Hydrogen powered cars may be fueled by stored ammonia

Ammonia may not explode, but it's hazardous enough that it needs to be approached with this sort of protective gear.

City of St. Louis

Every time a discussion of alternative energy and alternative fuels comes up, someone somewhere shouts, "hydrogen economy!" And every time someone shouts "hydrogen economy," a baby seal gets clubbed to death by an angry engineer.

Hydrogen is a Jekyll-and-Hyde character. It can have a relatively high energy density, and it's clean and abundant. The perfect fuel, right? Unfortunately, it's a gas, and a rather combustable one at that. To store it efficiently requires huge pressures and very heavy tanks, which are expensive. Hydrogen burns in the air at mixtures ranging from four percent to 75 percent and, unlike gasoline, the tiniest little spark will set it off. Expensive and dangerous, you say? Unless these problems are solved, the hydrogen economy (damn, another seal) will remain just over the horizon.

A recent publication has offered up ammonia as a compromise solution that, while still dangerous, is much more viable. Ammonia is a hydrogen-rich compound (three hydrogens and a single nitrogen atom). If you break ammonia up, you get nitrogen gas and hydrogen gas, so it's still clean. Best of all, though, storage is a lot more convenient. It liquifies at low temperature and pressure, so the tanks don't have to be so heavy. It is a bigger and heavier molecule, so leaks are far less common, and when it does leak, it doesn't diffuse so far or so fast.