Ethanol

You’ve probably been hearing a lot lately about ethanol. From politicians to advertisements by major automakers, ethanol is being discussed more regularly as an alternative to gasoline.

Ethanol is ethyl alcohol, also called grain alcohol. Chemically, fuel ethanol is identical—albeit in a purer form—to the alcohol we drink. To make sure fuel ethanol isn’t used for frat house punch, it’s denatured, which means it is mixed with another chemical (usually gasoline) that renders it undrinkable.

Where Does Ethanol Come From?

Ethanol comes from one of these three raw material groups:

  • starchy crops, such as corn
  • sugary crops, like fruit or sugarcane
  • cellulosic plants, such as trees or wild grasses

While the process for making ethanol varies somewhat depending on the feedstock, the basic steps are the same.

  1. The feedstock is milled or crushed, and may be treated with chemicals or enzymes. This step is designed to yield as much fermentable sugar as possible from the feedstock.
  2. Yeast is added to the prepared feedstock and sugars are converted to alcohol.
  3. The alcohol is extracted from the mixture by boiling it in a distiller.

Nearly all the ethanol made in the United States uses corn for a feedstock. Brazil, the world’s largest ethanol producer, makes ethanol from sugarcane. Other countries, such as France, use sugar beets and wheat as their primary feedstocks. With current technology, it is easiest and most efficient to produce ethanol from sugar crops, since the sugars in these feedstocks are readily available for fermentation. In the future, advances in ethanol production may increase yields and decrease the cost of producing ethanol from cellulosic material.

What are the chief benefits and drawbacks of ethanol?

The Blends

Most likely, you’re using ethanol in your car without even knowing it. In many regions, small amounts of ethanol are blended with gasoline to reduce emissions. Mixtures as high as E10 (10 percent ethanol and 90 percent gasoline) are safe for use in most vehicles, including hybrid models such as the Toyota Prius and Honda Civic Hybrid.

Much of the news lately has been about fuel blends that have higher ethanol content. The most common is E85 (85 percent ethanol and 15 percent gasoline), which only can be used in vehicles that are designed for that fuel. Currently, no hybrid models accept E85 fuel, but 22 E85-compatible cars and trucks (called “flexible-fuel vehicles”) are available now from four major manufacturers.