Decomposition Analysis of the Carbon Footprint of Primary Metals.

This study investigates how different technological and socioeconomic drivers have impacted the carbon footprint of primary metals. It analyzes the historical evidence from 1995 to 2018 using new metal production, energy use, and greenhouse gas (GHG) emission extensions made for the multiregional input-output model EXIOBASE. A combination of established input-output methods (index decomposition analysis, hypothetical extraction method, and footprint analysis) is used to dissect the drivers of the change in the upstream emissions occurring due to the production of metals demanded by other (downstream) economic activities. On a global level, GHG emissions from metal production have increased at a similar pace as the GDP but have decreased in high-income countries in the most recent 6 year period studied. This absolute decoupling in industrialized countries is mainly driven by reduced metal consumption intensity and improved energy efficiency. However, in emerging economies increasing metal consumption intensity and affluency have driven up emissions, more than offsetting any reductions due to improved energy efficiency.

Material and Carbon Footprints of Machinery Capital.

Machinery and equipment, integral as technology-specific capital goods, play a dual role in climate change: it acts as both a mitigator and an exacerbator due to its carbon-intensive life cycle. Despite their importance, current climate mitigation analyses often overlook these items, leaving a gap in comprehensive analyses of their material stock and environmental impacts. To address this, our research integrates input-output analysis (IOA) with dynamic material flow analysis (d-MFA) to assess the carbon and material footprints of machinery. It finds that in 2019, machinery production required 30% of global metal production and 8% of global carbon emissions. Between 2000 and 2019, the metal footprint of the stock of machinery grew twice as fast as the economy. To illustrate the global implications and scale, we spotlight key countries. China's rise in machinery material stock is noteworthy, surpassing the United States in 2008 in total amount and achieving half of the US per capita level by 2019. Our study also contrasts economic depreciation─a value-centric metric─with the tangible lifespan of machinery, revealing how much the physical size of the capital stock exceeds its book values. As physical machinery stocks saturate, new machinery can increasingly be built from metals recycled from retired machinery.