Well-to-wheel environmental implications of fuel economy targets for hydrogen fuel cell electric buses in the United States

Hydrogen fuel cell electric vehicle technology is emerging as a promising option for the electrification of school or transit buses. For fuel cell electric transit buses, the U.S. government has set the fuel economy target at 8 miles per diesel gallon equivalent (MPDGE). However, life-cycle environmental implications of the 8 MPDGE target are currently lacking in the literature. In addition, no comparable target exists for fuel cell electric school buses. This study shows that achieving the fuel economy target (8 MPDGE) for fuel cell electric transit buses is likely to result in reductions of overall energy consumption and air emissions on a well-to-wheel basis, in comparison with diesel buses. For fuel cell electric school buses, 13 MPDGE fuel economy is expected to bring comparable benefits to those of their transit bus counterparts, in terms of well-to-wheel energy use and air emissions reductions. When it comes to the life-cycle environmental performance of fuel cell electric school/transit buses, it is critical to acknowledge that results can vary significantly depending on duty cycles, geographical factors, hydrogen fuel production pathways, and regional electric grids. All of these factors introduce nested (multilayered) variations in comparisons of diesel and fuel cell electric buses.