Supplementary materials (SM)

Forecasting the temporal stock generation and recycling potential of metals

towards a sustainable future: The case of gallium in China

Disna Eheliyagoda a, Xianlai Zeng a,*, Zhishi Wang b, Eva Albalghiti a,c, Jinhui Li a,*

aState Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua

University, Beijing100084, China

bMacau Environmental Research Institute, Macau University of Science and Technology, Macau, China

cSchool of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, USA

* Corresponding authors: jinhui@tsinghua.edu.cn; xlzeng@tsinghua.edu.cn

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Table of Contents

1. Gallium supply and demand (2008-2015)····························································S3

Figure S1. Supply and demand of gallium from 2008 to 2015·······································S3

2. Gallium consumption in China·········································································S4

Figure S2. Consumption structure of gallium in China················································S4

Figure S3. Fluctuation in the production of major gallium consumed end-uses in China between

1998 and 2016·······························································································S5

Figure S4. The supply uncertainty for Chinese elements production································S6

3. Methods and data sources used in the study·························································S6

Table S1. Average life-time of Ga-based products·····················································S6

3.1. Determination of annual domestic gallium demand···················································S6

3.2. The projection of gallium stock generation using subjective factors································S7

4. Projected annual stock generation·····································································S9

Table S2. Gallium stock generation in urban mines – linear regression projection (in tons)·····S9

Table S3. Gallium stock generation in urban mines – population dynamics with annual increase

rate projection (in tons)···················································································S10

5. Projected annual domestic gallium demand in China············································S12

Figure S5. Linear regression projection on domestic gallium demand in China··················S12

Figure S6. Population dynamics with annual increase rate projection on domestic gallium

demand in China···························································································S13

Figure S7. The distribution of identified gallium resources in the world (kt)··························S14

References·········································································································S14

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1. Gallium supply and demand (2008-2015)

Fig. S1(A) shows that gallium supply (primary production + importation) and demand

(consumption + exportation) in China have progressively increased from 2009 to 2015 with

few deviations between 2008 and 2009. In recent years, the yield of primary gallium reached

200 t each year, which mainly supplied from four provinces of Shanxi, Henan, Guangxi, and

Guizhou (Antaike Metal, 2015). Fig. S1(A) also reveals that China’s consumption of gallium

has considerably increased between 2011 and 2015. The average discrepancy between imports

and exports was 90.82 tons in the period between 2012 and 2016.

Fig. S1. Supply and demand of gallium from 2008 to 2015 (A) China; (B) World and China.

Data sources from (Schulte and Foley, 2014; Xuan, 2010).

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Fig. S1(B) illustrates a comparison of gallium production and consumption in China with

global scenario from 2009 to 2015. It shows that China plays the major role in world overall

production and it is a high contribution to fulfil the demand. Compared with global situation,

China’s consumption pattern has grown from 2009 to 2015 which is expected to be flourished

in next consecutive decades (Elshkaki and Graedel, 2013). This comparison is an indicator to

demonstrate that China is one of the leading consumers of gallium. Available production data

focuses on primary production that mainly depends on virgin mining material such as

congregated ore and gallium related oxides. Therefore, the secondary production was not

taken into account. The reason for that is the unavailability of accurate secondary production

data especially for China.

2. Gallium consumption in China

Domestically, gallium is principally consumed by semiconductors in China. The second and

third places are acquired by LED and PV industries respectively.

Fig. S2. Consumption structure of gallium in China (A) Total amount; (B) Share. Data source

from (Antaike Metal, 2015).

Becoming the mainspring of Chinese LED market growth, in 2013, general lighting was

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responsible for around 45.1% of average package LED profits, afterwards, signage,

backlighting, and others accounted for 19%, 15.7%, and 20.2% respectively. In the meantime,

a Chinese company called MLS Electronics Co. Limited ranked as one of the top ten

worldwide packaging LED manufacturers, which had international shares in several countries.

Consequently, it is expected that the international LED market will annually increase by 17%

from 2016 to 2020. General lighting is also likely to remain the major portion of latest LED

market, followed by automotive lighting and backlighting. Meanwhile, the Asia Pacific region

is projected to be the foremost consumer of LED based products as a result of rapid

development of Asian region and continuous government encouragement with incentive

programs to highlight the importance in use of energy efficient lighting majority presenting

LED products (Peters, 2016). The cumulative installed capacity of PV modules in China is

also increasing since 2011. This drastic market change can be attributed to the implementation

of various incentive programs and projects in order to improve the renewable energy systems

and minimize the dependency of coal as a main source of energy (Peters, 2016).

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Fig. S3. Fluctuation in the production of major gallium consumed end-uses in China between

1998 and 2016. Data source from (NBSC, 1998-2016).

Fig. S4. The supply uncertainty for Chinese elements production. China is the leading

producer for all elements labeled in the figure. The relative supply risk index scores from 1 to

10; very low risk (below 4.50); low risk (4.50-5.40); medium risk (5.50-7.00); high risk (7.10-

9.50); very high risk (above 9.50). Data sources from (British Geological Survey, 2015).

*REE: Rare-earth elements

3. Methods and data sources used in the study

Table S1. Average life-time of Ga-based products.

ApplicationSemiconductor

materialLEDs

(Shao, 2006)Photovoltaics Others

Life-time (in years) 2 2 10 5

3.1. Determination of annual domestic gallium demand

The domestic demand is the crucial factor to understand the different sectoral consumption of

products within a state. The gallium consumption in China (domestic demand) consists of four

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application categories: semiconductor material, LEDs, photovoltaics, and other products.

Thus, domestic demand in China can be interpreted as in eq S1.

DtT=Dt

S+DtL+Dt

P+DtO Eq .(S 1)

Where DtT is the total domestic demand for gallium in year t; Dt

S, DtL, Dt

P, and DtO are the

domestic gallium demand for semiconductor material, LEDs, photovoltaics, and other

products in year t respectively. The annual consumption data of each application category

were obtained from Antaike Metal, 2015.

3.2. The projection of gallium stock generation using subjective factors

The individual (per capita) gallium stock generation between 2012 and 2016 was calculated

using annual population statistics of World Bank (World Bank, 2018). Considering the 2016

individual stock generation of each product category [i.e. semiconductor material (S), LEDs

(L), photovoltaics (P), and others (O)] as the baseline, it was multiplied by the yearly medium

population variant and average annual increase (from 0% to 3%) to determine the domestic

stock generation of each product category up to 2050. Then, the results of product categories

were summed to find the total domestic stock generation of gallium. We adopted the need of

224% average increase by 2050 compared to the 2010 production of gallium to meet the

global demand depicted by Elshkaki and Graedel, 2013 to determine annual increases.

Similarly, we assumed this demand growth will be required to fulfil the Chinese demand in

2050 since China has already acquired a major role in the gallium market. Accordingly, we

selected stabilized, 1%, 2%, and 3% annual increases to forecast the stock generation in urban

mines. The equations to calculate the total annual gallium stock generation are given below:

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Gallium stock generation (S) = Per capita stock generation (S) × Medium population variant of the year

× Annual increase Eq. (S2)

Gallium stock generation (L) = Per capita stock generation (L) × Medium population variant of the year

× Annual increase Eq. (S3)

Gallium stock generation (P) = Per capita stock generation (P) × Medium population variant of the year

× Annual increase Eq. (S4)

Gallium stock generation (O) = Per capita stock generation (O) × Medium population variant of the year

× Annual increase Eq. (S5)

Total gallium stock generation = Gallium stock generation (S) + Gallium stock generation (L) +

Gallium stock generation (P) + Gallium stock generation (O) Eq. (S6)

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4. Projected annual stock generation

Table S2. Gallium stock generation in urban mines – linear regression projection (in tons).

YearSemiconductormaterial (SCM) LED Photovoltaics (PV) Others

2014 14.50 4.002015 19.00 7.302016 27.00 7.902017 35.00 8.40 0.502018 41.00 9.50 1.102019 48.30 11.07 1.402020 55.20 12.28 1.802021 62.10 13.49 2.302022 69.00 14.70 1.00 2.712023 75.90 15.91 2.60 3.142024 82.80 17.12 3.70 3.572025 89.70 18.33 4.80 4.002026 96.60 19.54 7.20 4.432027 103.50 20.75 8.22 4.862028 110.40 21.96 9.68 5.292029 117.30 23.17 11.14 5.722030 124.20 24.38 12.60 6.152031 131.10 25.59 14.06 6.582032 138.00 26.80 15.52 7.012033 144.90 28.01 16.98 7.442034 151.80 29.22 18.44 7.872035 158.70 30.43 19.90 8.302036 165.60 31.64 21.36 8.732037 172.50 32.85 22.82 9.162038 179.40 34.06 24.28 9.592039 186.30 35.27 25.74 10.022040 193.20 36.48 27.20 10.452041 200.10 37.69 28.66 10.882042 207.00 38.90 30.12 11.312043 213.90 40.11 31.58 11.742044 220.80 41.32 33.04 12.17

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2045 227.70 42.53 34.50 12.602046 234.60 43.74 35.96 13.032047 241.50 44.95 37.42 13.462048 248.40 46.16 38.88 13.892049 255.30 47.37 40.34 14.322050 262.20 48.58 41.80 14.75

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Table S3. Gallium stock generation in urban mines – population dynamics with annual increase rate projection (in tons).

YearNo annual increase 1% annual increase 2% annual increase 3% annual increase

SCM LED PV Others SCM LED PV Others SCM LED PV Others SCM LED PV Others

2014 14.50 4.00 14.50 4.00 14.50 4.00 14.50 4.00

2015 19.00 7.30 19.00 7.30 19.00 7.30 19.00 7.30

2016 27.00 7.90 27.00 7.90 27.00 7.90 27.00 7.90

2017 35.00 8.40 0.50 35.00 8.40 0.50 35.00 8.40 0.50 35.00 8.40 0.50

2018 41.00 9.50 1.10 41.00 9.50 1.10 41.00 9.50 1.10 41.00 9.50 1.10

2019 41.11 9.52 1.40 41.52 9.62 1.40 41.93 9.715 1.40 42.34 9.81 1.40

2020 41.34 9.58 1.80 42.17 9.77 1.80 43.01 9.97 1.80 43.85 10.16 1.80

2021 41.44 9.60 2.30 42.70 9.89 2.30 43.98 10.19 2.30 45.29 10.49 2.30

2022 41.49 9.61 1.00 2.31 43.17 10.00 1.00 2.33 44.91 10.41 1.00 2.35 46.70 10.82 1.00 2.38

2023 41.54 9.62 2.60 2.32 43.65 10.12 2.60 2.37 45.86 10.63 2.60 2.41 48.15 11.16 2.60 2.46

2024 41.58 9.63 3.70 2.32 44.14 10.23 3.70 2.40 46.83 10.85 3.70 2.47 49.65 11.50 3.70 2.54

2025 41.63 9.64 4.80 2.33 44.63 10.34 4.80 2.42 47.82 11.08 4.80 2.52 51.20 11.86 4.80 2.62

2026 41.67 9.66 7.20 2.33 45.13 10.46 7.20 2.45 48.83 11.31 7.20 2.57 52.79 12.23 7.20 2.70

2027 41.72 9.67 7.22 2.33 45.63 10.57 7.29 2.48 49.86 11.55 7.36 2.63 54.43 12.61 7.44 2.79

2028 41.72 9.67 7.26 2.34 46.08 10.68 7.41 2.50 50.86 11.78 7.55 2.68 56.07 12.99 7.70 2.87

2029 41.72 9.67 7.28 2.34 46.54 10.78 7.50 2.53 51.87 12.019 7.72 2.74 57.75 13.38 7.95 2.96

2030 41.72 9.67 7.29 2.34 47.01 10.89 7.58 2.56 52.91 12.26 7.89 2.80 59.48 13.78 8.20 3.05

2031 41.72 9.67 7.29 2.34 47.48 11.00 7.67 2.59 53.97 12.50 8.05 2.85 61.27 14.20 8.46 3.15

2032 41.65 9.65 7.30 2.34 47.87 11.09 7.75 2.61 54.95 12.73 8.22 2.91 63.00 14.60 8.72 3.24

2033 41.58 9.63 7.31 2.34 48.27 11.18 7.84 2.64 55.96 12.97 8.40 2.97 64.78 15.01 8.99 3.34

2034 41.51 9.62 7.32 2.34 48.67 11.28 7.92 2.66 56.98 13.20 8.57 3.03 66.61 15.43 9.27 3.44

2035 41.44 9.60 7.33 2.34 49.07 11.37 8.01 2.69 58.02 13.44 8.76 3.08 68.49 15.87 9.56 3.53

2036 41.37 9.58 7.33 2.33 49.48 11.46 8.09 2.71 59.08 13.69 8.93 3.14 70.42 16.32 9.85 3.63

2037 41.30 9.57 7.33 2.33 49.89 11.56 8.17 2.73 60.16 13.94 9.11 3.20 72.41 16.78 10.14 3.74

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2038 41.30 9.57 7.33 2.32 50.39 11.68 8.26 2.75 61.36 14.22 9.29 3.25 74.58 17.28 10.45 3.84

2039 41.30 9.57 7.33 2.32 50.89 11.79 8.34 2.78 62.59 14.50 9.48 3.31 76.82 17.80 10.76 3.95

2040 41.30 9.57 7.31 2.32 51.40 11.91 8.41 2.80 63.84 14.79 9.65 3.37 79.13 18.33 11.06 4.06

2041 41.30 9.57 7.30 2.32 51.91 12.03 8.48 2.83 65.12 15.09 9.83 3.44 81.50 18.88 11.38 4.18

2042 41.12 9.53 7.29 2.32 52.21 12.10 8.55 2.85 66.13 15.32 10.01 3.51 83.58 19.37 11.70 4.31

2043 40.94 9.49 7.28 2.32 52.50 12.17 8.62 2.88 67.17 15.56 10.19 3.58 85.72 19.86 12.03 4.44

2044 40.76 9.45 7.26 2.32 52.80 12.23 8.69 2.91 68.22 15.81 10.38 3.65 87.91 20.37 12.37 4.57

2045 40.59 9.40 7.25 2.31 53.10 12.30 8.76 2.93 69.28 16.05 10.56 3.71 90.16 20.89 12.72 4.69

2046 40.41 9.36 7.25 2.30 53.40 12.37 8.85 2.95 70.36 16.30 10.78 3.77 92.47 21.43 13.10 4.81

2047 40.24 9.32 7.25 2.29 53.70 12.44 8.94 2.96 71.46 16.56 10.99 3.83 94.83 21.97 13.49 4.93

2048 40.24 9.32 7.25 2.28 54.24 12.57 9.03 2.98 72.89 16.89 11.21 3.89 97.68 22.63 13.90 5.06

2049 40.24 9.32 7.25 2.27 54.78 12.69 9.12 3.00 74.35 17.23 11.44 3.95 100.61 23.31 14.31 5.19

2050 40.24 9.32 7.22 2.26 55.33 12.82 9.17 3.01 75.84 17.57 11.61 4.01 103.62 24.01 14.68 5.32

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5. Projected annual domestic gallium demand in China

Fig. S5 illustrates the linearly forecasted demand of major gallium related industrial sectors in

China up to 2050.

Fig. S5. Linear regression projection on domestic gallium demand in China (A) Amount; (B)

Share.

Gallium is mainly consumed by semiconductors and also demanded for LED and photovoltaic

applications in China. Fig. S5(A) demonstrates an increasing consumption pattern of gallium

applications within industries, which is an evidence for continuous demand growth in the

future. Gallium demand reached 50 tons in 2015 and it will expand to 100.3 tons and 400.3

tons in 2020 and 2050, respectively. Fig. S5(B) shows the percentage demand of each gallium

application. Semiconductor material, LED, photovoltaics, and other gallium applications will

account for 69%, 15%, 12%, and 4% quantities in 2020, respectively. Furthermore, in 2050, it

is expected that the demand will change to 69%, 13%, 14%, and 4% regarding semiconductor

material, LED, photovoltaics, and other applications, correspondingly.

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Compared with linear model projection, a substantial reduction in the demand can be observed

in Fig. S6; however, it is also obvious that the gallium demand will consistently rise in next 31

years except the condition under non-annual increase scenario.

Fig. S6. Population dynamics with annual increase rate projection on domestic gallium

demand in China.

Semiconductor material becoming the highest demanding application will account for 56.08 t,

78.39 t, and 109.23 t under 1%, 2%, and 3% annual increases in 2050 respectively. At the

meantime, LEDs will account for 13 t, 18.16 t, and 25.31 t under 1-3% growth rates in 2050

respectively. Photovoltaics are demanding in emerging technologies such as renewable

energies since the recent decade; thus it is expected that the PV demand will contribute from a

considerable proportion to the gallium demand growth in the future. Overall, the total

domestic demand is projected to fall between 58 t and 160 t in 2050.

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Fig. S7. The distribution of identified gallium resources in the world (kt). Note: The circle size

indicates the resource amount and the bar chart indicates the comparison of main regions.

Data sources from (Dai et al., 2006; Schulte and Foley, 2014; Wang et al., 2011; Zhao et al.,

2017).

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