1
ELEC TRONIC SUPPLEMENTARY MATERIAL
ASSESSING AND MANAGING LIFE CYCLES OF ELECTRIC VEHICLES
Environmental impact of traction electric motors for electric vehicles applications
Maria Hernandez1 • Maarten Messagie1 • Omar Hegazy1 • Luca Marengo2 • Oliver Winter3 • Joeri Van
Mierlo1
Received: 29 January 2015 / Accepted: 24 September 2015
© Springer-Verlag Berlin Heidelberg 2015
Responsible editor: Steven B. Young
1
Vrije Universiteit Brussel, Faculty of Engineering, Mobility and Automotive Technology Research Group
(MOBI), Pleinlaan 2, 1050 Brussels, Belgium
2
Centro Richerche Fiat S.C.p.A, R&D Product Development, Strada Torino 50, 10043 Orbassano (TO),
Italy
3
AIT Austrian Institute of Technology GmbH, Mobility Department Electric Drive Technologies, 1210
Vienna, Austria
 Maria Hernandez
mahernan@vub.ac.be
2
Index
Production of rare earth elements…………………………………………………………………………2
Environmental concerns in the production of REE………………………………………………..5
Assumptions in the production of REE magnets….......................................................................6
List of tables
Table 1 Mass of materials (NdFeB permanent magnet)
Table 2 Inputs in magnet manufacturing process
Production of rare earth elements
Rare earth elements (REEs) are a group of 15 chemical elements in the
periodic
table:
cerium (Ce), dysprosium (Dy),
erbium
(Er), europium (Eu),
gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd),
praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium
(Tb),thulium (Tm), ytterbium (Yb) and yttrium (Y). Due to their strong affinity
with oxygen, REEs are primarily present as oxidic compounds.
These
elements
are
part
of
important
components
of
many
emerging
technologies and products, such as electric and hybrid vehicles, wind turbines,
and cell phones. Given this increasing global demand for green and sustainable
products in transport, energy production and manufacturing industries, REE
demand throughout the world is expected to increase. For the moment, the
production of rare earth oxides (or REOs) is highly concentrated in China, and
so it is the market for REOs, well consolidated in this one region of the world.
In consideration of this, the modelling in the study, ore types and processes
for extraction of Rare earth element (REE), processing and final manufacturing
of REE magnets, will follow the practices used in China.
3
Rare earth elements are not available as elemental metals in nature, but they
take part in a host mineral’s chemistry. For this reason the extraction and
production of REE can be complex, as it requires the separation and break
down of the material for the extracted mineral ore. Four principal stages can
be identified in the extraction and processing of REEs: (1) mining; (2)
beneficiation processes; (3) extraction processes; and (4) reduction. In our
study these stages are modeled using Ecoinvent V2.2 database. The processes
included by the database and their description, summarized from EPA (2012),
are explained below:
1) Mining
The methods used for mining of REE are in principle the same ones used for
the extraction of other metal ores, namely surface or underground mining in
hard rock, or in situ leaching. The method selected for the extraction of the
mineral will depend on the conditions (size and location of deposit), the type
of mineral ore, and the variety of accompanying elements that can be
extracted simultaneously.
Reference
EPA (2012) Rare Earth Elements: A Review of Production, Processing, Recycling,
and Associated Environmental Issues. EPA 600/R-12/572.
The two most common mining methods used are described:
In Situ Leach Mining: this is a method used commonly when the metal deposit
is deep
or whenthe ore grade is low. It consists of the injection of fluids such
as, water, acids or other chemicals through a circuit of drilled boreholes caved
around the mineral deposit. An ore containing solution is then pumped from
the deposit, which is then processed with a solvent extraction method in order
to recover the valuable metals.
Surface and Underground Mining: as for other conventional metals, surface and
underground mining for REEs, involves the use of explosive, excavators and
drilling equipment and removal equipment for waste rock and ore material.
Underground and open-pit mining are the more conventional methods used in
the hardrock mining industry, and they both generate large amounts of
overburden piles and waste rocks, that in some cases may be used as coproduct for other industries.
4
From the mining activities, two major mineral sources of REEs are obtained:
bastnasite and monazite. There is a wide variety of minerals from which REEs
can be obtained, including xenotime, apatite, yttrofluorite, cerite, and gadolinite,
however
they areless common.
In this study, the process includes material and energy input, emissions and
land use for the open-pit mining, and extraction of bastnasite ore, with a rare
earth oxide concentration of 6 %, as similar to conditions in China. Transport
and infrastructure required are also included.
Fig.
1
shows
a
representation
of
mining
process,
and
waste
managementassociated, until the final processing of REO concentrate:
Figure S1
Conventional hardrock resource processing and potential wastes
Mining
Mine water
Overburden
Waste rock
Sub-ore
Stockpile
Ore
Stockpile
Grinding
Flotation
Tailings
Acid digestion
Thickening
Rare earth
Drying
REO
concentrate
separations
Liquid wastes
Product
managementunit
Process
Waste management
5
(excluding emissions) diagram (Source: EPA 2012)
2) Beneficiation Processes
The beneficiation process involves the separation of the rare earth elements
from the mineral (bastnasite and monazite), without modifying the chemical
composition of the ore. Normally iron and other less valuable minerals are
separate. Crushing and grinding steps enable the grains of various minerals to
be separated from each other. Later separation processes typically employed
include (1) gravity separators, (2) electrical/magnetic separators, and (3)
flotation
separators.
The
end
result
of
the
beneficiation
process
is
a
concentrate containing high percentages of rare earth bearing minerals. We
have considered for this study mineral concentration by flotation separation
process, obtaining rare earth concentrate product with 70 % rare earth oxide.
3) Extraction Processes
Hydrometallurgy, pyrometallurgy and electrometallurgy are three rare earth
extraction methods used, hydrometallurgy being
the most common chemical
extraction method of separating individual REOs from the mineral concentrate.
Leaching, extraction, and precipitation are typical hydrometallurgy techniques
that allow the separation of mineral concentrates until the obtaining of usable
rare earth oxides.
Basicity differences between the various rare earths allow
the further separation by fractional crystallization, fractional precipitation, ion
exchange, and solvent extraction from which the individual REOs are obtained.
Although some of the individual co-products (REOs and rare earth chlorides
resulting from these processes) have market value, further processing and
refining are required to produce high-quality pure metal end products to
maximize value. This study includes leaching process using HCL. It includes
roasting and cracking of the rare earth concentrate with 98 % sulphuric acid,
as used in China. For the following separation of the different rare earth
oxides solvent extraction is used.
4) Reduction Processes
Further processing by techniques such as metallothermic reduction can refine
the oxides or metal mixtures into high-purity REMs. Due to their high stability
further purification of REOs can be difficult to achieve. Several methods have
been developed to accomplish this task. The three primary methods of
producing rare earth metals are (1) reduction of anhydrous chlorides or
fluorides, (2) reduction of REOs, and (3) fused salt electrolysis of rare earth
6
chlorides or oxide-fluoride mixtures. In our study reduction of REOs is
considered and the obtained rare earth oxide final product has a purity of up
to 99.9 %.
Environmental concerns in the extraction of REE
The main environmental concerns of REE extraction and early processing have
being associated to the mining activities for the metals, and particularly the
emissions
and
wastes
generated
during
this
activities
due
to
improper
treatment and disposal. These emissions typically contain high-surface-area
particles, wastewater, and process chemicals. In normal conditions these agents
can be adequately control and managed, however in impoundment areas,
exposed to weathering conditions, they have the potential to contaminate the
air, soil, surface, and groundwater. Typical pollutants that have been associated
with rare earth extraction and processing are:
-
ore-associated
metals
(e.g.,
aluminum,
arsenic,
barium,
beryllium,
cadmium, copper, lead, manganese, zinc);
-
radionuclides;
-
radon;
-
fluorides;
-
sulfates;
Fugitive dust can contaminate the air and surrounding soil. Similarly, surface
water runoff from precipitation events can transport pollutants from the
impoundment to surrounding soil and surface waterbodies, or contamination of
surrounding groundwater resources. However, these situations can be prevented
with adequate management of mining and the set in place of remediation
techniques for pollution control.
Assumptions in the production of REE Magnets
For the production of the magnet, we consider a stoichiometric composition of
the magnet in order to estimate the amount neodymium oxide, boric oxide and
iron necessary for the manufacturing. The magnet will have a nickel coating
assumed to be equivalent to 10% of the total weight of the magnet.
Table S1
Molecule
Nd2Fe14B
Nd2O3
Mass of materials (NdFeB permanent magnet)
Moles
Weight (%)
1
1
31.12
Mass (kg)
Material
1 Neodymium magnet
0.3112 Neodymium oxide
7
B2O3
Fe
Table S2
0,5
14
3.22
72.32
0.0322 Boric oxide
0.7232 Iron
Inputs in magnet manufacturing process
Data
Neodymium oxide
Pig iron
Boric oxide
Nickel coating
Electricity, medium voltage, at
grid, CN
Unit
Kg
Kg
Kg
Kg
kWh
Amount
Remarks
0.68
1.59
0.07
0.25
15.25