An ambitious new project is underway at Stanford University, as a team of scientists are hoping to replace the Haber-Bosch process for the manufacture of fertilizer.
With the energy consumed in the Haber-Bosch process contributing to climate change, if the research is successful then they may help solve two of mankind’s most pressing problems:
• How to feed a growing population
• How to use less fossil fuels
The team is based at the SUNCAT Center for Interface Science and Catalysis, a partnership between researchers from Stanford Engineering and the SLAC National Accelerator Laboratory. Where the team, “… is developing a fertilizer production process that can feed the world in an environmentally sustainable way,” says chemical engineer and SUNCAT director, Jens Norskov.
The SUNCAT project is being funded by a $7 million grant from the Villum Foundation, an international scientific and environmental philanthropy, which is focused on sustainable industrial chemicals, including a sustainable nitrogen-based fertilizer.
“One common thread across these projects is the need to identify catalysts that can promote chemical processes powered by sunlight, instead of relying on the fossil fuels now commonly used as energy sources and, often, as feedstock for reactions,” says Norskov. “We know of no manmade catalysts that can do what we require, [so] we will have to design them.”
Tom Jaramillo, deputy director of the SUNCAT Center and a member of the nitrogen synthesis project, put annual fertilizer production into perspective when he said, “Each year we produce more than 20 kilograms of ammonia per person for every person on the planet, and most of that ammonia is used for fertilizer.”
“We literally feed the world on fertilizers derived from the Haber-Bosch process,” adds Norskov. But the process is far from efficient, with the online scientific journal Phys.org, even stating that, “Due to the heat and pressure required by the Haber-Bosch process, ammonia catalysis accounts for approximately 1% of all global energy use. On top of that, between 3% and 5% of the world’s natural gas is used as a feedstock to provide the hydrogen for ammonia synthesis.”
Typically this process is carried out in large chemical plants, which adds cost to the fertilizer when fuel for transportation to the farm is factored in. To avoid this, the team is taking a different approach.
“We will harness solar energy in the presence of properly designed catalysts to create ammonia right in the agricultural fields. Think of it as a drip irrigation method of synthesizing ammonia, where it percolates into the roots of the crops.”
The theory behind the research is almost utopian; removing the need for fossil fuels as both a fertilizer feedstock and as an energy source, and with all processes working in the field, transportation costs will be miniscule.
As Norskovs explains, “You won’t need tremendous quantities of fossil fuels as an ammonia feedstock, or to drive the trucks that deliver the fertilizers or the tractors that apply it. And you won’t have a problem with excess application and fertilizer runoff, because virtually all the fertilizer that is produced will be consumed completely by the crops.”
Reporting on the SUNCAT team, the Phys.org report adds that, “The researchers aim to provide the benefits of fertilization without any of these [fossil fuel, transportation, application, feedstock] costs. The idea is to replace the centralized, fossil-fuel based Haber-Bosch process with a distributed network of ammonia-on-demand production modules run off renewable energy. These modules would use solar power to pull nitrogen from the atmosphere and also to catalyze the splitting of water molecules to get hydrogen and oxygen. The catalytic processes would then unite one nitrogen atom to three hydrogen atoms to produce ammonia, with oxygen as a waste product.”
However, finding the catalyst that can perform the function required will be far from easy. A point highlighted by Stacey Bent, a professor of chemical engineering at Stanford and a key member of the SUNCAT team, when she said, “While the catalyst must bind strongly enough to the target molecule to do the work required, it also has to release the end product.”
Jaramillo agrees, highlighting the complex chemical process that will need to be engineered. He said, “We have to design a series of reactions to cleave the nitrogen molecule from air, separate the hydrogen from water and combine them to form ammonia, with the only input energy coming from solar power.”
At the same time, there are other factors to consider in finding a catalyst, as the research team is aware that their end product must have a practical application. As Bent notes, “We have to design catalysts that can make and break bonds with atomic precision, and we have to ensure these materials can be mass produced at the necessary scales and price points, and are durable and simple to use in the fields.”
The challenge is clearly immense, but then so is the prize.
“Sustainable nitrogen production will only become possible with the cross-disciplinary collaboration of people working in fields such as materials science, chemical engineering and computer science,” Bent says. “It could literally change the world.”
And it seems that the researchers have the tools to make the dream a reality. “We are part of a very strong team, attacking some of the biggest challenges in chemistry, chemical engineering and sustainability,” says Jaramillo. Before adding, “We’re really just at the beginning.”
As they say, every journey begins with a single step, so being at the start of something holds no shame. How much scepticism Haber and Bosch received on beginning their journey is not known, but they must both have held large amounts of self-belief to achieve their goals; something that is clearly not missing from the SUNCAT team.
“Essentially we are attempting to restore the balance in the Earth’s carbon and nitrogen cycles that has been lost through the exponential increase in the demand for food and fossil fuels,” says Norskov. “The time to act is now.”
Like all great plans, it has strength in its simplicity. The challenge will come in working out the details, and in finding the exact catalysts that will work in harmony to provide solar-powered, in-field manufactured fertilizer. Whether they can complete their task and find a much needed replacement for the Haber-Bosch process, only time will tell.