Plant-e has managed to design products that can generate energy from living plants. They explain that it is now possible to utilize the space on your roof, not simply for growing plants, but, for harnessing electricity from those exact same plants!
They describe the process as being completely natural. It only needs three basic elements, light, carbon-dioxide and water. The harvesting process does not bring any harm to the plants and they naturally continue to grow. It all sounds like incredible stuff! Why not head to the site shown below and make up your mind for yourself!