It’s not entirely coincidence that the alcohol in your adult beverage and the ethanol in your gas tank are so similar in structure. After all, if one drink was no problem, then two or three would get the party started. Only in the harsh morning light do we see the logistical fallacy.

In the United States, ethanol is derived almost entirely from corn, a humble farm product with other obvious uses, but what could be more important that weaning America from polluting petroleum, much of it imported from places with little love for our way of life?

Corn, corn, American corn! We can grow our own motor fuel! See ya, Saudis!

Well, it seemed like a good idea at the time.

Ethanol does burn far cleaner than regular gasoline, but what we didn’t consider for too long was that this wasn’t something for nothing. Ethanol, in fact, consumes so much fertilizer and water to grow and energy to produce — and promotes the plowing of so much marginal cropland — that its environmental effects are negative (water quality, food availability).

Roughly 40 percent of U.S. corn goes into motor fuel, not to feed your family or your livestock. Federal studies also find that this artificial resource diversion inflates prices for every type of food that corn touches. And because ethanol is harder on your engine than gasoline alone, most fuel blends must be limited to about 10 percent.

So in a rare bit of good news from Washington these days, the Environmental Protection Agency surprised ethanol proponents and opponents recently by — for the first time — reducing the federal mandate for the amount of ethanol that must be mixed into the nation’s gasoline supply.

In technical terms, instead of the targeted renewable fuels quota of 18.15 billion gallons for 2014, the EPA dropped the requirement to 15.21 billion gallons. The vast majority of that amount — and the reduction — is corn-based ethanol.

It’s a win for taxpayers, who have peeled off about $40 billion in tax subsidies to prop up renewable fuel production since the first “gasohol” subsidies in the late 1970s. A 2007 energy security law requires refiners to blend in higher percentages of renewables each year, while giving the EPA the power to adjust the number, which it finally did.

Make no mistake, the ethanol lobby still has powerful friends in Congress, and Iowa remains a pivotal state in the presidential nominating process. And even if tapping the brakes on corn-based ethanol makes sense, the feds would be wise to continue to push development of non-food-based fuels, like cellulosic biofuels.