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Page 10 of 18 Tong et al. Carbon Footprints 2025;4:2 https://dx.doi.org/10.20517/cf.2024.44

The components of GHG emissions of automobile manufacturing
Table 2 presents the comprehensive decomposition of GHG emissions within the automobile
manufacturing industry. Remarkably, emissions stemming from the spillover component constitute over
98% of the total GHG emissions, indicating an unequivocally dominant presence. This finding not only
[18]
corroborates previous product-level Life Cycle Assessment (LCA) reports , but also highlights an even
more pronounced share. This discrepancy can be attributed to the methodology used in environmental
extended input-output analysis, which allocates emissions based on product value. Consequently, the high
monetary value of automobile products can artificially inflate their emission contributions relative to their
actual quantities.

On the other hand, emissions from the scale component account for a smaller yet significant proportion,
contributing 1.1% to overall GHG emissions. Conversely, emissions from both the internal and feedback
components are extremely low, to the point of being virtually negligible. These observations imply that the
majority of GHG emissions generated by China’s automobile manufacturing sector to satisfy its own final
demand originate predominantly from external industrial sectors outside the immediate system, notably
those involved in energy supply and materials production. As such, the automobile manufacturing industry
plays a pivotal role in driving GHG emissions from these interconnected sectors.

The detailed decomposition of carbon emissions in China’s automobile manufacturing sector shows that,
within the spillover effect, which represents emissions indirectly caused by upstream activities linked to the
sector, capital formation emerges as the most important driver of GHG emissions. Specifically, capital
formation accounts for 65.18% of total spillover emissions, totaling 283 billion tonnes. This significantly
outpaces both exports and final consumption in terms of their contribution to emissions growth,
highlighting that upstream industries are far more strongly driven by investment activities than by export
demands or final consumer demands. This underscores the crucial role that investment plays in shaping the
carbon footprint of the automobile manufacturing sector and its supply chain.

The driving mechanism of GHG emissions through the supply chain
Spillover emissions can serve as a mirror, reflecting the driving forces behind GHG emissions from both
within and outside a subsystem. Given that spillover emissions from China’s automobile manufacturing
industry constitute a significant portion of total emissions, a deeper dive into these emissions across various
associated industrial sectors is imperative to uncover the intricate mechanisms driving GHG emissions
within the automotive industry’s supply chain.

To achieve this, our paper performs an industrial linkage analysis of the spillover effects of GHG emissions
in China’s automobile manufacturing sector using Sankey diagrams. This analysis aims to pinpoint the key
contributors to spillover emissions, capturing the contribution ratios of 96% across all relevant industrial
sectors [Figure 1]. The diagram reveals five top industrial sectors, including ferrous metal smelting and
rolling, electricity and heat production, chemical products manufacturing (excluding petroleum products),
petroleum refining, and glass manufacturing, collectively accounting for over 75% of the total contributions,
as the “major contributors”. The remaining sectors are grouped under “other sectors”, within which non-
ferrous metal production is notably highlighted due to its significance in the production of new energy
vehicles.

Prominently, the steel-making sector stands out as the largest contributor, a fact that has been consistently
recognized in previous research [13,58] . This sector has been heavily influenced by massive investments over
the years, leading to the establishment of a high-carbon emission production model characterized by long
production processes. As a result, significant capacities have been built up, primarily relying on carbon-
intensive processes.