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Abstract

This paper addresses the global challenge of greenhouse gas emissions facing the aluminum industry. The demand, production and use of aluminum are increasing and so are the emissions. From bauxite mine to aluminum ingot, the total global average emissions vary somewhat in the literature, but most reported values are now between 12 and 17 metric tonnes of CO2-equivalents per tonne of aluminum, depending on the various estimates and assumptions made. Two-thirds of these gases are emitted because the electricity used for electrolysis is produced from fossil fuel sources, mainly coal but also natural gas. Reduction of these emissions is now the main environmental challenge for the aluminum industry. Globally, the best result is obtained by maximizing aluminum production using green electrical energy from renewable sources. Aluminum production is categorized as an activity at very high risk of carbon leakage, which occurs when there is an increase in carbon dioxide emissions by new production in one country as a result of ceased production with emissions reduction in a second country with a strict climate policy.
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Aluminum production in the times of climate change:
The global challenge to reduce the carbon footprint and prevent carbon leakage
GUDRUN SAEVARSDOTTIR1,4, HALVOR KVANDE2 and BARRY J. WELCH3
1. —Department of Engineering, Reykjavik University, 101 Reykjavík, Iceland. 2.—Previously: The Norwegian
University of Science a Technology, Trondheim, Norway. 3. —University of New South Wales, Sydney, Australia
and Consultant, Welbank Consulting Ltd, New Zealand. 4.—e-mail: gudrunsa@ru.is
Abstract
This paper addresses the global challenge of greenhouse gas emissions facing the aluminum industry. The demand,
production and use of aluminum are increasing and so are the emissions. From bauxite mine to aluminum ingot the
total global average emissions vary somewhat in the literature, but most reported values are now between 12 and 17
metric tonnes of CO2-equivalents per tonne of aluminum, depending on the various estimates and assumptions made
in the literature. Two-thirds of these gases are emitted because the electricity is produced from fossil fuel sources,
mainly coal but also natural gas. Reduction of these emissions is now the main environmental challenge for the
aluminum industry. Globally the best result is obtained by maximizing aluminum production using green electrical
energy from renewable sources. Aluminum production is categorized as an activity at very high risk of carbon
leakage, which occurs when there is an increase in carbon dioxide emissions by new production in one country as a
result of ceased production with emissions reduction in a second country with strict climate policy.
Introduction
The world is now pushing for a low-carbon future. The global aluminum industry, from bauxite mine to aluminum
ingot, has a challenge to reduce the CO2 emissions and the greenhouse effect that these emissions may have on
global warming and climate change. These emissions come both directly from the production processes, and
indirectly from the electric energy used to power it. The emissions are increasing because of the growing demand for
aluminum and the limited supply of electrical energy generated from renewables. Many countries are taking a
responsible approach to the impact of global warming, and taking actions to minimize their national footprint.
Meanwhile, the public and governments rightfully demand reductions of greenhouse gas emissions, thus requiring
strong actions from the aluminum industry in the coming years. While being commendable, in some instances it can
raise the possibility of “carbon leakage”, an expression that refers to transferring of industrial production from
countries with strict regulations on emissions towards regions with less restriction, thus relocating the process
related emissions. In the case of aluminum, which is deemed at a very high risk of carbon leakage, this may lead to
significantly increased total emissions, as most new capacity is added based on an energy mix dominated by fossil
fuels. This paper presents an analysis of the smelting trends in order to discuss the possibilities to reduce the overall
greenhouse gas emission rate from the aluminum industry.
What is Aluminum Used For?
Aluminum belongs to the so-called light metals with its density of 2.7 kg/dm3 at room temperature. This is only
about one-third of the density of iron and steel. The key benefits of aluminum to modern society arise from its
lightweight and high strength to weight ratio and great flexibility for efficient formability into complex shapes using
modern design features. It is also durable and infinitely recyclable. The many uses of aluminum can be traced to its
versatile properties. A significant proportion of the products arising from the finished articles using aluminum are
themselves energy saving, and thus reducing the carbon dioxide emission that would otherwise arise from the
population.
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The most common uses of aluminum include:
Construction (buildings and structures)
Transportation (automotive, trains, boats and airplanes)
Electrical conductors (power transition lines and consumer electronics)
Consumer goods (packaging)
Currently, aluminum has one of the fastest growing demands among metals in the world. Specifically, the demand is
driven by a transport sector that needs to improve fuel efficiency and reduce energy use and emissions through
lighter cars, trucks and trains. The positive expansion in aircraft capabilities and size coupled with safe air travel has
been greatly enabled by advances in aluminum technology. Furthermore, aluminum is a key to zero-energy
buildings, solar applications and packaging that preserves food and drinks and requires less energy to transport.
Thus, aluminum is used extensively in the modern world and has a variety of uses. It has practically limitless areas
of application and has made an immeasurable contribution to the quality of life.
Global Production of Aluminum - It will continue to Increase
The total world production of primary aluminum was 64.3 million metric tonnes in 2018, according to data from
World Aluminium [1]. China contributed 57%. In addition about 28 million tonnes were recycled from new and old
aluminum scrap that year. This is considerably less than the industrial production of iron and steel, but it is more
than the production of all other non-ferrous metals together.
To meet the increasing demand for aluminum there has been a continuous rise in its production for many years. The
global aluminum production has grown by 52% from 2010 to 2018. The incremental capacity introduced by new
technology introduces significant steps in energy supply needs, but the rate of increase in potential supply of “green
energy” to match the incremental demand has resulted in much of the energy generation being from coal-fired power
plants. This has driven a significant growth in the industry’s total energy use and also CO2 emissions.
At the 2019 TMS conference in the USA, Bayliss from the International Aluminium Institute [2] presented a
scenario that would see a need to increase the annual primary aluminum production over the next 20 years up to 90
million tonnes. This means an increase of about 25 million tonnes from 2018 to 2040. Compared with the present
global average values the emissions would then increase by about 400 million tonnes of CO2 equivalents. Such an
increase in emissions may not be accepted by the world public in 2040 and solutions enabling a shift to power
production from only low emission sources should be developed to power this production increase. However, even
if all new capacity in the next 20 years came from renewable power sources, the absolute global emissions would
not decrease.
The Aluminum Production Process
Metallic aluminum does not occur in nature but rather in chemically very stable combined forms, particularly
oxides. Bauxite is mined and refined to produce alumina, which is the feedstock in aluminum electrolysis cells.
Primary aluminum ingot production is a complex system, which includes bauxite mining, alumina refining, carbon
anode production, electrolysis and ingot casting.
To produce 1 tonne of aluminum from alumina by electrolysis the following approximate amounts of raw materials
are needed:
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2.0 tonnes of smelter-grade cell-feed secondary alumina (Al2O3) from dry scrubbers
0.40 to 0.46 tonnes of carbon (in the form of carbon anodes used in the electrolysis process)
12 500 to 16 000 kWh/tonne Al of electrical energy (direct current, DC).
We can call these the three main raw materials that are transformed during aluminum production. Unfortunately,
production of alumina, carbon anodes and aluminum emits CO2. This is also strongly the case for electricity when it
is produced from fossil fuels.
During electrolysis the alumina is dissolved in a sodium-aluminum-fluoride molten salt mixture (mainly cryolite,
Na3AlF6) at about 960 oC to form an ionic conducting medium that enables the products to be formed via three
processes that occur between the two electrodes. These are:
- electrochemical reduction of the aluminum-containing species to aluminum metal at the cathode
- electrochemical oxidation of the oxide-containing species with simultaneous reaction with the carbon
anode to predominantly form CO2
- energy (heat) transfer to enable the reaction products to achieve a state that enables removal from the cell.
The Anode Gases CO2 and CO
Alumina reacts to form molten aluminum and the gases CO2 and CO according to the overall chemical equations:
½ Al2O3 (dissolved) + ¾ C (s) = Al (l) + ¾ CO2 (g) (1)
and:
½ Al2O3 (dissolved) + 3/2 C (s) = Al (l) + 3/2 CO (g) (2)
It is impossible to make aluminum with CO2 as the only anode product, because carbon monoxide is also co-
evolved. We cannot start making carbon dioxide until the electrode is polarized sufficiently to lift the electrode
potential above that of carbon monoxide formation, so there is always some direct electrochemical formation as well
as quite a bit of indirect reaction. We get a mixture of the products with CO2 being the dominant one. There are
unavoidable secondary reactions in the cell that lead to extra CO but all processes must be assessed according to the
overall and not just one of several processes that occur. Virtually all of the CO is oxidized in the flame of the cell
gases, an almost spontaneous reaction with the oxygen of air mixing. The thermodynamic equilibrium between CO,
O2 and CO2 favors CO2 at low temperatures..
The lowest amount of CO ever found in an anode gas sample in the cell is about 12%, and the industry average is
about 20% CO using the best quality anodes. All CO electrochemically and chemically formed within the cell
reports as CO2 ultimately in the atmosphere. Carbon monoxide is short-lived with an average lifetime of about one
to two months in the atmosphere and it is not known as a direct contributor to global warming. However, it has
indirect effects because it reacts in the atmosphere to CO2 and also methane.
Eqn. (1) shows that ¾ moles of CO2 are formed for every mole of Al produced. If we recalculate the moles into
weights, we find that the electrolytic process theoretically gives 1.22 tonnes of CO2 for each tonne of aluminum.
However, the process is not ideal, and we know that CO is formed and carbon losses occur. The amount of CO2
depends on the quality of the anode, and is more closely related to the net anode consumption. This is defined as the
net mass of carbon anodes consumed in the electrolysis cell and is given in kg C/t Al. Table I shows calculated CO2
emissions as a function of the net anode consumption for aluminum electrolysis cells.
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Table I. Calculated CO2 emissions as a function of net anode consumption for aluminum electrolysis cells with
prebaked and Soderberg anodes [3]. Assumption: 97.6% carbon content in the prebaked anodes.
Net Anode Consumption
(kg C/t Al)
Calculated CO2 Emission
(t CO2/t Al)
390 1.395
400 1.431
410 1.466
420 1.502
430 1.538
440 1.574
450 1.609
460 1.645
517 (Soderberg) 1.849
Typically, for the prebaked anode cell technologies between 390 and 460 kg of anodes are used per tonne of
aluminum produced by a combination of the reactions according to eqns. (1) and (2), as well as excesses through
current efficiency losses and secondary reactions and processes. This leads to emissions between 1.4 and 1.6 t CO2/t
Al from the electrolysis process.
CO2 Emissions - The Main Environmental Challenge for the Aluminum Industry
The world’s primary aluminum producers, together with their power suppliers, now emit about 1,000 million metric
tonnes of CO2-equivalents annually [2]. In comparison, the estimated worldwide emissions from all human activities
in 2010 were about 50 billion tonnes of greenhouse gases each year [4]. This is higher now, and it is estimated that
aluminum production contributes nearly 2% of the world’s total emissions.
The expression carbon footprint is now commonly used. It is generally defined as the total amount of greenhouse
gases produced directly and indirectly to support human activities. The gases are then expressed in carbon dioxide
equivalents, CO2e, so that they can be compared in terms of their climate effect. Burning of fossil fuels always
releases CO2 as well as CH4 and these gases are the main anthropogenic contributors to global warming and climate
change among the greenhouse gases.
Table II shows that since year 2000, when around 50% of the power used for aluminum production was low-
emission renewable or nuclear, the non-renewables (fossil sources like coal and natural gas) have taken over as the
main electrical energy generation sources for aluminum electrolysis, and in 2018 they reached 71%. The majority of
this energy, 61%, came from coal-fired power plants, while 10% of the world’s aluminum producers used electricity
from natural gas-fired power plants. These percentages contrast with the situation before the turn of the century,
when hydroelectric power generation was the largest source of electricity for the global aluminum production. This
change has a very important global environmental consequence because of the high CO2e emissions from electricity
production from non-renewable energy sources, which give emissions several times higher than the aluminum
electrolysis process itself plus the production of the raw materials alumina and carbon anodes.
Table II. Main sources of electric power used in the global aluminum production. Data is taken from [1].
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Percentages from non-renewable
fossil energy sources
Percentages from
renewable energy
sources
Source/
year
Coal Natural
gas
Oil Hydro Other
renewable
s
Nuclear
1980 25% 8% 10% 51% 6%
1990 34% 4% 1% 56% 5%
2000 40% 8% 0.7% 46% 5%
2010 51% 5% 0.07% 41% 2%
2013 54% 8% 0.08% 36% 1.4%
2014 58% 10% 0.14% 31% 1.2%
2015 59% 9% 0.03% 30% 1.6%
2016 61% 10% 0.06% 27% 1.0% 1.5%
2017 61% 9% 0.02% 25% 2.8% 1,3%
2018 61% 10% 0.02% 26% 0.9% 1.3%
Indirect CO2e Emissions from Aluminum Production due to Energy Source Because aluminum production is
very energy intensive, the indirect emissions due to the production of electric power used in the electrolytic process
must be taken into account. Table III shows the CO2e emissions from the four main types of power plants that supply
electricity to the world’s aluminum plants. These data are given for the production of the amount of electric AC
power that is needed to produce one ton of aluminum. This includes rectification from AC to DC and also normal
smelter auxiliaries including pollution control equipment.
Hydroelectric power generation produces very small amounts of CO2e and the only emissions are attributable to its
construction, or indirectly through vegetation lost to reservoirs. Some methane is given off by water reservoirs in
tropical regions, but the typical CO2e emissions are very low, in particular at high latitudes. The CO2e emissions
from a gas-fired power plant are about 50% larger than the combined emissions from the electrolysis cells plus the
production of the raw materials alumina, calcined petroleum coke and carbon anodes. For coal-fired power plants
the CO2e emissions are nearly twice as high as from natural gas-fired power plants.
Table III. Approximate global average CO2e emission values from the four main types of commercially available
power plant technologies that supply electric power to the world’s aluminum plants [4, 5]. Assumption: Average AC
energy consumption for aluminum production is 14.2 kWh/kg Al. CCS is Carbon Capture and Storage.
Power technology
Global average value
for typical emissions
(t CO2e/t Al) Minimum emission
for Best Available
Technology (BAT)
(t CO2e/t Al)
Minimum emission
for BAT and CCS
(t CO2e/t Al)
Hydroelectric[4] 0.3 0.01 0.01
Nuclear[4] 0.17 0.05 0.05
Coal [4] 11.6 10.5 2.7
Chinese mix average
(GaBi) [5]
13.6
Natural gas (combined
cycle process) [4]
7.0 5.8 1.3
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Combining the information from Tables II and III with region specific information from ref. [1] we get Fig. 1, which
shows how the carbon footprint associated with the power production for aluminum electrolysis has developed since
2000. The increased production in areas reliant on fossil fuel and the reduction in areas with renewable energy have
led to an increase in the average global carbon footprint of 3 t CO2e/t Al in these 18 years. This is significantly more
than the total emissions from the electrolysis process, as listed in the next section.
Fig.
1. The carbon footprint of power-production for aluminum electrolysis for different regions [1, 4, 5)..
The Main Sources of Direct CO2 Emissions from Aluminum Production
CO2 emissions are generated in almost all of the stages in aluminum production from mine to metal. Data for the
CO2-equivalent emissions for the main processes from bauxite mine to aluminum ingot is shown in Table IV. For
comparison data for the Best Available Technology (BAT) is also included.
From Table IV we see that the total average CO2 emissions from aluminum production, including the indirect
emissions from electric power production, are 14.4 t CO2e/t Al produced on a global basis. The weighted total global
average emission value from electricity production is now 10.2 t CO2e/t Al. The majority of the greenhouse gases
from aluminum production, close to two thirds, are then indirect electricity-related emissions.
Using industry values for the carbon footprint associated with bauxite processing and anode production and the
world’s best practice for net anode carbon consumption (400 kg C/t Al) and energy consumption (12.7 kWh/kg Al),
the emissions would have been about 70% lower if we had green electrical energy only . Table IV shows that the
electrolysis process contributes about 1.7 t CO2e/t Al, which is only about 12% of the total global average CO2-
equivalent emissions from aluminum production.
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Table IV. Data for the global average and the Best Available Technology emissions from the various aluminum
production steps, bauxite mining, alumina production, prebaked anode production, electrolysis and ingot casting,
given in tonnes of CO2-equivalents per tonne of Al produced [3]. The data marked with an asterisk is taken from
Bayliss [2].
Processes Global
average CO2
emissions
(t CO2e/
t Al)
Percentages
for the
global
average
emissions
Best Available
Technology
(BAT)
emissions
(t CO2e/t Al)
Percentages
for the BAT
emissions
Bauxite mining 0.03 0.2% 0.03 1%
Alumina production 1.5 10.5% 1.4 40%
Calcined petroleum coke
production
0.3 2.1% 0.3 8.6%
Carbon anode production (anode
baking)
0.3 2.1% 0.2 5.7%
Anode rodding 0 0% 0 0%
Cathode and spent potlining
(SPL)
0.03 0.2% 0.03 1%
Net cell carbon consumption 1.5 10,5% 1.4 40%
Perfluorocarbon (PFC) emissions 0.2 1.4% 0.02 0.6%
Ingot casting from fuel
combustion*
0.3 2.1% 0.1 3%
Electricity (world average) 10.2 70.6% 0.01 0.3%
TOTAL 14.4 ~ 100% 3.5 ~ 100%
Table V. Comparison of data for CO2e emissions from aluminum production, from ref. [2, 3] and Table IV.
Processes Data from ref. [2] Data from Table IV
Electricity 10.6 10.2
Direct process 2.66 1.7
Thermal energy 2.3 2.46
Ancillary materials 0.6
Transport 0.54
TOTAL 16.7 14.4
It is noted that the global average total value in Table IV is 3 t CO2e/t Al lower than the value of 16.7 t CO2e/t Al
given by Bayliss [2]. A part of the difference (1.14 t CO2e/t Al) is due to the two processes called “ancillary
materials” and “transport” (raw materials transport), which are not included in Table IV. Thermal energy in Table V
is fuel combustion for heating and steam in alumina production, anode production and casting.
The data in Table IV for the Best Available Technology (BAT) processes shows a different picture. The large
contribution from the power source is then negligible and it can be set to zero. The other contributions are not
reduced very much, but the relative percentages have changed considerably. The alumina production and the net cell
carbon consumption now constitute about 40% each and are then the two dominating sources of CO2e emissions,
while the combined emissions from production of the anode raw materials and anode baking contributes 14%. A
total emission of about 3.5 t CO2e/t Al is then possible for cells with today’s modern prebaked anodes and Best
Available Technology in all parts of the aluminum production steps, including renewable power production.
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During anode effects in the electrolysis cells perfluorocarbon (PFC) greenhouse gases are being co-emitted, as CF4
and C2F6. PFC co-evolution also occasionally occurs at much lower rates in localized zones of the cell when
operating conditions change through spatial or operating reasons and the interfacial potential at the anode is
exceeding a critical value. The main operating factors that cause this localized potential increase are having zones
where the alumina concentration has dropped substantially, or electrodes are carrying a very high electrochemical
current density.
Based on global average data PFC greenhouse gases now contribute less than 2% of the greenhouse gas footprint
and there has been a focus for the industry to reduce the level. There is still an ongoing effort in the aluminum
industry to minimize the frequency and duration of anode effects and thereby minimize the production of these
gases. Many producers using cells with prebaked anodes have been able to reduce these PFC emissions. The average
value in 1990 was 5 t CO2e/t Al and now it has been reduced to below 0.2 t CO2e/t Al for prebaked anode cells, as
calculated by the industry standard method, with the best approaching one tenth of that value [1]. However, the
industry method of calculation does not include all the PFCs, because low levels of PFCs are also emitted from cells
without having an anode effect.
The electrolysis step happens in aluminum plants that in many cases are located separately from the alumina
production sites, and in some cases also in different parts of the world. For the electrolysis step the average
emissions from a plant powered by hydro power are only one tenth of the total world average.
How to Reduce the CO2e Emissions
For all aluminum smelters it is both economically and environmentally advantageous to reduce the energy
consumption, irrespectively of their power source. Minimum emissions require operations at minimum energy
consumption, given in DC kilowatt-hours per kilogram of aluminum, but because of the physics of the process this
comes at the expense of the productivity of a cell. With the growing demand for the metal, high capital cost of the
cell technology and competitive markets, this is a challenge for smelters and therefore there is a tendency to increase
potline current to operate at maximum productivity. This approach is not environmentally sound, not only does it
“waste energy” but also increases the carbon footprint by requiring more coal-fired power. Furthermore, it also
reduces cell life and thereby increase the toxic waste the industry generates in the form of spent potlining. Using
efficient modern technology is also important, in particular in regions using fossil power. For example, the reported
average DC energy consumption in Chinese smelters for 2018 is 12.9 kWh/kg Al, compared to the world average of
13.4 kWh/kg Al [1].
An obvious approach to reducing emissions globally is to increase the share of low-emission energy sources in
aluminum production. The world is running out of substantial hydro capacity growth, but solar photovoltaics and
wind power have grown rapidly in recent years, accompanied by sharp cost reductions [7], and they are becoming a
viable supplementary source in some areas. However, these two latter sources of electrical energy will never enable
total reduction of fossil fuel fired power, as their generation rates are variable with the weather and therefore “swing
generation capacity” will always be needed. Apart from regions where there is access to hydroelectricity for
regulating, this is mostly supplied by fossil fuel based power. Nuclear power is a reliable technology to produce
baseload with very low emissions. It is statistically the safest way to produce electricity but as the exceptions to this
track record are very well known, the public perception does not reflect that because of the storage of nuclear waste
and the potential for catastrophic accidents. In many countries authorities are closing nuclear capacity.
It will be a slow process to reduce the amount of fossil fuel generated capacity, as the aluminum production will
continue to increase. One may hope for CO2 gas separation and removal (Carbon Capture and Storage, CCS) for
coal- and gas-fired power plants. From Table III it is calculated that CCS is estimated to be able to reduce the
emissions from coal-fired power plants by 75% but at present this is economically unfavorable. However, even if an
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economically viable CCS process could be developed, the coal power to the cells will still emit between 1.5 and 2 t
CO2e/t Al.
The process gas from aluminum electrolysis cells generally has a CO2e concentration close to 1 volume-%, which is
usually considered too low for economically viable CO2e capture. A radical overhaul of the cells and the potrooms
would be required to make this option viable, even if technically possible. Thus, it will be a long time until total
CO2e emission-free generation is achieved for the present aluminum electrolysis cells with carbon anodes.
A Carbon-Free Electrolysis Process with Inert Anodes - Is this the Future?
Can the present carbon anodes be replaced with inert, non-reactive and non-carbon containing anodes in the
electrolysis cells? Then the anode gas would be oxygen and there would not be any CO2, CO or perfluorocarbon
emissions at all from a carbon-free electrolytic process. This means that we can eliminate the emissions from the
electrolysis step and also the perfluorocarbon emissions in Table IV. This would result in a reduction of between 1.4
and 1.7 t CO2e/t Al, depending on whether we are comparing industry best practice or typical average data with the
current world operations.
Optimistically assuming that the new inert anodes and cathodes and their raw materials can be produced with low or
negligible CO2e emissions, then by deleting the emissions from the production of the carbon anodes and their raw
materials (see Table IV) would eliminate about 2.7 tonnes of CO2e emissions, or about 16%. With inert anodes and
hydroelectric power the only main process emissions would be the 1.5 tonnes of CO2e coming from the production
of alumina from bauxite, and this means a total reduction of more than 90% from the overall process.
However, it should be noted that an oxygen-evolving electrolysis process for aluminum production requires more
energy, as O2 is a higher energy compound than CO2 [8]. This ideally requires a cell design that will give a reduced
heat loss of ~ 2.8 kWh/kg Al from the electrolysis cells to avoid an even higher energy requirement for an inert
anode process [3], as compared to the traditional one, combined with a cell design of lower Ohmic resistance in the
electrolyte. If or when a successful technology is developed, it is likely to be constrained to companies that have
access to surplus renewable energy capacity, unless there is a major breakthrough in materials technologies that
enable substantial heat conservation for the cells. Of course such breakthroughs would also prove beneficial for
lowering the energy consumption of the existing cell technologies as well. A lot of research and development work
has been done and is on-going. Inert anodes for aluminum smelting is now a technology in pilot testing, with the aim
of commercializing an inert anode electrolysis process by 2024 [9. 10].
In summary, carbon-free anodes would mean a revolution of the aluminum process by producing oxygen instead of
CO2. It will replace all direct greenhouse gas emissions from the traditional aluminum electrolysis process. The
emissions from the production of alumina from bauxite remains but if all existing smelters were retrofitted with inert
anodes up to 16% reduction in total global emissions from aluminum production could be achieved. In comparison,
if there are substantial reductions through successful development of low-emission electric power sources, then this
in itself could enable up to about 70 % reduction in the emissions from the present global aluminum production.
However, it has been claimed that the higher energy consumption in a cell with inert anodes will cause more CO2e
emissions when the power is generated in a coal-fired power plant than can be saved in the electrolysis process [11].
Where to Build New Aluminum Plants?
While the demand for aluminum continues to increase, new aluminum smelters will be built somewhere in the
world. However, the focus should not just be on construction of new smelters with the latest technologies. Since the
cost of a new plant is so high, many companies will continue operating older facilities by necessity. This means that
there will be a need for brownfield expansion of some of the existing plants in addition to new greenfield aluminum
plants. Where will the new aluminum plants be constructed?
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Affordable electricity has traditionally been a deciding factor for the location of aluminum plants. Greenfield and
brownfield plants were therefore built in regions where production and energy costs were low. This approach
dominated where there were sources for generating electricity from hydro or geothermal sources at a rate far in
excess of the regions` demand. As growth in aluminum consumption, living standards and population have resulted
in increased alternative demand for electrical energy, and economic prosperity has increased the emphasis on nature
preservation rather than power development. The availability of sites for this type of expansion is therefore limited.
Increased production in China and other Asian countries is a part of the economic growth and infrastructure
development in the region. This has resulted in a shift to generation of electricity from coal and hydrocarbon
sources.
Historically, in the oil and gas rich countries of the Middle East they used to flare off (burn) the associated natural
gas. So utilizing this to generate electricity, and simultaneously increase the supply of potable water, have provided a
growth opportunity for generating sufficient electrical energy for aluminum production with a lower carbon footprint
than from coal and oil. In the Middle East production capacities are being built up simultaneously. At the same time
they are putting in substantial amount of solar power capacity and also nuclear power in order to lower their national
carbon footprint. Today the world has limited supply potential for clean green electricity expansion, but aluminum is
a globally traded commodity, with an ever growing demand and simultaneously much reduced profit margins.
Producers are therefore forced to prioritize production costs.
Energy cost can amount from 30% and up to 40% of the total production cost of aluminum from alumina [12].
Reliable, long-term and economical sources of electricity are a deciding factor for location of aluminum plants.
Industries are relocating to regions with lower energy costs (e.g., the migration from Europe and North America to
the Middle East). New plants will therefore be built in regions where production and energy costs are at the lower
end of the spectrum. China and the Middle East will most likely have new production capacities being built up,
based on fossil fueled power.
Bayliss [2] concluded that the primary aluminum production will continue to meet the bulk of metal demand, at least
until mid-century. In his primary aluminum production 2040 scenario he estimated that the new production will come in
China, the GCC countries, Other Asia and “Rest of the World”. The locations of new aluminum plants are uncertain in
his opinion, but his assumption was that most likely the majority of the new production capacity will use fossil fueled
power.
In China more than 90% of the aluminum is now produced with electricity from coal power plants, while the remaining
10% comes from hydro power. On the other hand, China is attempting to constrain coal-generated electricity and
more than 7% of the country’s electrical energy of the grid comes from wind and solar power. Limited production
growth in China in 2018 is due to supply reforms that have set an upper limit for capacity. To keep the market stable a
primary aluminum company can only open new capacity when older capacity have been shut down first [2]. Low
metal inventory levels outside of China, combined with strong consumption growth, mean that aluminum plants need to
be built also outside of China.
CRU has incorporated a number of greenfield and brownfield aluminum plant expansions into their long-term output
forecasts. Although they still expect China to account for the majority of the new production capacity, a large
proportion of this capacity is yet to have started construction [13]. CRU also expects more capacity to be added in
the Middle East. There 100% of the aluminum is produced with electricity from natural gas-fired power plants. One
recent example is Alba's line 6 brownfield expansion in Bahrain, which will contribute to increase the company’s
total production capacity from 960,000 tpy to 1.5 Mtpy by 2019.
In Norway there are seven and in Iceland three primary aluminum production plants. The newest plant in Iceland is
now about twelve years old, and in 2018 a small brownfield pilot plant was started in Karmøy, Norway. The total
11
annual production of all these ten plants is now just above 2 million tonnes, which means 3% of the global
production.
All of these plants use renewable power, mostly hydroelectric, but also geothermal in Iceland. Admittedly, the
aluminum production increases the greenhouse gas emissions locally in these countries, but it decreases the global
emissions significantly, when it replaces aluminum produced with electrical energy from fossil fuels, like coal and
natural gas. The hydroelectricity based aluminum produced in Iceland and Norway is definitely an advantage, and
they have some of the world’s lowest CO2e-emitting aluminum production. These plants locally contribute only one-
sixth of the average specific greenhouse gas emissions from the world’s aluminum electrolysis plants. This means
that the aluminum production in these countries is greatly advantageous for the climate, because they are using
renewable energy sources. The same analysis applies to Canada, Russia and New Zealand.
It is seen in Fig. 2 that the CO2e emissions during aluminum production vary considerably between countries. The
largest volumes are produced in regions with relatively high emission intensity in electric power supply. This
illustrates the point discussed above; that the location of aluminum plants and the energy source have a significant
influence on environment and sustainability.
Fig. 2. The aluminum production given in Mtonne/year and the corresponding average CO2 emission intensity given
in g CO2e/kWh for different aluminum-producing countries [1,14 - 17].
10Effect of Climate Policies on Aluminium Related Emissions - Risk of Carbon Leakage
Aluminum is a commodity on the world marked and is subject to international trade. Fig. 3 shows the use of
aluminum in the European industry within the EU countries from 1980 to 2016. It is seen that at the beginning of the
period Europe was able to fill the demand mostly by production within the union, but after 2000 the demand has
increased by 30%, while primary aluminum production in Europe has been reduced by 40%. This reduction has been
most significant after 2006, but since then the production has dropped by almost 60%. Recycled aluminum, which
12
is by far the best environmental option with respect to both energy consumption and greenhouse gas emissions, fills
around 36% of the demand, which is an increase from 22% in the beginning of the period.
Fig. 3. The figure shows how much aluminum was used in the EU by source per year in the period from 1980 to
2016, and where it came from. Source: European Aluminium Statistics [18].
In an effort to reduce emissions the European Union adopted the Emissions Trading Scheme (EU - ETS) in 2005 and
started pricing of CO2 emissions within the European Community. This system was implemented for the ten
aluminum plants in Iceland and Norway that adopted the system through the European Economic Area (EEA) in
2013. This is a cornerstone of EU's policy to combat climate change and is its key tool for reducing greenhouse gas
emissions. It is the world's first major carbon market and remains the biggest one. Europe is responsible for around
10% of the total global greenhouse gas emissions, but takes the battle against climate change very seriously. And EU
is on track to meet their 20% reduction target for 2020.
Regulators have been aware of the risk of industries moving production and associated emissions offshore to avoid
costs associated with the system, see Sartor [19]. Therefore EU policy makers have used measures such as the
allocation of free emissions allowances, to reduce such carbon leakage.
Carbon leakage is defined by the EU as the situation that may occur if, for reasons of costs related to climate
policies, businesses were to transfer production to other countries with laxer emission constraints. This could lead
to an increase in their total emissions. The risk of carbon leakage may be higher in certain energy-intensive
industries [20].
The ETS system is now in its third phase (2013 - 2020) and for this period the definition of a sector or sub-sector
deemed as being at significant risk of carbon leakage is based on the outcome of the following two indicators [21]:
- Carbon Cost (i.e., (Direct carbon costs + Indirect carbon costs)/(Gross value added))
- Trade Intensity (i.e., (Imports + Exports)/(Production within ETS + Imports)).
But carbon cost has proven difficult to quantify. The sectors that are deemed at the highest risk of carbon leakage are
categorized as level 1 in the carbon leakage list. In phase 4 of the ETS system, which covers the period 2021-2030,
13
sectors are deemed eligible for level 1 evaluation if a carbon leakage indicator, a CL indicator as defined below, is
above 0.2. If the CL indicator is below 0.2 but above 0.15, further assessment is needed to decide if the sector is at
risk.
CL indicator = Trade Intensity · Emission Intensity (3)
Where:
Trade Intensity (TI) = (Imports + Exports)/(Imports + Turnover) (4)
Emission Intensity (EI) = (Direct Emissions + Indirect Emissions (kg CO2))/GVA (Euro) (5)
Here GVA (Euro) means euro area gross value added. The Carbon Leakage list for phase 4 (2021-2030) of the ETS
system, as well as previous lists, includes aluminum on the first level assessment list with CL indicator above 0.2
[22], but the quantitative values for sectors have not been published yet for phase 4.
Fig. 4 is reproduced from a European Commission staff working document for impact assessment [23] and shows
the quantitative assessment parameters based on 2009-2011 data for some of the sectors deemed at the greatest risk
for carbon leakage. These data are indicative as the current assessment is based on more recent data, but those have
not been published. Indeed, aluminum production, along with fertilizers and steel, is deemed to be at a “Very high”
(100%) carbon leakage risk, according to Fig. 4. These data is the most recent published by the European
Commission [23].
The price of European Union Allowances (EUAs) emissions has tended to be passed on by generators into the price
of wholesale electricity. For example, Sijm et al. [24] found that in Germany and the Netherlands – two significant
primary aluminum producing countries – the average pass-through rates of carbon costs to electricity price were
roughly 90% and 70%. The pass-through rate in Norway has been estimated as 67%. It is 75% in Finland and 71%
on average in the Nordic countries, according to a recent report from Pöyry [25]. As the cost of electrical energy can
amount to up to 40% of the production cost in an aluminum plant [7], the associated increased electricity cost is
indeed significant for the competitiveness of the industry.
14
Fig. 4. Selection of sectors plotted by trade intensity and total emission intensity/GVA(Euro), indicative carbon
leakage groups in the “Limited changes” option package based on 2009-2011 data, reproduced from [23].
Iceland is without a direct connection to the European energy market and therefore a pass-through rate has not been
estimated. The electricity sector in Iceland is almost exclusively based on renewable energy sources. The National
Power Company (Landsvirkjun), which has a dominating position with 70% of the overall power production
capacity and almost 100% of the hydroelectric power production in Iceland, offers long-term electricity contracts of
$43 per MWh. The official policy of the company is to be competitive within the European market [26]. Thus, the
argument can be made that there is significant pass-through rate of carbon cost in Iceland as well.
As the European aluminum industry has faced increased energy prices as a result of the system, Article 10a(6) of the
Revised EU - ETS Directive [25] allows specific provision of State Aid to a small number of energy intensive
sectors, deemed at risk of leakage, in order to compensate for the part of the higher electricity price attributed to the
ETS system. Electricity intensive sectors in countries where the carbon cost pass-through is relatively high, such as
for primary aluminum production in Germany and Norway, have therefore received such State Aid for a number of
years, counteracting the risk of relocation. A total of 10 EU countries, as well as the European Economic Area
(EEA) country Norway, offer such support, in many cases going back to 2013 [27].
As the EEA country Iceland is not directly connected to the European market, the industry in Iceland receives no
such mitigating State Aid. Aluminum production in Iceland is therefore at a particular risk of relocation in the future,
as industries are offered contracts at European market prices when their long-term contracts at lower prices run out.
However, such State Aid to counter the direct push of carbon pricing regulation on industries to relocate offshore is
controversial. The balance between mitigating genuine risk of carbon leakage and apparent welfare to industry is a
matter of debate. The State Aid can be as much as 25% of the total energy cost if the cost of emission allowances is
over 20 Euro, as was the case in April 2019. This is clearly an important factor for the competitiveness of the
sectors.
15
All of this infers that the electricity market is divided in two parts. Sectors that are not on the carbon leakage list pay
the market price and receive no subsidies, while sectors at risk for carbon leakage receive State Aid reducing their
electricity costs by 25-30%. In the case of Iceland, which does not offer subsidies, data centers and other activities
not seen as at risk of carbon leakage may find the available power prices competitive and locate to Iceland, while
aluminum and silicon production, which are at high risk for carbon leakage, may be forced to relocate offshore. The
likely increase in carbon emissions attributed to offshore relocation is (600-1000)%, if production capacity in
Iceland, Norway or Canada is replaced by increased capacity based on the world aluminum energy mix.
As a result of these mitigating actions, carbon leakage was not detected for aluminum production early in the period.
According to a study by Sartor [19] published in 2012. More recent data by Healy et al. [28] in 2018 show that total
EU-28 imports have increased and intra EU-28 production has decreased since 2012. The authors concluded that this
is an indicator of carbon leakage that warrants further investigation. This is supported by Fig. 3, which shows that
both the use of aluminum and the import fraction have increased in Europe since 2010. A likely reason for this delay
in carbon leakage from the initiation of the ETS-system is the fact that most smelters were benefiting from long-
term power contracts at prices that reflected the market before the carbon pricing. As the companies lose the
contracts, they become vulnerable to the higher prices, in particular in the countries that do not offer subsidies, such
as seen in recent smelter closures in Spain.
Concluding Remarks
Increasing climate-consciousness and sustainability demand from customers are now main challenges for the
aluminum producers. Converting energy sources to cleaner energy will remain a key focus in coming years in order
to adhere to a sustainable aluminum production process. Several producers running hydro-powered plants are now
charging a premium for their end product, which they call “low-carbon” or “green” aluminum. The expression “low-
carbon” has nothing to do with the content of carbon in the aluminum metal itself, because this is always negligible.
Instead it refers to the production processes, where they are offering low CO2e emissions guarantees on their
product. Indeed there is a growing sustainability demand among environment-conscious consumers for this “low-
carbon” metal. Some aluminum producers have launched hydropower-based aluminum produced with a maximum
carbon footprint of 4.0 t CO2e/t Al. Examples of such low-carbon brands are Ecolum (Alcoa), ALLOW (UC Rusal)
and REDUXA (launched by Norsk Hydro). The data in Table IV shows that with Best Available Technology it may
be possible to come slightly further down towards 3.5 t CO2e/t Al, but 4.0 is indeed a good and realistic number.
With inert anode cells this value can become down towards 2.0 t CO2e/t Al and then the main contribution comes
from the alumina production. Certification and pricing of low-emission aluminum are probably the way to go to
counter the downward spiral of reduced fraction of low-emission energy in the energy mix for aluminum production.
So what can the aluminum smelters do to minimize their greenhouse gas emissions? Operations can contribute to the
reduction by closing down inefficient technology designed more than half a century ago and it could be replaced by
more than 20% more efficient modern cell technology and control strategy. Almost all smelters make more money
by running their cells for productivity and low energy efficiency. Indeed there is a need for people to run their
smelters efficiently. Faced with this problem there are four main cell operational possibilities for mitigating the
emissions:
Reduce the energy consumption for all smelters and particularly for those with electricity from fossil fuels.
Reduce the net prebaked anode carbon consumption through better anode quality, work practices and
improved anode cover.
Reduce the anode effect frequency and duration through better anode effect control, which will reduce the
PFC emission intensity.
16
Reduce also the non-anode effect PFC emissions through shorter alumina underfeeding periods and higher
and more uniform average alumina concentrations in the electrolyte, particularly before and during anode
change.
The ultimate target for the aluminum industry is to become CO2e emission free. This is not possible with the process
technologies we have today, but current initiatives to develop an inert-anode process and CCS may contribute
strongly to that in the future. The largest challenge is, however, the indirect emissions due to the production of
electrical energy, which now amounts to about 70% of the global average emissions from aluminum production.
This has increased significantly during this century, with the carbon footprint of the energy production increasing by
an amount comparable to the total emissions related to the electrolysis process, including anode production. If all
smelters were converted to an inert anode process today, the carbon footprint from aluminum production would be
about the same as in 2000 due to the increase of coal power in the energy mix!
Aluminum is a highly recyclable light metal with good corrosion properties, which contributes to weight reduction
in transport vehicles and building materials with a long lifespan. Therefore the task is not to reduce its use, but rather
to encourage recycling and reduce emissions from the primary production. The single most important contribution to
this is the power use. Governments need to be aware of the risk of carbon leakage, which occurs when restricting
carbon regulations cause production to relocate from one region to another with laxer regulations. This dos not save
overall emissions, as the associated process emissions will occur in the new location offsetting the reduction in the
previous location, but in many instances the indirect emissions from energy production will be higher, and in some
cases much higher. The primary reason why the carbon footprint from aluminum production has increased since
2000 is that new capacity is primarily based on fossil fuel. Industry and governments must collaborate to reverse this
trend, with the goal of radically reducing the power-related emissions, as well as the process emissions.
References
1. World Aluminium: http://www.world-aluminium.org/statistics/primary-aluminium-smelting-energy-
intensity/#data Accessed 30 August 2019
2. Chris Bayliss, Presentation at the 2019 TMS Annual Meeting, San Antonio, Texas, March 2019, see also Light
Metal Age, 77 No. 3, 38 (May/June 2019)
3. Halvor Kvande and Barry Welch, Light Metal Age, 76 No. 1, 28 (January/February 2018)
4. T. Bruckner, I. A. Bashmakov, Y. Mulugetta, H. Chum, A. de la Vega Navarro, J. Edmonds, A. Faaij, B.
Fungtammasan, A. Garg, E. Hertwich, D. Honnery, D. Infield, M. Kainuma, S. Khennas, S. Kim, H. B. Nimir, K.
Riahi, N. Strachan, R. Wiser, and X. Zhang, 2014: Energy Systems. In: Climate Change 2014: Mitigation of Climate
Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on
Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I.
Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C.
Minx (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
5. IKE, 2017b. Life-cycle model of Chinese grid power and its application to LCAs of aluminium. Available from
http://www.world-aluminium.org/publications/tagged/life%20cycle/ Accessed 15 June 2018
6. http://www.world-aluminium.org/media/filer_public/2018/09/20/addendum_to_lca_report_2015__aug_2018.pdf
7. International Energy Agency ETP2017-scenario; https://www.iea.org/topics/renewables/ Accessed 31 August
2019
8. Warren Haupin and Halvor Kvande, Light Metals 2000, Proceedings from the 129th TMS Annual Meeting, 379
(2000).
17
9. Media Release, “Alcoa and Rio Tinto Announce World’s First Carbon-Free Aluminum Smelting Process”,
Pittsburgh, 10 May 2018
10. ELYSIS Exclusive, Aluminium International Today, 32, No. 3, 8 (May/June 2019).
11. Asbjørn Solheim, Light Metals 2018, Proceedings from the 147th TMS Annual Meeting, 1253 (2018)
12. OECD (2019-01-07), OECD Trade Policy Papers, No. 218, OECD Publishing, Paris, 120 pp.
http://dx.doi.org/10.1787/c82911ab-en
13. Media Release from CRU, “Understanding Where Future Aluminium Smelters will Develop”. Published in London,
22 March 2018
14. Overview of electricity production and use in Europe © European Environment Agency, 18 December 2018
15. https://www.nve.no/energy-market-and-regulation/retail-market/electricity-disclosure-2017/ Accessed 10 April
2018
16. Larissa Kyzer, The Environment Agency of Iceland, “NATIONAL INVENTORY REPORT, Emissions of
Greenhouse Gases in Iceland from 1990 to 2016”, Reykjavík, 13 April 2018
17. Alberto Moro and Laura Lonza, . European Aluminium Statistics, EU15, data until 1999
18. EU25 data for 2000-2004 and EU27 data for 2005-2015. Reproduced from: https://www.european-
aluminium.eu/data/economic-data/eu-aluminium-imports-dependency/, Accessed 8 April 2019
19. Oliver Sartor, “CDC CLIMAT RESEARCH WORKING PAPER N° 2012-12”, (February 2012)
20. EU-2019, European commission website, Accessed 1 April 2019
https://ec.europa.eu/clima/policies/ets/allowances/leakage _en
21. EU-ETS handbook, @European Union 2015.
22. ANNEX to the Commission Delegated Decision supplementing Directive 2003/87/EC of the European
Parliament and of the Council concerning the determination of sectors and subsectors deemed at risk of carbon
leakage for the period 2021 to 2030, European Commission, Brussels, 15.02.2019, C(2019) 930 final
23. EUROPEAN COMMISSION, SWD(2015) 135 final, Brussels, (July 15, 2015), 351 pp
24. Jos Sijm, Karsten Neuhoff and Yihsu Chen , Climate Policy, 6:1, 49 (2006)
DOI:10.1080/14693062.2006.9685588
25. Pöyry, “CARBON TRANSFER FACTOR IN THE NORDIC POWER MARKET”, a report to Norsk Industri,
(August 2018), 51 pp
26. DIRECTIVE (EU) 2018/410 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 14 March
2018 amending Directive 2003/87/EC to enhance cost-effective emission reductions and low-carbon investments,
and Decision (EU) 2015/1814, Official Journal of the European Union, 19 March 2018
27. Report on the functioning of the European carbon market, REPORT FROM THE COMMISSION TO THE
EUROPEAN PARLIAMENT AND THE COUNCIL, COM (2018) 842 final, Brussels, 17 December 2018
18
28. Sean Healy, Katja Schumacher and Wolfgang Eichhammer, Energies MDPI, Open Access Journal,
vol. 11(5), pp. 1-25(May 2018). doi:10.3390/en11051231
1. World Aluminium, Current IAI Statistics, http://www.world-aluminium.org/statistics/primary-aluminium-
smelting-energy-intensity/#data Accessed 30 August 2019
5. World Aluminium Publications. http://www.world-aluminium.org/publications/tagged/life
%20cycle/ Life-cycle model of Chinese grid power and its application to LCAs of aluminium,
Accessed September 9, 2019
6. World Aluminium Addendum to the Life Cycle Inventory Data and Environmental
Metrics for the Primary Aluminium Industry, 2015 Data, Final August 2018,
http://www.world-aluminium.org/media/filer_public/2018/09/20/addendum_to_lca_report_2015__aug_2018.pdf
7. International Energy Agency, ETP2017-scenario, Renewables, https://www.iea.org/topics/renewables/ Accessed
31 August 2019
12. OECD (2019-01-07), “Measuring distortions in international markets: the
aluminium value chain”, OECD Trade Policy Papers, No. 218, OECD Publishing, Paris.
http://dx.doi.org/10.1787/c82911ab-en
13. Media Release CRU, “Understanding Where Future Aluminium Smelters will Develop”. Published in London, 22
March 2018 https://www.marketwatch.com/press-release/cru-understanding-where-
future-aluminium-smelters-will-develop-2018-03-22
14. European Environment Agency (DK), “Overview of electricity production and use in Europe”, Last modi;ed
29 April 2019 https://Overview of electricity production and use in Europe — European Environment
Agency
15. NVE, Electricity Disclosure 2017, published 27 June 2018, last updated 1 April 2019
https://www.nve.no/energy-market-and-regulation/retail-market/electricity-disclosure-2017/ Accessed 9 September
2019
18. European Aluminium EU Aluminium Imports Dependency, EU25 data for 2000-2004 and EU27 data for 2005-
2015. Reproduced from: https://www.european-aluminium.eu/data/economic-data/eu-aluminium-imports-
dependency/, Accessed 8 April 2019
20. EU-2019, European commission website, Accessed 1 April 2019
https://ec.europa.eu/clima/policies/ets/allowances/leakage _en PAGE NOT FOUND
21. EU-ETS Handbook, @European Union 2015, 140 pp
https://ec.europa.eu/clima/sites/clima/;les/docs/ets_handbook_en.pdf
22. European Commission, ANNEX to the Commission Delegated Decision supplementing Directive 2003/87/EC of
the European Parliament and of the Council concerning the determination of sectors and subsectors deemed at risk
of carbon leakage for the period 2021 to 2030, Brussels, 15.02.2019, C(2019) 930 final
19
23. European Commission, Commission Sta> Working Document Impact Assessment, SWD
(2015) 135 final, Brussels, (July 15, 2015), 227 pp
26. Anonymous, Official Journal of the European Union, DIRECTIVES, Directive (EU) 2018/410 of the European
Parliament and of the Council of 14 March 2018, 19 March 2018
27. Anonymous, Report on the functioning of the European carbon market, Report from the Commission to the
European Parliament and the Council, Com (2018) 842 final, European Commission, Brussels, 17 December 2018
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Intra-diffusion coefficients (DSi) have been measured for the ionic liquid constituent ions and aluminium-containing species in aluminium chloride (AlCl3) solutions in the ionic liquids 1-(2-dimethyl-aminoethyl)-dimethylethylammonium bis(trifluoromethylsulfonyl)amide ([C2TMEDA][Tf2N]) and N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C4mpyr][Tf2N]), to investigate whether spectroscopically detected interactions between the ions and AlCl3 affect these properties. Such electrolyte solutions are of interest for the electrowinning of aluminium. The temperature, composition and molar volume dependences are investigated. Apparent (Vϕ,1) and partial molar (V1) volumes for AlCl3 have been calculated from solution densities. For [C2TMEDA][Tf2N] solutions, Vϕ,1 increases with increasing solute concentration; for [C4mpyr][Tf2N] solutions, it decreases. In pure [C2TMEDA][Tf2N], the cation diffuses more quickly than the anion, but this changes as the AlCl3 concentration increases. In the [C4mpyr][Tf2N] solutions, the intra-diffusion coefficient ratio remains equal to that for the pure ionic liquid and the aluminium species diffuses at approximately the same rate as the anion at each composition. The intra-diffusion coefficients can be fitted to the Ertl-Dullien free volume power law by superposing the iso-concentration curves with concentration dependent, but temperature independent, molar volume offsets. This suggests that they are primarily dependent on the molar volume and secondarily on a colligative thermodynamic factor due to dilution by AlCl3. AlCl3 complexation by [Tf2N]- and [C2TMEDA]+, confirmed by 27Al, 15N and 19F NMR spectroscopy, seems to play a minor role. Our results indicate that the application of free volume theories might be fruitful in the study of the transport properties of ionic liquid solutions and mixtures.
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Aluminum is extensively used in construction, infrastructure, transportation, and consumer durables. China's aluminum in-use stocks (AIUS) are rapidly accumulating with accelerated industrialization and urbanization. Although previous research has illustrated AIUS at the national level, a lack of understanding of the spatial patterns of AIUS in China remains. This study used a bottom-up method to calculate the provincial-level spatial distribution of China's AIUS in 2018. The main conclusions are threefold. (1) The total AIUS across the country were 201.21 Tg, approximately 80% deposited in five subsectors, including residential buildings, non-residential buildings, power transmission, passenger cars, and power production. (2) The three regions with the most AIUS were Jiangsu, Shandong, and Guangdong, while the three regions with the least AIUS included Tibet, Hainan, and Qinghai. Per capita aluminum stock decreased from northwest to southeast, varying from 105 to 265 kg/capita. In contrast, the geographic density of AIUS gradually increased from the northwest to the southeast, ranging from 1 to 527 t/km² (3) A considerable disparity exists between urban (120 kg/capita) and rural (62 kg/capita) areas regarding the AIUS of buildings, consumer durables, private cars, and motorcycles. This difference illustrates the extreme imbalance between urban and rural social development. The above findings can provide some implications for advancing the management and recycling of aluminum resources.
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China's aluminum in-use stocks (AIUS) have rapidly accumulated since the reform and opening-up, but its growth driving forces and decoupling from the economy remain unclear. Here we develop a dynamic top-down model to quantify China's AIUS during 1978–2018, analyze the driving force of its rapid growth, and discuss the coupling relationship between it and economic growth. China's AIUS has grown from 4 Tg in 1978 to 255 Tg in 2018. Although the current per capita AIUS (182 kg/capita) is still lower than that of developed countries, the total AIUS has become the first in the world. The population and GDP per capita (demand side) have been driving AIUS growth throughout the survey period, while three factors from the supply side have had different effects on AIUS growth over time. The decoupling analysis results indicate that the absolute decoupling of AIUS from economic growth could be achieved around 2040.
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This report builds on the OECD’s longstanding work measuring government support in agriculture, fossil fuels, and fisheries in order to estimate support and related market distortions in the aluminium value chain. Results show that non-market forces, and government support in particular, appear to explain some of the recent increases in aluminium-smelting capacity. While government support is commonly found throughout the aluminium value chain, it is especially heavy in the People’s Republic of China and countriesof the Gulf Cooperation Council. Looking across the whole value chain also shows subsidies upstream to confer significant support to downstream activities, such as the production of semi-fabricated products of aluminium. Overall, market distortions appear to be a genuine concern in the aluminium industry, and one that has implications for global competition and the design of trade rules disciplining government support
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This paper contributes to the existing literature on carbon leakage by using a range of different publically available datasets in order to develop a systematic approach for identifying whether products are potentially at risk of carbon leakage. The scope of this paper focuses on the cement and aluminium sectors at different levels of product aggregation to demonstrate the variation in trade patterns that exist over time. The evolution of EU-28 trade flows with third countries for these sectors between 2000 and 2016 enables the selection of key third countries that could warrant further investigation via more quantitative techniques in order to determine the impact of carbon pricing on trade patterns. This systematic approach could be replicated for additional sectors in further research as part of a more regular assessment to provide evidence of carbon leakage for European industry. No evidence of carbon leakage is found in this paper for clinker and cement, while there is no conclusive evidence for unwrought non-alloyed aluminium and aluminium products.
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The Well-To-Wheels (WTW) methodology is widely used for policy making in the transportation sector. In this paper updated WTW calculations are provided, relying on 2013 statistic data, for the carbon intensity (CI) of the European electricity mix; detail is provided for electricity consumed in each EU Member State (MS). An interesting aspect presented is the calculation of the GHG content of electricity traded between Countries, affecting the carbon intensity of the electricity consumed at national level. The amount and CI of imported electricity is a key aspect: a Country importing electricity from another Country with a lower CI of electricity will lower, after the trade, its electricity CI, while importing electricity from a Country with a higher CI will raise the CI of the importing Country. In average, the CI of electricity used in EU at low voltage in 2013 was 447 gCO2eq/kWh, which is the 17% less compared to 2009. Then, some examples of calculation of GHG emissions from the use of electric vehicles (EVs) compared to internal combustion engine vehicles are provided. The use of EVs instead of gasoline vehicles can save (about 60% of) GHG in all or in most of the EU MSs, depending on the estimated consumption of EVs. Compared with diesel, EVs show average GHG savings of around 50% and not savings at all in some EU MS.
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This paper analyses the implications of the EU ETS for the power sector, notably the impact of free allocation of CO2 emission allowances on the price of electricity and the profitability of power generation. Besides some theoretical reflections, the paper presents empirical and model estimates of CO2 cost pass through, indicating that pass through rates vary between 40 and 100 percent of CO2 costs, or – in absolute terms – between 3 and 18 €/MWh, depending on the carbon intensity of the marginal production unit and other, market or technology specific factors concerned. As a result, power companies realise substantial windfall profits, indicated by empirical and model estimates presented in the paper. In order to avoid these windfall profits, the paper concludes that free allocation to power companies should be phased out in favour of auctioning.
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The introduction of inert anodes in alumina reduction cells may bring about some advantages, but also a number of serious drawbacks. In view of the developments in the Hall-Héroult process during the last decades, it was considered desirable to make a critical evaluation of the inert anode concept as compared to state-of-the-art electrolysis cells. It was found that the DC energy consumption will be about 3 kWh/kg Al higher with inert anodes, partly because the 1 V higher isothermal cell voltage cannot be fully compensated, but mainly because a cell with inert anodes requires similar heat loss as a cell with carbon anodes. Consequently; the total carbon dioxide footprint will be higher with inert anodes when the power is generated in a coal fired plant, while there is not much difference if the power comes from a gas fired plant. The full carbon dioxide reduction potential with inert anodes can only be realized when using renewable energy sources. However, a Hall-Heroult plant with carbon capture and sequestration will still require less electric power than a plant with inert anodes.
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  • Pöyry
Emissions of Greenhouse Gases in Iceland from
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National Inventory Report, Emissions of Greenhouse Gases in Iceland from
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