Lifecycle analysis (LCA) is a very popular form of environmental assessment. A good number of academics and others assert that it is the ideal way to examine greenhouse gas emissions impacts and so advocate LCA as a way to compute "carbon footprints."
This view has come to dominate energy policy discussions of ways to reduce GHG emissions from transportation fuels. In particular, nearly everyone involved in the issue says that biofuels should be evaluated according to their full lifecycle impacts. As the major UNEP report on Assessing Biofuels puts it, "Environmental and social impacts need to be assessed throughout the entire life-cycle."
However, biofuel LCA has become ever more complex and has resulted in models that are no longer even close to being scientifically verifiable. Therefore, no amount of new data that one puts into a lifecycle study can put an end to the disputes over LCA-based estimates of the net GHG impact of biofuels. This argument is made in the paper "Biofuels and Carbon Management" Climatic Change (2012), which then proposes a different approach to analysis.