The Alchemy Of Wastewater: Turning Harmful Pollutants Into One Of The World's Most Important Chemicals

Engineering postdoc Navid Noor has discovered a way to convert wastewater nitrates to ammonia, one of the world’s most important chemical compounds.

Most mornings, if he’s not already in the lab, Navid Noor goes for a run.

These early morning runs start in Bayfront Park and end at Princess Point or Cootes Paradise. Here, he observes the algal blooms in the bay, a telltale sign of nitrate pollution.

Noor is a postdoctoral fellow in McMaster Chemical Engineering researcher Drew Higgins’ lab. He’s exploring ways to convert nitrates in wastewater into something useful.

These runs also give Noor the chance to think a bit more about his vision for the future.

It’s a future that involves farms, ponds and localized fertilizer production that doesn’t release harmful pollutants into the environment.

The key to making this a reality starts with developing a greener way to produce ammonia.

And Noor might have just figured out how to make that a reality.

One industry’s trash is another’s treasure
Ammonia is arguably the world’s most important chemical compound, but its production is energy-intensive and a major contributor to global greenhouse gas emissions.

Noor’s work focuses on developing a way to extract nitrates from the environment and convert the pollutant into ammonia in a sustainable way.

But how does he do it?

It all starts with wastewater, explains Noor.

While you can collect wastewater from anywhere, he prefers the stuff from creeks around farmlands because “it is rich in nitrates from agricultural runoff.”

In the lab, he extracts the nitrates from the wastewater, adds an iron-based molecular catalyst and places them in an electrochemical reactor.

The reactor is hit with clean electricity — Noor uses hydroelectric since it’s in abundant supply in Ontario, but wind and solar power are also feasible — and, through the electrochemical process, the nitrates are transformed from harmful pollutants to ammonia.

“No extreme heat, no crushing pressures, no fossil fuels,” he explains. “Instead of destroying a pollutant, we recycle it into fertilizer or fuel.”

Pros and cons
Modern life depends, in large part, upon ammonia.

When it’s not the key ingredient in the nitrogen-based fertilizers that feed nearly half of the world’s population, it’s making headlines as a carbon-free fuel for ships, power plants and heavy industry because it stores and moves energy more easily than hydrogen.

The way we currently produce ammonia, called the Haber-Bosch process, is an industrial method that forces nitrogen and hydrogen atoms together using pressure that is more than 200 times that of our atmosphere, and temperatures between 400 and 500 degrees Celsius.

The importance of this process cannot be overstated, says Higgins, associate professor of Chemical Engineering. In his mind, and the minds of the Nobel committee in 1918 and 1931, it’s one of the most important scientific and technological innovations of the 20th century.

“It’s estimated that our world could sustain about two or three billion people,” explains Higgins. “The Haber-Bosch process alone, which allows us to develop these nitrogen-based fertilizers, helps us make enough food to feed 8 billion people.”

But it’s not without its drawbacks.

The industrial process emits incredible amounts of waste heat and pollution. In fact, the Haber-Bosch process is responsible for nearly two per cent of the world’s carbon dioxide emissions and energy consumption.

This is something that needs immediate action, says Navid.

“The Paris Agreement predicts that, by the year 2050, our production of ammonia will need to increase by four times to meet our global needs,” says Navid.

And that’s precisely where Navid’s method comes in.

While it happens on a much smaller scale than the Haber-Bosch process, Navid explains, developing green, sustainable alternatives to the process will help offset the increasing demand predicted by the Paris Agreement while simultaneously limiting our emissions.

Scaling up a dream
Right now, Navid’s work has been produced in a controlled lab environment. The next phase of the project, he says, is to start scaling this work up and testing it in more difficult environments.

“We are going to test these catalysts at higher production rates, over longer operating times and under the messier conditions of real wastewater,” says Navid. “The goal is to find out whether materials that shine in our lab can hold up where it counts.”

If these materials do hold up, that opens up a world of possibilities, explains Navid. One where wastewater treatment plants both remove pollution from water and become producers of fertilizer and clean fuel; where farmers gain access to a sustainable nitrogen source; and where the chemical industry takes a major step towards a circular model where waste becomes a resource.

This is the type of world Navid imagines on his early morning run and it drives his work.

His method won’t be replacing the Haber-Bos ch process any time soon, he says with a laugh. But he can take comfort in knowing that it “shows, with certainty, that there are pathways to a more sustainable way of producing ammonia.”

And that certainty means he’s one step closer to making his dream of a cleaner, more sustainable future a reality.