| Why Hydrogen? Hydrogen, first on the periodic table of the elements, is the least complex and most abundant element in the universe. Using hydrogen as fuel can fundamentally change our relationship with the natural environment. As a nearly ideal energy carrier, hydrogen will play a critical role in a new, decentralized energy infrastructure that can provide power to vehicles, homes, and industries. Hydrogen boasts many important advantages over other fuels: it is non-toxic, renewable, clean to use, and packs much more energy per pound. Hydrogen is also the fuel of choice for energy-efficient fuel cells. Health and Environmental Safety Hydrogen, which exists as a gas under normal atmospheric conditions, is odorless, colorless, and tasteless. It is both non-toxic and safe to breathe. It can also be safely transported. In a hydrogen-based energy economy, environmental disasters like the Exxon Valdez debacle would be relegated to history. Because hydrogen dissipates when leaked, a major hydrogen spill would amount to little more than a waste of precious fuel. The Many Problems with Fossil Fuels To appreciate the various benefits of hydrogen as an energy carrier, it is important to understand the shortcomings of fuels we depend upon today. Conventional petroleum-based fuels like gasoline or diesel, as well as natural gas and coal, all contain carbon. When these fuels are burned, their carbon recombines with oxygen from the air to form carbon dioxide (CO2), the primary greenhouse gas that causes global warming. Furthermore, combustion of fossil fuels at the high temperatures and pressures reached inside an internal combustion (IC) engine (what powers most vehicles) or in an electric power plant produces other toxic emissions. Carbon monoxide (a poison), oxides of nitrogen and sulfur (NOx and SOx), volatile organic chemicals, and fine particulates are all components of air pollution attributable to the refining and combustion of fossil fuels. When released into the atmosphere, many of these compounds cause acid rain or react with sunlight to create ground-level smog. Vast ecosystem damage, increased lung disease and cancer are the ultimate price we pay for consuming these fossil fuels. Superior Efficiency Modern industrial development relied upon the widespread exploitation of these carbon-rich fuels. Mined in abundance, they were burned with little regard for overall system efficiency. But the search for alternatives has exposed another major shortcoming of carbon-based fuels: their energy is difficult to capture. Harnessing explosions—the process by which an IC engine converts chemical energy into mechanical energy—is inherently inefficient. Even after more than a century of refinement, most IC engines capture only 15–20 percent of the energy in gasoline. The rest of that energy is lost as waste heat and vibrational noise. Centralized electricity generation is similarly inefficient. The current U.S. electric system converts 33 percent of fuel energy into electricity and squanders most of the remaining heat. In stark comparison, fuel cells running on pure hydrogen are dramatically more efficient. By harnessing the fuel's energy via a chemical reaction rather than combustion, a fuel cell can convert 40–65 percent of hydrogen's energy into electricity. While a hydrogen-burning IC engine pollutes less than one running on gasoline, its energy efficiency is still less than half that of a fuel cell. Because a fuel cell's energy efficiency is not scale-dependent, stationary fuel cells can be sited locally where the waste heat can be used. This cogeneration of heat and power brings a fuel cell's energy efficiency close to 90 percent. All the while, this unparalleled energy efficiency arises from a reliable device that emits only drinkable water and scant traces of other emissions. Decarbonization: the Trend Towards Clean Renewables Post-industrial nations tend to favor energy-fuel decarbonization—a migration toward fuels with lower concentrations of carbon (exemplified by the shift from coal- to natural gas-fired electricity in the United States). Less carbon implies a greater concentration of hydrogen, which boasts a much greater specific energy density and burns more cleanly. As the trend progresses, pure gaseous hydrogen fuel waits as the ultimate goal. Looking ahead, it is also important to consider that fossil fuels are finite: we will eventually run out of them. This is not the case with hydrogen. Because this renewable energy carrier can be made from the electrolytic decomposition of water, and becomes water again when joined with oxygen in a fuel cell, hydrogen is inexhaustible. And when the process of electrolysis is powered by renewable electricity, the energy lifecycle of hydrogen is entirely pollution-free. In the meantime, transitional methods exist to make hydrogen with relatively moderate environmental impact. We currently consume fossil fuels 100,000 times faster than they are made, inspiring much speculation about how long our worldwide supplies will last. But the actual date of empty wells is largely irrelevant. The many benefits of hydrogen will make petroleum fuels obsolete at low prices before their scarcity sends drilling costs skyward. In the coming years, we will begin to see our energy economy, now rooted in fossil fuels, replaced by a hydrogen economy. 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