sequester the CO2 that results lest it go into the atmosphere. That kind of dilemma is confronted in virtually all of the proposed routes for hydrogen production: We find a way of supplying the energy to create the stuff, but then we have to develop other new technologies to deal with the consequences of supplying that energy. In short, as the Viewpoint by Turner in this issue (p. 972) makes clear, getting there will be a monumental challenge.