Generating energy from crops instead of oil and coal can have counterproductive effects. “The use of biomass can lead to additional emissions of greenhouse gases”, says lead author Alexander Popp of the Potsdam Institute for Climate Impact Research (PIK). “This is the case if forests get cut down to plant energy crops instead.” Forests are important CO2 sinks. At the same time, biomass is expected to play an important role in  future energy systems.

http://iopscience.iop.org/1748-9326/6/3/034017/fulltext