Exploring and estimating in-use steel stocks in civil engineering and buildings from night-time lights

Abstract

Steel is the most widely used metal in the world, and numerous studies have investigated its stock and flow. Two basic methods for analysing material flow and accounting for stock are the top-down and bottom-up approaches. Their applicability, however, largely depends on data availability. To overcome this limitation, we have contemplated using satellite imagery as a proxy for missing data. In a previous study, we confirmed the correlation between night-time light radiance and civil engineering/building in-use steel stocks in Japan. In this study, the scope of the investigation was expanded to a global scale, examining correlations in different regions of the world. We found that night-time light radiance and in-use steel stocks have region-specific linear correlations, which are influenced by construction styles, which in turn depend on climate, seismic activity, cultural preferences, etc. The results were then applied to countries in the various regions whose in-use steel stocks were previously unreported. This technique produced an estimate of the global civil engineering/building in-use steel stock of around 9 × 109 tonnes (9 Gt), with 1.24 Gt being previously unreported. As a further step, this study shows the spatial distribution of civil engineering/building in-use steel stock in each region.