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Influence of Indirect Land Use Change on the GHG Balance of Biofuels – A Review of Methods and Impacts

The greenhouse gas (GHG) balance or carbon footprint of biofuels is heavily influenced by the modeling of land use changes (LUC). This includes direct land use changes (DLUC) and indirect land use changes (ILUC). Various methodical approaches for the quantification of ILUC and the effects on GHG balance have recently evolved. These are economic modeling, deterministic modeling and regional modelling. Papers published on this topic since 2007, when the ILUC debate began, are reviewed in this paper considering the following criteria: methodological approach, uncertainties of assumptions, and the level of the GHG emissions due to ILUC. The results show that the existing approaches lead to strongly divergent results. This is due to uncertainties about relevant assumptions, e.g. the methods of linking commodity prices to ILUC, assumptions about yields, soil carbon contents, and the effect of by-products.