“What’s that got to do with the price of tea in China?” my grandmother used to ask me when she thought I was veering off-topic in a conversation. Her voice came back to me recently, as I read about food riots in Mexico, and wondered what that had to do with the price of motor fuels in America.

Everything, apparently.

America’s corn producers are resourceful, if not downright aggressive, when it comes to finding new ways to get people to consume their product: corn oil, corn chips, corn dogs, corn liquor, corn syrup and its obesity-inducing cousin high fructose corn syrup. I used to like plain ol’ corn on the cob. Whatever happened to that?

Of course, the latest incarnation of corn is as a motor fuel product called ethanol. Ethanol is created by converting the starches found in corn into a combustible liquid that can be mixed with gasoline, or burned straight – if your vehicle has had the minor modifications needed to allow it to run on ethanol.

The spin is that ethanol is good for the environment because it will “reduce our dependence on foreign oil.” But there are mixed opinions over the energy gains from ethanol. In 2006, a study out of the University of Minnesota found that ethanol returns only 25 percent more energy than it takes to produce it — and critics have suggested that the study didn’t calculate all the variables that go into producing it, such as the power to irrigation equipment to water the corn crop being used, the power consumed in making the fertilizers that nourish the crop, the cost of the farm equipment used to harvest it (and the fuel to power that farm equipment).

Recent scientific studies have also found ethanol will make smog – particularly ozone pollution – worse, not better.

But ethanol is another way for corn producers to make money. So it seems everyone is jumping on-board the ethanol-power bandwagon – from American automakers, who desperately want their massive S.U.V.s and trucks to appear to be guzzling less gas (even when they really aren’t), to the oil industry (after all, they will sell even more oil to rubes trying to make ethanol).

Did you miss General Motors’ popcorn-popping “Live Green Go Yellow” ad campaign, touting its pseudo-green ethanol-burning E85 vehicles? Do you not own a TV?

United States ethanol production increased from 1.6 billion gallons in 2000 to 5 billion gallons in 2006. Ethanol production is now diverting 20 percent of the U.S. corn crop – and that percentage could go as high as 50 percent this year – away from food production. Hence, a so-called “tortilla crisis” has erupted in Mexico, where corn meal and flour (used in tortilla production, among other things) prices have gone up at least 25 percent recently.

This “tortilla tax” becomes a public relations challenge: How is it more socially and environmentally responsible to starve the poor to run your S.U.V? No doubt the corn industry will come up with some clever new and diverting way to spin this. They always do.

Meanwhile, copycats in the soybean industry are already plotting ways to get in on this cash-green bonanza in alternative fuels. This year, soybean prices are expected to hit their second highest mark ever, the U.S. Department of Agriculture reports, thanks to diversion of soybean oil to use as a biodiesel fuel. Two years ago, only two percent of the soybean crop went into bio-fuels; it is estimated that that figure could climb to as high as 12 percent this year.

So far, Americans haven’t really caught on to what is happening to the price of products such as soybean or corn-based foodstuffs. But that may change if and when this rush to all fuels allegedly more environmentally friendly affects the price of beer.

It could happen; Heineken, the brewery giant, said beer prices might have to be raised because so many crops are being planted and diverted to bio-fuel production that the supply of barley and hops is being reduced.

Where will this all stop? Actually, it has barely even begun; most ethanol and bio-fuel production is merely in the planning stages, or under construction (as in the case of refineries to produce this stuff), and years from coming on-stream. At what point might it dawn on people that the “cure” for reducing our dependence on foreign oil is worse than the original disease?

The oil and corn industries might not appreciate this suggestion, because they stand to lose money from it, but why not just try driving less? Why not choose to drive more fuel-efficient cars and trucks? Those are things we can do to save the environment, and protect the price of nachos.