At the end of the first Back to the Future, Dr. Emmett Brown returns to 1985 from 2015 to find Marty McFly and transport him 30 years into his future in order to save himself. He arrives in an even more souped-up version of the time machine he'd first fashioned from a Delorian in 1985, which at that time was fueled by plutonium, a rare and radioactive toxic chemical.

The 2015 version relied on greener gas: garbage, mostly. More like a compost heap than a gas tank, this time machine was a repository for anything Doc could dig out of the trash at McFly's suburban house.

Now, just seven years shy of that prophetic glimpse into the future, Doc's fuel system is starting to look less and less like science fiction. By the end of 2009, two Silicon Valley entrepreneurs will begin selling the MicroFueler, a small machine that creates fuel for automobiles out of mostly sugar, or feedstock, and a pre-packaged yeast the company will sell with the machines. (The company's founder, Floyd S. Butterfield, says he sometimes even collects left-over alcohol from restaurants and bars in Los Gatos, California, where he lives, and converts it into ethanol.)

Selling for $9,995, the MicroFueler will be manufactured and sold in the United States, China, and Britain in the first phase. Should all go well, future markets are almost certain.

The beauty of the MicroFueler, say the founders and news reports on the invention, is that it will allow people to rely less on foreign oil, save a little money on gas, and reduce their carbon footprints.

And it may do some of all three, but if it takes off, here's something else it will do: drastically increase our reliance on sucarcane and the none-too-green (or ethical) system by which it reaches the US. As one of the world's most widely traded commodities, sugar reaches us by way of an immense industrial apparatus consisting of machines, boats, and trucks that leave a pretty deep carbon footprint themselves. And the people who farm our sugarcane are generally among the multitudes of overworked, underpaid laborers in poor nations whom we are unwittingly exploiting each time we sweeten our coffee.

This isn't to say the MicroFueler is a bad idea. To the contrary, it is clearly a step in the right direction. Self-reliance and homemade products will doubtless help curb environmental destruction. But as with most things, it's not as easy as one-two-three, and presto!, problem solved.