In Minnesota, there’s a research farm peppered with wind turbines that, when in full swing, boasts an astonishingly low carbon footprint. The wind powers a chemical plant that makes ammonia, which can not only be spread as fertilizer under the turbines, but also fuels an experimental tractor, stores energy for a non-windy day, and—soon—will heat the barns that dry their grains. All without producing CO2.
“For deep decarbonization of agriculture, you switch to green ammonia,” says Michael Reese, director of the University of Minnesota project. The university’s studies have shown that using green ammonia (“green” in the sense that it is made with renewable energy) for fertilizer, fuel, and heat could drive down farming’s carbon footprint by as much as 90 percent for corn and small grain crops. “That’s transformative,” Reese says.
Advocates of this alternative, zero-carbon liquid fuel see green ammonia’s reach expanding far beyond farms. They predict a vast new market for green ammonia as a fuel, eventually outstripping the planet’s already enormous (and growing) demand for ammonia as fertilizer. A 2021 International Energy Agency report forecasts that to hit zero emissions by 2050, hydrogen-based fuels (including ammonia) should account for nearly 30 percent of transport fuels by 2050, up from basically zero today. That report predicts that cars will run on batteries and planes on biofuels, but ammonia will be vital for the shipping industry, which is currently responsible for 3 percent of global emissions and trying hard to whittle that down fast.
Ammonia is also one of the top contenders for storing and transporting energy from renewable power plants so that electricity is available when and where it’s needed. The idea is to use renewable power to produce green ammonia from non-fossil fuel sources, send it off by pipeline or ship, and burn it in power production plants with turbines customized to run on ammonia. While batteries are efficient, they are best suited to storing smaller amounts of electricity for hours or days; a 2020 Oxford Institute of Energy Studies report concluded that for large-scale, long-term energy storage, liquid ammonia is hard to beat. Countries including Japan, Australia, the Netherlands, and the United Kingdom have national plans to use green ammonia to store (and export) their renewable energy surpluses.
All told, chemist Douglas Macfarlane at Monash University in Melbourne, Australia, anticipates that ammonia production will go up about 100-fold in decades to come.
For now, though, ammonia production is anything but green. The world currently produces a vast 175 million tons of ammonia per year, mostly for use as fertilizer, employing an energy-intensive, century-old industrial process that produces a lot of greenhouse gas: The industry is responsible for about 1 to 2 percent of global carbon emissions, making it one of the dirtiest on the planet.
That will need to change if ammonia is to become part of the world’s climate change solution. To ensure all this ammonia is green, not dirty, is a huge task. Of course, the ammonia being made to store wind and solar power will be produced using that renewable energy. But to fill requirements for fuel and fertilizer will mean much more renewable energy on top of that. Ammonia plants will need to alter—or even reinvent—their production systems. And engines will need to be reconfigured to run on the new liquid fuel. Along the way, producers and users will have to overcome hurdles: Ammonia is toxic, and burning it can potentially produce an even more potent greenhouse gas than CO2.