The ‘environmentally friendly’ rhetoric with respect to biofuel production and consumption, such as that advanced by Shapouri et al. (1995, 2002), has often been disputed, most emphatically by Henke et al. (2005) and Patzek et al. (2005). Some have suggested that, up until this point, the net contribution of biofuels to reducing global GHG emissions might have been negative (Eggert et al. 2011), mainly as a result of (1) land-use changes (LUC) and (2) deforestation in tropi­cal areas, particularly so as to allow the planting of biomass used for biofuel pro­duction (Searchinger et al. 2008; Fargione et al. 2008). Moreover, Anderson and Fergusson (2006) contend that biofuels, regardless of type, cannot be regarded as truly carbon neutral (or even carbon negative) when the stages of production, transportation and processing are taken account. Patzek et al. (2005) accepted this contention after a meta-analysis of a wide array of previous studies.

To gain a deeper insight into whether biofuels represent an improvement over conventional liquid fuels with respect to their overall GHG footprint, it is necessary to consider the entire biofuel life cycle, including the production phases. In addition to the tailpipe emissions discussed earlier, these include (1) type of feedstock, (2) processing of feedstock and (3) the cultivation and harvesting of the feedstock.