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Editor's Note: The following article is part of an ongoing science series, written by Arkansas State University faculty members and published periodically by The Sun.

By Elizabeth E. Hood

Plants are power.

They capture the sun's energy and give food, shelter and heat. Historically (long before humans) plant matter decayed, was pressurized and eventually formed oil. The oil formed from these ancient plants is the source of many modern day conveniences such as plastics, chemicals, transportation fuels and the basis for much of our manufacturing sector.

We are using up these non-replaceable oil reserves at an alarming rate. Moreover, the reserves are primarily in places in the world other than North America, creating a precarious political situation because disruptions in the supply could have an enormous impact on the U.S. economy and functionality.

Renewable energy resources based on today's green plants make economic, environmental and political sense. Ethanol from plants in place of gasoline for transportation fuels is a strategy that is being employed today and is gaining acceptance. There are two basic green plant materials that can be used to produce ethanol: grain (seeds) and stems and leaves.

Most grain is full of starch -- a bad thing if you are on a "low carb" diet, but a good thing for the plant. Starch is just a long chain of simple sugar molecules (glucose) strung together with one connection each. Starch is relatively easy to break down into its simple sugar components. These components can then be fed to yeast for fermentation into ethanol -- a process very similar to making beer.

The problem with using grain in this way is that it takes food away from people, and there is not enough grain to supply our transportation appetite even if we used all the corn grain available.

One solution to the grain problem is production of ethanol transportation fuels from stalks and leaves, thus utilizing large volumes of agricultural waste products (including rice hulls) that are left behind after harvest or processing. In principle, the process of getting ethanol out of plant stems and leaves or rice hulls is easy. In practice it has been very difficult, especially economically.

Each plant cell is surrounded by layers of cellulose that provide structure to the plant. Cellulose is a long chain of glucose, like starch, but the connection is different, and when it is taken apart the result is glucose. This glucose can also be fed to yeast to produce ethanol; again, the process is similar to making beer. The ethanol is distilled away from the mash, and the result is blended with gasoline for your car.

Researchers at Arkansas State University are working on technology that can be used to break down cellulose into glucose so it can be fermented into ethanol. The technology is to make enzymes -- proteins that perform jobs in biological systems -- in large enough quantities to take apart cellulose cheaply. The cost of these enzymes is at present a significant barrier to the cost-effective manufacture of ethanol.

Gathering up the raw materials -- the agricultural waste products -- cheaply is also a significant cost barrier, and researchers are working on ways to solve this problem also. With these two solutions, we will have traveled a long way toward making ethanol that is cost competitive with gasoline.

The good news here is that the United States has ample agricultural waste, such as corn stalks, sawdust and of particular interest to Arkansas, rice straw and hulls. All these materials are useful as ethanol sources. A balance can be achieved between using waste materials as a soil amendment and using them to make fuels.

In the case of rice, the hulls are harvested with the grain and become a disposal problem, and the stubble is burned in the fields, creating a smoke hazard. Wouldn't it be great to make gasoline replacements with these materials instead?

So one of the reasons that plants are power is that there is very little of the plant that cannot be used, especially with new technology. And not only can we use most plant parts, the plants can be grown again -- they are renewable.

So plants of the ancient past produced power in the form of coal and oil. Plants of the present produce power in the form of food. Plants of the future will produce fuels and chemicals as well as food.

For more information contact the ASU Department of Biological Sciences at biology@astate.edu.

Dr. Elizabeth E. Hood is associate vice chancellor for research and technology transfer and a professor of biology at Arkansas State University.