The three main reasons for a hydrogen economy to be so
desirable consider that a) a reversible cycle can be
established, with hydrogen made from water and turning
back into water when used; b) a variety of (renewable)
sources can be used to make hydrogen, and c) the
conversion of hydrogen into other forms of energy results
in (near-) zero emissions. Further advantages for the case
of hydrogen powering an internal combustion engine
include combustion engines to be an extremely mature
technology and their producibility from recyclable materials
which both reduce cost. In addition the internal
combustion engine route opens up a multifuel option
where hydrogen is used when available and another fuel is
used when it is not. Finally, this article clearly makes a case
for the high efficiency potential of hydrogen internal
combustion engines.