Bioethanol production from agricultural raw materials can be carried out to produce liquid fuels and reduce CO2 emissions from the combustion of fossil fuels and hence its impact on climate. Crop production and transformation processes have been investigated by the traditional energy and carbon analyses and the more recent emergy analysis. The latter is able to account for, on the same basis, both renewable and non-renewable inputs, including goods and labour involved in a process. The combination of such analyses provides a deeper insight into the problems of converting biomass to fuel. In particular it is shown that emergy analysis can evaluate long-term sustainability and comparisons of emergy-based indices can be used to compare efficiency and environmental input between various production systems. Copyright (C) 1996 Elsevier Science Ltd.