What are the expected relative GHG emission savings of biofuels: uncertainty

Blog summary so far: We have seen that while biofuels may have acted as a carbon sink historically, their properties seem to have changed since then due to the new factors that arose. It has also been shown that the calculations of GHG savings from biofuels contain large uncertainties and also vary significantly between the different materials. In my next post I will attempt to explain the uncertainties in the savings estimates.

Uncertainty - an introduction: A number of reports currently state that 1^st generation biofuels, which include mainly food crops high in starch and sugars, such as corn and sugar cane (Tao et al., 2011) are estimated to produce ~60% GHG saving compared to fossil fuels, while 2^nd generation biofuels, which include mainly cellulose-rich materials, such as corn stover, switchgrass and jatropha (Tao et al., 2011), are expected to produce ~80% carbon saving (figure 1).

 Figure 1.

However these figures are not an accurate representation of the reality, as they greatly mask the complexities underlying the issue of GHG emissions estimation of biofuels, which can be partially seen in the wide uncertainty level in the data from my previous post and from the wide uncertainty level bars in figure 1. Please also note that the figure does not incorporate the future 3^rd and 4^th generation biofuels which are likely to have even larger uncertainty levels at the moment.

To better understand the current and future carbon reduction potential of biofuels, in my next post I will explain some of the assumptions made in these calculations and the factors that produce the high uncertainty levels and the wide range of outcomes before presenting the GHG reduction potential data in greater detail.