Researchers at Vanderbilt University have discovered how the enzyme TrCel7a–which breaks down cellulose, the most plentiful natural polymer on the plant– works like a microscopic wood chipper. It swallows strands of tightly bound cellulose and breaks them down into simple sugars. It works very slowly but, like a truck operating at a very low gear, it is extremely difficult to stop once it gets going. It is also self-propelling, powered in large part by energy from the cellulose bonds that it breaks. Finding ways to make enzymes like TrCel7a operate faster and more efficiently could be the key to transforming ethanol made from cellulose into a major new renewable fuel source. In the U.S. each year an estimated 323 million tons of cellulosic wastes are thrown away–enough to provide as much as 30 percent of current fuel consumption.