Limitations of Ammonia as a Hydrogen Energy Carrier for the Transportation Sector

Annual global carbon dioxide (CO2) emissions reached 34.2 gigatonnes (Gt) in 2019 as a result of extensive and unrestricted use of fossil fuels to fulfill ∼80% of society’s energy needs at the current level of ∼585 exajoules (EJ)/year.1,2 Transportation that provides mobility to passengers and freight is responsible for approximately 25% of the overall CO2 emission.3,4 Considering the current rate of population growth and associated increases in energy consumption, it has been projected that the corresponding global energy demand will be increased by at least 50% before 2050.1,2,5 To meet such needs while minimizing the environmental impacts by curtailing anthropogenic CO2 emissions, large-scale deployment of low-carbon renewable energy (RE) is necessary.6−8 Despite a moderate increase in the overall share of RE in the current energy landscape, recent studies indeed indicated that a full transition to 100% RE is attainable within the next 3 decades or so with a cost-efficient vision of deep electrification of heat and transportation sectors around the globe.9−11 Thus, this energy transition is no longer a matter of technical feasibility or economic viability, but political will.