While new drilling technologies and oil reserves are taking the pressure off gasoline prices and peak production issues, demand for alternative fuel vehicles continues to grow. Environmental concerns and government regulations have made finding substitutes for the conventional gasoline-powered internal combustion engine a priority for both manufacturers and consumers. The federal government is demanding an average of 54.5 miles per gallon by 2025 -- a challenging target for traditional technologies. California is requiring increasing numbers of zero-emission or plug-in hybrid cars.
But what direction to go? Depending on considerations like usage patterns, efficiency, and cost, there are at least a dozen substitutes for gasoline as motor fuel, including electricity, natural gas, vegetable oil, and even sunlight. Even the most promising ones like natural gas, as John O'Dell of Edmunds.com points out, are handicapped by the same thing: a lack of infrastructure for refueling or recharging.
With that in mind, here's a look at the alternatives that are available today, along with some tentative predictions about their prospects for the future.