How Clean Are Hydrogen Fuel Cell Electric Vehicles?

New hydrogen-powered cars produce substantially less global warming emissions than their gasoline counterparts.

The automobile industry’s first production-version hydrogen-powered fuel cell electric vehicle (FCEV) in the United States was introduced by Hyundai in June 2014. Other automakers plan to bring more models to market over the next few years. Like all electric vehicles, FCEVs have a clean electric motor, but instead of needing to charge they can be quickly refilled with hydrogen fuel at stations similar to those that serve today’s gasoline cars. Also like plug-in cars, FCEVs produce no harmful tailpipe emissions.

Their total emissions, however, depend on how the hydrogen fuel is made and delivered. Full lifecycle “well-to-wheels” global warming emissions analyses show that even when using hydrogen from natural gas, today’s early hydrogen-powered FCEVs reduce emissions by over 30 percent compared with conventional gasoline vehicles and under California’s renewable hydrogen requirements, reductions are over 50 percent. Future FCEVs will likely be even cleaner.

Hydrogen Fuel Has Different Sources

The carbon emissions associated with hydrogen-fuel production depend on the source of hydrogen (typically, natural gas or water), the process used to extract it, and the source of the energy driving that process. Currently, most hydrogen is made by converting natural gas into hydrogen gas and carbon dioxide. The hydrogen can be made either at a central facility and trucked to a filling station or, if natural gas is available on-site, right at the station. However, hydrogen can also be produced from sources of energy that are lower in carbon than natural gas. Electricity from solar or wind power, for example, can be used to split water into hydrogen and oxygen through electrolysis. Another low-carbon source of hydrogen is methane gas from landfills and sewage treatment facilities, provided that methane leakage is minimized.

How Clean Are Hydrogen Fuel Cell Electric Vehicles?

To compare the global warming emissions of hydrogen-fueled and gasoline-fueled vehicles, it is necessary to examine the emissions from each stage of the fuel lifecycle, including extraction (in the cases of petroleum and natural gas, both of which are fossil fuels), production or refining, distribution to the fueling station, and, finally, consumption of the fuel in the vehicle. The hydrogen lifecycle also includes the electricity needed to pressurize the hydrogen gas for dispensing to vehicles. The full lifecycle analyses of both vehicle types capture each stage of fuel production in order to allow an apples-to-apples emissions comparison between fuels. Emissions are typically measured in grams of carbon dioxide equivalent per mile driven (g CO2 eq/mile). To make the comparison of emissions easier, we also use mpgGHG , which is the combined city/highway fuel-economy rating of a gasoline vehicle that would have global warming emissions equivalent to a fuel cell vehicle.

Future Improvements for Fuel Cell Vehicles

The Hyundai Tucson FCEV provides just one early example of the emissions reductions possible from hydrogen-powered vehicles. For example, the limited-production Honda Clarity fuel cell vehicle is rated at 65 mpgGHG on the 33 percent renewable California hydrogen mix, despite using older technology. Similarly, a demonstration-model Toyota Highlander SUV reached the equivalent of 75 mpgGHG during on-road testing in Los Angeles in 2009 (Wipke, Anton, and Sprik 2009). With advances in fuel cell performance and in automotive technologies such as the electric drivetrain, and as lower-carbon hydrogen becomes more widely available, fuel cell vehicles that come to market over the next few years will likely cut emissions relative to gasoline vehicles even more. Such evolution has already been the norm among plug-in electric vehicles, including the Nissan Leaf; in just three years on the market, the Leaf lowered its electricity consumption by more than 10 percent, from 0.34 to 0.30 kWh/mile. And because fuel cell vehicles share many components with plug-in electric vehicles, advances such as improved electric motors or more efficient power systems will benefit fuel cell vehicles too. Policies such as California’s, which mandate lower-carbon hydrogen production, will further improve the benefits of switching from gasoline to fuel cell vehicles.