The support of sustainable energy innovations has become a dominant topic on the political agenda of many countries. Providing this support remains difficult, since the processes constituting such innovation trajectories are poorly understood. To increase insight in such processes, this paper takes the historical development of biofuels in the Netherlands as the topic of study. Special attention is paid to the simultaneous development of two technology generations within the field: a first generation (1G) and a second generation (2G) of biofuels. A critical question asked is whether deployment programmes for a I G technology may have positive effects on the development of later generations. Two archetypical support strategies are identified: one is to keep investing in R&D concerning 2G technology, where the expected outcome is a fast move from one technology generation to the other. The other strategy is to focus on learning-by-doing in the 1G technology. In that way progress can be made in 1G technologies but the effects on 2G technologies are uncertain. We apply a Technological Innovation System perspective to analyse the strategies followed and their effects. From the results we draw lessons of relevance for practitioners who aspire to understand and influence emerging energy technologies. (c) 2008 Elsevier Ltd. All rights reserved.