Estimating energy and greenhouse gas balances of biofuels

Feb 2008

The interest in developing biofuels has rapidly increased during the last decades followed by a strong controversy about their sustainability. Diverting a large amount of land from agriculture to fuels, impacting forests and grasslands, loss of biodiversity due to large monocropped fields are some threats that inhibit the momentum towards a significant substitution of fossil fuels by biofuels. From a methodological point of view, several estimations of the reduction of greenhouse gas (GHG) emissions from biofuels lead to a large variability of results even if they address the same biofuel pathway. It has been shown that the methods used and the assumptions on data inventories, system boundaries, allocation of resources and emissions may significantly impact the results. In different countries and regions in the world, sustainability standards are being developed in order to limit the promotion of biofuels to those that are environmentally sound, socially responsible and economically effective. Global warming is of a particular interest when assessing the sustainability of biofuels as one of the main drivers of their development is their potential to mitigate GHG emissions. Therefore global sustainability standards include GHG balances as a main point. In many cases, Carbon reporting is separate from the reporting on other sustainability criteria (e.g. UK and California initiatives), reflecting the importance given to that item. Furthermore, the general impression is that at policy level it is easier to quantify Carbon balances than local environmental and social impacts. However evaluating GHG balances of biofuels is not straightforward. This paper aims at investigating the main assumptions made in the literature when estimating the reduction of GHG emissions of biofuels in comparison with their fossil competitors. In section 2 the main items that structure the Life Cycle Analysis (LCA) of biofuels are commented and methodological choices are addressed from a constructive criticism point of view. Section 3 analyses selected papers and works on biofuels. Finally, the conclusion highlights the necessity of transparency and gives some recommendations for estimating the reduction of GHG emissions.

 
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