The world of alternative fuels works in funny ways. Take hydrogen, which was close to gaining hero status a decade ago. In fuel-cell form, it emits little except for heat, electricity and pure water. Hydrogen appeared to be our ticket out of the fossil-fuel cycle for good.
Today, however, natural gas, a fossil fuel (albeit a cleaner-burning one than many other mainstream fuels), is the alternative du jour, while hydrogen takes a back seat. What happened?