Technology Status of Hydrogen Road Vehicles

! HC and CO emissions from hydrogen vehicles with no after-treatment of exhaust gas are about an order
of magnitude lower than HC and CO emissions from catalyst-equipped gasoline vehicles of similar age
and engine condition;
! CO 2 emissions will be lowered by two or more orders of magnitude, depending on the oil consumption
of the engine;
! hydrogen vehicles would emit or produce close to zero ozone, particulates, sulfates, sulfur oxides,
aldehydes, benzene, and other toxic and carcinogenic compounds commonly found in the exhaust of
petroleum-fuel vehicles;
! dual-fuel operation with hydrogen and gasoline or diesel fuel can substantially reduce emissions of all
regulated pollutants.
.......
It (also) appears that LH 2 vehicles may be quieter that gasoline vehicles, and hydride vehicles louder, but it
is not known if this difference is important.
Concerning hydrogen vehicles and the Greenhouse effect, the use of hydrogen made from non-fossil electricity
and water is one of the most effective ways to reduce anthropogenic emissions of Greenhouse gases.
.......
On the other hand, the use of coal to make hydrogen would cause a substantial increase in emissions (per km)
of Greenhouse gases....(up to) 100 % (hydride vehicles) and 143 % (LH 2 vehicles) with respect to current
emissions of Greenhouse gases from petroleum use.
Ironically, it thus turns out that hydrogen is either the best or the worst fuel from a Greenhouse perspective,
depending on the feedstock...... Hydrogen from non-fossil power, or a combination of electric vehicles and
ICE vehicles using biofuels, would be the only effective long-term options for eliminating emissions of
Greenhouse gases from transportation sector.
.......
Much more water vapor is formed by hydrogen combustion than by the burning of fossil fuels. Moreover,
water vapor is actually the most important Greenhouse gas in the atmosphere, controlling many times more
infrared flux than CO 2. However, even if hydrogen replaced all fossil fuels world-wide, the increase in water
vapor emissions would amount to only 0.003 % of global evaporation. This is a negligible amount... (but)
some monitoring over the long term might be prudent, since small changes in water vapor or cloud cover can
significantly affect climate.
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