Published data were used to develop an integrated spreadsheet-based model to estimate total water requirement for 12 biomass conversion pathways. The water requirement for crop production was attributed only to the grains in the estimates since agricultural residues are produced irrespective of their use for fuel or electricity. Corn stover- and wheat straw-based ethanol production pathways are water efficient, requiring only 0.31, whereas biopower production pathways (i.e. direct combustion and bio-oil production) require about 0.8-0.91 of water per MJ. Wheat- and corn-based ethanol production pathways consume 77 and 108 I of water per MJ, respectively. Utilization of switchgrass for production of ethanol. biopower through the direct combustion, and pyrolysis consume 128, 187 and 229 I of water per MJ, respectively. Biodiesel production from canola seed consumes 1241 of water per Mj. Corn stover- and wheat straw-based conversion pathways are most water efficient. (C) 2010 Elsevier Ltd. All rights reserved.