I recently had the pleasure of interviewing John Holbrook, the Executive Director and Board Member of the NH3 Fuel Association. I’ve talked many times in the past about ammonia and in particular NH3 being a hydrogen-rich fuel of the future.
So, I wanted to ask Mr. Holbrook a few questions about how hydrogen-rich NH3 may be used in the future to solve our nation’s transportation, clean air and energy independence issues.
HydroKevin (HK): The Holy Grail for hydrogen cars is to use H2 that has been created renewably. But, ammonia (NH3) can also be created renewably, correct?
John Holbrook (JH): Yes, of course, NH3 can be produced renewably. The venerable Haber-Bosch (H-B) process, with its H2 for the reaction 3H2 + N2 –> 2NH3 derived from a non-fossil hydrogen source is one way. Usually the hydrogen source is water. Another method, recently patented, is Solid State Ammonia Synthesis (SSAS) where the SSAS reactor takes water directly to produce NH3. With SSAS, as with H-B, the nitrogen comes from air. Another patented, renewable method of producing NH3 uses biomass as input. One planned biomass for this process is spent corn cobs.
HK: What type of ammonia is most suitable to use as fuel for vehicles with internal combustion engines?
JH: The only ammonia form that can be used as a fuel is pure anhydrous ammonia, NH3. NH3 can be used directly in a spark ignited engine, and can be used to supply as much as 95-percent of the energy for a diesel engine. Other forms of ammonia, e.g. aqueous ammonia or urea cannot be used directly as a fuel and must have the NH3 separated from the water or CO2 and water, respectively. There is some recent work looking at anhydrous ammonia and NH3 salt blends. Those blends have also been shown to be satisfactorily combustible in internal combustion engines.
HK: Do you consider ammonia-powered cars to be hydrogen cars?
JH: Yes and no, I guess. A lot of us in the NH3 Fuel Association think and talk of NH3 being “the other hydrogen” because all the chemical energy in NH3 is delivered by burning/oxidizing the hydrogen in the NH3. But, we are not talking about only using NH3 as hydrogen carrier, where H2 would be liberated by thermo-catalytically cracking NH3, although it is quite possible and efficient to do that, i.e. store H2 in dense, liquid NH3. We also look at NH3 as a direct fuel. For instance, NH3 can be used directly as a fuel in engines, gensets, combustion turbines and direct-NH3 fuel cells.
HK: How can NH3 be used in conjunction with fuel cells?
JH: NH3 has a problem with low temperature PEM fuel cells because the PEM membrane can be destroyed by even low levels of NH3. That has not prevented some companies from successfully using cracked NH3 with PEM fuel cells. Also, there are at least two types of NH3 fuel cells that use un-cracked NH3 directly.
Many thanks to Mr. Holbrook and his insight into how ammonia may one day be created in mass quantities locally powering future vehicles cleanly so that we call can breathe a little easier.