Climate impact assessment in life cycle assessments of forest products: implications of method choice for results and decision-making

Abstract

As life cycle assessments are often conducted to provide decision support, it is important that impact assessment methodology is consistent with the intended decision context. The currently most used climate impact assessment metric, the global warming potential, and how it is applied in life cycle assessments, has for example been criticised for insufficiently accounting for carbon sequestration, carbon stored in long-lived products and timing of emission. The aim of this study is to evaluate how practitioners assess the climate impact of forest products and the implications of method choice for results and decision-making.To identify current common practices, we reviewed climate impact assessment practices in 101 life cycle assessments of forest products. We then applied identified common practices in case studies comparing the climate impact of a forest-based and a non-forest-based fuel and building, respectively, and compared the outcomes with outcomes of applying alternative, non-established practices.Results indicate that current common practices exclude most of the dynamic features of carbon uptake and storage as well as the climate impact from indirect land use change, aerosols and changed albedo. The case studies demonstrate that the inclusion of such aspects could influence results considerably, both positively and negatively. Ignoring aspects could thus have important implications for the decision support. The product life cycle stages with greatest climate impact reduction potential might not be identified, product comparisons might favour the less preferable product and policy instruments might support the development and use of inefficient climate impact reduction strategies.