Ethanol and policy issues

Recently, the U.S. government increased the cap on the amount of ethanol that can be used in gasoline from 10% to 15%. Upping this limit should encourage the development of alternative sources of ethanol, but changing this limit affects the car manufacturers.

A proposal to require cars to use an E85 blend (that is, 85% ethanol, 15 % petroleum) could be accommodated by car manufacturers, but it is not known whether this ethanol-rich blend would damage engines designed to operate on the current 10% blend.

Scaling up the use of cellulosic biofuel is not just a scientific or technological issue, but a policy issue as well. One scenario would be to have the ethanol limit gradually increase from to 85%; the current increase to 15% is a down payment on this strategy.

Learn more about E85 and "flex fuel" vehicles here.

Photo: an E85-powered Chevrolet HHR.

Growing Green

A major roadblock to scaling up the use of cellulosic biofuel is the difficulty and expense of extracting the ethanol from these materials.

The ethanol currently used in gasoline mixtures come from fermentation of sugars present in corn kernels, and is a relatively simple and inexpensive process. However, the sugar in cornstalks and other cellulosic biofuel is locked in chemical structures that are harder to break and the ethanol yield is lower, which means that manufacturers of cellulosic ethanol require much more raw material than the ethanol manufacturers.

Scientists are exploring ways to extract cellulosic ethanol more effectively. One possible solution is to engineer new microbes that can break down cellulose into sugars that can more easily be fermented to form ethanol.

The Great Lakes Bioenergy Research Center is a consortium of organizations working to conduct this sort of "transformational biofuels research". Go Green!

Biofuels

Ethanol is a fuel derived from plant material, primarily corn kernels. Although a renewable resource, one of the down-sides of using corn-derived ethanol as fuel is that it diverts grain from food to energy use, driving up food prices. This concern was addressed by research into using biowaste, that is, grasses, cornstalks, and wood chips not used for food.

The problem with using this “cellulosic” ethanol is that the ethanol is much harder to extract. Currently, just 40% of the energy content available in cellulosic plant sources is recoverable, compared to 90% of the energy in kernal ethanol.

But another issue with ethanol from corn is that the process requires a lot of energy, and the end-product ethanol does not represent a big savings in the use of fossil fuels in the process and still contributes to greenhouse gas emissions.

More on the pros and cons of ethanol, here.