Facilitating dynamic life cycle assessment for climate change mitigation

Abstract

Dynamic life cycle assessment (LCA) explicitly takes into account the dynamics of carbon storage and release in the impact assessment of biomass use on climate change, although such approach requires more data and increases the complexity of the calculation. The aim of this work is therefore to assess how the application of dynamic LCA can be facilitated based on: the modelling tool Temporalis, the time dimension of the functional unit, and the contribution of the time dimension to the accuracy of results. Firstly, Temporalis was tested and improved, proving to be an efficient tool for performing dynamic LCA. Secondly, two functional units were compared: ‘total number of units produced over the whole lifespan of the plant’ (FU1) and ‘1 unit produced at $t_0$’ (FU2); the results are equivalent when the lifespan of the plant is short compared to the studied time horizon. FU1 should be used for assessing the potential impact of the entire system on climate change relative to climate goals on a calendar-based timeline. Conversely, FU2 should be used for comparing systems that do not share the same temporal distribution of production and for generating inventory data that can be reused as background inventory data in other life cycles. Thirdly, the variation in results induced by the dynamic characterisation of the impact was compared with the variations induced by the uncertainties in the inventory data, which are not always significant. The mathematical properties of the absolute global warming potential were investigated for a time horizon that tends towards infinity, thus generalising previous observations and predicting some of these results derived from simplified temporal information. Further investigation would allow for the development of a method for selecting flows to be distributed over a timescale prior to a full dynamic LCA, using only simplified temporal information.