The Energy Evolution - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 16

es 40 to 90% lower hydrocarbon emissions than gasoline. There are also 40
to 90% lower carbon monoxide emissions and 10% lower carbon dioxide
emissions than gasoline.
Natural gas can also be less expensive than gasoline on a per gallon-
equivalent. Maintenance costs can also be lower compared to gasoline en-
gines since natural gas causes less corrosion and engine wear.
The larger, heavier fuel tank that is used has a limited range of about
100 miles. Refilling takes two to three times longer than refilling from a
gasoline pump. Some slow fill stations can take several hours and the lim-
ited availability of filling stations can be a problem.
ALTERNATIVE FUEL COSTS
Cost differences between gasoline and most alternative fuels are a
barrier to wider use of these fuels. Conversion technologies may become
more efficient and more cost-competitive over time, but as long as gasoline
prices remain relatively low, alternative fuels will not become cost-com-
petitive without government help, in the form of subsidies or tax credits.
However the cost difference between untaxed renewable fuels and taxed
gasoline can be rather small. In the early 1990s, methanol was about $0.75
per gallon without federal or state tax credits.
The cost of wood-derived ethanol dropped from $4.00 to almost
$1.10 before any tax credits. The federal government provided a tax credit
of $0.60 per gallon, which was further subsidized by some states with an
additional $0.40 per gallon. These tax credits allowed ethanol to be com-
petitive with gasoline.
A comparison of the per gallon costs of methanol, ethanol and gaso-
line requires multiplying the gallon cost by the number of gallons needed
for the same distance as gasoline. Methanol's energy density is about half
that of gasoline, so it takes about two gallons of methanol to get the same
amount of power as one gallon of gasoline. A gallon of ethanol contains
about two-thirds the energy as a gallon of gasoline.
Most of the initial interest in alternative fuels started after the oil cri-
sis in the 1970s. It has grown more recently by concerns about supply in-
terruptions, high prices, air quality and greenhouse gases.
GOVERNMENT ACTIONS
The U.S. has seen legislation on cleaner-burning gasoline substitutes,
gasoline enhancers and more efficient automobiles. This includes the 1988