Environmental Engineering Reference
In-Depth Information
space shuttles burned hydrogen as propulsion fuel). In fuel cells, hydrogen and oxygen are
used as the anode and cathode of a battery, between which an electron flow occurs.
If hydrogen is such a plentiful, versatile and clean fuel, why has it not already replaced
fossil fuels? There are two main reasons. First, hydrogen is extremely difficult to store
and it ignites easily, as was dramatically demonstrated by the Hindenburg airship disaster
in 1937. The second, and arguably greater, obstacle to a future hydrogen age lies with
economics rather than technology. Most of our fuels are a gift of time and nature; we have
simply learned to refine them. Hydrogen is different, as it must first be manufactured using
other energy sources. Hydrogen is plentiful but is locked in molecular bonds (e.g., in water
or methane) that take considerable energy to break. That energy has to be generated by
other means, in most cases by burning fossil fuels. This entails a net loss of energy and the
emission of pollutants.
Figure 2.8.
A hydrogen-powered car at a filling station. Safety concerns still exist, but
the main hurdle to widespread use of hydrogen is economic.
Source:
U.S. Navy.
At an industrial scale, hydrogen is mainly produced from methane (CH
4
), in a process
known as reforming, where the hydrogen atoms are unlocked from natural gas molecules.
If the current shale gas boom in North America continues, a plentiful supply of methane
