The Material and Carbon Footprint of Machinery Capital: A Dual Role in Climate Change

This article is prepared by Meng Jiang from NTNU based on the joint work with Edgar Hertwich and colleagues

Our world is increasingly mechanized, with machinery and equipment being integral to both industrial processes and our daily lives. From agricultural machines to advanced technology like graphics processors and renewable energy tools like solar panels, machinery is ubiquitous. However, while these tools are essential for modern living, they also contribute significantly to environmental impacts due to their carbon-intensive lifecycle.

The Carbon and Material Footprint of Machinery

In this study, we integrated input-output analysis with dynamic material flow analysis to understand the material and carbon footprints of machinery. In 2019, machinery production required 30% of global metal production and contributed to 8% of global carbon emissions. Moreover, from 2000 to 2019, the metal footprint of machinery stocks grew at a rate twice that of the global economy.

We highlight the complexity of machinery’s role in climate change. On one hand, machinery is crucial for climate mitigation technologies and services, but on the other, its production and lifecycle are heavily carbon-intensive.

Key Findings and Global Implications

The study provides a detailed breakdown of the carbon footprints of machinery production and a regional comparison of carbon, material, and metal footprints in machinery and equipment capital stock.

Industrialized countries use 2−4.5 tons of metals per capita to build their stock of machinery and equipment, while many developing countries dispose only of a tenth of that amount.

This analysis offers insight into the significant growth in machinery material stock, particularly in China. Notably, by around 2008, China’s total machinery capital stock (proxied by metal footprint of machinery stock) surpassed that of the United States, doubling by 2019, yet its per capita level remains only half that of the US.

Figure 1. Metal footprints in machinery and equipment capital stock: in 2019, 2000 and changes in the global share.
Figure 2. Metal footprint embodied in machinery stock: Comparison of the physical world vs financial present values. The metal footprint is calculated by using the survival curve (SV) and depreciating rates (DP) for different countries.

Towards a Circular Economy

We discuss the concept of depreciation” in the financial sector and its discrepancy with the actual service life of physical machinery. For instance, a five-year-old car might lose half its value on the book, but more than 50% of such cars are still in use. It indicates that the physical assets continue to serve long after their book value has depreciated.

Understanding the relationship between a machinery’s tangible value and its environmental impact is vital for both financial and environmental strategy. For instance, in scope3 emissions accounting, the methodology a company uses to calculate capital-related emissions greatly affects reported data and shapes responsibility allocation.

Our findings point towards an essential transition: as physical machinery stocks saturate, new machinery can increasingly be built from metals recycled from retired machinery. This shift is vital for moving towards a more sustainable and circular economy, where waste is minimized, and resources are reused efficiently.

Conclusion

Machinery plays a dual role in our fight against climate change. While it is an indispensable part of our industrial and daily life, its environmental impact cannot be ignored. This study provides a foundation for future research and policy-making, emphasizing the need for strategies that consider both the utility and the environmental footprint of machinery. It’s a call to action for industries and policymakers alike to balance the benefits of machinery with the need for environmental sustainability.

The detailed paper is available at : https://pubs.acs.org/doi/10.1021/acs.est.3c06180

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