In her search for a better way to put fuel in your tank, biological engineer Ratna Sharma-Shivappa is working on a chemical juggling act: She is trying to break down the problematic woody material in grasses without harming the energy-containing carbohydrates that the plants also contain. If she can perfect the process, it could lead to inexpensive biofuels that are made from inedible crops—not from corn like most of today’s ethanol.
By exposing ground-up miscanthus grass (a relative of sugarcane) to ozone gas, Sharma-Shivappa and her colleagues at North Carolina State University were able to break down the tough structural molecule called lignin, allowing them to access the valuable carbohydrates without degrading them. Enzymes then split the carbs into sugars, which are fermented to make ethanol. Although ozone is pricey, the technique works at room temperature and does not require high pressure, advantages that Sharma-Shivappa believes will help keep it cost-effective. Next she will test the ozone treatment on other potential biofuel plants. “This should be applicable to most lignin crops,” such as switchgrass, she says.
Chemical engineer Rajai Atalla of the University of Wisconsin is attacking another fibrous plant component, cellulose. His aim is to convert it into useful glucose, which can then be fermented into ethanol. Atalla finds that briefly soaking corn stover (the leftover parts of the plant, such as husks) in a solution of sodium hydroxide, ethanol, and water changes the molecular structure of the cellulose, allowing him to convert nearly twice as much of it as is possible with existing methods.