A comparison of induced land-use change emissions estimates from energy crops
The introduction of the first generation of biofuels made from food crops has been controversial largely due to concerns over competition for land with food crops, thus raising global crop prices and generating induced land-use change (ILUC). For many food-based fuels, ILUC emissions could undermine the climate benefits of biofuels and reduce the effectiveness of alternative fuels policies. Lignocellulosic energy crops present a promising alternative to food crops because they can theoretically be cultivated on marginal, low-productivity land and thereby minimize competition with existing food crops. However, the existing literature on energy crop ILUC is sparse relative to the body of analysis conducted for first-generation biofuel feedstocks.
ILUC estimates within the literature are highly disparate, though most studies estimate lower ILUC emissions for energy crops than food crops, as they project that energy crops are unlikely to displace existing food and fiber crops at a large scale. This study highlights three critical assumptions that influence ILUC estimates for energy cropping: yield, distribution of land conversion, and soil carbon stock change. From there, we assess the existing body of of ILUC studies for energy crops and compare their treatment of these assumptions and the extent to which each assumption influences the studies’ final results.
Overall, we find that ILUC emissions from energy cropping are highly sensitive to assumptions of the composition of marginal lands. Modeling assumptions that accommodated greater direct and indirect deforestation resulted in greater emissions attributed to energy crops. Most ILUC assessments assume that energy cropping increases soil carbon stocks in marginal lands, reducing the emissions impact of cultivation. However, while there is some evidence that energy crops increase soil carbon stocks on depleted lands, the impact of energy cropping on pasture or abandoned land is less certain. This suggests that additional sustainability safeguards may be necessary for energy cropping in order to ensure that it only occurs on low-carbon stock land.