Executive Summary
In recent years, the use of hydrogen as a fuel for cars has become an increasingly popular idea. Many influential people endorse the idea as an important milestone on the road to U.S. energy independence. Others support it because they see hydrogen as the ultimate clean fuel to help the environment. But can the mass conversion of vehicles to hydrogen power significantly improve the environment? And given the high cost of building the infrastructure necessary to transport and distribute hydrogen, would it be worth it? This study sets out to answer these very questions.
When a vehicle’s engine burns gasoline, carbon dioxide (CO2) is produced in the exhaust gases that then enter the air around the car. Proponents of using hydrogen to power automobiles generally point out that a hydrogen-fueled car produces only water in its exhaust, and no CO2. While this is true, it is an incomplete picture. This study, unlike many others, opens the aperture in which CO2 emissions are measured, to include not only the release caused by vehicles, but the emissions caused by the manufacture, transport and distribution of both hydrogen and gasoline, to foster a more accurate comparison of their relative benefits. Using various hydrogen production methods depicted by 11 case studies, this study measures hydrogen fuel cells and liquid fuel cells against a base case of the modern, internal combustion engine, gasoline-powered vehicle to assess which results in the least CO2 emissions and the relative value of converting vehicles to hydrogen power.
We performed a simulation for each case study based on a 300-mile drive for the candidate vehicle. Results, including raw materials, energy requirements, and atmospheric CO2 production, were calculated based on the resources required to generate the fuel necessary to drive the car 300 miles. To standardize for the various types of power generation infrastructures, we used the state of California as the geographic area for this study. Additionally, hydrogen-powered vehicles require a far heavier weight to achieve the same horsepower performance of gasoline-powered vehicles. We therefore did not normalize for relative vehicle performance; as a result, the fuel cell vehicles used in this study will not perform as well as the gasoline-powered one.
We found that while hydrogen fuel cell cars powered by hydrogen manufactured using hydroelectricity resulted in the least CO2 emissions, this case was rendered impractical due to the limited amount of electricity generated by a hydroelectric source. In California, hydrogen would most likely be manufactured through electrolysis produced via natural gas, which resulted in the highest CO2 emissions. We found the decline in emissions to be barely discernible, leading to the conclusion that the reduction in CO2 emissions gained by using hydrogen-powered vehicles is not significant.
To assess the significance of the impact of converting to hydrogen-powered cars we projected the effect on CO2 emissions if all cars in California had converted to hydrogen in 1981. We found the decline in emissions to be barely discernable and probably not even measurable, leading to the conclusion that the reduction in CO2 emissions gained by using hydrogen-powered vehicles is not significant.
The most compelling reason for the inability of hydrogen-powered vehicles to significantly affect CO2 emissions is that total vehicular emissions pale in comparison to the total CO2 emitted statewide from all hydrocarbon (fossil fuel) combustion. In fact, this study found that if vehicular emissions were entirely eliminated, total emissions statewide would fall by 10 percent or less. This fact, combined with the CO2 emissions generated by hydrogen manufacture and distribution, calls into question the value of converting the present gasoline-powered vehicle into the expensive hydrogen-powered vehicle considered by so many to be the answer to today’s global warming problems.
Our study concludes that converting vehicles to run on hydrogen would have at best a marginal effect on CO2 emissions. In fact, if hydrogen-powered vehicles are made to have the same performance characteristics as gasoline-powered ones, the use of hydrogen may actually increase atmospheric CO2 emissions.
There are far simpler, less expensive, and more effective ways to reduce carbon dioxide emissions. People and businesses already have strong incentives to conserve energy, and competitive electricity markets and real-time pricing of electricity will strengthen those incentives. Gasoline cars are increasingly efficient and targeting gross polluting vehicles on the road today will greatly reduce auto emissions. None of these alternatives requires constructing a hydrogen generation and distribution infrastructure, a massive and expensive undertaking.