Scientists Propose a More Efficient Way to Make Ethanol

Producing ethanol from corn is relatively easy: the corn’s abundant sugars are readily fermented into alcohol. But using what is essentially a food crop to produce fuel has been criticized as a misuse of resources that can harm both agriculture and the environment.

Better, critics say, to make what is called cellulosic ethanol from leaves and stalks or other crop waste or nonfood crops like switchgrass. The process uses lignocellulose, the basic structural material of all plants and the most abundant organic compound on the planet.

But cellulosic ethanol is more difficult to make. The lignocellulose must first be broken down into sugars, which can then be fermented. Current techniques use costly enzymes or highly concentrated acids that are difficult to handle.

Now, Ronald T. Raines and Joseph B. Binder of the University of Wisconsin are proposing a different way. In a paper in The Proceedings of the National Academy of Sciences, they describe a process that uses an ionic liquid — a salt with a low melting point — in combination with water and acids at lower concentrations to produce fermentable sugars.

The researchers found that water was the key to making the process efficient. Without water, the sugars produced by the action of the ionic liquid and the acid rapidly degraded into other compounds. But water keeps chloride ions in the salt from further reacting with the sugars.

The researchers say their process produces sugar yields approaching those obtained by enzymatic methods. While much work remains, they say the process may prove useful in converting agricultural waste to a useful fuel.