Researchers have worked for decades to improve schemes to convert agricultural wastes into ethanol. Now, the first of these commercial-scale cellulosic ethanol facilities in the United States is coming online, with additional plants set to open within the next few months. When fully operational, these plants are expected to produce about 340 million liters of fuel per year. But big hurdles remain for the cellulosic ethanol industry. The new plants must show that they can produce ethanol cheaply enough to compete with conventional ethanol plants that convert corn kernels to fuel. And government mandates for how much ethanol is used may also have to rise to ensure that there's a market for the newly produced fuel.