NOVELTY - The method comprises cultivating Pennisetum, selecting flood land and waste mountain with water source of rich rainfall or coastal beach polder, excavating the Pennisetum plant gap after plowing harrow, spreading matured organic fertilizer and soil composition and then enchasing germchits, wetting the land by the water, harvesting the Pennisetum after one year of cultivation, allowing the leaves of the Pennisetum to be dry and yellowish color, and passing nutrient of leaves and stalk of the Pennisetum to underground.    USE - The method is useful for producing Pennisetum biological carbon, which is useful as a soil conditioner and strategic reserve energy for generating electricity (claimed).    ADVANTAGE - The Pennisetum biological carbon improves the fertility of soil thus improving the photosynthetic efficiency of the plant.    DETAILED DESCRIPTION - The method comprises cultivating Pennisetum, selecting flood land and waste mountain with water source of rich rainfall or coastal beach polder, excavating the Pennisetum plant gap after plowing harrow, spreading matured organic fertilizer and soil composition and then enchasing germchits, wetting the land by the water, harvesting the Pennisetum after one year of cultivation, allowing the leaves of the Pennisetum to be dry and yellowish color, passing nutrient of some leaves and stalk of the Pennisetum to underground, harvesting the Pennisetum with a professional harvester after the leaves are totally dried-up, pre-processing the dried stalk of the Pennisetum, cutting the dried stalk of the Pennisetum into a 2.5 cm lengthen part and a 3.5 cm lengthen part using a knife mill according to different smokeless coking processes, cutting stalk with a length of 1-1.5 m, binding the cut stalk into wisp having a diameter of 50-70 cm, where the portable smokeless coking process is applicable to a large stationary smokeless coking furnace, and performing smokeless coking process on the pre-processed Pennisetum to obtain biological carbon in anaerobic cases at 180-550 degrees C. An INDEPENDENT CLAIM is included for a method for preserving Pennisetum biological carbon.