More to the point, he was the product marketing manager for Alan F. Shugart’s pioneering hard disk drive when the personal computer was shifting from a hobbyists’ niche to a major industry. “I remember people laughing at us and saying what a stupid idea it was to do that disk drive,” Mr. Quinn says.

Mr. Butterfield thinks that the MicroFueler is as much a game changer as the personal computer. He says that working with Mr. Quinn’s microelectronics experts  E-Fuel now employs 15 people  has led to breakthroughs that have cut the energy requirements of making ethanol in half. One such advance is a membrane distiller, which, Mr. Quinn says, uses extremely fine filters to separate water from alcohol at lower heat and in fewer steps than in conventional ethanol refining. Using sugar as a feedstock means that there is virtually no smell, and its water byproduct will be drinkable.

E-Fuel has bold plans: It intends to operate internationally from the start, with production of the MicroFueler in China and Britain as well as the United States. And Mr. Butterfield is already at work on a version for commercial use, as well as systems that will use feedstocks other than sugar.

Ethanol has long had home brewers, and permits are available through the Alcohol and Tobacco Tax and Trade Bureau. (You must be a property owner and agree to make your ethanol outdoors.) But there are plenty of reasons to question whether personal fueling systems will become the fuel industry’s version of the personal computer.

For starters, sugar-based ethanol doesn’t look much cheaper than gas. It takes 10 to 14 pounds of sugar to make a gallon of ethanol, and raw sugar sells in the United States for about 20 cents a pound, says Michael E. Salassi, a professor in the department of agricultural economics at Louisiana State University. But Mr. Quinn says that as of January this year, under the North American Free Trade Agreement, he can buy inedible sugar from Mexico for as little as 2.5 cents a pound, which puts the math in his favor. While this type of sugar has not been sold to consumers, E-Fuel says it is developing a distribution network for it.

In addition, it’s illegal in the United States to operate a car on 100 percent ethanol, with exceptions for off-road vehicles like Indy cars and farm equipment. Mr. Quinn has a federal permit to make his own fuel, and believes that if MicroFuelers start popping up like swimming pools, regulators will adapt by certifying pure ethanol for cars.

Despite all the hurdles, Mr. Quinn and Mr. Butterfield may be on to something. There are plenty of consumers who want to reduce their carbon footprint and are willing to make an upfront investment to do it  consider the success of the Prius.