In case your view of biofuels had not yet shifted to something more nuanced than they being a universally great alternative to petroleum products, a new study from Switzerland's Federal Laboratories for Materials Science and Technology (Empa) summed up in the graphic below, should definitely change your mind.
Summing up the findings, via Science Daily:
Biofuels from deforested areas usually emit more greenhouse gases than fossil fuels. This also applies to indirect land usage changes if existing agricultural land is used for the first time for biofuel production and, as a consequence, forested areas have to be cleared in order to maintain the existing foodstuff or animal feed production.
On the other hand, positive effects can be achieved if energy plant cultivation increases the carbon content of the soil, for example via the cultivation of oil palms on unused grazing land in Columbia or via jatropha plantations in India and eastern Africa, making deserted land arable again. "Despite this, you can't speak in general terms of Jatropha as being a 'wonder plant', as its ecobalance is very much dependent on the agricultural practices at the site in question and the land's previous use," says Zah. Each (new) biofuel must therefore be examined separately and in detail.