Concern about combustive hazards is slowing the urgently needed expansion of LNG-import capacity in the US. From the public, however, no comparable worry has yet emerged about an energy alternative for which popular hopes are very high: hydrogen. Hazards exist with hydrogen, nevertheless. That they have received little general attention so far while LNG fears influence events reveals much about US energy politics.
Producers, transporters, and users have handled hydrogen and LNG safely for decades. The safety challenges will escalate, of course, as production scales up to make hydrogen a widespread vehicle fuel, as envisioned by the administration of US President George W. Bush, and as LNG trade expands to meet growing demand for natural gas. In neither case should the challenges be insurmountable.
Fear and energy
Yet the US public seems to fear LNG excessively and hydrogen not at all. LNG import facilities may be impossible to build near gas-hungry markets because people in those areas see them as deadly threats. Except among specialists, on the other hand, discussion about hydrogen as a vehicle fuel proceeds as though no hazard exists. The thinking about hydrogen seems to be that safety advantages go hand in hand with environmental virtues. That's incorrect. If perceived threats to public safety can block LNG terminals, they logically will block hydrogen development, too, once they come into broader light. This shouldn't happen to either fuel.
So what are hydrogen's risks? In general, the gas is flammable over a wide range of concentrations in air and ignites easily. Hydrogen flames are hotter than those of most other fuels and invisible. With its rapid release of energy during combustion, the gas can explode, although it's so light that it disperses quickly in air.
Because the molecule is small, hydrogen leaks through many materials able to contain other gases. It makes some metals brittle. Lacking odor or color, it's hard to detect, and adding odorants or dyes usually isn't practical because the additives interfere with end-use processes. With its very low density, hydrogen has to be compressed or liquefied for storage, transport, and use. Compression and cryogenics introduce risks.
Does all this make hydrogen less safe than, say, LNG? In some ways, yes, and in some ways, no.
LNG involves cryogenics, pressurization, and difficulties of leak detection, too. And it packs great quantities of chemical energy into relatively small volumes. Explosions involving LNG can happen. Total failure of pressure-management systems and unregulated vaporization theoretically can cause an explosive bursting of containment systems. But the conditions under which this might occur are very unlikely and preventable. A more likely but also preventable LNG accident is the explosion-like rapid phase transfer, which can occur with a large LNG spill onto water. The multi-walled, heavily insulated containers and elaborate pressure equipment essential to liquefaction and LNG transfer provide inherent protection against mishaps like these.
Vaporized LNG is flammable over a much narrower range of concentrations in air than hydrogen is, but the lower limits of the two ranges—the ones most likely to be involved in accidental combustion from leaked gas—are about the same. Natural gas contains more energy per unit of volume at a given pressure than does hydrogen but much less energy per unit of mass—a category in which hydrogen leads all fuels.
Broader dynamic
So which is the superior fuel? A gloss like this of risks posed by each gas can't yield the answer. Combustive hazards must be considered in relation to a much broader dynamic that includes costs (including those of safety management), convenience, supply potential, energy need, environmental risks, and competition from other fuels.
Energy discourse in the US must acknowledge that nature does not offer a hazard-free energy option. The risks presented by most energy forms can be managed but never eliminated. Much of the public apparently lacks confidence in hazard management and doesn't see or heed the risks in politically favored energy sources. These are not the origins of sound energy choices. Continuation of risk tolerance at currently low levels would keep the American public from having all the natural gas it is expected to need in coming years and any of the hydrogen it so evidently wants for coming decades.
