Ammonia production is helping to nourish the world – and simultaneously threatening it.
A critical component of nitrogen-based fertilizers, ammonia also releases carbon dioxide, a harmful greenhouse gas, into the atmosphere through its production process.
PhD student Chris Bartel is seeking a way to eliminate those harmful gas emissions while ensuring the compound remains available for global food production.
“It would be impossible to feed the world without synthetic ammonia,” Bartel said.
Close to 200 million tons of ammonia are produced each year, most of which is used to make fertilizer. Inexpensive ammonia production allowed for the population to boom after World War II by rejuvenating soil that would be unable to recover on its own from intense farming.
But the current method of ammonia production also releases carbon dioxide at a rate 10 times that of the ammonia it is creating, accounting for 2 percent of all CO2 emitted each year, Bartel said.
So the fourth-year doctoral student in computational chemistry in the Department of Chemical and Biological Engineering is working to create a process that would not have any CO2 as a byproduct. To do this, he needs to create a new material using elements found on the periodic table.
The periodic table is a swath of 118 elements that act as building block for everything we see, touch and taste. And of those 118, as Bartel puts it, “there are about 80 that matter. The rest are not available in sufficient quantities to be technologically useful.”
The creation of new materials from elements is called “materials by design.” While it may seem like wizardry to some, materials by design dates back at least to the Bronze Age, when humans found that mixing copper and tin and other elements created materials with unique properties not found in copper or tin alone.
“Copper was not strong enough, so people tried mixing it with other elements,” Bartel said.
Bartel is searching for a catalyst that will turn air and water into ammonia. A catalyst enables one chemical to convert into another, much like platinum in a car turns noxious gas into something that can be released back into the atmosphere. The material Bartel is looking for is an inexpensive and durable ceramic powder, but the number of known ceramics is in the millions.
“We want property X, and we have no idea how to make that property or even what that material is or what atom it is made of,” he said.
Bartel has already gained some insights into how his catalyst would produce ammonia, and he has published this work in the journal American Chemical Society Applied Materials & Interfaces. But the challenge of working in theoretical materials chemistry is that the material you are looking for may not actually exist. And if it does exist, it may be too costly to ever be utilized.
“It is possible it never becomes financially feasible,” Bartel said. “It might require the government disincentivizing CO2 to be realistic. But it could also work.”
With 118 elements, there are millions of combinations for how those elements could be combined into different materials. About 3 million of these combinations have already been recorded in online “materials databases.”
To navigate this nearly impossible search, Bartel is coding a machine-learning program into which he will insert data about the material he wants to create. Since the material is still theoretical, he must slowly narrow his field of search by inputting different constraints into the program. As he finds recipes for materials that are closer and closer to the catalyst he is looking for, he adds different properties he needs in the catalyst, which further trains the program what to look for.
Even if Bartel does not find the catalyst he is looking for, with the mindset of a scientist, even an apparent failure is a success.
“No matter what, we learn something,” Bartel said.