Skip to main content


Archive / Current Issue

Green ammonia in the energy transition—the opportunities and challenges

Hydrogen Mobility and Transportation

S. MAHDY, Howden, Renfrew, Scotland

Ammonia is one of the most well-known and important industrial chemicals in the world. More than 50% of the world’s food production depends on fertilizers that are produced using ammonia. One hundred years ago, ammonia helped the world overcome a major food crisis caused by the growing population. The question now is, “Can ammonia once again help the world face another serious crisis: climate change?” 

Green ammonia is created by combining hydrogen (H2) and nitrogen (N) molecules at high pressure to produce 100% carbon-free ammonia. The resulting liquid has a potential variety of uses, including as an energy carrier for H2 or directly as a fuel. However, whether green ammonia can become widely used in these ways remains to be determined. In addition to the potential opportunities to harness green ammonia, there are also many challengesit is important to explore how green ammonia might impact the future of the energy transition.

Opportunities for using green ammonia. Ammonia can help in the world’s energy transition in numerous ways. First, in contrast to other forms of chemical storage, ammonia is the only carbon-free H2 carrier. It has also a high H2 content, a reasonable-sized existing infrastructure, the ability to be liquefied at mild conditions (both temperature and pressure) and very mature production technologies. 

One of the biggest challenges the renewable energy industry faces in generaland with H2, in particularis transportation between exporting and importing markets. Many countries do not benefit from renewable energy potential, so straightforward transportation of supply is vital. Converting H2 into liquid ammonia may be a feasible solution and a potential opportunity for the industry to solve this conundrum. 

Another key opportunity for using green ammonia is the volume of energy it stores. Liquid green ammonia volumes can store three times as much pressurized gaseous H2 as equivalent fossil fuels, making it a much more economical process across the supply chain. As discussed above, because the infrastructure for H2 transport continues to develop, H2 can be stored within green ammonia to enable a more feasible transportation and storage process. 

As energy demands fluctuate and grids must respond to varying demands inherent in the intermittency of solar and wind power, storage is vital. Reliable energy storage technologies are indispensable to the smooth functioning of power distribution networks—during times of excess, it is vital to store energy that is ready for use when demand outstrips supply. Green ammonia, with its high energy volumetric density and straightforward storage requirements, is well-placed as a long-duration energy store, complementing the rapid response that can be achieved with batteries and pumped hydro. 

Alternatively, green ammonia itself can also be used directly as a low-carbon fuel in internal combustion engines, or to generate electricity via fuel cells. As the pace of the energy transition quickens, exploring options for every possible fuel source becomes increasingly important. 

Challenges of using green ammonia. Like all new energy sources or carriers, harnessing green ammonia inevitably presents several challenges that must be considered. One of these challenges is the process of converting ammonia back to H2 if it is used as a carrier, as the process is presently inefficient and still requires more energy, which in turn puts more feasibility pressure on the H2 value chain. 

A further barrier to overcome in using ammonia as a fuel is that when ammonia is combusted, the fuel releases environmental pollutants like nitrous oxides (NOx) and nitric oxides (NO) into the atmosphere. Additionally, there is a risk in using ammonia within a marine environment, either as a fuel or in its large-scale global transportation. Should ammonia leak into water, it is difficult to contain and would cause damage to marine life. However, ammonia has been shipped for many years without any major safety incidents, so it should continue to be manageable with the right safety standards and precautions. 

Another significant challenge is simply the availability of sufficient green clean ammonia to meet demand. Global ammonia production now stands at ~180 metric MMtpy, but projected demand is forecast to reach 1 metric Btpy if ammonia is used as an energy carrier or fuel. This level of supply would require significant investment in both production facilities and infrastructure expansion. Even with the required investment, ammonia may yet prove to be a more economical alternative where other options require infrastructure to be built from scratch.  

The future of green ammonia. Some countries, like Japan, have already made some progress in using green ammonia as a direct fuel source with a solid plan for the future. The author’s company is working with several project developers that are planning to build green ammonia projects around the world, delivering its advanced compression solutions to these projectsan increased demand is being seen, so clearly there is growth in the market. Projects within major markets include Australia, the Middle East and the U.S.  

The use of green ammonia requires further research and testingand safety mitigation is at the top of that listand it is an attractive option worth exploring further. Ammonia is already in use on tankers, in pipelines, and spread across crop fields as fertilizer. If its use as an efficient energy carrier for H2, or as a direct fuel source, means that we are able to speed up the energy transition, then the investment is certainly warranted. 

The energy transition requires the exploration of all possibilities. Based on current outputs, global net-zero targets cannot be met without testing and trialing every resource available. H2, green ammonia, eFuels and other options will all contribute to lowering carbon emissions over time, but it is unlikely that any one of them will be the single ‘answer’ or ‘solution’ society is looking for. Adding green ammonia to the R&D mix is definitely an effort worth making.H2T


SALAH MAHDY is the Global Director for Renewable Hydrogen at Howden and leads the company’s hydrogen business globally. With more than 20 yr of professional experience, he has delivered high-profile green and blue hydrogen, and ammonia projects and studies, including several of the world’s first projects in this space.  

Under Mahdy’s leadership, Howden’s advanced hydrogen compression solutions have been selected to be in the heart of key projects for the global energy transition, such as the world’s first green steel plant, the world’s largest hydrogen refueling station, the world’s first eFuels plant, the world’s first container vessel (ship) operating on carbon-neutral fuel, and Europe’s first hydrogen underground storage project.  

Prior to his current role with Howden, Mahdy held senior business and engineering positions in several global companies, such as Worley, Honeywell UOP, AspenTech and ITM Power. He holds an MS degree in chemical engineering and an MBA.