Let's Talk Green Ammonia Production
The Basics of Ammonia Production
Ammonia has been produced commercially since the beginning of the 20th century. Ammonia Fertilizer is a vital part of the world’s food supply. Before the commercialization of synthesized ammonia fertilizer farmers relied on animal based fertilizers and mined nitrate salts. The Haber-Bosch process, a method of synthesizing ammonia was invented in 1909 because of the ever-increasing need for nitrogen based fertilizers. Ammonia is synthesized by combining nitrogen and hydrogen using a catalyst at high temperatures. This process requires a significant amount of energy, because of the heat, and the production of hydrogen and nitrogen gas. Ammonia production plants require enormous reactors to be cost effective, due to the low efficiency of the nitrogen and hydrogen reaction, and the need to keep the reactor at high temperature and pressure. The hydrogen therefore comes from on-site steam methane reformation. Ammonia is the largest industrial greenhouse gas emitter, converting hydrogen and nitrogen into ammonia accounts for about 1% of the worlds energy consumption and 1% of global greenhouse gas emissions. On top of all that Ammonia is transported long distances from where it is produced to where it is used creating further carbon emissions.
There needs to be a greener and more energy efficient way to produce ammonia. This is where on-site gas generation comes into play. On-site gas generators produce green hydrogen using electrolyzers and nitrogen using pressure swing absorption via renewable energy sources. The electrolysis and pressure swing absorption processes do not emit greenhouse gases. With these green sources of hydrogen and nitrogen gas, ammonia can be produced closer to the point of use utilizing a small-scale Haber-Bosch reactor. Local ammonia production via renewable resources reduces the carbon emissions related to transporting ammonia long distances as well. The University of Minnesota has demonstrated low carbon ammonia production using wind power to produce hydrogen and nitrogen paired with a small-scale Haber-Bosch reactor. This demonstration resulted in the production of green ammonia, but also highlighted the negative affect the small-scale reactor has on the overall efficiency and the importance of high efficiency sources of heating and cooling for the remaining system balance of plant such as electricity to heat the reactor, to heat and cool the buildings and to cool the product ammonia.
A Better Way to Produce Green Ammonia
Much of the work in green ammonia production has involved reducing carbon emissions by creating green sources of hydrogen and nitrogen, but the bulk of the potential improvements in cost and energy efficiencies are to be gained through perfecting a new method of synthesizing ammonia at scale using an Alkaline Exchange Membrane (AEM) to synthesize ammonia. The energy efficiency advantage from AEM’s is gained because the technology uses one electrochemical reaction to synthesize ammonia as opposed to three. AEM’s also don’t require high heat or pressure. AEM’s use a membrane similar to a Proton Exchange Membrane (PEM) but utilize a base chemistry as opposed to the acidic chemistry of a PEM Membrane. This base chemistry of AEM’s is appropriate for ammonia synthesis because it doesn’t react with the ammonia as it does with acidic based membranes. When combined with an effective and stable catalyst, AEM could be a viable high efficiency alternative to largescale production via the Haber-Bosch method of ammonia production.
Nel Hydrogen’s recent acquisition of Proton OnSite has created the world’s largest electrolyzer manufacturer. Proton OnSite has added Nel’s alkaline based electrolyzers to its line of PEM electrolysis systems, as well as its hydrogen storage and refueling station capabilities. Our R&D department has conducted extensive research in electrochemical ammonia production, and are hoping that breakthroughs in the development in AEM technology and alternative catalysts fuel growth in green and sustainable ammonia production.