Sustainable ammonia can be produced today: doing so would use electrolyzers to make hydrogen to feed the traditional Haber-Bosch process. In a very few years, new technologies will skip this hydrogen production phase altogether and make ammonia directly from renewable power in an electrochemical cell. Further down the pipeline, next generation technologies will mimic nature, specifically the nitrogenase enzyme, which produces ammonia naturally.
One of these next generation technologies is currently producing impressive results at the US Department of Energy's (DOE) National Renewable Energy Laboratory (NREL).
The Institute for Sustainable Process Technology (ISPT) recently published a detailed analysis of three business cases for producing renewable ammonia from electricity: Power to Ammonia. The feasibility study concludes that, in the near term, ammonia production using clean electricity will likely rely on a combination of two old-established, proven technologies: electrolysis and Haber-Bosch (E-HB). To reach this conclusion, however, the study also assessed a range of alternative technologies, which I summarize in this article.
Let’s say there is such a thing as the “hydrogen consensus.” Most fundamentally, the consensus holds that hydrogen will be at the center of the sustainable energy economy of the future. By definition, hydrogen from fossil fuels will be off the table. Hydrogen from biomass will be on the table but the amount that can be derived sustainably will be limited by finite resources like land and water. This will leave a yawning gap (in the U.S., 60-70% of total energy consumption) that will be filled with the major renewables -- wind, solar, and geothermal -- and nuclear energy.
This may be as far as the consensus goes today, but more detail is now emerging on the global system of production and use that could animate a hydrogen economy.
This week, an important new voice joined the chorus of support for renewable ammonia and its potential use as an energy vector - the International Energy Agency (IEA).
In his article, Producing industrial hydrogen from renewable energy, Cédric Philibert, Senior Energy Analyst at the IEA, identifies a major problem with the hydrogen economy: hydrogen is currently made from fossil fuels. But his argument for producing hydrogen from renewable energy leads almost inevitably to ammonia: "In some not-too-distant future, ammonia could be used on its own as a carbon-free fuel or as an energy carrier to store and transport energy conveniently."
There will be many ways to make ammonia in the future and, regardless of breakthroughs in chemical catalysts and engineering design, genetically modified organisms will play an increasingly important role.
At this week's American Chemical Society meeting, Daniel Nocera from Harvard University introduced his new ammonia synthesis technology. It builds on his "artificial leaf" that produces and stores hydrogen using power from sunlight. Nocera's latest innovation is to couple this system with a microbe that naturally contains nitrogenase, the enzyme that fixes atmospheric nitrogen into ammonia.
The end result - a robust population of nitrogen fertilizer-emitting microbes - can be delivered to the soil simply by watering the plants.
The Institute for Sustainable Process Technology has just published a feasibility study that represents a major step toward commercializing renewable ammonia.
It examines the "value chains and business cases to produce CO2-free ammonia," analysing the potential for commercial deployment at three companies with existing sites in The Netherlands: Nuon at Eemshaven, Stedin at Goeree-Overflakkee, and OCI Nitrogen at Geleen. The project is called Power to Ammonia.
In recent months, research teams from both Canada and Italy have published comparative analyses of sustainable ammonia production pathways.
These projects aim to quantify the costs and benefits of combining Haber-Bosch with a renewable hydrogen feedstock. Both projects examine the carbon intensity of ammonia production but, while the Canadian study broadens its remit to a full life cycle analysis, including global warming potential, human toxicity, and abiotic depletion, the Italian study focuses primarily on energy efficiency.
The US Department of Energy (DOE) is currently supporting six fundamental research projects that will develop "novel catalysts and mechanisms for nitrogen activation," which it hopes will lead to future sustainable ammonia synthesis technologies.
These projects, announced in August 2016 and administered by the Office of Basic Energy Sciences, aim "to investigate some of the outstanding scientific questions in the synthesis of ammonia (NH3) from nitrogen (N2) using processes that do not generate greenhouse gases."
I recently wrote about a vast future market for merchant ammonia: transporting carbon-free energy from Australia's deserts to Japan's electricity grid.
Now, however, it is clear that Japan could face international competition for Australia's solar-ammonia resources. Jeff Connolly, CEO of Siemens Pacific, wrote last month about his ambitions for ammonia as an energy export commodity.