Due to the growing demand for electricity, it seems advisable to explore and use new sources of renewable energy. The most widely used renewable energy source is biomass. In addition to commonly used types of biomass, such as wood or energy crops, waste from the care of urban greenery, such as mowed grass, collected leaves, or wood waste, can be used for energy purposes. The aim of the paper is to present the possibilities of managing waste from the maintenance of urban greenery in Warsaw. In the paper the possible amount of obtained green waste as well as the energy potential of this biomass is estimated.