Comparing the incomparable? A review of methodical aspects in the sustainability assessment of wood in vehicles

Purpose The choice of materials used for a vehicle can contribute to reduce negative environmental and social impacts. Bio-based materials are considered a promising solution; however, the sustainability effects still need to be assessed. Depending on the material assessed, it is questionable which environmental and social impact categories or subcategories should be included since recommendations in guidelines are vague and case studies in this regard are limited. Therefore, this study aims to shed light on the choice of impact categories, methods, and indicators for E-LCA and S-LCA when assessing wood as substitute for conventional materials in automotive applications. Method The research is based on a literature review covering 115 case studies of S-LCAs and E-LCAs focusing either on wood-based products or on components in automotive applications. The selected case studies were analyzed according to the following criteria: considered stakeholder groups and chosen subcategories (S-LCA sample), sector or product system (S-LCA sample), year of publication and geographical scope (S-LCA and E-LCA sample), chosen LCIA method(s) and impact categories, objective(s) of the studies, analyzed materials and used software support (E-LCA samples). Results and discussion For S-LCA some relevant social topics for bio-based product systems, like food security or land- and worker-related concerns, could be identified. The E-LCA literature suggests that the objective and material type determine calculation approaches and impact category choices. Some material-related environmental issues like biodiversity loss in the case of bio-based product systems or ecotoxicity for steel and toxicity in the case of aluminum could be identified. For S-LCA the geographical and sectorial context and the affected stakeholders are the determining factors for methodical choices, however, the results show almost no difference in subcategory choice and geographical context. Influencing factors for methodical choices in E-LCA might be the objective of the study, data availability, the up-to-dateness of the LCIA approach, the geographical scope of the study, the materials analyzed, and the availability of software support. Conclusion Some relevant environmental and social impact categories as well as influencing factors on methodical choices could be identified from existing literature. However, a clear picture on these issues could not be drawn. Further research is needed on the motivation of researches on certain methodical choices as well as on environmental issues connected with materials or geographical-related social topics.