There are various ways to perform environmental assessment of emerging technologies, to be used as a base for decision-making. For instance, direct effects of a technology investment can be assessed, as in consequential studies, or the environmental impact in a number of possible future scenarios can be calculated, using an attributional approach. Here, we propose a consequential approach that includes socio-technical change, to account for contributions of an investment to system change and the resulting improvements (or deterioration) in environmental performance. We have earlier performed a socio-technical analysis of the development of alternative transport fuels in Sweden, both in a historic perspective and with scenarios for the coming years. Our aim was to investigate how new technologies emerge and grow, and how investments in one technology affect the growth of others. The results show for instance that a research program on coal gasification in the 1970’s, or an investment in a few ethanol buses in the 1980’s, have far-reaching effects on the development of alternative fuels in general. New actors are involved and institutions are adjusted that are in favour of the technology concerned (and related ones), thus stimulating further investments in new (and improved) technologies. Accordingly, some of the resulting environmental improvements could be allocated to early investments, and we would like to pose the question of how this could be accounted for in environmental assessment of emerging technologies. To illustrate this issue by an actual example, we use published LCA data to calculate the environmental impact of the use of ethanol as a vehicle fuel in Sweden at three points in time: 1990, 2005 and 2020. First, for each year, this will give us the LCA results traditionally used as a base for decision-making. Then we look at the factors related to socio-technical change: How does the environmental impact change between the years, both per functional unit and when looking at the total use of petrol and diesel replaced? These changes are compared with the LCA results for the three years to highlight the proportions, and it is discussed how they could be taken into account when performing and using environmental assessment as a base for decision-making regarding strategic technology choice.