Once upon a time, biofuels like wood and cow dung were simply gathered and burned for heat, light, or energy. This was both straightforward and carbon neutral. Plants captured the carbon, fire released it, and nature stayed in balance. It was only when we started burning the stored carbon held in oil, natural gas, and coal that the balance was upset. So the idea of returning to the old ways of generating power has a simplicity that's attractive-assuming there's a fuel source that doesn't involve cutting down the world's remaining forests. A few possibilities have emerged in recent years, the most interesting of which is a tall decorative grass called miscanthus. Scientists have been growing test fields of it and have found that it yields acceptable amounts of energy and can be mixed with coal and burned in existing power plants.