A Carbon Intensity Analysis of Hydrogen Fuel Cell Pathways

A hydrogen economy is an increasingly popular solution to lower global carbon dioxide emissions. Previous research has been focused on the economic conditions necessary for hydrogen to be cost competitive, which tends to neglect the effectiveness of greenhouse gas mitigation for the very solutions proposed. The holistic carbon footprint assessment of hydrogen production, distribution, and utilization methods, otherwise known as “well-to-wheels” carbon intensity, is critical to ensure the new hydrogen strategies proposed are effective in reducing global carbon emissions. When looking at these total carbon intensities, however, there is no single clear consensus regarding the pathway forward. When comparing the two fundamental technologies of steam methane reforming and electrolysis, there are different scenarios where either technology has a “greener” outcome. Despite misconceptions, steam methane reforming produces fewer total carbon emissions than current on-grid electrolysis due to the carbon emissions released by power plants. Similarly, for storing and deploying hydrogen, the optimal solution set will depend upon use case and geographic location. For example, truck transportation of gaseous hydrogen becomes less carbon efficient than liquification for distances greater than 614 miles. This paper explores the nuances of the factors of production that affect the total carbon footprint of a given technology, and how other emerging complimentary technologies, such as carbon capture storage and utilization, may change this carbon footprint calculation. As new technologies are evaluated, there are technological, political, and economic factors that will shape the landscape of how and where, hydrogen is produced, and the global infrastructure by which it is distributed.