Time and scale in Life Cycle Assessment: the case of fuel choice in the transport sector

Life Cycle Assessments (LCA, including Well-to-Wheel studies) that are to support decisions that strive to change large technical systems need to consider time and scale related factors, which are given little attention in standard LCA procedures. In this paper, the authors address 3 issues and provide examples from the case of alternate fuels. First, shifting time frame gives room for technical development that should affect not only the choice of performance data, but perhaps also the functional unit and selection of technologies under study. Secondly, background systems, such as heat and power production, change over time and increased production volumes of the alternative fuel change the transport system that is used to produce transport fuel. It is shown that such changes have consequences not only for greenhouse gas (GHG) emissions from each fuel-chain, but also for the ranking order of Rapeseed Methyl Esther (RME) and ethanol in terms of GHG emissions. Lastly, different types of feedstock are available in different quantities and different byproduct markets vary in size. Key markets for RME byproducts in the EU correspond to an RME production that covers about 3% of transport fuel demand. Consequently, GHG emissions allocated to the fuel should change with the scale of adoption.