Increasing oil prices and growing environmental concerns in recent years have driven the development of renewable biofuels. Until now, most of the bioethanol production concepts are based on sugar and starch crops as feedstock, while research on second generation of bioethanol concepts is investigating the use of cellulosic biomass such as straw, wood, etc. as feedstock. The first part of the paper will review membrane opportunities in the present bioethanol production concepts, while the second part will provide an outlook on the future potentials of membrane technologies in the second generation concepts. For both production concepts, application opportunities for conventional membrane processes such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) as well as the emerging membrane processes pervaporation (PV) and vapour permeation (VP) will be presented. Overall, this paper demonstrates that membrane technology as a highly selective and energy-saving unit operation has a great potential in the bioethanol industry of today and in future. Hence, membrane technology will contribute to solving future energy and environmental problems. (C) 2009 Elsevier B.V. All rights reserved.