The life-cycle inventory (LCI) is used to estimate the direct and indirect inputs and releases at each step of a biofuel pathway. The results are the use of resources (e. g., energy consump­tion) and the environmental emissions (e. g., carbon dioxide, sulfur oxides, nitrogen oxides). Through characterization factors, the outcomes of LCI are utilized to assess impact categories such as climate change, stratospheric ozone depletion, photo-oxidant formation, acidification, eutrophication, ecotoxicity, human toxicity, depletion of biotic resources, and depletion of abiotic resources. The impact categories describe environmental mechanisms which convert the outcomes of the LCI into environmental damages. Indicators can be derived from these mechanisms at intermediate levels (midpoints) or damages levels, (endpoints) after normali­zation and sometimes weighting approaches. The use of endpoint methods to derive a global indicator of impact is controversial. The proponents claim for simplicity in communication of the results of the LCA to nonscientific public. The opponents emphasize the subjective nature of the weighting process and on the reductionism related to that approach.