WHICH COMMODITIES ARE INVOLVED?

* Ethanol, an alcohol most often made from grains and sugar cane. In the United States it is primarily made from corn, but last August's US energy law pushes ethanol producers to use alternatives such as barley, wheat and rice.

Bush's plan also calls for millions of dollars in production incentives for ethanol derived from cellulose-based and forest materials now burned or deposited in landfills.

* Biodiesel, which works in all diesel engines, is a clean-burning fuel derived from any fat or vegetable oil. About 90 percent of US biodiesel is made from soybean oil.

* Bush also said he would ask next week for a 22 percent increase in funding for clean-energy research in his 2007 budget, to develop solar and wind energy, cleaner-burning coal, nuclear energy and gasoline-electric hybrid vehicles that can be recharged in ordinary home outlets.

WHAT WILL IT TAKE TO MAKE IT ECONOMICALLY FEASIBLE?

The president set a six-year goal for making ethanol practical and competitive as an alternative fuel. The relatively high cost of producing the fuel from corn, a lack of land and water to grow it, and difficulty transporting ethanol in pipelines are hurdles.

Brazil is the world's leading producer and exporter of ethanol, derived from its huge sugar cane crop. It already blends its domestic gasoline with 25 percent ethanol and is looking to the United States, Japan and India to double exports in coming years.

The Energy Department's analytical arm predicts ethanol made from corn and cellulose will account for just 4.3 percent of US gasoline demand in 2025.

WILL HOUSTON AND DETROIT ADJUST?

The automobile and oil industries will need to produce the cars and the fuel distribution network to adjust.

Ford Motor Company issued a statement after Bush's speech applauding the move.

The National Petrochemical and Refiners Association, which represents 450 US oil companies, said it supported the plan to diversify fuel supply, but added it was concerned about the possibility it would come with more regulation.

WHAT'S THE ENVIRONMENTAL POINT OF VIEW?

The call to reduce US oil dependence could help curb global warming but does not herald conversion to a UN-led plan to slow climate change, experts say.

"This is fairly positive ... the very mention of solar, wind and other clean energies is a huge step," said Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research in Germany.