Hydrogen fuel cells are also used to power some vehicles.  The hydrogen combines with oxygen and releases energy.  The byproduct is only water.  There are also hydrogen burning internal combustion engines similar to gasoline burning internal combustion engines.

Hydrogen filling stations would need to be built for this type of vehicle to become commonly used.  Hawaii may become a new testing area for hydrogen powered cars.  Hydrogen is a byproduct of producing synthetic natural gas.  The gas company in Hawaii wants to sell the hydrogen to power cars.

The problem with hydrogen is its extreme reactivity.  It explodes and burns easily.  Hydrogen fuel systems must be built to be very stable and safe.

What a good question. Hydrogen has the atomic number 1 in the periodic table. It is usually found in compounds with other elements. Contrary to popular belief, Hydrogen is not commonly found alone, even if it does power the stars and is the most common in the universe (as far as we know). Free hydrogen is found in small amounts in the atmosphere.

The two greatest uses of hydrogen is the space program, which needs hydrogen to fuel the space crafts, and the oil industry. In regards to the former, hydrogen is the perfect element for making rocket fuel. In regards to the second, the oil industry needs hydrogen to convert crude oil into gasoline. Of the two industries, the most common use for hydrogen is the big oil companies.

In the future, hydrogen may play a bigger role in fueling our world.