Due to concerns about climate change and the growing fear of dwindling fossil fuel reserves, governments all over the world have committed themselves to search for an alternative, "greener" fuel source. Biofuels have been heralded as a panacea to climate change, but recent studies demonstrate that the costs of biofuel production, namely the harmful environmental impact of the process, may outweigh the benefits. This Master's thesis aims to provide a comparison of studies on first- and second- generation biofuels in order to assess their environmental, social, and economic sustainability. The numerous technical barriers hindering the commercialization of lignocellulosic biofuels are addressed and the benefits of using agricultural and forestry residues for biofuel production are analyzed. By means of a material flow analysis, the CO2 emissions resulting from the use of gasoline and bioethanol at the stage-of-use are compared. It is shown that the combustion of bioethanol results in lower CO2 emissions than those from the combustion of gasoline. Despite these favorable results, it remains to be seen if biofuels are viable, when the entire life-cycle, from feedstock cultivation to fuel production, is taken into consideration.