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The significant increase in metal mining and the inevitability of the continuation of this trend suggests that environmental pressures, as well as related impacts, have become an issue of global relevance. Yet the scale of the impact remains, to a large extent, unknown. This paper examines the mining sector’s demands on CO2 emissions, water use, as well as demands on land use focusing on four principal metals: iron, aluminium (i.e., bauxite ore), copper, and gold. These materials represent a large proportion of all metallic materials mined in terms of crude tonnage and economic value. This paper examines how the main providers of mining data, the United Nations, government sources of some main metal producing and consuming countries, the scientific literature, and company reports report environmental pressures in these three areas. The authors conclude that, in the global context, the pressure brought about by metal mining is relatively low. The data on this subject are still very limited and there are significant gaps in consistency on criteria such as boundary descriptions, input parameter definitions, and allocation method descriptions as well as a lack of commodity and/or site specific reporting of environmental data at a company level.
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sustainability
Article
Metal Mining’s Environmental Pressures: A Review
and Updated Estimates on CO2Emissions, Water Use,
and Land Requirements
Michael Tost 1,*, Benjamin Bayer 1, Michael Hitch 2, Stephan Lutter 3, Peter Moser 1ID
and Susanne Feiel 1
1Mining Engineering and Mineral Economics, Montanuniversitaet Leoben, 8700 Leoben, Austria;
benjamin.bayer@stud.unileoben.ac.at (B.B.); peter.moser@unileoben.ac.at (P.M.);
susanne.feiel@unileoben.ac.at (S.F.)
2School of Science, Department of Geology, Tallinn University of Technology, 19086 Tallinn, Estonia;
michael.hitch@ttu.ee
3
Institute for Ecological Economics, Vienna University of Economics and Business (WU), 1020 Wien, Austria;
stephan.lutter@wu.ac.at
*Correspondence: michael.tost@unileoben.ac.at; Tel.: +43-664-452-9872
Received: 28 June 2018; Accepted: 10 August 2018; Published: 14 August 2018


Abstract:
The significant increase in metal mining and the inevitability of the continuation of this
trend suggests that environmental pressures, as well as related impacts, have become an issue of
global relevance. Yet the scale of the impact remains, to a large extent, unknown. This paper examines
the mining sector’s demands on CO
2
emissions, water use, as well as demands on land use focusing
on four principal metals: iron, aluminium (i.e., bauxite ore), copper, and gold. These materials
represent a large proportion of all metallic materials mined in terms of crude tonnage and economic
value. This paper examines how the main providers of mining data, the United Nations, government
sources of some main metal producing and consuming countries, the scientific literature, and company
reports report environmental pressures in these three areas. The authors conclude that, in the global
context, the pressure brought about by metal mining is relatively low. The data on this subject are still
very limited and there are significant gaps in consistency on criteria such as boundary descriptions,
input parameter definitions, and allocation method descriptions as well as a lack of commodity
and/or site specific reporting of environmental data at a company level.
Keywords: mining; gold; bauxite; copper; iron ore; environmental pressure; CO2; water; land use
1. Introduction
The environmental impact of metal mining has been an issue for centuries (e.g., [
1
3
]),
maybe even millennia. For most of this time however, these impacts have been mainly local
such as deforestation (e.g., in Saxony/Germany), water pollution (e.g., Rio Tinto/Spain), and soil
contamination (e.g., in Bleiberg/Austria).
Today, largely due to the “great acceleration” of economic growth after World War II [
4
] and
ever-increasing globalization of trade, global metal mining is increasing significantly (e.g., [
5
,
6
] (p. 10))
and environmental pressures such as land and water use, as well as related environmental (and social)
impacts have become an issue of worldwide relevance. There is an expectation that this trend will
continue in alignment with society’s increasing demand for raw materials. Yet the question remains:
how big is this issue?
To answer this question, the authors focus on four metals–iron, aluminium (i.e., bauxite ore),
copper, and gold. Iron, aluminium, and copper represent over 96 percent of all metals mined globally
Sustainability 2018,10, 2881; doi:10.3390/su10082881 www.mdpi.com/journal/sustainability
Sustainability 2018,10, 2881 2 of 14
in terms of bulk tonnage [
7
], and together with gold they possess over 68% of industrial value [
8
].
In addition, the extraction technologies can be considered representative, making the results indicative
for metal mining as a whole. To evaluate environmental pressures, the authors focus on data for
three categories considered highly relevant to mining, admittedly by the industry itself (e.g., [
9
12
]),
including climate change (i.e., CO
2
emissions), water use, and land use. To assess responses, the authors
look at the main providers of mining data, the United Nations (UN), government sources of some
main metal producing and consuming countries, the scientific literature, and company reports.
The main providers, i.e., US Geological Survey (USGS) [
13
], British Geological Survey [
14
], World
Mining Data (WMD) [
7
], and S&P [
15
], of mining data often do not include environmental data in their
publications. Their annual reports and S&P’s database focus on production and economic data only,
which, the authors would argue, means that aggregated environmental data are not yet considered as
material mining data for public disclosure.
The same can be said for UN and independent government sources: the International
Resource Panel (IRP) has produced various reports looking into the material flows of metals [
6
]
and their environmental impacts, including data for water consumption and greenhouse gas
emissions [16] (pp. 101–105)
—based on scientific literature further discussed below, but the IRP also
acknowledges that further research is required:
“Important knowledge is still missing in the linkages that exist between different types of
resources: metals, energy, water, and maybe others. This refers both to the resources needed
in the chain of the metals (e.g., energy for refining) and to the fact that metals are in some
cases mined as a by-product of other materials (mostly other metals, but sometimes other
materials, e.g. mercury production from natural gas). In scenario explorations for the future,
this is essential knowledge. It requires an interdisciplinary approach and the cooperation of
researchers from different fields to build up this type of knowledge.” [16] (p. 21).
The United States Geological Survey’s (USGS) webpage, makes reference to material flows and
that “understanding the whole system of material flow, from source to ultimate disposition, can help
us better manage the use of natural resources and protect the environment” [
17
], but none of the
studies listed include current or timely environmental data as described above. The European Union’s
Raw Material Information System (EU RMIS) also includes a section on environmental and social
sustainability, listing “water”, “air emissions and climate change”, and “land and biodiversity” as
areas, but they do not include specific environmental data required for meaningful analysis [
18
].
Other government websites, such as the Australian Bureau of Statistics [
19
], Natural Resources
Canada [
20
], the Chinese National Bureau of Statistics [
21
], or Statistics South Africa [
22
] all focus
on economic indicators such as production, sales, and gross value added or employment and not
environmental impact in our focus areas.
At the company level, in response to conflicts and increasing societal pressure, the majority of
mining companies have committed themselves to sustainability [
23
] and the reporting of environmental
data has become relevant, either through legal requirements such as the European Union’s (EU)
non-financial reporting directive [
24
], voluntary industry iniatives such as the International Council
for Mining & Metals’ (ICMM) requirement for its member companies to annually publish reports in
accordance with the Global Reporting Initiative (GRI) [
25
] or pressure from customers/consumers
and/or financiers for companies to respond to initiatives such as the CDP [
26
] or the Dow Jones
Sustainability Index [
27
]. However, such reporting is not mandated yet for all mining companies,
as it is either
not legally required or only required above a certain size, as is the case with [
24
] and
hence segmented environmental data is not consistenly available.
Given that data are not readily available on a commodity and/or mine site specific level from the
sources described above, the authors focus efforts on a review of scientific literature and company data
as described in Section 2, with the main aim to compile data on the environmental pressures brought
about by mining for four metals (iron, aluminium, copper, and gold), focusing on CO
2
emissions,
Sustainability 2018,10, 2881 3 of 14
water use, and land use. For each metal, an estimated range (minimum, average, and maximum) for
the year 2016 and a comparison with company data is shown in Section 3. Section 4discusses the key
results and proposes a way forward.
2. Materials and Methods
The base of the data compilation is a literature review of existing scientific studies. In order
to check for the comparability of the data stemming from different sources and to select useful
publications a set of criteria is applied:
Boundary descriptions
The authors consider this as the main criterion. A data sample should include only production
sites at the same position in the value chain. Looking at mining, the production steps (i.e., mining,
concentration, purification, refining) are different depending on the metal in focus. Even for one
metal, processes applied at a site differ greatly, e.g., in copper production with pyro-metallurgical or
hydro-metallurgical routes [
28
] (p. 120), [
29
] (p. 24ff). Publications that separate process steps are rare,
because companies report for a production site and not for a production step. The majority of the
studies listed in Table 1consider the shipment of (concentrated) iron ore and bauxite from the mine
as the boundary. For copper and gold, the boundary includes purification and refining, but it does
not differ between underground or open pit mining and production routes. This study uses the same
definitions, but also presents estimates for downstream steel and aluminium production processes for
CO2and water use to allow for ‘mine to metal’ comparisons for all four metals.
Input parameter definitions
A clear definition of the parameters considered is needed. This is the case for CO
2
with the GHG
Protocol [
30
], but not for water data ([
31
,
32
]). In this study, we consider data for water withdrawal
and consumption.
Allocation method
In the case of companies/mines that produce more than one commodity; input/output
measurements alone do not provide enough information to attribute e.g., water consumption or
CO
2
emissions to a single commodity. A description of the subsystems (processes) would be necessary.
To overcome this problem, volume flows are attributed to a commodity by allocation, e.g., based on
revenues achieved from the commodities [
33
] (p. 68). Reporting companies as well as authors of
publications should describe their allocation methods, otherwise they are not considered in this study.
Purpose of the publication
The purpose of the publication can influence the result because of sample bias, boundaries,
allocation method, input parameters, and other parameters connected to the intent. The result may be
good for a specific purpose, but may not be usable in the context of this study, which the authors check
against the first three criteria.
Table 1contains a basic description of the publications analyzed and if they were considered in
the analysis. It gives an overview of the purpose of the respective publication, the allocation method,
type of data, boundaries, if input parameter definitions exist and, based on these, our decision for
consideration and inclusion in the data summaries shown in the results section below.
Sustainability 2018,10, 2881 4 of 14
Table 1. Studies analysed for this paper.
Name Purpose Allocation Method Type of Data Boundary Definitions
(Water/CO2/Land)
Considered
(Yes/No)
Gold Mining in Australia: Linking
Historical Trends and Environmental
and Resource Sustainability [34]
Assess the development of
production and environmental data
of gold mining in Australia
None. By-products
not considered. Company reports
Au: Mine to Metal
(MtM)
Yes/Yes (scope
1)/-(not applicable) Yes (Water only)
Global Trends in Gold Mining:
Towards Quantifying Environmental
and Resource Sustainability [35]
Assess the sustainability of global
gold production in the context of
reporting, declining grades,
increasing efficiency, etc.
No information
provided Company reports Au: MtM Yes/unclear (?)/- Yes (Water only)
Sustainability Reporting and Water
Resources: a Preliminary
Assessment of Embodied Water and
Sustainable Mining [36]
The data have been grouped into
principal ore type to better assess the
effect on grade, scale, and sector
No information
provided Company data
Bauxite (B): Ore
Product (OP), Cu:
MtM, Au: MtM
Yes/-/- No (recycled
water is included)
Water Use in Metal Production:
A Life Cycle Perspective [37]
Estimate water consumption for
several commodities Unknown LCA B: OP, Cu: MtM,
Au: MtM ?/-/- No
Quantifying, Reducing, and
Improving Mine Water Use [33]
Estimate global water withdrawals
of the metals mining sector Economic Company data B: OP, Cu: MtM,
Au: MtM, Fe: OP Yes/-/- Yes
Energy and Greenhouse Gas Impacts
of Mining and Mineral Processing
Operations [38]
Assist the Australian minerals
industry in identifying potential
areas of improvement of their
environmental performance
None. All mines in
LCA produced only
one product
LCA
B: OP, Cu: Mine to
Concentrate
(MtC), Fe: MtC
-/Yes/-
Yes (not Cu due to
boundary
difference)
Using Life Cycle Assessment to
Evaluate Some Environmental
Impacts of Gold Production [39]
Compare refractory to
non-refractory ore. Identify impacts
of various production steps.
Mass and economic
for comparison LCA Au: MtM Yes/Yes/- Yes
Using Sustainability Reporting to
Assess the Environmental Footprint
of Copper Mining [28]
Show opportunities and limits of
reported data for creating
environmental footprints
Economic Company reports Cu: MtM Yes/Yes/- Yes
Assessing the Environmental Impact
of Metal Production Processes [40]Show various impacts
None. All mines in
LCA produced only
one product
LCA Cu: MtM -/Yes/- Yes
Good Practices and the Efficient Use
of Water in the Mining Industry [41]
Show the freshwater consumption of
Chilean copper mines. Compare
concentrators with hydro-metallurgy.
Show development
No information
provided Company data Cu: MtM Yes/-/- Yes
Sustainability 2018,10, 2881 5 of 14
Table 1. Cont.
Name Purpose Allocation Method Type of Data Boundary Definitions
(Water/CO2/Land)
Considered
(Yes/No)
Global Area Disturbed and
Pressures on Biodiversity by
Large-Scale Metal Mining [29]
Estimate the specific direct land use
for Au, Cu, Ag, Bauxite, and iron
ore mining
Economic
USGS satellite images
plus random sample
of mines
B: OP, Cu: MtC,
Au: MtC, Fe: MtC -/-/Yes
Yes (boundary
difference not
material)
Unearthing the Carbon
Footprint [42]Unknown Unknown Value for base
metal ores
Comparable to
[38], but actually
unknown
-/?/- No
Quantifizierung der
Umwelteinwirkung des
Bauxitbergbaus [43]
Quantification of land use for
bauxite mining None Company data
and modelling B: OP -/-/Yes Yes
A Global Environmental Impact
Assessment for Bauxite
Mining—Land Use and Soil
Erosion [44]
Quantification of land use for
bauxite mining None Company data
and modelling B: OP -/-/Yes Yes
Flächeninanspruchnahme des
Kupferbergbaus [45]
Quantification of land use for
copper mining None Company data
and modelling Cu: MtC -/-/Yes
Yes (boundary
difference not
material)
Entwicklung eines
Betriebsübergreifenden
Resourcenmanagementsystems [46]
Quantification of land use for
copper mining None Company data
and modelling Cu: MtC -/-/Yes
Yes (boundary
difference not
material)
Sustainability 2018,10, 2881 6 of 14
For the calculations of the specific environmental pressures and the comparison of results,
this study applies the averages from the literature considered and also provides the minimum and
maximum numbers to show the range identified in the literature. Since the values are from different
years, the authors then update all pressures to 2016 by using the production data from WMD [
7
].
In the cases where no data on gross ore extraction but only data on net metal content are reported,
estimations were required, in order to transform all reported net metal content values into equivalents
of gross ores. For these estimations of ore grades, the data from the UN IRP Global Material Flows
Database [
47
] is used. In the evaluation, the assumption is that the average mined ore grade did
not change and that the specific environmental pressure (e.g., due to process changes or efficiency
gains) remained relatively constant. The authors are aware of the errors implied by these assumptions,
but data availability does not allow for a more accurate estimation.
For comparison, the environmental data publicly reported for 2016 by the top five mining
companies listed in Table 2, who represent between 19% and 68% of mine production for the four focus
metals, is analyzed. Since most of these companies produce multiple commodities and do not report
their data broken down to the commodity level (in some cases the organization of companies is based
on commodity and therefore the data might be reported), an additional survey is used to ask for their
commodity specific data. Finally, the authors extrapolate these data, based on production share, to the
overall 2016 production of each metal, allowing for an approximate comparison of the results from
literature with actual data reported by companies.
Table 2. List of companies and their share of production for each commodity.
Copper (2016) Units Gold (2016) Units
Codelco 1.827 Mt Barrick 5.52 Moz
Freeport-McMoRan
1.696 Mt Newmont 4.9 Moz
Glencore 1.288 Mt Anglo Gold Ashanti 3.63 Moz
BHP 1.113 Mt Goldcorp 2.87 Moz
Southern Copper 0.9 Mt Kinross 2.79 Moz
Share of WMD 33.4 % Share of WMD 19.1 %
Bauxite (2015) Units Iron ore (2015) Units
Rio Tinto 44 Mt Vale 345.9 Mt
Alcoa 38 Mt Rio Tinto 327.6 Mt
Chalco 18 Mt BHP 227 Mt
CBG 15.2 Mt FMG 169.4 Mt
Hydro 10.1 Mt
Share of WMD 43.2 % Share of WMD 68.0 %
Sources: https://www.statista.com/statistics/274260/market-share-of-major-copper-producing-companies/;
http://www.mining.com/update-worlds-top-10- gold-producers/;https://www.alcircle.com/news/bauxite/
detail/26315/top-five-bauxite-mining- companies-in- the-world;https://news.steel-360.com/worlds-top-iron-
ore-producers-h1- 2016/; Company reports, WMD [7]; all links accessed 12 June 2018.
3. Results
Overall, the authors find 16 publications of which 13 are considered in this study, which means
that the number of publications investigating the environmental pressures of mining for iron, bauxite,
copper, and gold is limited to between one and five per commodity.
The variation in the results from the different publications is within a factor of three for the
specific environmental pressure of a commodity, even after considering the selection criteria. In some
cases, the variation of data for mine sites can be within a factor of 100, as in [
28
], with a range of
9.8 to
1046.9 m3/t
Cu of water consumption. This is due to different mine types and processing routes.
The detailed results for CO2, water, and land are described below.
The company survey the authors wanted to use to get more reliable data for comparison had a
very poor response rate. Of the companies listed in Table 2, only one—Rio Tinto—sent back data as
requested. Four companies said that they do not disclose any additional data other than what they
Sustainability 2018,10, 2881 7 of 14
disclose in company reports or to initiatives such as the CDP or sustainability rating organizations
and the remaining companies did not respond at all. Therefore, the comparison of company data with
literature data is very limited, and we are only able to compare specific factors rather than overall
values for 2016. Given these limitations, the numbers are shown below, but the results are not discussed
any further since they show some large variations, which might be explained by variations in the
selection criteria listed above and which are not analysed at this stage, given the very limited company
data. We also do not show the company names in the tables.
3.1. CO2Emissions
Literature on CO
2
emissions is closely linked to literature on energy consumption. Declining ore
grades and the increasing geologic and metallurgical complexity of orebodies are leading to increased
energy demands [
38
] (p. 266), that might ultimately be offset by the development of more energy
efficient technology [
48
] (p. 2). Reporting methods/definitions [
49
], [
30
], emission factors [
28
] (p. 125),
allocation methods, and the minor significance compared to the downstream processes (i.e., aluminium
or steel making) [38] (p. 266) are further key factors in this discussion.
Table 3shows the literature data for all four commodities. Estimations for CO
2
emissions of
copper and gold show a similar variation to water below. It is notable that all values from life cycle
analysis are higher than results from studies based on company reports. Tables 4and 5show the
data (average of studies, minimum and maximum) updated to 2016 and the available company data
for comparison.
The estimations in Table 4show that copper and gold (with both calculation routes delivering
similar results) cause the highest emissions, followed by iron ore and bauxite, which causes by far the
lowest emissions of the four commodities.
The authors estimate that the average of the literature values updated to 2016 is 190.5 Mt of CO
2
emissions for the mining of bauxite, copper, gold, and iron ore based on commodity produced. For ore
based values combined with the global ore processed, the result is very similar at 189.8 Mt respectively.
The minimum and maximum values from literature lead to a range of 149.6 Mt to 233 Mt.
Table 3.
Summary of literature values for CO
2
emissions of bauxite, copper, gold, and iron ore mining.
Bauxite
Max. Min. Average Units Source
Ore 4.9 kg CO2/t [38]
Copper
Metal
8.5 0.9 2.6 kg CO2/kg [28]
3.3 kg CO2/kg [40]
6.2 kg CO2/kg [40]
Gold
Ore 61.7 kg CO2/t [39]
77.2 kg CO2/t [39]
Metal
26,840 kg CO2/kg [39]
17,560 kg CO2/kg [39]
19,520 kg CO2/kg [39]
29,820 kg CO2/kg [39]
Iron Ore
Ore 11.9 kg CO2/t [38]
Sustainability 2018,10, 2881 8 of 14
Table 4. Global CO2emissions of bauxite, copper, gold, and iron ore mining in 2016.
Result of the Literature Review CO2emissions 2016 [Mt]
Bauxite
Ore Average 4.9 kg CO2/t 1.4
Copper
Metal
Average 3.7 kg CO2/kg 75
Max. 4.8 kg CO2/kg 97
Min. 2.6 kg CO2/kg 53
Gold
Ore
Average 69.5 kg CO2/t 74.6
Max. 77.2 kg CO2/t 82.9
Min. 61.7 kg CO2/t 66.3
Metal
Average 23,435 kg CO2/kg 75.3
Max. 29,820 kg CO2/kg 95.8
Min. 17,560 kg CO2/kg 56.4
Iron Ore
Ore Average 11.9 kg CO2/t 38.8
Table 5. CO2data from company sustainability reports and comparison to literature average values.
Commodity Specific CO2Emissions Units Average of Literature Values
Bauxite 10 kg CO2/t 4.9
Copper 2.46 kg CO2/kg Cu 3.7
Copper 8.8 kg CO2/kg Cu
Gold 23,300 kg CO2/kg Au 23,435
Iron Ore 10.39 kg CO2/t
11.9
Iron Ore 9.3 kg CO2/t
Iron Ore 13 kg CO2/t
Global CO
2
emissions from fossil fuels and industry for 2016 are estimated at about 36 Gt [
50
,
51
],
which means that the mining of bauxite, copper, gold, and iron ore contributes approximately between
0.4 and 0.7 percent to these CO
2
emissions. Considering only fossil fuel combustion, the International
Energy Agency (IEA) estimates CO
2
emissions at 32 Gt [
52
], of which 36 percent can be attributed to
industry (p. 12). Using this as a baseline, mining of these four metals contributes between 1.3 and
2 percent of all industrial emissions.
The picture changes completely in consideration of the downstream, highly energy intensive
processes for iron ore/steel and bauxite/aluminium, where emissions for 2016 were about 3.1 Gt [
53
]
(p. 4) and 1 Gt [54].
3.2. Water Withdrawals
Based on the reasons discussed above, i.e., different definitions regarding water withdrawals
and consumption, the literature does not show as much coherence about mine water use as would be
desirable. Gunson [
33
] is the most comprehensive publication dealing with water withdrawals of the
mining industry and he describes this problem of coherence much in the same way.
Table 6shows the literature data for all four commodities. For bauxite and iron ore, little data is
available. For copper production, some publications distinguish pyro-metallurgical production from
concentrate and hydro-metallurgical production without previous concentration. The publications
show that hydro-metallurgical production consumes significantly less water. Tables 7and 8show the
Sustainability 2018,10, 2881 9 of 14
data (average of studies, minimum and maximum) updated to 2016 and the available company data
for comparison.
Table 6. Summary of literature values for water use of bauxite, copper, gold, and iron ore mining.
Bauxite
Max Min Average Units Source
Ore 1.154 0.022 0.404 m3/t [33]
Copper
Ore
3.065 0 0.521 m3/t [33]
0.432 0.1 0.22 m3/t [33]
1.4 0.92 1.16 m3/t [41]
Metal
1046.9 9.8 70.4 m3/t [28]
402.61 0.013 88.03 m3/t [33]
96.18 27.77 48.01 m3/t [33]
Gold
Ore
1.72 0.67 0.88 m3/t [34]
2.87 0.72 1.42 m3/t [35]
10.9 0.003 0.745 m3/t [33]
Metal
666,000 224,000 325,000 m3/t [34]
1,783,000 224,000 691,000 m3/t [35]
259,290 m3/t [39]
288,140 m3/t [39]
4,742,000 610 400,000 m3/t [33]
Iron Ore
Ore 3 0.094 0.598 m3/t [33]
Table 7. Global water withdrawals of bauxite, copper, gold, and iron ore mining in 2016.
Bauxite
Result of the Literature Review Withdrawals 2016 (Mm3)
Ore Average 0.404 m3/t 115
Copper
Ore
Average 0.765 m3/t 1730
Max. 1.16 m3/t 2630
Min. 0.371 m3/t 840
Metal
Average 69.21 m3/t 1413
Max. 70.4 m3/t 1440
Min. 68.02 m3/t 1389
Gold
Ore
Average 1.015 m3/t 1090
Max. 1.42 m3/t 1530
Min. 0.745 m3/t 800
Metal
Average 422,428.75 m3/t 1358
Max. 691,000 m3/t 2221
Min. 273,715 m3/t 880
Iron Ore
Ore Average 0.598 m3/t 1950
Sustainability 2018,10, 2881 10 of 14
Table 8.
Water data from company sustainability reports and comparison to literature average values.
Commodity Specific Withdrawals Units Average of Literature Values
Bauxite 0.604 m3/t 0.404
Copper 245 m3/t 69.21
Gold 0.379 m3/t 1.015
Iron Ore 1.047 m3/t 0.598
Iron Ore 1.410 m3/t
As Table 7shows, iron ore causes the largest water withdrawals, followed by copper and
gold (with some variation in the calculation routes) and once again bauxite with the lowest
water withdrawals.
The sum of the global water withdrawals we estimated from the minimum and maximum values
from literature for bauxite, copper, gold, and iron ore mining in 2016 is between 3705 and 6225 Mm
3
,
with an average of about 4850 Mm3.
To put these numbers into a global context: The Food and Agriculture Organization of the United
Nations (FAO) estimates the global water withdrawal for 2010 as almost 4000 Gm
3
, with industrial
withdrawals accounting for about 19 percent [
55
]. Assuming the same growth rate as in the years
1900–2010 of about 31 Gm
3
per year for the years 2010–2016, bauxite, copper, gold, and iron ore
mining is in a range of 0.09 and 0.15 percent of global water withdrawals and 0.46 and 0.78 percent of
industrial withdrawals.
Same as for CO
2
emissions, this changes significantly if downstream water withdrawals for
steelmaking (estimated at 45.8 Gm
3
based on [
56
] (p. 4)) and aluminium production (estimated at
1.3 Gm3based on [54] (appendix A)) are considered.
3.3. Land Use
According to S&P Global Market Intelligence there are over 36,000 mining properties in the world [
15
].
Estimates for the global area disturbed by mining range from 0.3 [
57
] to 1 [
58
] percent of terrestrial land
surface. The estimations have in common that they are vague. Either the basis for the estimation is unclear
as in the case of Norse et al. [
59
], suggesting a global area disturbed by mining of 0.5 to 1.0 Mkm
2
, or data
was only available for some countries and the global estimate is an extrapolation [57].
A key publication on the subject is by Murguia [
29
], who based his study on mine sites visible on
satellite images. Table 9shows the specific values from literature for land use for each commodity analyzed
in this paper. The data is complemented by older studies on direct land use for copper and bauxite.
Table 9. Summary of literature values for land use of bauxite, copper, gold, and iron ore mining.
Bauxite
Ore
Max Min Average Units Source
7.98 ha/Mt [29]
21 ha/Mt [43]
13 ha/Mt [44]
16 ha/Mt
International Aluminium Institute, 2009, cited in [
29
]
Copper
Ore
4.5 ha/Mt [29]
2.3 ha/Mt [45]
2 ha/Mt [46]
Gold
Ore Max Min Average Units Source
6.7 ha/Mt [29]
Iron Ore
Ore Max Min Average Units Source
4.25 ha/Mt [29]
Sustainability 2018,10, 2881 11 of 14
Tables 10 and 11 show the data (average of studies, minimum and maximum) updated to 2016
and the available company data for comparison.
Table 10. Newly disturbed global land use for bauxite, copper, gold, and iron ore mining in 2016.
Bauxite
Result of the Literature Review Land Use 2016 (km2)
Ore
Average 14.5 ha/Mt 41.3
Max. 21.0 ha/Mt 59.8
Min. 7.98 ha/Mt 22.7
Copper
Ore
Average 2.9 ha/Mt 66
Max. 4.5 ha/Mt 100
Min. 2 ha/Mt 45
Gold
Ore Average 6.7 ha/Mt 72
Iron Ore
Ore Average 4.25 ha/Mt 139
Table 11.
Land data from company sustainability reports and comparison to literature average values.
Commodity Specific Land Use Units Average of Literature Values
Bauxite 23 ha/Mt
14.5
Bauxite 33.2 ha/Mt
Bauxite 107.6 ha/Mt
Iron Ore 11.86 ha/Mt 4.25
To sum up, 318 km
2
have been newly disturbed by mining of bauxite, copper, gold, and iron ore
in 2016 using the average values from literature, with a range of 278 km
2
to 370 km
2
using minimum
and maximum values. Since the area is very small, we did not put this in a global context.
Murguia also calculated the cumulative net area disturbed for these four commodities in 2011
as 11,485 km
2
[
29
] (p. 163) and looked into the types of land disturbed as a proxy for the impact
on biodiversity.
4. Discussion
In this paper, the authors analysed three categories of environmental pressures—CO
2
-emissions,
water use, and land use—related to global mining of bauxite, copper, iron ore, and gold-making results
indicative for metal mining. The available numbers show that in absolute terms and on the global
level the overall dimension of the pressures put on the environment—about 190 Mt of CO
2
emissions,
4850 Mm
3
of water use and 318 km
2
of newly disturbed land in 2016—are comparably low However,
this must not be seen as a charter to not taking mining activities into environmental considerations.
These remain relevant, especially as the local impacts are increasing, and will do so even more in the
future, as demand for metals increases and accessibility declines. These numbers change of course
significantly for CO
2
emissions and water use in the case of iron ore and bauxite when including the
production of steel and aluminium in the analysis.
The data review reveal that, to carry out such environmental analyses, available data are still
very limited, and there are significant gaps in comparability of different sources, especially related
to the identified boundary conditions (including type of mine and process routes), input parameter
definitions, and the applied allocation methodology. Hence, further work is needed to align these
assessments with the identified criteria. Another key limitation is the lack of detailed reporting of
Sustainability 2018,10, 2881 12 of 14
environmental data at the company level, a concern which Mudd [
36
] and Northey et al. [
28
] raised in
their studies and which has not changed since. Similar to (economic) production data, where this is
largely already the case, environmental data would need to be reported consistently, at the commodity
and at the site, ideally even process, level. This would allow for further comparison of process routes
and technologies, but also for better modelling of future environmental pressures from increased metal
demand, as well as better policy making related to metal mining, for example in areas such as mining’s
role in achieving the Sustainable Development Goals (SDGs), the circular economy, responsible supply
chain management, and trade agreements or the transition of our energy system towards a low
carbon footprint.
Suggesting a way forward to overcome these limitations, organizations like GRI, ICMM, and the
commodity specific associations should collaborate to define (and standardize) the criteria mentioned
above and update standards for companies to report at the site level. Data providers such as WMD,
USGS, or S&P should then think about broadening their services to include environmental (and social)
data in their products.
Author Contributions:
Conceptualization, M.T.; Methodology, M.T. and B.B.; Validation, M.H., S.L., and P.M.;
Formal Analysis, B.B., M.T., and S.L.; Investigation, B.B. and M.T.; Writing—Original Draft Preparation, M.T.;
Writing—Review & Editing, M.H., S.L., and S.F.; Supervision, M.H. and P.M.
Funding: This research received no external funding.
Acknowledgments:
The authors would like to acknowledge the cooperation and assistance of Diego Murguia and
Aaron Gunson concerning questions about their studies and would like to express appreciation to the anonymous
reviewers, who helped to improve this paper.
Conflicts of Interest: The authors declare no conflict of interest.
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... No hard rock operational data was found. Land disturbed in HMS mining is higher than that seen for copper extraction at 2-4.5 ha/MT of ore, and comparable to iron ore at 4.25 ha/Mt ore but was significantly lower than bauxite which requires 7.98-21 ha/Mt ore (Tost et al., 2018). No correlation between land disturbed and mined grades were found; this is likely because the land disturbed during any one year does not necessarily correspond to ore mining (i.e. ...
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