Washington State U. study: Sustainable fertilizer production method proves cost-effective

A Washington State University (WSU) study has found that sustainable methods to produce synthetic ammonia for fertilizer can be cost competitive with the current, fossil-fuel based method, creating a commercial option that can reduce carbon emissions.  

According to a Jan. 17 release by WSU Insider, researchers from the Voiland College of Engineering and Architecture at WSU conducted a study in which they discovered that the cost of producing ammonia sustainably using either steam or water electrolysis was comparable to the current method. 

Synthetic ammonia is critically important for feeding the world’s growing population. Around 180 million metric tons of artificial fertilizer provides about 40% of the world’s food each year, all of which is made from fossil fuels like coal or natural gas.

“It’s an irreplaceable product and probably the most important achievement of the 20th century,” says Peter Pfromm, lead author on the paper and a professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering. “But right now you and I, to a large part, are fossil fuel-based life forms, and that’s not really sustainable.”

The current method of producing synthetic ammonia for fertilizer, called the Haber-Bosch process, is more than a century old. The process requires high temperatures and pressure to convert nitrogen from the air and hydrogen to produce ammonia. Because the process relies on natural gas or coal, farmers are at the mercy of fluctuations in the markets. 

Fertilizer prices shot up from about $400 to $1,500 dollars a ton this spring, causing some fertilizer plants in the United Kingdom to close. WSU researchers compared the energy costs of the Haber-Bosch process to two types of electrolysis, which can use electricity generated from renewable sources to split water into hydrogen and oxygen. 

They found that the energy cost of solid oxide electrolysis and water-based electrolysis ranged from $153 to $197 per ton of ammonia, which is comparable to the fossil-fuel based technology.

The researchers hope their findings will help reduce carbon emissions, increase market stability and provide a cost-effective option for sustainable fertilizer production. They believe the simple process and modularity of the renewable-based electrolysis could make it appealing for local-level ammonia production. They anticipate that small-scale, renewable ammonia production could begin at the county level or on large farms as soon as 2024. 

The work was funded by the National Science Foundation, and the study was published in the Journal of Renewable and Sustainable Energy.