Life cycle assessment of two alternative bioenergy systems involving Salix spp. biomass: Bioethanol production and power generation

Two energy production systems using short rotation coppice (SRC) willow chips were evaluated: bioethanol production via enzyme-catalyzed hydrolysis and electricity production following a biomass integrated gasification combined cycle scheme. The most relevant input and output flows of each renewable energy system were identified and quantified throughout the life cycle from the SRC willow plantation to the bioenergy plant gate. Both bioenergy systems were found to be feasible from an energy perspective. Moreover, they entailed environmental benefits when compared to conventional energy practices. However, improvements relating to not only willow biomass production but also bioenergy conversion-related activities should be considered. In this respect, the process steps that provided the highest environmental impacts have been highlighted. Furthermore, well-to-wheels environmental characterization results were estimated and compared for the bioethanol and bioelectricity scenarios. In this sense, the identification of the most appropriate processing route for willow chips was found to be highly dependent on the impact category under assessment. In particular, global warming and energy parameters led to opposite conclusions. While the bioethanol scenario arose as the potentially best choice from an energy perspective, the bioelectricity scenario seems to be a more suitable alternative when global warming is the decisive factor. (C) 2012 Elsevier Ltd. All rights reserved.