This new paper (pdf) by Harry de Gorter and David R. Just, published in the Cato Institute’s journal, Policy Analysis, looks interesting.
From the executive summary:
Sustainability standards are based on “lifecycle accounting,” in which ethanol is assumed to replace gasoline; but in fact, it may be replacing coal or other energy sources. Life-cycle accounting also fails to recognize that if incentives are given for ethanol producers to use relatively “clean” inputs (e.g., natural gas), the “dirtier” inputs (e.g., coal) that might otherwise have been used for the ethanol production will simply be used by other producers to make products that are not covered by the sustainability standard. Sustainability standards reshuffle who is using what inputs—with no net reduction in national emissions.