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The idea of using trees to combat climate change is nothing new, indeed a whole industry is growing up around using trees to offset our carbon footprint.  Besides the arguments about the cop-out nature of carbon offsetting, the fact is the planting of trees does not permanently remove CO2 from the atmosphere: it merely delays its release date.

In an essay in the journal ChemSusChem, Fritz Scholz and Ulrich Hasse from the University of Greifswald introduce a possible approach to a solution: deliberately planted forests bind CO2 through photosynthesis and are then removed from the global CO2 cycle by burial. "For the first time, humankind will give something back to nature that we have taken away before," says Scholz.

"Whereas other environmental problems can, at least in principle, be solved by the appropriate modern technology," reports Scholz, "there are no realistic solutions for the CO2 problem." At present, a daunting 32 gigatons of CO2 are released into the atmosphere every year.

There has been a lot of talk about Carbon Capture and Storage (CCS), where CO2 is extracted out of the atmosphere and pumped into geological seams deep underground (often the same seams from which oil or natural gas are extracted).  The technology is still new and not without its problems and controversy.

Scholz and Hasse suggest the only possible way to bind sufficiently large quantities of CO2 from the atmosphere is photosynthesis. However, the resulting biomass cannot be burned or composted, because this would release the bound CO2 again. The trick is to make the biomass "disappear".

Scholz recommends planting forests whose wood will subsequently be buried. 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.

According to estimations made by Scholz and Hasse, we would have to plant a little over one billion hectares of forest in order to bind all of the carbon dioxide produced in a year. This corresponds roughly to the surface of the virgin forest cut down in the last century. They go on to suggest this project could be financed by an additional tax of €0.11 per litre of gasoline or €0.003 per kilowatt-hour of electricity.

"The forests should be planted in countries that are suitable for growing forest and also have the necessary sites for burial of the wood," stresses Scholz. "Other countries, the primary consumers of fossil fuels, can pay them for it. This would produce a global trade that would benefit everyone involved."