Hydrogen-as-Ammonia: Solving the Hydrogen Transportation Conundrum

As interest grows in using hydrogen gas as a clean energy source, there is still one significant hurdle for its practical application: How to transport it efficiently and safely from its production point to the end user.

Like natural gas, hydrogen production opportunities are abundant in remote areas with plenty of sun, wind and water to manufacture green hydrogen. But most consumers for hydrogen are likely in urban and industrial areas, creating a need for transport and distribution networks.

Across North America, pipelines deliver natural gas to homes, businesses and power plants. It is proven to be the most efficient method of moving gaseous energy, and there are some hydrogen pipeline networks in operation today. But hydrogen gas, with a significantly lower BTU energy density value than natural gas, requires a larger pipe diameter and/or higher delivery pressure to meet the energy demand. This makes a hydrogen pipeline less efficient and more costly, especially over long distances.

It is possible to liquefy hydrogen to accommodate surface, rail or water transport. This approach works successfully with liquefied natural gas (LNG), where the gas is cooled to -160 degrees Celsius and shipped to its destination. Then after regasification, it is delivered to customers through pipelines.

Unfortunately, liquefying hydrogen gas requires significantly lower temperatures, adding more energy consumption as compared to LNG. When you look at the massive energy consumption needed to produce the gas and then liquefy it, hydrogen becomes a commercially impractical fuel source based on today’s technologies.

But there is a third solution showing real promise: Converting hydrogen gas to ammonia.

Ammonia is a chemical compound combining nitrogen with hydrogen. Liquefying hydrogen into ammonia requires application of pressure or the lowering of the temperature to a comparatively manageable -35 degrees Celsius. Pressurized ammonia is easily transported by pipeline and refrigerated ammonia can be transported in carriers in a similar way to LNG, making ocean transport and industrial-scale export more cost effective. By contrast, transporting hydrogen in gas or liquid form would require construction of new vessels, pipelines and other costly infrastructure overhauls.

Many industrial projects are already viewing ammonia as the most efficient way to move large quantities of hydrogen as a liquid.

Once hydrogen-as-ammonia reaches its destination, it can be converted back to hydrogen gas. But that process will require more energy and creates additional safety and community preparedness protocols.

What if the ammonia could become the fuel source itself?

Ammonia is currently being manufactured and sold as a carbon-free fuel, particularly in Europe and Asia, which have demand for imported clean energy and high conviction policy support. There are already developments from original equipment manufacturers, such as Mitsubishi and GE, for fuel switching of turbines in power generation, integral to global energy decarbonization.

Using alternative energy sources to produce hydrogen and convert it to ammonia markedly reduces its carbon impact at the production point. The market exists to make this a viable low-carbon energy option.

As with any liquid fuel, public safety concern for hydrogen-as-ammonia primarily centers around leak risks and toxicity. If a pipeline is breached, liquid ammonia immediately vaporizes upon contact with the atmosphere, creating a potential health hazard.

To mitigate impact, pipelines have isolation valves that seal off sections of the pipe to reduce the amount of gas released. WSP has studied pipelines for this purpose, and the most practical solution lies in the installation of more valves, particularly in populated areas, so that the amount of ammonia that escapes and any resulting gas plume poses no greater health risk than other gas and liquid fuels using similar systems of transport.

Ammonia provides some unique advantages building off existing, proven transport methods and infrastructure. Long-distance ammonia pipelines have been operating in the U.S. and other countries for more than 50 years. Most are smaller, low-pressure eight-inch diameter pipelines, so the environmental impact would be less, but the transportation technology is proven.

Like the LNG carriers that can be adapted, these existing liquid pipelines can also be converted to transport hydrogen-as-ammonia.

To serve as a reliable fuel source, low-carbon hydrogen production will need to consistently match demand. WSP has been at the forefront of design for hydrogen storage projects, which combine massive hydrogen energy production with the capability to store it for extended periods of time until needed.

This trend demonstrates the growing interest in hydrogen as a fuel source, and WSP is working on several pipeline design projects that are considering either hydrogen or ammonia to move it from hubs to existing gas-fired power plants or export facilities.

At the appropriate scale, keeping hydrogen in a refrigerated or pressurized state will work. This is particularly true for mobility applications where it can be transported as compressed or liquified hydrogen in smaller containers for use in hydrogen fueling stations to power a bus fleet and other heavy or long-range vehicles. Compressed fuel is used extensively and safely in bus fleets across the U.S. Hydrogen is already distributed in this way for these growing mobility markets.

Hydrogen and hydrogen-as-ammonia provide the benefit of clean, carbon-free fuel, and will play an important part in our energy future. Before that can happen, transportation challenges must be evaluated and addressed. That assessment is happening today. 

While ammonia is already produced and distributed today, it’s going to take some patience for these energy options to be socialized and adapted to the infrastructure before becoming practical for broader applications to support the energy transition.

As technology progresses, WSP will provide boots on the ground to make it happen.