Greifswald (Germany) - German students have come up with a down-to-earth idea how to bind the global output of carbon dioxide emissions. They suggest to simply plant enough trees to absorb carbon dioxide through photosynthesis. The question is: How many trees do you need, how much space do they need and how much will that cost?

Fritz Scholz and Ulrich Hasse from the University of Greifswald believe that the carbon dioxide problem can be buried, literally. The two students claim that "deliberately planted forests" can bind carbon dioxide through photosynthesis.

Scholz said that the resulting biomass needs to "disappear", which could happen simply by burying the wood: "Possible burial sites include open brown coal pits or other surface mines. These should be filled with wood and covered with soil. Cut off from the air in this manner, the wood would not change, even over long periods. It could in principle be dug up in the future and used."

If we assume for a moment that it is feasible to bury all the wood and replant trees, how many trees would you need to bind carbon dioxide emissions? According to Scholz, about 32 Gtons of carbon dioxide is released into the atmosphere every year. He estimates that about 2.47 billion acres of trees are required to remove these emissions - which, according to U.S. government guidelines, translates into a number of 250 to 750 billion trees (the number varies depending on the type and maturity of trees as well as their location; this example uses mature Red Maple tress).

So, how much is 2.47 billion acres? It is slightly larger than the area size of the U.S., which measures about 2.38 billion acres. The total land mass of the earth is 36,677,592,320 acres, which means that about 7% of the surface need to covered with trees to offset our current carbon dioxide emissions, if Scholz and Hasse are right. However, these estimates always have to be taken with a grain of salt, as scientists have come up with different numbers how many trees are necessary to battle carbon dioxide emissions: For example, one U.S. government source suggests that one acre of trees can handle 2210 pounds or 1.1 tons of carbon dioxide per year. Put against 32 Gtons (32 billion tons), we would need about 35 billion trees. We will leave it up to you to decide you may be right and who may be wrong.

However, Scholz and Hasse also came up with an idea how these 2.47 billion acres of trees could be financed. We did not get details whether their model includes the acquisition of land, but they claim that the project could be financed through a 65 cent tax per gallon of gasoline or a 0.4 cent charge per kilowatt-hour of electricity.