Different technology packages for aluminium smelters worldwide to deliver the 1.5 °C target
nature climate change
Article
https://doi.org/10.1038/s41558-024-02193-x
Different technology packages for
aluminium smelters worldwide to deliver
the 1.5 °C target
Received: 12 March 2024
Accepted: 23 October 2024
Published online: 2 January 2025
Check for updates
Chang Tan
Dabo Guan
, Xiang Yu
1
2,3
, Dan Li4, Tianyang Lei
, Qi Hao1 &
5
1,5
Production of aluminium, one of the most energy-intensive metals, is
challenging for mitigation efforts. Regional mitigation strategies often
neglect the emissions patterns of individual smelters and fail to guide
aluminium producers’ efforts to reduce GHG emissions. Here we build a
global aluminium GHG emissions inventory (CEADs-AGE), which includes
249 aluminium smelters, representing 98% of global primary aluminium
production and 280 associated fossil fuel-based captive power units.
We find, despite the installation of more efficient and higher amperage cells,
that the share of aluminium production powered by fossil fuel-based
captive power units increased from 37% to 49% between 2012 and 2021.
Retiring fossil fuel-based captive power plants 10 years ahead of schedule
could reduce emissions intensity by 5.0–10.5 tCO2e per tonne of aluminium
for dependent smelters. At least 18% of smelting capacity by 2040 and
67% by 2050 must be retrofitted with inert anode technology to achieve
net-zero targets.
Aluminium, the second most-used metal after steel, is integral to various industries1,2, including clean energy infrastructures3–6 such as photovoltaic panels7–9 and electric vehicles10,11, which are driving increased
aluminium demand12. Owing to its high chemical reactivity, the energy
required to produce aluminium can be up to ten times greater per
tonne than that for crude steel13–15. The primary method for aluminium
production is the Hall–Héroult process16,17, involving the dissolution
of aluminium oxide in molten salts at ~960 °C and the application of
electrical current to facilitate the reaction18.
Recent advancements have focused on optimizing cell designs19–21,
electrode configurations22–26 and operational adaptability27–29 to reduce
the energy intensity of the Hall–Héroult process30. However, the benefits of reduced energy intensity are offset by the increased use of fossil fuel-based captive power plants, which have reduced the share of
non-fossil energy in the aluminium industry from 60% to 33% over the
past three decades14. Additionally, the electrolysis process emits not
only CO2 but also perfluorocarbons (PFCs), which have a substantially
higher global warming potential than CO2 (refs. 31,32).
Given the growing demand for aluminium, technological innovations in production are important. Mitigation efforts at the facility level
are crucial because of their direct impact on the production processes
adopted. We developed a smelter-based bottom-up global aluminium
GHG emissions inventory (CEADs-AGE), which includes 249 aluminium
smelters and 280 associated fossil fuel-based captive power units. This
inventory covers a wide range of technologies and configurations,
providing a detailed assessment of emissions at the facility level. Our
study utilizes the latest smelter survey data to compile GHG emissions
inventory, identifying patterns and presenting tailored mitigation
strategies for global aluminum smelters. Detailed methodology and
data descriptions are provided in the Methods section.
Department of Earth System Science, Ministry of Education Key Laboratory for Earth System Modeling, Institute for Global Change Studies,
Tsinghua University, Beijing, China. 2University of Chinese Academy of Social Sciences, Beijing, China. 3Research Institute for Eco-civilization (RIEco),
Chinese Academy of Social Sciences, Beijing, China. 4China Nonferrous Metals Industry Association, Beijing, China. 5The Bartlett School of Sustainable
Construction, University College London, London, UK.
e-mail: ;
1
Nature Climate Change | Volume 15 | January 2025 | 51–58
51
Article
https://doi.org/10.1038/s41558-024-02193-x
a
Fjardaál
Sunndal
Karmoy
Warrick Alma
Smelter amperage (kA)
[100,200)
[200,300)
[300,400)
[400,500)
[500,600)
[600,700)
Distomon
≥2.0
Tomago
Puerto Madryn
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Capacity (GW)
5
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12,000
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0.8
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Weiqiao
Average
0.3
CC
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Generation technology
tr
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0.4
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Gas-based
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Coal: ultrasuper
Unknown
1.2
rit
Yuxin
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Coal: supercritical
rc
14,000
Arvida
AP60
Coal: subcritical
0.6
Capacity Country
(MW)
Brazil
100
China
300
India
600
Kazakhstan
1,000
United
States
Average
Angul
rit
Sarawak
Gas: GT
Coal-based
pe
Average
Seydisehir
Gas: CC
bc
Tomago
Generation technology
Capacity of single unit
Gas Coal
≤100 MW
≤300 MW
≤600 MW
≤1,000 MW
>1,000 MW
Su
16,000
(60,65]
(55,60]
(50,55]
(40,45]
(35,40]
(30,35]
(28,30]
(24,26]
(22,24]
(20,22]
(18,20]
(16,18]
(14,16]
(12,14]
(10,12]
(8,10]
(6,8]
(4,6]
(2,4]
(0,2]
Su
[0,5)
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[10,15)
[15,20)
[20,30)
[30,40)
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[50,60)
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–1
Age (years)
≤0.1
(0.1, 0.3]
(0.3, 0.5]
(0.5, 1.0]
>1.0
d
Captive electricity emission factor (kgCO2e kWh )
Capacity (Mt yr–1)
Captive power units age (years)
17,000
–1
Baise
Angul
Boyne Island
c
13,000
Weiqiao
Aditya
Hillside
b
Smelter energy intensity (kWh t Al)
Ardal
Ras Zurrayed
Barcarena
Gas
15,000
Huomei
East Hope
Al Taweelah
Capacity (Mt yr–1)
≤0.5
Captive power
[0.5, 1.0)
units type
[1.0, 2.0)
Coal
Edea
Bratsk
Pavlodar
Arvida AP60
Smelter amperage (kA)
Fig. 1 | Technology and emission patterns of global aluminium smelters and
their fossil fuel-based captive power units in 2021. a, Geographical distribution
of aluminium smelters and fossil fuel-based captive power units. Icons may
overlap because of the close proximity of many units. b, Energy intensity of
smelters categorized by different age groups within each amperage category.
c, Distribution of captive power units by installed capacity (left) and generation
technology type (right), across different age groups. d, Electricity generation
emission factors for coal-based (left, by unit) and gas-based (right, with the
error bars showing maximum and minimum emissions intensity range from
literatures) captive power units, categorized by generation technology.
The average energy intensity of each smelter amperage group and the average
electricity emission factor of each generation technology are shown by purple
dots in b and d, respectively.
Technologies and emission patterns
This share has increased by 12% over the past decade, up from 37%
in 2012. Of this capacity, 70 GW was built after 2010, meaning that
these units are still relatively young. The majority (85%) of total captive power capacity is coal-based, primarily subcritical units, which
accounts for 51 (...truncated)
