ST. LOUIS | Corn-and-soybean farmer John Adams considered the pitch too good to pass up.

The 58-year-old Adams, who works 950 acres in central Illinois, didn't immediately join the farmer cooperatives pooling together to build a 100-million-gallon-a-year ethanol plant. But when he dropped by an informational meeting a few months ago, he had to have a piece.

"I was impressed," he recalled. "I had to do a lot of thinking about where the ethanol market was and where I think it's going."

Ethanol, for decades largely an afterthought in the global fuels market, is in the midst of a booming renaissance, despite a host of questions.

It is a hot topic from agribusiness boardrooms to Midwestern diners to world capitals including Washington. President Bush says the fuel additive distilled from mashed and fermented grain is a cheap-and-easy alternative to high-priced foreign oil, and some day it's already been an economic boon for moribund rural stretches.

Yet skeptics wonder if the rush to ethanol makes sense given the murky outlook for demand. They worry, too, about ethanol's fuel efficiency -- lower than traditional gasoline -- and its effects on both the environment and food prices as corn chews up more farmland.

"There have been ethanol booms before, not with quite this much fire behind it," said David Sykuta, executive director of the Illinois Petroleum Council trade group. "The thing that should make people cautious is the irrational exuberance, that somehow ethanol is going to be the silver bullet that gets us out of our energy woes. That's just not true."

Still, ethanol remains a darling of Capitol Hill lawmakers yearning to curb the nation's reliance on foreign crude.

"As long as they're committed, it'll be more than just a flash in the pan," said Darrel Good, a University of Illinois crop marketing specialist. "It's basically growing because of fairly large subsidies and mandates; right out of the chute, that philosophically doesn't sit well with some folks."

Long history

Ethanol has been around in the U.S. since Henry Ford rolled out his Model T in 1908, making it capable of running on gasoline or ethanol. The relatively cheap price of oil -- and gasoline from it -- marginalized ethanol until the oil shock the 1970s, when Congress began giving oil companies tax credits for every gallon of ethanol they blended into gas.

When oil prices retreated beginning in the late 1980s, U.S. dependence on imported oil spiked, relegating ethanol to little more than a blending component for some Midwestern gas. The Iraq war and higher oil prices have since put ethanol and other so-called alternative fuels at the forefront of the energy policy debate.

How big is the boom? Americans last year harvested 10.5 billion bushels of corn -- the third-largest crop ever -- after planting 78.3 million acres. The Agriculture Department predicts U.S. farmers this year will plant 90.5 million acres of corn, the most since 1944, and harvest a record 12.2 billion bushels.

Of that, an estimated 3.2 billion bushels will go into ethanol -- a whopping 49 percent increase from last year.

"It's a gold-rush mentality," said Dennis Conley, agricultural economist in University of Nebraska's Institute of Agriculture and Natural Resources.

What to do?

Ethanol is more pricey than gasoline and has about two-thirds the energy value of conventional gas, meaning lesser fuel economy. Only a sliver of the nation's gas stations offer E85 -- mostly in the Midwest -- though the number has more than doubled from about 600 in January 2006 to 1,170 now, according to the National Ethanol Vehicle Coalition.

To broaden ethanol use, the industry must overcome considerable challenges that include distribution. Oil relies on pipelines, while ethanol is largely shipped by rail or truck, said Sykuta, head of the Illinois oil group.

"If you're going to be a player nationwide, you're going to have to build you're own pipeline system, or it's just not going to be the level of market penetration some of the advocates would suggest," he said.

U.S. automakers have vowed to boost production of flex-fuel vehicles, restating recently to Bush their plans to double production to about 2 million a year by 2010. Detroit automakers say they've already produced about 6 million of the vehicles and could make half of all their vehicles capable of running on alternative fuels by 2012, if enough E85 is available.

Environmental groups and supporters of higher gas mileage standards consider emphasizing ethanol blends wrong-headed, pointing to the fraction of vehicles actually using E85 and the seeming lack of interest among consumers in owning one.