Rep. Mark Udall, D-Colo., went to a biodiesel and ethanol gas station in this Denver suburb to illustrate his answer to the energy conundrum.

"This is the most patriotic thing we can do, is invest in all these technologies and make our country more energy self-reliant," Udall said.

America will still rely on oil for the foreseeable future, he said, but prices could fall if the country invests more in renewable fuels such as ethanol and biodiesel, which can be grown from U.S. crops.

Udall is running against Republican Bob Schaffer, a former Colorado congressman.

Schaffer was not available to respond to Udall, but his campaign manager, Dick Wadhams, said Udall was being hypocritical because he voted against drilling in the Arctic National Wildlife Refuge and in offshore fields and voted to delay commercial oil shale leases in Western Colorado.

Wadhams said that "Udall and people like him are primarily responsible for the dramatic increase in gas prices."

Schaffer likes renewable energy, too, but he supports drilling in the Arctic refuge and offshore and wants "responsible rules to allow Colorado to develop oil shale," according to his campaign literature.

But energy companies already have 68 million acres of U.S. oil and gas leases that they haven't developed, Udall said.

"To focus solely on drilling isn't going to get us where we need to go," Udall said.

Udall did say it might be time to "responsibly drill" in places that have been closed. But some places should stay off-limits, he said.

"I think there are some areas that we've decided as a society have value greater than the oil and gas you could produce off them," Udall said.

Udall appeared with fellow Democratic Congressman Ed Perlmutter, who represents Denver's northern suburbs.

The two also said they're worried about speculators in the oil market. Udall doesn't know how much they have driven up prices, but he said the volume of trade on the oil markets has swollen since prices ran up this year.

Biodiesel at the gas station was selling for $4.51 Monday, three pennies cheaper than regular diesel. E85 Ethanol was selling for $2.80 a gallon, $1.03 cheaper than regular gasoline.

Biodiesel produces almost the same energy per gallon as regular diesel, said Troy Hill, general manager of Hill Petroleum, which owns the station. Ethanol, however, packs 18 percent to 30 percent less energy per gallon than regular gasoline, Hill said.

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