Ammonia saved the world once; it might do it again.
A century ago, the world faced a looming food crisis. A booming population was pushing farmers to grow crops faster than nitrogen-fixing bacteria in the soil could keep up, and the South American deposits of guano and natural nitrates they applied as fertilizer were dwindling.
In what may still be the biggest global problem solved by chemistry, Fritz Haber and Carl Bosch developed a process to react hydrogen and atmospheric nitrogen under pressure to make ammonia, which farmers adopted in place of natural fertilizers. The Haber-Bosch process is still responsible for nearly all the world’s ammonia, as well as derivatives like urea and ammonium nitrate.
Today’s crisis is climate change. This time, ammonia could come to the rescue by capturing, storing, and shipping hydrogen for use in emission-free fuel cells and turbines. Efforts are also underway to combust ammonia directly in power plants and ship engines.
Chemical companies smell an opportunity. Several firms are developing green ammonia, a route to ammonia in which hydrogen derived from water electrolysis powered by alternative energy replaces hydrocarbon-based hydrogen, making ammonia production virtually carbon dioxide–free. They are also investing in carbon capture and storage to minimize the carbon impact of making conventional ammonia, creating what the industry refers to as blue ammonia.
Tony Will, CEO of the world’s largest ammonia producer, CF Industries, sees a fundamental shift in the industry’s prospects. “Up to this point, we have made a business by selling the nitrogen value of the molecule,” he says. “What’s really exciting about this is now there is an opportunity and a market that values the hydrogen portion of the molecule.”
But establishing an ammonia fuel industry won’t be easy. By most estimates, green ammonia will cost two to four times as much to make as conventional ammonia. And some of the technologies needed to harness the molecule, such as ammonia-burning engines, are still experimental. Governments and the marketplace will have to decide if green ammonia is worth the effort.
Nature has given ammonia attributes that seem to make it a perfect commodity for a future hydrogen economy.
A report compiled last August by Haldor Topsoe, an ammonia production technology firm, and other companies noted a number of those qualities. Ammonia has a higher energy density, at 12.7 MJ/L, than even liquid hydrogen, at 8.5 MJ/L. Liquid hydrogen has to be stored at cryogenic conditions of –253 °C, whereas ammonia can be stored at a much less energy-intensive –33 °C. And ammonia, though hazardous to handle, is much less flammable than hydrogen.
Furthermore, thanks to a century of ammonia use in agriculture, a vast ammonia infrastructure already exists. Worldwide, some 180 million metric tons (t) of ammonia is produced annually, and 120 ports are equipped with ammonia terminals.
The ammonia industry has informally adopted a color scheme to describe the carbon intensity of the different methods for making ammonia. The system also applies to hydrogen.
Also called brown ammonia, this is conventional ammonia that has been made the same way for 100 years. The Haber-Bosch process, responsible for nearly all of the world’s 180 million t of annual ammonia production, reacts hydrogen and atmospheric nitrogen. The hydrogen often comes from the steam reformation of methane, a process that emits CO2.
Blue ammonia is conventional ammonia for which by-product CO2 has been captured and stored, reducing climate impact compared with gray ammonia. Many fertilizer makers have embarked on such projects in recent years. Blue ammonia is controversial and in need of industry standards. Using CO2 for enhanced oil recovery, for example, isn’t as environmentally beneficial as injecting it into the ground permanently.
Green ammonia is made with hydrogen that comes from water electrolysis powered by alternative energy. Projects abound, though most are on a modest scale of tens of thousands of tons, an order of magnitude smaller than a typical ammonia plant. A massive project in Saudi Arabia, however, aims to make more than 1 million metric tons of ammonia per year.
This process uses pyrolysis to convert methane into pure carbon and hydrogen, which is reacted with nitrogen to make ammonia. The industry thinks of turquoise ammonia as somewhere between green and blue. A prominent project is Monolith Materials’ carbon black plant in Nebraska.
But pivoting all that infrastructure toward environmentally friendly fuels will take time. Until last year, most proposed green ammonia projects were small, tens of thousands of metric tons rather than the half million metric tons per year, or more, that a conventional ammonia plant puts out.
Several are government-supported projects in Australia. For example, the Norwegian fertilizer maker Yara intends to install electrolyzers to make 3,500 t per year of green ammonia at its plant in Pilbara, and the ammonium nitrate explosives makers Dyno Nobel and Queensland Nitrates are studying 9,000 and 20,000 t of green ammonia output, respectively. Pilot programs are also underway in New Zealand and Chile.
Several much larger projects were announced last year. By far the most ambitious one is in Saudi Arabia. The $5 billion project is a partnership between the US company Air Products and Chemicals, the local firm ACWA Power, and NEOM, a developer building a carbon-free city in Saudi Arabia.
Slated for completion in 2025, the installation will sit on the Red Sea coast. Solar cells will harness the sun during the day, while turbines will capture nighttime winds to generate 4 GW of electricity for water electrolysis plants. The hydrogen will be fed into a traditional Haber-Bosch plant to produce 1.2 million t per year of ammonia—a large amount even by conventional standards.
Air Products will spend an additional $2 billion to set up a novel distribution scheme. It will ship the ammonia around the world to specialized plants installed at depots for buses and trucks fueled by hydrogen cells. These units will dissociate the ammonia to recover the hydrogen, enough for up to 15,000 trucks and buses in all.
When Air Products CEO Seifi Ghasemi unveiled the project last summer, he told analysts that he sees it as a feasibility study for an entirely new industry. “We are proud to be part of this undertaking because it is the first and largest and the most innovative project to make mankind’s dream of carbon-free energy a reality,” he said.
Other firms followed suit with big projects. In October, Yara said it was considering installing electrolyzers at its ammonia plant in Sluiskil, the Netherlands, to generate enough hydrogen for 75,000 t of ammonia. The plant would run on 100 MW of power from a new offshore wind farm.
And in December, the company announced an even larger project: new electrolyzers at its plant in Porsgrunn, Norway, for 500,000 t per year of ammonia production.
The energy would come from Norway’s energy grid, which is already 98% renewable thanks to the country’s lush hydroelectric resources. Yara wants to sell the ammonia as a fuel for ships. The company is seeking incentives from the Norwegian government before it moves forward.
CF Industries is launching the first big green ammonia project in the US. Over the next 3 years, the company will spend $100 million to convert 20,000 t per year of conventional ammonia at its flagship plant in Donaldsonville, Louisiana, to green by installing electrolyzers. The electricity for the plant will be renewable power purchased from the grid.
By CF’s estimates, green ammonia will cost about $500 per metric ton to make, about three times as much as conventional ammonia. But the company estimates that it could fetch $2,200 per metric ton in the alternative energy marketplace, about eight times as much as conventional.
Moreover, Will says, the market is potentially huge. “Ammonia taking even a relatively small portion of marine applications, let alone overall hydrogen applications, and you’re talking about more than doubling the current production capacity of global ammonia,” he says.
CF has been studying ammonia fuels for some time and has lately been getting a lot of “inbound inquiries,” Will says. Many have come from Japan, where power companies are experimenting with cofiring ammonia in coal-based power plants with the aim of converting entirely to ammonia one day.
Not everyone is as bullish as Will. Andrea Valentini, a principal for Asia-Pacific and the Middle East at Argus Consulting Services, points to a number of hurdles the industry must clear if it is to establish green ammonia as an alternative fuel.
One problem is that marine engines capable of using ammonia aren’t available yet. “Developers are talking about 2024, perhaps, as a timeline,” Valentini says. “I don’t think that’s unrealistic.”
In one such initiative, the Finnish engine maker Wartsila is beginning this year to test an ammonia-fueled four-stroke marine engine. In another, MAN Energy is perfecting a two-stroke ammonia engine.
Other unknowns abound. “We have a very large number of projects around the world, especially in Australia and Saudi Arabia, which are going to produce green hydrogen at volumes that will require significant improvements in electrolyzer costs and efficiency,” Valentini says. And firms are hoping to address a market that doesn’t exist yet. “So on paper it is a risky proposition.”
And where companies see high profit margins for green ammonia, Valentini sees costs. “From a supply side, talking about a premium is always a nice thing, but a premium for a supplier means that someone else further down the line will have to bear the brunt, and that means us as consumers,” he says.
Another question for the green ammonia sector is whether there will be enough renewable power to support it. Forecasts for renewables are bullish. For example, BP’s latest Energy Outlook says renewables will grow from 5% of the world’s energy supply in 2018 to 45–60% by 2050 as costs decline by 30–70%.
Blue ammonia might offer a quicker and cheaper route to a hydrogen economy, according to Valentini. “Perhaps the market has been focusing more on green ammonia because of the perfectly green credentials,” he says. “But if you look at the potential of using existing facilities and existing energy resources, blue ammonia should play an important role, whether it’s a role as a transition or it’s a role as part of the long-term energy mix.”
This could be especially true in North America, where the large oil and gas industry keeps the cost of producing conventional ammonia low and creates opportunities to use carbon dioxide in enhanced oil recovery (EOR) or to store the greenhouse gas permanently underground.
Indeed, as CF announced its green ammonia project, it also promised to pursue 3.5 million t per year of blue ammonia projects. These will be relatively low cost, akin to that of conventional ammonia, Will says, noting that the company already captures CO2 for urea production.
Little additional capital investment is needed to compress the CO2 and get it to pipelines for sequestration, Will says. And tax breaks would offset those expenses. For instance, the new 45Q tax credit in the US offers $50 per metric ton for permanent CO2 storage and $35 per metric ton for use in EOR.
A half-dozen sequestration projects are already in the works not far from CF’s Donaldsonville plant, Will says. A pipeline that serves the EOR market is also nearby.
Another fertilizer producer, Nutrien, is also betting on blue ammonia. In 2019, the company started up a system in Redwater, Alberta, to inject nearly 300,000 t per year of CO2, the by-product of about 250,000 t of ammonia production, into a new, $1.2 billion EOR pipeline. Since 2013, Nutrien has been selling about 250,000 t per year of CO2 into the EOR market from its Geismar, Louisiana, plant.
At present, according to Ashley Harris, Nutrien’s senior director of environmental performance and innovation, the only financial benefit of capturing CO2 is the additional revenue stream from selling it. “As we look forward, if a market for blue ammonia emerges where we find partners that are willing to pay for the low-carbon ammonia, then that would be a different type of business,” he says.
Experts say blue ammonia is in need of certified industry standards, similar to the distinction the 45Q tax credit makes between CO2 permanently sequestered or reused. Some shades of blue ammonia are lower carbon than others, and not one is as low carbon as green ammonia.
Ammonia makers hope to have standards in hand by the end of the year. “End markets need clarity,” Harris says. With certification, a premium for blue ammonia would likely emerge. Nutrien is “working with potential end users on determining the value of the product for them,” Harris says.
Unlike CF, Nutrien has kept the focus on blue ammonia in the short term and hasn’t thus far made an investment in green ammonia. “We have a low-carbon solution that significantly reduces carbon intensity at a much lower cost than the green technology today,” Harris says.
Another approach, called turquoise ammonia, is the path that the start-up Monolith Materials is taking. Last July, the company completed a plant in Hallam, Nebraska, that breaks down natural gas into hydrogen and elemental carbon, a material known to industry as carbon black. Carbon black is sold as a filler for tires and rubber.
The plant’s reaction is initiated by a plasma torch powered with renewable energy. “The beauty of this plant is that we can make hydrogen from natural gas without emitting any CO2,” says Monolith CEO Rob Hanson.
The plant started with a capacity of 14,000 t per year of carbon black. As a follow-up, Monolith is now building a new, 180,000 t carbon black plant and will use the coproduct hydrogen to make 270,000 t of ammonia.
Making ammonia is a relatively new idea for Monolith. Its original plan was to sell the hydrogen to the Nebraska Public Power District to burn for electricity. But Monolith executives with experience in fertilizers had other ideas when they studied the project. “It is certainly going to be more valuable to make ammonia with hydrogen than it is to burn it to make electricity,” Hanson says.
The company has a different model than the green ammonia developers, however. The plant, which sits in the middle of the US Corn Belt, will sell the ammonia as low-carbon fertilizer rather than as fuel.
Valentini, the consultant, continues to be cautious about low-carbon ammonia, but he does see an important sign that the approach might prevail: ammonia makers, end users, and governments seem to want it to succeed and are backing it with real time and money. “Many stakeholders across different levels of the value chain are all going toward the same direction,” he says. “They all have pretty much the same goals.”