Estimating the Carbon Footprint of ICT Using Input-Output Analysis: Dealing With Overcounting and Other Challenges

Estimating the carbon footprint of an economic sector like the ICT sector is subject to bias and uncertainty. For instance, using the weighted inventory methods of the GHG Protocol, there is an underestimation bias due to the incompleteness of the inventories carried out on economic sectors. On the other hand, when using Input-Output Analysis (IOA), an overcounting bias occurs systematically when one simply adds up upstream scope 3 footprints of two or more sectors. The goal of this paper is to explore how to apply IOA to the estimation of the global ICT footprint. We first introduce a method to calculate the bias-free upstream scope 3 footprint of aggregated sectors. We then evaluate the magnitude of the overcounting effect. For small scale sectors, this effect can often be neglected, but it becomes significant for large sectors. Also, looking at companies' carbon reporting, such overcounting may turn out to be smaller than the undercounting bias due to cut-off and omissions, although this may not be true when aggregating activities that strongly interact together. When looking at downstream scope 3 footprints, such overcounting effect also exists but it seems negligible compared to the downstream energy consumption. Then, using the described bias-free method, we compute a rough estimate of the world footprint of the ICT sector using the Inter-Country Input-Output database (ICIO). This ICT footprint raw estimate appears to be significantly higher than the estimates of the previous in-depth studies, but we were able to reconcile the figures. First, we reduced their discrepancy by analyzing and estimating the differences between the reference ICT scope and the significant larger scope we used due the ICIO sector classification. Secondly, it is plausible that the remaining discrepancy be explained by the underestimation of impacts by the previous methods due to LCA cut-off rules.