On Earth it is less abundant, although it occurs in water, petroleum, coal, and all living matter. Except in negligible quantities, it does not occur naturally as a free element. In consequence it is not placed in a group in the periodic table. Hydrogen is formed industrially from steam or oxygen and methane, or from steam and coke. It is used in the manufacture of ammonia by the Haber-Bosch process , in hydrotreatment, in making methanol and petrochemicals, and in the hydrogenation of foodstuffs, such as the manufacture of margarine.
Liquid hydrogen is used as a fuel for rocket motors.
Hydrogen is in many ways the ideal fuel, providing large amounts of energy when burned, with water vapour as the only combustion product. Oxford Paperback Encyclopedia 2. The Macmillan Encyclopedia 2001 5. All rights reserved.