Potential environmental impact of bioethanol production chain from fiber sorghum to be used in passenger cars

A life cycle assessment (LCA) was applied to assess the environmental load of a prospective local bioethanol (EtOH) production system in Southern Italy by using lignocellulosic Fiber sorghum (FS) feedstock. A two steps analysis was carried out considering: (i) a "cradle-to-farm gate" LCA to investigate thoroughly the FS cultivation on hilly marginal land and (ii) a "cradle-to-wheels" system boundary encompassing the environmental pressure of the whole EtOH supply-use chain. Primary data related to lignocellulosic biomass production were combined with experimental feedstock conversion processes through advanced second generation technology. The purpose was the evaluation of the environmental performance of different EtOH-gasoline mixtures in midsize passenger cars: E10 (10% of EtOH and 90% of gasoline) and E85 (85% of EtOH and 15% of gasoline). N fertilization appeared as the prevailing contributor of the crop phase. The "cradle-to-wheels" results concerning E10 passenger car disclosed that the main hotspots were represented by the input of low sulphur petrol (66%) and the linked tailpipe emissions (15%), for almost all the impact categories. Otherwise, for E85 flex-fuel vehicle, the major drivers were represented by the feedstock production (46%) and the imported electricity used in the conversion facility (18%). The FS EtOH blends entailed potential environmental benefits compared with the fossil counterpart (gasoline) for climate change, ozone and fossil depletions. Otherwise, they evidenced a worse profile in terms of acidification, eutrophication and particulate matter formation. Within the context of a the prospective territorial bio-refinery network, the comparison of the annual FS bioethanol based systems with similar EtOH scenarios from giant reed perennial crops highlighted: (i) the importance to optimize the N-management for FS feedstock cultivation and (ii) the need to increase the use of the renewable energy carriers along the industrial conversion pathway.