Integrating ecological and water footprint accounting in a multi-regional input-output framework

Carbon, ecological, and water footprints (CF, EF, and WF) are accounting tools that can be used to understand the connection between consumption activities and environmental pressures on the Earth's atmosphere, bioproductive areas, and freshwater resources. These indicators have been gaining acceptance from researchers and policymakers but are not harmonized with one another, and ecological and water footprints are lacking in their representation of product supply chains. In this paper we integrate existing methods for calculating EF and WF within a multi-regional input-output (MRIO) modelling framework that has already been successfully applied for CF estimation. We introduce a new MRIO method for conserving the high degree of product detail found in existing physical EF and WF accounts. Calculating EF and WF in this way is consistent with the current best practice for CF accounting, making results more reliable and easier to compare across the three indicators. We discuss alternatives for linking the MRIO model and the footprint datasets and the implications for results. The model presented here is novel and offers significant improvements in EF and WF accounting through harmonization of methods with CF accounting, preservation of product-level detail, comprehensive inclusion of sectors of the global economy, and clear representation of flows along supply chains and international trade linkages. The matrix organization of the model improves transparency and provides a structure upon which further improvements in footprint calculation can be built. The model described here is the first environmentally extended MRIO model that harmonizes EF and WF accounts and aligns physical unit data of product use with standard economic and environmental accounting.