In his State of the Union address, President George W Bush focused on a strategy to expand the use of alternative fuels - mainly ethanol - in an effort to slow America's oil consumption. "Twenty by Ten", as the strategy is known, aims to cut projected petrol consumption by a fifth within a decade.
What is Twenty By Ten?
It is a strategy to cut projected petrol consumption by 20% over the next ten years. The aim is to replace about 15% of the petrol used in vehicles with renewable fuels, or biofuels, and cut petrol use by a further 5% by improving the fuel efficiency of the cars driven by Americans.
The 20% petrol saving would be the equivalent of 75% of current oil imports from the Middle East.
Where are the biofuels meant to come from?
Production of biofuels will have to increase fivefold over current requirements.
The chief biofuel promoted by Mr Bush is ethanol, much of which would come from growing corn crops. But he also said he envisaged it being produced from "everything from wood chips, to grasses, to agricultural wastes".
Mr Bush is seeking $3.6bn for researching and developing the new fuels.
How more fuel-efficient will American cars become?
Mr Bush envisages the first major changes to US vehicle fuel economy standards in decades but the cuts are relatively modest, at an annual average of 4% for new cars from model year 2010. Bluewater Network, which lobbies for better fuel economy standards, dismissed the proposal as being a "gift" to the motor industry. "If the president were serious he would call for a doubling of the nation's fuel economy standards," it said.
What is Mr Bush's priority on energy?
National security. The US, said Mr Bush, had been "too long dependent on foreign oil" and was "vulnerable to hostile regimes and terrorists".
What about climate change?
The president, whose country accounts for about 25% of global greenhouse gas emissions, called climate change a "serious challenge". He said it should be tackled through technology but he did not talk of specific limits on emissions and there was no sign of him adopting a comprehensive strategy. However, he did call for more electricity to be produced from carbon-free sources like wind, solar and nuclear power plants.
Is the petrol still proving addictive?
Mr Bush also said he was also looking to increase domestic oil production and he wanted to strengthen America's energy security, doubling the country's Strategic Petroleum Reserve by 2027.
How do environmentalists rate the 2007 initiatives, including the use of ethanol?
The US green charity National Environmental Trust (Net) notes that energy and the environment have featured in every State of the Union address Mr Bush has made but, they say, his policies have never matched his goals. However, the United Nations' chief on climate change, Yvo de Boer, welcomed Mr Bush's embrace of more sustainable forms of energy and noted that he had used the word "serious" when talking about the challenge of climate change.
Kurt Davies from the environmental lobbying group, Greenpeace USA, has serious doubts about whether ethanol is the ideal solution to America's energy crisis.
"All the fossil fuels that are used in the production of corn, in the fertilisers and in the fuel, in the ploughs and transportation and so on and in the distillation process, it becomes almost a very dirty fuel," he said.