In order to mitigate climate change, one of the major challenge humanity has to face is to decarbonize energy consumption through the use of sustainable sources of energy. Among these sources, several options are considered such as wind, solar, geothermy or biomass. Biomass is a promising option for small tropical islands as it is continuously available with an affordable technology and can be locally grown. The use of energy cane, a highly productive variety of sugarcane specifically dedicated to energy production, is currently investigated in Guadeloupe. In order to help local stakeholders to promote the best options in Guadeloupe, we used an Emergy approach to assess ex ante the environmental sustainability of electricity produced with energy cane for four contrasted scenarios depending on 1) the power of the electric plant, 2) the plant's feedstock, based on a mixture of energy cane, bagasse and imported wood pellets, 3) the location of the plant in the island and 4) the type of crop management system (Tab. 1). Our results (Tab. 2) show that the renewability (%R) of the electricity produced with the baseline scenario is 30%. This is much better than oil plant (7%), photovoltaic (2%) and also windfarm (20%). However it is lower than geothermy (63%) and results obtained with much bigger CHP plant in other context (61%). This latter can be explained by a lower renewability of energy cane compared to wood and the absence of valorisation of low pressure vapor in our case. The analysis of the scenarios show that the %R can be improved by 1 to 8% through the choice of appropriate options (cf. S1 and S4, Tab. 3). Our study demonstrates the negative influence of the use of imported wood pellets but also the key role of crop fertilization for ensuring sustainability of biomass-based electricity.