Assessing the Climate Effects of Biofuels Using Integrated Assessment Models, Part I: Methodological Considerations

Estimates of the climate†change mitigation benefits of biofuels are varied and controversial. Some analysts rely on attributional life cycle assessment (ALCA), limiting the analytic scope to the direct supply chain, whereas others supplement an ALCA result with an estimate of land†use change (LUC) emissions intensity. Other analysts have used consequential life cycle assessment (CLCA), with methods ranging from static market assessments to identify the likely marginal product and supplier, to running partial and general equilibrium models to estimate changes in global production and consumption. In this article, we consider another alternative—using an integrated assessment model (IAM) as a platform for CLCA of biofuels. In this article (part I of II), we focus on the methodological challenges of this approach. In part II, we present a case study using one IAM—the global change assessment model (GCAM)—to estimate the climate effects of several biofuels.