Abstract:As commonly employed, life-cycle analysis (LCA) cannot accurately represent the climate impacts of complex systems such as those involved in making and using biofuels for transportation. LCA generally is linear, static, highly simplified, and tightly circumscribed. The real world, which LCA attempts to represent, is none of these. Among LCA’s major deficiencies are: its failure to explicitly specify alternative courses of action; its incomplete accounting for price effects; its incomplete treatment of land-use change; its neglect of the nitrogen cycle; and its omission of climate-impact modeling steps and climate-relevant pollutants. In order to better represent the impacts of complex systems such as those surrounding biofuels, analysts need a different tool — one that has the central features of LCA, but not the limitations. I propose as a successor to LCA a method of analysis that combines integrated assessment modeling, life-cycle analysis, and scenario analysis. I call this method integrated modeling systems and scenario analysis (IMSSA). IMSSA uses dynamic, nonlinear, feedback- modulated representations of energy, economic, ecological, and technological systems in order to estimate the physical and economic impacts of policies or actions, particularly those related to biofuels.