单项选择题

A Hydrogen Future
In the minds of some analysts, hydrogen is finally emerging as a nonpolluting, renewable form of energy that could supplant fossil fuels in the near future.
Since the 1930s, environment-minded scientists, academics, energy planners, industrial executives, and even some farsighted politicians have been thinking of and supporting the concept of hydrogen as an almost ideal chemical fuel, energy carrier, and storage medium.
Buckminster Fuller and other observers have described humanity’s ongoing use of fossil fuels--such as energy supply, comparable to depleting a savings account. From the standpoint of long-term energy security, environmentalists are strongly advocating the option of tapping into nature’s current energy account: abundant, and essentially free, solar energy.
Solar energy has been a viable means of home heating, but for large-scale use, that energy must be converted into electricity. In this context, hydrogen may be prominent in future energy systems because it is capable of storing large amounts of electricity for later use.
Although it is the most abundant element in the universe, hydrogen is not a primary energy source that exists in nature, as do crude oil and natural gas. Rather, it is an energy carrier ——a secondary form of energy that cannot be found freely in usable form, but has to be manufactured, like electricity. Today, most hydrogen is extracted from fossil fuels. In the future, hydrogen will be made from clean water and clean solar energy.
Hydrogen can match the effectiveness of fossil fuel in powering cars, planes, and ships and in heating homes, schools, and office complexes ——without creating pollution. When burned in an internal-combustion engine, hydrogen emits a virtually harmless water-vapor exhaust. When hydrogen is burned with atmospheric oxygen in an engine, the resulting emission is clean: no unburned hydrocarbons, no carbon monoxide or carbon dioxide.
Hydrogen is an essential component of fuel cells for vehicles and other applications. Fuel-cell engines can be more than twice as efficient as internal-combustion engines, argues Hoffmann. Fuel-cell engines electrochemically combine hydrogen and oxygen in a flameless process that produces heat, electricity, and distilled water. The fact that it is environmentally benign has made hydrogen energy an increasingly attractive alternative to fossil fuels as concerns about resource depletion and global warming have been growing.
"The question is no longer whether we are headed toward hydrogen, but how we should get there, and how long it will take," says Worldwatch Institute research associate Seth Dunn.

Which of the following is not the reason for people lo advocate the use of hydrogen energy().

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