Ammonia rarely makes headlines, but much of modern life depends on it. The compound of nitrogen and hydrogen is the key ingredient in the fertilizers that help feed roughly half of the world’s population. It is also attracting serious attention as a carbon-free fuel for ships, power plants and heavy industry.
The problem is how we make it. Nearly all of the world’s ammonia comes from the Haber-Bosch process, a century-old technology that forces the nitrogen from air and hydrogen together at temperatures of 400 to 500 C and pressures more than 200 times that of the atmosphere.
It works remarkably well, but it is also energy intensive. The process consumes about two per cent of the world’s energy supply and produces between one and two per cent of global carbon dioxide emissions.
Our research at McMaster University points to a different path: using renewable electricity to turn nitrate, one of the most common water pollutants, directly into ammonia.
In our recently published study, we showed how carefully designed iron-based catalysts can make this conversion more efficient. The approach tackles two environmental problems at once. It removes a harmful pollutant from water and produces a chemical the world urgently needs.
The timing matters. The International Renewable Energy Agency projects that global ammonia demand could approach 700 million tonnes a year by 2050, nearly four times more than what is produced today, driven by growing food demand and ammonia’s emerging role as a clean energy carrier. Meeting that demand with today’s technology would lock in decades of emissions.
A growing pollution problem
(AP Photo/Marta Lavandier)
Nitrate contamination is a widespread and growing problem. Fertilizer runoff from farms, municipal wastewater and industrial discharge can all carry nitrate — a chemical compound containing nitrogen and oxygen — into rivers, lakes and groundwater.
Too much of it feeds harmful algal blooms, degrades drinking water and creates expensive treatment challenges for cities and industries.
Conventional water treatment deals with nitrate by converting it into nitrogen gas, which simply returns it to the air.
That solves the pollution problem but wastes the nitrogen entirely; nitrogen that took enormous amounts of energy to capture from the atmosphere in the first place.
There is a better option. Using electricity from wind or solar power, an electrochemical reactor can convert nitrate in water into ammonia at room temperature and normal pressure.
No extreme heat, no crushing pressures and no fossil fuels. Instead of destroying a pollutant which comes from use of ammonia as a fertilizer, we can recycle it into fertilizer or clean-burning fuel.
What we discovered
The heart of any electrochemical technology is the catalyst: the material that drives the chemical reaction. We designed and tested four versions of an iron-based molecular catalyst, each modified with a different chemical group attached to its edges.
Going in, we expected the winner would be the catalyst that moved electrons most efficiently, the conventional wisdom in our field. The experiments, however, told a more interesting story.
It turns out that how the surface of the catalyst interacts with water and dissolved nitrate is just as important as how well it conducts electrons. The surface of a catalyst can be more or less water-attracting and more or less hospitable to nitrate molecules trying to land on it.
These properties control how easily the raw ingredients (water and nitrate molecules) reach the active sites where the chemistry actually happens. Think of it like a busy kitchen: having a powerful stove matters, but so does how easily a chef can reach the ingredients.
In our experiment, we passed an electric current through a water solution containing nitrate, the same compound found in agricultural runoff and industrial wastewater. In the solution, the electric current triggers a chemical transformation, converting nitrate into ammonia, molecule by molecule.
The best-performing catalyst didn’t just deliver electrons efficiently; its surface chemistry also welcomed water and nitrate molecules in, keeping the active sites well-supplied.
More research needed
(AP Photo/Terry Chea)
We want to be clear about where this technology stands. Our experiments were done under controlled laboratory conditions, and significant engineering challenges remain before electrochemical nitrate conversion can operate at industrial scale.
The next phase of our research focuses exactly on addressing that gap: testing these catalysts at higher ammonia production rates, over longer operating times and under the messier conditions using real wastewater. The goal is to find out whether materials that shine in the lab can hold up where it counts.
If they can, the payoff could be considerable. Wastewater treatment plants could become more than facilities that remove pollution; they could become local producers of fertilizer and clean fuel, powered by renewable electricity.
Water utilities would gain a revenue stream. Farmers would gain a sustainable nitrogen source and the chemical industry would take a step toward a circular model where waste becomes a resource.
That future is not here yet. But every scientific and engineering breakthrough that lets us make ammonia from pollution rather than fossil fuels brings that future a little closer.
