Various approaches exist for quantifying environmental footprints of biomass consumption by estimating the virtual natural resources (e.g., land and water) embodied in international trade flows. These can be classified into a) final demand approaches, applying environmentally extended input-output analysis, and b) apparent consumption approaches, using a physical accounting framework. The results of recent studies vary widely, thus hampering their application in policymaking.
To study the disparities a literature review was performed and differences in the applied methodologies and base data were identified. Furthermore, a multi-regional input-output model based on the GTAP database (GTAP-MRIO) was set up and used to calculate global virtual land flows and footprints. The results were then compared to those from IIASA's LANDFLOW model, a comprehensive physical accounting model following the apparent consumption approach. The land use data were harmonized to exclude this as a source of divergence.
The literature review showed that the two approaches have evolved in distinctly separate ways during the past decade within their research communities. The differences in the results, base data, and methodologies are tremendous. The greatest share of the variance results from differences in the coverage of crops, processed products, and supply chains. The use of different data sources and weighting procedures for the land use data in some cases may also result in differences up to an order of magnitude. Technical specifics such as the application of monetary versus physical accounting or differences in the handling of re-exports still often cause differences of more than 100%.
A hybrid model combining the advantages of both approaches could provide a framework for the robust and transparent assessment of environmental footprints of global biomass flows. Such an accounting framework should be based on (corrected) statistical data reporting land use, crop production, and bilateral trade in physical units, supplemented by monetary data for the sectors and supply chains not covered elsewhere. The mathematical system of input-output analysis (a simple matrix structure) is well suited for the integration of physical and monetary information in varying levels of detail and for dealing with indirect effects and re-exports.
Martin Bruckner, of the University of Natural Resources and Life Sciences, Vienna, Austria, is an Austrian citizen. He was funded by IIASA's Austrian National Member Organization and worked in the Water (WAT) Program during the YSSP.
Please note these Proceedings have received limited or no review from supervisors and IIASA program directors, and the views and results expressed therein do not necessarily represent IIASA, its National Member Organizations, or other organizations supporting the work.
Last edited: 19 August 2015
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