This article evaluates the environmental performance of a biofuel production system based on the fast pyrolysis of short-rotation poplar biomass using a Life Cycle Assessment (LCA) approach. The system includes a circulating fluidized bed reactor followed by bio-oil upgrading through hydrotreating and hydrocracking to produce gasoline and diesel. The investigated system was selected on the basis of an overview of available technologies for the production and upgrading of fast pyrolysis bio-oil. Inventory data for the whole system were collected and used in order to carry out the life cycle impact assessment. Seven impact categories were evaluated: cumulative energy demand, global warming, ozone layer depletion, photochemical oxidant formation, land competition, acidification and eutrophication. Feedstock pre-treatment, pyrolysis and steam reforming for the production of the hydrogen required for hydroprocessing were identified as the subsystems with the highest contributions to the potential impacts. Within these subsystems, natural gas production, electricity generation and direct emissions to air were the main contributors. Special attention should also be paid to the production of the lignocellulosic biomass feedstock, especially to the associated land occupation and fertilizer requirements. (C) 2012 Elsevier Ltd. All rights reserved.