Last year the world used seven hundred million tons of hydrogen, almost all produced from natural gas. In the future the world will use many, many times more,

Last year the world used seven hundred million tons of hydrogen, almost all produced from natural gas. In the future the world will use many, many times more, on top of all current uses producing steel, ammonia, and even methane, liquifying for aviation, and pushing underground to produce power from later. The authors have no crystal ball. But need for lots of hydrogen is an easy call, and motivates better ways to produce it. Once produced, it will be used according to the needs of those producing it. The authors' speculations on such use do not bear on the value of the work.