From fertilizer to fuel: how ammonia may break the hydrogen deadlock

As the world grapples with climate change, hydrogen fuel cells have emerged as a compelling alternative to battery-powered electric vehicles, offering rapid refueling and longer range without the polluting tailpipe emissions. These cells, which combine hydrogen with oxygen to produce electricity while emitting only water vapor, could revolutionize transportation, particularly for heavy-duty vehicles where batteries prove impractical due to weight constraints.

However, the mixing of hydrogen and oxygen inherently presents risks. The Achilles heel of hydrogen fuel cells has always been the risks associated with storage and transportation of hydrogen gas — history buffs will recall images of the flame-engulfed Hindenburg above Lakehurst, New Jersey. As the lightest element, hydrogen must be heavily compressed or liquefied at extremely low temperatures, requiring specialized infrastructure, expensive materials and extensive safety precautions. This “hydrogen logistics problem” has created a chicken-and-egg scenario: without infrastructure, there is little demand for hydrogen vehicles, and without vehicles, there is little incentive to build infrastructure.

Enter ammonia, a simple molecule of a single nitrogen bound to three hydrogen atoms that could be the key to unlocking the hydrogen economy. A key reagent in the production of agricultural fertilizers, ammonia is already mass-produced on a gargantuan scale, estimated at 150 million metric tons in 2023, by a reaction known as the Haber-Bosch process, which combines nitrogen, the main component of atmospheric air, with hydrogen obtained from natural gas.

The concept is elegantly simple: transport ammonia to fueling stations, where on-site “crackers” would split it back into nitrogen and hydrogen on demand. The hydrogen would fuel vehicles, while the nitrogen would simply return to the atmosphere. This approach would leverage existing infrastructure for transporting liquid-based fuels, while solving the problem of hydrogen storage and transportation.

At atmospheric pressure and modest cooling, ammonia becomes a liquid that is roughly 50% more dense than liquid hydrogen, making it far easier to transport and store. Crucially, unlike the electric vehicle market, extensive infrastructure for ammonia transport already exists, built up over decades to support the fertilizer industry. Major ports are already handling ammonia regularly with well-established safety protocols for its transport. Moreover, existing pipelines, storage tanks, and shipping networks can be readily adapted to handle ammonia. Additionally, unlike oil reserves and lithium mines, the Haber-Bosch process is already widely employed around the globe with no single economy monopolizing the production of ammonia, helping to overcome the gross unfairness and exploitation associated with the Li-ion battery sector.

Despite clear incentive, challenges remain before this vision becomes reality. Current ammonia cracking technology requires high temperatures and expensive catalysts, making the process energy-intensive and costly. It is not yet at a point where this can be done economically at the scale of a typical fueling station, and research is needed to develop more efficient on-demand cracking methods. Additionally, the production of ammonia is itself a contributor of greenhouse gas emissions, though work is well underway towards improving the efficiency of the Haber-Bosch process to make it truly sustainable.

Despite these hurdles, ammonia-based hydrogen delivery represents one of the most promising paths toward truly sustainable transportation. As cracking technology improves and the economics of scale-up develop, this approach could finally break the infrastructure deadlock that has held back the hydrogen economy. Research in this field must continue with an emphasis on sustainability, efficiency and safety. The foundations are already in place — they just need to be built upon.