For everything that alternative fuels promise to save -- resources, money, the environment -- they also ignite controversy. With natural gas, fracking shale rock can contaminate water supplies. With biodiesel, the Internal Revenue Service gets angry when car owners filter their own french fry oil without paying excise tax. When it comes to wind, well, the late Sen. Edward Kennedy, D-Mass., spent many of his last moments fighting wind farms off Cape Cod. (All he wanted was to preserve his family’s vacation home from being spoiled by giant fans.)

When we talk about ethanol, though, there’s more agreement about what it can’t do and hasn't done. Thirty years ago, Congress passed a federal subsidy for the alcohol-based fuel -- derived from corn, starch, sugar and other renewable organics -- to help prop up the U.S. corn industry. There were also perceived benefits to producing an American-made motor fuel, one that could put a serious dent in U.S. gasoline consumption and cut oil imports. None of that happened, and the subsidy -- up to $6 billion worth of tax breaks and incentives every year, plus a 45-cent-per-gallon fuel credit -- finally expired in December.

Let’s not ignore the good parts of ethanol. First, it’s renewable, and doesn’t require imported oil to refine. Second, it was a far cleaner oxygenate than MTBE, an additive that was designed to reduce gasoline emissions but that also seeped into water supplies. Third, its increased octane boosts horsepower in engines built to run on high ethanol concentrations, plus it acts as an engine detergent. Fourth, when one does not account for the production process, ethanol fuel produces less greenhouse gas emissions than gasoline.

Up until about 2003, U.S. gasoline contained only 3 percent ethanol, but in the following years and through today, the mix increased to 10 percent thanks to the Energy Policy Act of 2005, which mandated that ethanol production shoot up to 36 billion gallons per year by 2022. To receive alternative-fuel tax credits, more manufacturers touted “flex fuel” vehicles able to tolerate up to an 85-percent ethanol blend known as E85. In 2006, an enthusiastic General Motors ran a “Live Green, Go Yellow” ad campaign, with yellow Avalanches and Impalas and smiling college students in corn fields.

“What if an answer to our dependence on oil was growing right in front of us?" a bunch of 20-somethings asked in a Super Bowl commercial. "What if we could lower greenhouse gas emissions with a fuel that grew back every year?” You half-expected Kevin Costner and James Earl Jones to reveal the magic sauce, to let us all in on GM’s big miracle.

By 2007, we had some surprising answers. Researchers and policy analysts studied ethanol’s detrimental effects on corn prices, particularly in poorer countries such as Mexico where corn is absolutely essential to local diets. It turns out that when you use food to make fuel, something has to give way ... like, say, food. Farmers were being paid to replant their fields to grow corn instead of other crops. That was strike one.

From there, it became obvious that we wouldn’t be able to grow enough corn or sugar to feed our thirsty cars and trucks, nor would it be sustainable for the land. Then there was the issue with national distribution. Ethanol, due to its corrosive effects, could not be shipped in traditional oil pipelines from the Midwest and Gulf States. (In 2008, one oil company managed to do it, but most ethanol shipments require tanker trucks, hence its limited availability on the coasts.) At the same time, government leaders such as Massachusetts Gov. Deval Patrick were promising tax breaks for cellulosic biofuels, or ethanol and biodiesel derived from nonfood sources such as switchgrass and decaying trash. Problem is, it’s not even close to getting started.

The short of it is this: In 2011, the U.S. consumed 134 billion gallons of gasoline and just about 14 billion gallons of ethanol. What about reducing oil imports? In 1985, the U.S. imported about 1.8 billion barrels. By 2009, the first significant drop in 24 years, it was 4.3 billion. When combined with E85’s lower energy content -- about 20 to 30 percent fewer miles per gallon -- there is no economic or physical way for ethanol to make serious sense.

The Massachusetts Institute of Technology couldn’t understand it, either. In an all-too-detailed study of the oil industry’s production and pricing models, the university called bluff on an advertising campaign by the Renewable Fuels Association, which claimed that ethanol had saved the average driver more than $1,200 in fuel costs last year. “While an instantaneous surprise elimination of all ethanol sold in the U.S. might raise gasoline prices for a short time period, one cannot assume these instantaneous effects would persist for more than a few weeks,” the report said.

Even so, the ethanol industry has every right to protect its livelihood, just as any trade should. In April, it successfully lobbied the Environmental Protection Agency to grant a waiver for fuel stations to sell E15, a 15-percent ethanol blend, despite engineering studies that show the fuel damages engines and fuel systems in cars older than 2001. Only one station in America has E15 -- and no surprise, it’s in Kansas.

Where are all the car commercials touting ethanol today? GM and Ford are silent. Even Bentley, which once attempted to show how eco-friendly a 12-cylinder Mulsanne luxury saloon could be on E85, doesn't talk about it anymore. It's a dead subject.

Natural gas, while primarily nonrenewable, at least has 90-plus years left of reserves to go around (much less if all cars ran on natural gas, of course). Electricity, if enough rare-earth metals can be extracted to make batteries and if our power grid is substantially upgraded for clean generation, is the most promising.

Ethanol can never be more than an additive in limited quantities; we simply don’t have unlimited space to grow plants, and lack the means to process all of our waste into fuel. There will never be enough of it. How, exactly, the U.S. will abide by the law and process 2.5 times the amount of ethanol used today within 10 years is a complete and utter mystery. Where is Costner when you need him?

Clifford Atiyeh has spent his entire life driving and riding in cars he doesn't own. He was raised in Volvos and has grown to love fast, irresponsible vehicles of all kinds. He lives in Boston, is a member of the New England Motor Press Association, and has reported for The Boston Globe, Car and Driver, Popular Mechanics and The Times of London.