The aim of this paper is to find a green way to reduce the carbon dioxide released into the environment due to the heating system for buildings. The amount of carbon dioxide is 10500 kg per year for University of Pitesti. For compensation this is necessary to plant trees around the building of Faculty of Sciences. We studied about the advantages of Paulownia trees in terms of absorption of carbon dioxide and quick-growing speed. In the first three years they reach maturity and have a height of about 20 meters. Our researches estimate that a number of 40 Paulownia trees could eliminate this pollution.