Here we often discuss hydrogen connected to carbon in forms from methane and methanol up to propane and butanol as ways to substitute using gasoline. All of the fuels from single carbon atom methane and up that can be sourced from anything other than oil imports are good ideas. The issue then becomes a steady supply at sensible costs and the fuel storage and conversion expense for engines. The compressed natural gas (methane primarily) requires tanking and engine metering while butanol is a near complete direct to gasoline replacement and can in large proportion be a gasoline replacement with nearly equivalent energy and higher octane. Hydrogen with carbon makes lots of potential fuels that can be utilized.
Today we’re going revisit hydrogen connected to nitrogen and leave the carbon out. Hydrogen and nitrogen can be formed to NH3, with one nitrogen and three hydrogen atoms. It does work well as an internal combustion fuel. For purists of a hydrogen economy absent the idealized enemy of carbon NH3 is very attractive. You have seen this, may even use it, as its readily available as anhydrous ammonia.
NH3 is similar to propane, known as Liquid Petroleum Gas (LPG), as both are gaseous at ambient temperatures at one atmosphere of pressure. A little confinement, a little more pressure and they both liquefy into dense fuels. NH3 offers a way to store high-density hydrogen, leaving all known and proposed storage solutions way behind. It sometimes marvels one to think about the effort to store hydrogen when NH3 is already at hand. The same unit volume of NH3 contains 50% more hydrogen than cryogenically chilled liquid hydrogen, the densest form of pure hydrogen that has be achieved. NH3 is 4.5 times the energy of pure hydrogen gas at 5000 psi. NH3 is about half as energy dense as gasoline – so its similar to methane as compressed natural gas.
NH3 can be used directly in modified internal combustion engines and direct ammonia fuel cells now. With processing the ammonia can be used in hydrogen fuel cells. It’s a ready answer.
There have to be glitches or it would be all the rage now wouldn’t it? The glitch in production is the world has set up NH3 production from stripping the hydrogen from natural gas (33 MBtu as 9500 kWh/ton). So it is simpler to use the methane directly. The glitch in use is that NH3 isn’t something to handle without care. Its not going to kill short of jumping in a barrel of it, but it comes out cold when decompressing and it is a chemical that can “burn” organic tissues in higher concentrations. Spilling it or inhaling it is a truly bad idea. Its possible if determined or in a case of incredible bad conduct and bad luck to get seriously injured. But factually, the risk of minor injury might be a little higher than gasoline and major injury much lower than the ignitable fuels. NH3 isn’t classified as a flammable liquid nor can it be an explosion hazard like gasoline, methane, propane or hydrogen. It must be oxygenated and compressed to ignite.
NH3 again raises the question, where is all the hydrogen going to come from? NH3 is an easy process alone (the Haber-Bosch Process) to form the product and the nitrogen is in the air at near 78% concentration. That leaves us with coming up with a way to free hydrogen from water. First up is using electricity to drive electrolysis of water (12,000 kWh/ton). Nuclear has been proposed for years with wind now getting more attention as small wind turbine and NH3 process units are being tested now, especially where the wind turbine is far from transmission. These wind projects are up to demonstration size, near or at small commercial sizes. The research goals will stay in place as NH3 can be used for motor fuel or fertilizer. The research projects are intensely working to refine the units to drive a lower fuel or fertilizer cost vs. natural gas.
The most interesting innovation is making NH3 while skipping the electrolysis step entirely, going from water and air directly to NH3. The new process is called “Solid State Ammonia Synthesis” (SSAS). (PDF File) In this research process the electrical demand is reduced by a claimed 35 to 50% and simpler production units lower the capital cost (7000-8000 kWh/ton). In the earliest stages, these process claim NH3 can be made using nuclear power or wind cheaper “than today’s gasoline or diesel fuel.” Keep in mind that at $3.00 gasoline, even using an electrolysis process and the Haber-Bosch process NH3 is cheaper per unit.
NH3 fuel has been in consideration for decades. In 1935 Ammonia Castle, Ltd received a patent for a system to burn ammonia and hydrogen in an internal combustion engine. During WWII Belgium used NH3 as a substitute for diesel fuel when mixed with coal gas. The U.S. Department of Defense studied NH3 as it could be made with portable nuclear reactors using only water and air to make vehicle fuels. NASA’s X-15 Rocket Plane was powered by NH3.
While NH3 can cause mild reaction burns to skin and harm eyes and lung tissues when sprayed or inhaled in concentrated amounts, it’s not a “greenhouse gas” or does it attack the ozone layer. So far there are no safety standards for on road in vehicle tanks, refueling devices to safely handle it by average folks, or kits to buy to do a conversion.
It’s a good likelihood that these matters will get addressed. As SSAS comes along the renewable electrical business could find a ready market in producing NH3 motor fuel.
Here is the puzzle – if hydrogen is the ultimate answer, there is proven technology from production, transport, storage and engine modification right now, what is the hold up? Electricity generation, then marketing, and consumer acceptance, and lots of interim steps along the way. Lastly, keep in mind that NH3 is a primary ingredient for making the horrid drug methamphetamine.
NH3 is Great Stuff, but not so simple to implement, but it should see quicker adoption in areas where natural gas is expensive, or where NH3 for fertilizer is used in large amounts or when the oil skyrockets again.