Environmental assessment of black locust (Robinia pseudoacacia L.)-based ethanol as potential transport fuel

Lignocellulosic ethanol has received special research interest, driven by concerns over high fuel prices, security of energy supplies, global climate change as well as the search of opportunities for rural economic development. A well-to-wheel analysis was conducted for ethanol obtained from black locust (Robinia pseudoacacia L.) by means of the life cycle assessment (LCA) methodology. This study assesses the environmental profile of using ethanol in mixtures E10 and E85 as transport fuel in comparison with conventional gasoline (CG). In addition, the best model of black locust cultivation was analysed under an environmental point of view. The standard framework of LCA from International Standards Organisation was followed. To compare the environmental profiles, the study addressed the impact potentials taking into account the distance travelled by vehicles with the fuel tank full of CG. The product system includes all the processes involved from the black locust cultivation to the final use of fuels in a vehicle. The transport of all the chemicals and products is also included in the system boundaries. According to the results, fuel ethanol derived from black locust biomass may help to reduce the contributions to global warming, acidification, eutrophication and fossil fuels use specifically due to the low input production regime of the agricultural stage. These reductions would be increased with the increasing ratio of ethanol in the blend. Moreover, the use of lignin, biogas and other solid waste as fuel to meet the energy requirements of the plant, positively contribute to the environmental profile of cellulosic ethanol. On the contrary, ethanol blends are less environment friendly that CG in terms of photochemical oxidants formation. The cultivation of black locust following a low-input production regime, without agrochemicals application and extra irrigation is an important reason for the environmental improvement. Efforts should be made to promote the production of black locust according to principles of sustainable cultivation. Moreover, technological development in ethanol production could help to improve the environmental profile in the life cycle of ethanol-based fuels. It could be interesting to develop a strategic planning which allows identifying the potential regions not only in Italy but also in other European countries in order to increase the black locust biomass yield. The cultivation of short rotation forestry and/or short rotation coppices under low-input regimes presents potential environmental benefits and advantages for the future of second-generation ethanol production in Europe.