Purpose The ISO 14044 standard for life cycle assessment (LCA) provides the reference decision hierarchy for dealing with multi-functional processes. We observe that, in practice, the consistent implementation of this hierarchy by LCA practitioners and LCA guidance document developers may be limited. In an attempt to explain this observation, and to offer suggestions as to how consistency in LCA practice might be improved, we identify and compare the rationales for (and limitations of) different common approaches to solving multifunctionality problems in LCA. Methods The different prevalent understandings of specific approaches for dealing with multi-functional processes were identified, and their respective rationales were analyzed. This takes into account identifying the implicit underlying assumptions regarding the nature and purpose of LCA that support each approach. Results and discussion We identified what we believe to be three internally consistent but mutually exclusive schools of thought amongst LCA practitioners, which differ in subtle but important ways in terms of their understanding of the nature and purpose of LCA, and the multi-functionality solutions necessary to support them. These three divisions follow two demarcations. The first is between consequential and attributional data modeling approaches. The second is between adherence to a natural science-based approach (privileging physical allocation solutions) and a socioeconomic approach (favoring economic allocation solutions) in attributional data modeling. Conclusions We conclude that the ISO 14044 multifunctionality hierarchy should explicitly differentiate between attributional and consequential data modeling applications. We question the feasibility and practical utility of system expansion (currently privileged in the ISO hierarchy) in attributional data modeling applications. We suggest that ISO 14044 should also make explicit its rationale for privileging natural science-based approaches to solving multifunctionality problems and to more clearly differentiate between natural science and social science-based approaches. We also call for the formulation of additional guidance for solving multi-functionality problems, in particular for justifying the use of lower-tier solutions from the ISO hierarchy when these are applied in LCA studies. We suggest that this additional guidance and clarity in ISO 14044 will contribute to increased consistency in LCA practice and also increase the potential for users of information from LCA studies to make informed decisions as to their relevance within the context of specific intended applications.

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Background, aim and scope Records over the last decades indicate a high growth rate for tourism, making it one of the most important industries in the world economy. Since estimates outline a consolidation of this trend, an accurate identification and assessment of the environmental impacts related to the life cycle of tourist products is increasingly necessary. By reviewing and comparing Life Cycle Assessment (LCA) case studies in the tourism sector, this paper aims to identify life cycle approaches that may be used as a basis for the subsequent development of sectorial Life Cycle Thinking guidelines. Main Features The following characterising elements were analysed for each case study reviewed, bearing in mind ISO 14044:2006 contents: goal, functional unit, system boundaries, inventory data quality and assessment methods of the environmental impacts. Results The few LCA implementations found in the literature vary considerably as regards the object studied and the methodological choices made. Specifically, the objects studied could be categorised as follows: accommodation services; buildings (hotel structures); tourist package holiday; the entire tourism industry. The main methodological choices made regard: system boundaries, data quality requirements and methods for assessing environmental impacts. Discussion A critical analysis of case studies revealed considerable dissimilarities as regards time reference and methodology application. Even though these differences made any comparison of results difficult, a few findings on methodological approaches might be outlined. Because the goal and scope definition profoundly affects LCA results, particular emphasis has been given to objectives and system boundaries.Conclusions The low number of studies found in the literature could indicate either that there are significant obstacles to adopting this approach or the limited awareness of LCA in tourism's drivers. The main obstacles might be: the complicated nature of the tourism system; the lack of specific LCA databases for tourism and related sectors; the tourism industry's low consideration of the environmental impact categories that are generally taken into account in impact assessment methodologies. Perspectives In order to promote the applicability and dissemination of LCA within the tourism sector, a number of methodological approaches and guidelines should be developed further. Moreover, it might be necessary to look into the possibility of integrating LCA with other instruments, such as environmental support tools for assessment, management, and design, as well as communication and marketing. Further synergies should be investigated regarding environmental instruments for passenger transportation, and specific tools that focus on the economic and social aspects of sustainability.