Supplementary Information for submission to resource, conservation and recycling

Component- and alloy-specific modeling for evaluating aluminum recycling strategies for vehicles

Authors:

Roja Modaresi1)*, Amund N. Løvik1), Daniel B. Müller 1)

1) Industrial Ecology Programme (IndEcol), Department of Energy and Process

Engineering - EPT, NTNU, NO-7491 Trondheim

Roja Modaresi Phone: +47 -735 93194 E-mail: [email protected] Industrial Ecology Programme and Department of Energy and Process Engineering - EPT Norwegian University of Science and Technology (NTNU)

NO-7491 Trondheim Norway

Amund N. Løvik Phone: +47 -735 93194 E-mail: [email protected] Industrial Ecology Programme and Department of Energy and Process Engineering - EPT Norwegian University of Science and Technology (NTNU) NO-7491 Trondheim Norway

Daniel B.Müller Phone: +47 -735 94754 Fax: +47 -73591298 E-mail: [email protected] Industrial Ecology Programme and Department of Energy and Process Engineering - EPT Norwegian University of Science and Technology (NTNU) NO-7491 Trondheim Norway

1. Model formulation Determining the vehicle stock and flow: The basic principle of the global dynamic MFA model is described in a previous paper (Modaresi and Müller, 2012) and here the SI explains

1 the aspects specific to this application. Figure S1 shows the dynamic model for aluminium in passenger cars. There are two steps in the model calculation. First, vehicle stocks and flows are calculated for the five car segments. Subsequently, aluminium stocks and flows are determined, in 14 different components. The parameters are population (Pop), lifestyle as vehicle per capita (Vp), vehicle lifetime (L), penetration of car segments, and aluminium content for the distinguished component and segments. All these parameters are functions of time. For each of these 14 component groups, the content of various alloy classes (1xxx,

3xxx, 5xxx, 6xxx, 2xxx/7xxx/6xxx with Cu content >1%, 4xxx + low impurity cast alloys, and cast high Si (high impurity cast alloys) are defined, and assumed that alloy content is valid for the whole period of time.

Reliable information for the lifetime distribution is essential for determining current and future ELV flows, and for designing ELV management strategies. Result of evaluation of different distribution functions such as weibull distribution, and lognormal compared to normal distribution in a study for service lifetimes of minerals end uses from U.S.G.S shows that passenger cars tend to follow normal distributions function(Müller et al. , 2007)

2 Mathematical illustration for stock, inflow and outflow calculation is shown in figure S2 and equations (S1) and (S2). S0 denotes the initial stock in the year 0 and stock change (∆St) for each year is St+1 – St. input of new and output of retired passenger cars is determined by a given stock development and lifetime. The lifetime is estimated assuming a normal distribution with mean τ and standard deviation σ:

(S1)

(S2)

Figure S2: System of in-use stocks. I is the input into use, O the output from use, and ∆S is the rate of change in stock. t’ is the vintage year (year of manufacturing), t the actual time of the system state.

3 2. Parameter estimation Population (Pop): Population data are estimated using UN national population statistics and the UN Population Projection is used for the scenarios (UN, 2003, 2010). Base scenario is the medium growth assumption with a thick line in figure 2.

Vehicle ownership (Vp): Passenger car stock data were compiled and used to estimate weighted-average vehicle ownership on a global scale (Mitchell, 2007a, b, c, UN, 2010).

Future scenarios for car ownership are estimated based on regional IEA projections (IEA,

2010) and other studies(Joyce Dargay, 2007). All scenarios assume a logistic growth in car ownership with saturation around 2100. The saturation levels were chosen to be 450cars per

1000 capita in this study.

Life time (L): Based on previous studies on the lifetime from the US, Norway and Japan

(Kagawa et al. , 2011, Müller, Cao, 2007, Scacchetti, 2009), we assume for the global level a constant lifetime approximated using a distribution function with a mean (τ) of 16 years and a standard deviation (σ) of 3 years. We further assume that the lifetime of aluminium components in cars is the same as the lifetime of the cars. A lifetime analysis for passenger cars in the U.S. using combined vintage output approach showed 15.9 years (Müller, Cao,

2007). In a case study from Norway by analysing stock dynamics of car vintages, the result shows that the lifetime of a car in Norway is between 15 to 19 years. The average age of

ELVs has been variously estimated at 15.3 years (Netherlands, 2004), 12.1 years (UK) and more than 11 years (Hungary). In the UK, TRL (2003) estimated the average age of ELVs as a whole at 12.1 years, with the average age of natural end of life vehicles at 12.8 years(Kagawa et al. , 2011).

Alloy composition for vehicle groups: Each of the 14 component groups is produced using different alloys (see figure 2). It is assumed that the share of an alloy in a component does not differ between years, and is valid for the entire time series. The following alloys categories

4 are differentiated: 1xxx, 3xxx, 5xxx, 6xxx, 2xxx/7xxx/6xxx with Cu>1%, 4xxx + cast alloys

(AlSi, AlMg) with low alloying/impurity content (<0.5% each), and cast alloys with high

silicon content and higher alloying/impurity contents. Table S1 shows the alloy composition

for vehicles components.

Table S1: Alloy composition for vehicle components.

Allo ys categories 4xxx + cast 2xxx/7xxx/ alloys with High Si Components 1xxx 3xxx 5xxx 6xxx 6xxx low impurity cast alloys C1 0 % 0 % 40 % 45 % 0 % 15 % 0 % C2 0 % 0 % 35 % 65 % 0 % 0 % 0 % C3 0 % 0 % 5 % 80 % 15 % 0 % 0 % C4 75 % 25 % 0 % 0 % 0 % 0 % 0 % C5 45 % 25 % 5 % 5 % 0 % 20 % 0 % C6 0 % 0 % 0 % 0 % 0 % 45 % 55 % C7 0 % 0 % 40 % 20 % 0 % 40 % 0 % C8 0 % 0 % 5 % 80 % 0 % 15 % 0 % C9 0 % 0 % 0 % 10 % 0 % 90 % 0 % C10 0 % 0 % 0 % 10 % 0 % 10 % 80 % C11 0 % 0 % 10 % 30 % 0 % 60 % 0 % C12 0 % 0 % 5 % 10 % 5 % 0 % 80 % C13 0 % 0 % 10 % 25 % 0 % 25 % 40 % C14 30 % 5 % 10 % 40 % 0 % 15 % 0 %

ELV index: ELV indexes are based on experts assumptions considering economical

feasibilities with the current available technology (EAA, 2012). The following three ELV

indexes are assigned to the parts (see figure 2):

ELV1 = Components which are easy to dismantle and to separate into alloy groups. For

instance, wheels (C9) has ELV1= 100%, which means they are easily dismantled. While

ELV1 is equal to zero for BIW (C1), and components C10:14.

ELV2 = Components which are possible to dismantle, but present some difficulties. A fraction

of closures, engine blocks and cylinder head, and other engine components are among these

components.

5 ELV3 = Components which are difficult to dismantle and separate into alloy groups, and therefore have to be shredded. For instance, brake components (C11), and other steering components (C13) are among those that end up in shredders.

Based on the ELV indexes, the sum of ELV1 and ELV2 is considered as a high dismantling strategy.

3. Source-sink diagram The calculation of the alloy-recycling matrix: The alloy recycling matrix (fig. 1) illustrates the maximum recycled content for combinations of two alloys, one as the produced alloy

(sink) and the other as scrap (source). The calculations are based on the chemical composition limits given by industry standards (ASTM International, 2011, The Aluminum Association,

2009) and includes 9 elements as potential limiting factors: Al, Si, Fe, Cu, Mn, Cr, Zn, Ni and

Ti. Magnesium was not considered because it is partially lost in the remelting process and may be removed further by chlorination if necessary. Composition limits are given as ranges with a lower and an upper level for each element. The chemical composition limits are given in table S2.The maximum recycled content can be calculated as:

cmax RC = sink max cnom source (2)

cmax cnom Here, sink is the upper limit of the limiting element in the produced alloy, and source is the nominal concentration in the source alloy. In reality, producers will use narrower ranges than what is given in specifications, and therefore, the figure is slightly on the optimistic side.

Aluminum itself can also be considered as a limiting element in cases where the sink alloy requires high concentrations of alloying elements. The chemical composition limits are given in table S2.

6 Table S2 Composition limits for 10 typical automotive alloys (ASTM International, 2011, The Aluminum Association, 2009)

Si Fe Cu Mn Mg Cr Ni Zn Ti 1070 0-0.2 0-0.25 0-0.03 0-0.03 0-0.03 0-0.03 0-0.03 0-0.07 0-0.03 3103A 0-0.5 0-0.7 0-0.1 0.9-1.5 0-0.3 0-0.1 0-0.05 0-0.2 0-0.1 5182 0-0.2 0-0.35 0-0.15 0.2-0.5 4.0-5.0 0-0.1 0-0.05 0-0.25 0-0.1 5754 0-0.4 0-0.4 0-0.1 0-0.5 2.6-3.6 0-0.3 0-0.05 0-0.2 0-0.15 6061 0.4-0.8 0-0.7 0.15-0.4 0-0.15 0.8-1.2 0.04- 0-0.05 0-0.25 0-0.15 6082 0.7-1.3 0-0.5 0-0.1 0.4-1.0 0.6-1.2 0-0.250.35 0-0.05 0-0.2 0-0.1 A356 6.5-7.5 0-0.2 0-0.2 0-0.1 0.25-0.45 0-0.05 0-0.05 0-0.1 0-0.2 301 9.5-10.5 0.8-1.5 3-3.5 0.5-0.8 0.25-0.5 0-0.03 1.0-1.5 0-0.05 0-0.2 319 5.5-6.5 0-1.0 3.0-4.0 0-0.5 0-0.1 0-0.5 0-0.35 0-1.0 0-0.25 A380 7.5-9.5 0-1.3 3.0-4.0 0-0.5 0-0.1 0-0.5 0-0.5 0-3.0 0-0.5

Alloys selection

1070A: The 1xxx-series alloys are essentially unalloyed aluminium, with a minimum aluminium content of 99%. Formability, good corrosion resistance and high heat conductivity are characteristics that grant these alloys application in components such as heat exchangers and heat shields (EAA, 2011). The alloy 1070A was chosen as an example with intermediate impurity levels between those of 1050 and 1100. For the purpose of the calculations, it does not make a significant difference, as their capacity to absorb scrap is close to zero, and it will be unproblematic to use 1xxx alloys as source material for any of the other alloys shown.

3103: The 3xxx-series alloys are little used in vehicles compared to 6xxx or 5xxx, but might be important from a recycling perspective because manganese, the main alloying element, is undesirable in many of the other alloys. Main applications are fins and tubes in heat exchangers, due to high formability and corrosion resistance, and medium strength (Kaufman,

2002). Typical alloys are 3003 and 3103 (EAA, 2011, Rossel, 1998), which have similar concentration ranges for all elements.

5182 and 5754: Alloys with magnesium as the main alloying element (typically 2-5%) have excellent corrosion resistance, toughness and weldability, and can be strain hardened for

7 improved strength (Kaufman, 2002). In passenger cars they may be used in sheet form in for example axle subframes, structural BIW components and inner panels of doors and hoods. doors or hoods. Alloy 5754 is a typical choice where temperatures might exceed 80°C; in other cases 5182 may be used for increased strength (Benedyk, 2010, EAA, 2011, Fridlyander et al. , 2002, Koganti and Weishaar, 2008).

6061 and 6082: The 6xxx-series alloys are alloyed mainly with silicon and magnesium, and may be strengthened by heat treatment. They are used in both sheet and extruded form, and in many different parts of the vehicle. Alloys 6061 and 6082 are typical selections where a higher strength is required, for example in bumpers, suspension arms or wheels (EAA, 2011,

Koganti and Weishaar, 2008, Yotsuya G and Yamauchi R, 2013), 6061 being more common in the U.S. and 6082 in Europe (Benedyk, 2010, EAA, 2011).

A356, 301, 319 and A380: Cast alloys with silicon and copper or silicon and magnesium belong to the 3xx-series and are the most widely used of cast alloys. Silicon levels may reach up to 20%, and there is often a high concentration of other alloying elements (ASTM

International, 2011). Alloy A356 was chosen as an example of a primary cast alloy, being widely used in wheels, as well as other structural components such as suspension frames or body-in-white (Benedyk, 2010, EAA, 2011, Tirelli et al. , 2011). Alloy 301, commonly used in pistons, contains around 1% Ni, and was included in the figure mainly to illustrate how the diversity of cast alloys may further complicate recycling. Alloys 319, A380 and variations, used in cylinder heads and engine blocks (Bendyk 2010; European Aluminium Association

2011), are the most important secondary alloys in terms of production volume (Bray, 2012) and currently the main sinks for scrap.

8 References

ASTM International. ASTM B179-11 Standard Specification for Aluminum Alloys in Ingot and Molten Forms for Castings from All Casting Processes. ASTM International; 2011. Benedyk JC. Aluminum alloys for Iight weight automotive structures. 2010. Bray EL. USGS Aluminum minerals yearbook 2011 U.S. Geological Survey2012. EAA. The Aluminium Automotive Manual. 2011. EAA. ELV index. 2012. Fridlyander IN, Sister VG, Grushko OE, Berstenev VV, Sheveleva LM, Ivanova LA. Aluminum alloys: Promising materials in the automotive industry. Metal Science and Heat Treatment. 2002;44. IEA. Energy Technology Perspectives, Scenarios Strategies to 2050 Paris: OECD/IEA; 2010. Joyce Dargay DGaMS. Vehicle Ownership and Income Growth, Worldwide: 1960-2030. Institute for Transport Studies, University of Leeds; 2007. Kagawa S, Nansai K, Kondo Y, Hubacek K, Suh S, Minx J, et al. Role of Motor Vehicle Lifetime Extension in Climate Change Policy. Environmental Science & Technology. 2011;45:1184-91. Kaufman JG. Applications of aluminum alloys, in Handbook of Materials Selection: John Wiley & Sons, Inc., New York; 2002. Koganti R, Weishaar J. Aluminum Vehicle Body Construction and Enabling Manufacturing Technologies. SAE Int J Mater Manuf. 2008;1. Mitchell BR. International historical statistics: Africa, Asia & Oceania, 1750-2005. Houndmills: Palgrave Macmillan; 2007a. Mitchell BR. International historical statistics: Europe 1750-2005. Houndmills: Palgrave Macmillan; 2007b. Mitchell BR. International historical statistics: the Americas 1750-2005. Houndmills: Palgrave Macmillan; 2007c. Modaresi R, Müller DB. The role of automobiles for the future of aluminum recycling. Environmental Science and Technology’. 2012. Müller DB, Cao J, Kongar E, Altonji M, Weiner P-H, Graedel aTE. Service Lifetimes of Mineral End Uses. U.S. Geological Survey (USGS),; 2007. Rossel H. New recycling approach- generation of aluminum wrought alloy scrap of old cars. Light metals, edited by Barry Welch. 1998:7. Scacchetti S. Stock Dynamics Model for Forecasting Aluminum Flows in the Norwegian Passenger Car System: Norwegian University of Science and Technology; 2009. The Aluminum Association I. International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys. 2009. Tirelli MA, Colosio MA, Santos JC. Evaluation of Aluminum Wheels with Focus on Specification Materials and Manufacturing. SAE Technical Paper Series. 2011;36. UN. World Population In 2300 In: Devision UNS, editor.: Department of Economic and Social Affairs; 2003. UN. Statistical Yearbook. United Nations, New York. In: Devision UNS, editor.2010. Yotsuya G, Yamauchi R. Lightening Approach for Small Vehicles by Developing Extruded Aluminum Suspension Arm. SAE Int J Mater Manf. 2013;6.