This series of articles on the future of ammonia synthesis began with a report on the NH3 Energy+ conference presentation by Grigorii Soloveichik, Program Director at the US Department of Energy's ARPA-E, who categorized the technologies as being either improvements on Haber-Bosch or electrochemical (with exceptions).
ARPA-E invests in "transformational, high-risk, early-stage research," and recently began funding ammonia synthesis technologies, not to make renewable fertilizer but to produce "energy-dense zero-carbon liquid fuel." This article will introduce the six electrochemical technologies currently in development with funding from ARPA-E.
Last week, in Part 1 of this series on electrochemical ammonia synthesis technologies, I quoted a recent article by researchers at MIT that identified avenues for future research and development. One option was a biomimicry approach, learning from "enzymatic catalysts, such as nitrogenases," which can "either be incorporated into or provide inspiration for the design of electrocatalytic processes."
The nitrogenase enzyme, nature's ammonia synthesis technology, was developed in an iterative innovation process, otherwise known as evolution, that took hundreds of millions of years to reach this level of efficiency. According to one group of electrochemists, who presented their results at the recent NH3 Energy+ conference, nitrogenase produces ammonia in nature with an enviable 75% process efficiency - so it's no surprise that they are basing their industrial technology on it.
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).