Stanford researchers discover new method to produce ammonia that doesn’t emit CO2

In a venture out of Stanford’s Zarelab, scientists Richard Zare, Xiaowei Tune and Chanbasha Basheer found a brand new, eco-friendly chemical course of that they are saying may rework how we create ammonia, the premise of the world’s commonest fertilizer. In 2022, the worldwide manufacturing of ammonia was round 150 million metric tons. 

Ammonia (NH₃), an inorganic compound of nitrogen and hydrogen, serves because the constructing block to create chemical fertilizers for agricultural crops. Round 70 p.c of ammonia is used for fertilizers to help in plant development whereas the opposite 30 p.c is primarily used for plastics, explosives and artificial fibers. 

For over 100 years, ammonia has been created with the Haber-Bosch course of, which converts nitrogen into ammonia for fertilizers. The method makes use of round 2 p.c of the world’s vitality and contributes to 1.3 p.c of worldwide emissions of carbon dioxide every year, in keeping with Richard Zare, the pinnacle of the Zarelab and the Marguerite Blake Wilbur Professor in Pure Science at Stanford.

“It’s nicely acknowledged that the Haber-Bosch course of is without doubt one of the most necessary industrial processes in chemistry. It’s in any case what folks use to feed the world,” Zare mentioned. “Individuals thought on the finish of the 1800s that we had been all going to starve finally as a result of the inhabitants was rising quicker than we may make vegetation to eat. What saved us was an incredible improvement by Fritz Haber who realized find out how to take nitrogen and switch it into ammonia.”

Based on Zare, this course of is vitality intensive as a result of the nitrogen molecule is kind of inert, that means it doesn’t simply react with hydrogen to kind the specified ammonia. The hydrogen atoms want to come back from a supply, and the Haber-Bosch course of makes use of steam (H₂O) to transform pure fuel (methane, CH₄) into H₂ and CO, acquiring the hydrogen atoms. With extra steam added, the CO is then transformed into carbon dioxide (CO₂), and extra hydrogen atoms are generated. 

This course of is subsequently an enormous emitter of greenhouse gasses. Zare mentioned it’s estimated that 7 p.c of industrial-produced world CO₂ comes from the manufacturing of ammonia. 

In Zare, Tune and Basheer’s new course of to create ammonia, the supply of hydrogen shouldn’t be methane, however as a substitute water, and as such, no carbon dioxide is emitted. Their course of additionally entails no utilized voltage, no irradiation by a light-weight supply and is carried out at room temperature and ambiance strain. 

Their discovering builds on latest analysis from the Zarelab that examines the excessive reactivity of water microdroplets. Bulk water tends to be benign and inert, however water droplets are extremely reactive. Based on Tune, these microdroplets might be considered mist from a humidifier. “These are tiny properties,” he mentioned. 

Zare mentioned the lab discovered that microdroplets of water produce a robust chemical response when hitting laborious surfaces. To provide ammonia, the crew of scientists break nitrogen bonds by shifting water microdroplets, nitrogen fuel and iron oxide by way of a gas-powered sprayer. The method depends on water microdroplets’ potential to react on laborious surfaces. 

The iron oxide serves because the catalyst for the response –– accelerating the response with out being modified by the response. The researchers put the catalyst in a graphite mesh for the sprayer. The sprayer then releases microdroplets, the place the pumped water and nitrogen react with the assistance of the catalyst to kind ammonia (NH₃). 

When the crew discovered that they may create ammonia with out CO₂ they had been excited, in keeping with Tune, however cautious.

“We needed to be torturous about whether or not it was our anticipated outcome, and we wanted to have many controls,” Tune mentioned. 

“For this to be an enormous deal, it must be scaled up and demonstrated that every one the steps concerned make good financial sense,” Zare mentioned. “We now have not but solved the issue –– these are nonetheless little droplets we’re speaking about.”

Zare mentioned the subsequent step for scaling this venture is collaborating with engineers. He mentioned the timeline to have ammonia at scale ought to take lower than 5 years, however it would take a minimum of one yr. He added that the Haber-Bosch course of took 5 years to complete. 

“This can be a key advance that may considerably improve the sustainability of ammonia manufacturing if deployed at scale,” mentioned Eric McShane, a post-doctoral scholar in chemical engineering with Stanford’s Cargnello Group. “Utilizing water as a substitute of hydrogen as a feedstock for ammonia manufacturing may cut back the general vitality requirement for ammonia manufacturing.” 

McShane additionally agreed with the researchers that “the problem is scaling their course of and guaranteeing sufficiently excessive ammonia yield.”

“If it actually works, it’s big,” Zare mentioned. “It will lower the price of meals, and it could assist us in regard to local weather change. It’s big if it actually might be completed.”