For Dan Norte, deciding where to fuel up his Ford F150 pickup is not always as simple as scanning pump prices. When he heads to Iowa to see family, the synthetic-oil dealer from Owatonna, Minnesota, burns an 87-octane Minnesota-mandated gasoline blend that is 10 % corn-based ethanol. It costs about the same as comparable-grade gasoline.
For the trip back he has a 15-% option -- an Iowa blend rated at 89 octane that can be up to a nickel a gallon cheaper. But Mr Norte has figured out that his savings would probably be erased by lost miles per gallon from the faster-burning fuel.

Reasons to switch:
With energy independence increasingly cast as a matter of national security, and the doubling of biofuel output by 2012 mandated by last summer's energy bill, plenty of other Americans are finding more cause for making complex calculations that involve alternative fuels. Some 90 % of 1,000 voters surveyed in March by the non-partisan Energy Future Coalition in Washington supported the notion of having one-quarter of domestic energy demand met by renewables by 2025.
"We have a new reality," says Ron Cogan, editor of the Green Car Journal in San Luis Obispo, California. "And I think that's changing the way people look at the vehicles they want to buy and operate on a daily basis.”

Things have changed:
"Two years ago, it looked like the alternative-fuels business was going to atrophy," says Fred Mayes, who tracks renewable-fuel data for the Energy Information Administration, a quasi-independent arm of the Department of Energy. "There was no interest, no direction, no incentives, no major breakthroughs. It was stuck in low gear."
Barriers still exist, including not enough filling stations and a projected shortfall of ethanol production that will contribute to higher gas prices this summer, many experts say.

Still, energy remains in an evolutionary mode. Mayes says government analysts trying to make projections can barely keep up with all the emerging options. As gas-electric hybrids fill a gap, and hydrogen fuel cells remain a holy grail, old-school combustion engines show signs of hanging on -- and leaving fewer smudges -- because of what they can burn. That has alternative-fuel vehicles merging out of the slow lane for the near term -- and consumers facing more signposts than they can easily read.
"There are so many balls up in the air," says Mayes.

Consider:
Biodiesel made from soy or other forms of biomass; cellulosic ethanol, derived from corn husks and other organic waste rather than corn; E85 ethanol that's only 15 % gasoline; even "petro" diesel that burns cleaner than the diesel used in the smoke-belching cars many Americans recall -- and that is made cleaner still by exhaust-treatment technologies like DaimlerChrysler's BlueTec, announced in March.
Mayes has just returned from a conference at which he heard of a new "biomass gasification" technology that "can produce ethanol cheaply in huge quantities from trash, coal, wood, switchgrass -- anything you name that has carbon in it," he says.

Government stays away:
Don't expect a federal decree favouring sales of one fuel, like the legislation of unleaded in the 1970s, experts say. If anything, Washington might step back and let automakers go nose-to-tailpipe with states. A federally sponsored panel (the National Academies' National Research Council) this month strongly urged that states should have the power to follow California's lead in adopting emissions standards tougher than the federal ones.
Many automakers have several horses in the alt-fuels race. Perennial innovator Honda -- a leader, with Toyota, in hybrids -- also has its hydrogen FCX and its natural-gas-powered Civic GX, "the cleanest internal-combustion ever," Mr Cogan says.

GM, which has pushed ahead with hybrids, has also ramped up marketing for flexible-fuel vehicles that can run on either straight gasoline or E85. It sold 270,000 E85-ready vehicles in 2005, says Sherrie Childers Arb, director of environment and energy communications at GM, and estimates it will sell 400,000 this year.
The main gains: fewer pollutants and a tilt toward a domestic, renewable resource. But note: Experts say costs associated with ethanol remain, for now, too high to provide workable margins for anyone in the sales chain.

"We're not suggesting that you'll replace all gasoline with E85 ethanol," says Ms Childers Arb. "We continue to believe that a lot of technologies and alternative fuels will coexist in the marketplace of the future.”
"In fact, none of the alternative fuels currently on the horizon have a chance of replacing gasoline anytime soon," says Jim Motavalli, author of "Forward Drive" (2004). He cites, among other limitations, insufficient agricultural production for biofuels to make a dent in fossil-fuel consumption.

Mr Motavalli also hopes carmakers will keep tweaking other factors, such as composite materials that reduce weight but still provide safety.
"One trend that I see in hybrids is very regrettable," he says. "That's the trend toward hybridizing bigger and heavier luxury cars with the advantage being that they have more performance." He urges car shoppers to inquire about PZEVs, partial-zero-emissions vehicles.

Now on the market in many states, PZEVs are cleaner editions of gasoline models -- Toyota Camrys, BMW 325s -- that cost a few hundred dollars more.
"Something like 20 manufacturers make them," Motavalli says.
Whichever way the alt-fuel road goes, potholes lie ahead.
"There are always unintended consequences," says Cogan. If demand for farmed biomass surges, for example, questions will arise: Should crops be expended as fuel or used to feed the world?
"You just need to think ahead," he says.

The global market for biofuels hit $ 15.7 bn last year, says Clean Edge, a Portland, Oregon, research firm. In a decade, it could be $ 52.5 bn.
"At some point" says Cogan, "we will move on from the age of oil."