Dynamics of aluminum use in the global passenger car system: Challenges and solutions of recycling and material substitution
Doktorsavhandling, 2015

This thesis analyzes the relationship between the design of vehicles, end-of-life vehicle

(ELV) management, and global material production using aluminum as an example.

Vehicle manufacturing, material industries and ELV management face different

challenges. An important challenge for vehicle manufacturers is the design of

lightweight vehicles to reduce energy use and greenhouse gas (GHG) emissions in the

use phase for which an increased use of aluminum of different alloys is an attractive

option. The aluminum industry has an interest in reducing energy consumption and

GHG emissions, which can be accomplished effectively through recycling. ELV

management must be improved to enable the first two systems to use aluminum scrap in

a sustainable manner. Today, the sorting of different alloys is limited. As a result of

having mixed scrap at the ELV phase and limited opportunities for aluminum refining,

there may be a future scrap surplus that cannot be absorbed by the aluminum-recycling

sink, which is passenger cars. These three sectors are connected through material flows,

and a change in one of the sectors can severely affect the others' options for reaching

their goals.

This thesis addresses the following questions: 1) How are the dynamics of the global

vehicle stock changing the boundary condition for aluminum recycling? 2) What are the

most effective interventions to minimize a future aluminum scrap surplus? 3) What are

the options for material substitution in vehicles to reduce direct and indirect GHG

emissions over time?

To answer these questions, a system approach is employed to analyze how these three

sectors are linked and to explore options for all sectors to reach their objectives in the

long term. This thesis employs global bottom-up stock-driven models of the aluminum

cycle. A basic model was used to identify the scrap surplus problem. A refined model

with segments, components and alloys resolution combined with a source-sink diagram

was used to evaluate different solution options. In addition, a global dynamic fleetrecycling

MFA model was developed to simulate the future impacts of material

substitutions of conventional steel with high-strength steel (HSS) and aluminum on

material cycles, energy use and GHG emissions related to the global passenger vehicle


The main findings in this thesis are: i) a continuation of the current practice of cascadic

use would eventually result in a scrap surplus because this practice depends on the

continuous and fast growth of the secondary casting stock in the global vehicle fleet, a

condition that is unlikely to be met. Model simulation indicated a non-recyclable scrap

surplus by approximately 2018±5 if no alloy sorting is introduced. The surplus is

potentially substantial and could grow to reach a level of 0.4-2 kg/cap/yr by 2050,

thereby significantly reducing the option of the aluminum industry to reduce its energy

consumption through recycling. ii) Drastic changes in ELV management practices are

necessary to make use of the growing scrap flow in the future, including further

dismantling and efficient component-to-component recycling, alloy sorting of mixed

shredded scrap, and designing recycling-friendly alloys that function as alternative sinks

for aluminum scrap. iii) Light-weighting has the potential to substantially reduce global

emissions of vehicles (9-18 gigatons cumulative CO2-eq. between 2010 and 2050). In

the medium term (5-15 years), global emissions reductions from substituting standard

steel with aluminum are similar to those achievable by HSS; however, over a longer

term (after 15-20 years), substitution with aluminum can reduce total emissions more

effectively, provided that the wrought aluminum will be recycled back into automotive

wrought aluminum.

The environmental consequences of products in general and passenger cars in particular

have led to an increasing awareness of the dependencies between the shaping of

vehicles and the shaping of the environment. Governments and intergovernmental

bodies have formulated quality goals for the environment, such as the 2-degree target,

and have introduced emissions standards, thereby extending the responsibility of

automobile manufacturers to the use phase. On the materials side, legislation has been

introduced to extend producer responsibility, mainly with the goal of avoiding toxic

substances and reducing the amount of waste, as is noted in different end-of-life vehicle

(ELV) legislation and directives. The current ELV directives do not sufficiently address

the management of material systems as a whole or quality issues related to material

recovery. To harmonize ELV management with goals for the global aluminum cycle and

its impacts for the environment, it is essential to understand how the above-mentioned

systems interact.
Has parts
Paper 1: Modaresi, Roja; Müller, Daniel B.. The Role of Automobiles for the Future of Aluminum Recycling. Environmental Science and Technology 2012 ;Volum 46.(16) s. 8587-8594 http://dx.doi.org/10.1021/es300648w Copyright © 2012 American Chemical Society

Paper 2: Rombach, Georg; Modaresi, Roja; Müller, Daniel B.. Aluminium Recycling- Raw Material Supply from a Volume and Quality Constraint System. World of Metallurgy - ERZMETALL 2012 ;Volum 65.(3) s. 157-162

Paper 3: Modaresi, Roja; Løvik, Amund Nordli; Müller, Daniel Beat. Component- and Alloy-Specific Modeling for Evaluating Aluminum Recycling Strategies for Vehicles. JOM: The Member Journal of TMS 2014 ;Volum 66.(11) s. 2262-2271., The article is not included due to copyright available at http://dx.doi.org/10.1007/s11837-014-0900-8

Paper 4: Løvik, Amund Nordli; Modaresi, Roja; Müller, Daniel Beat. Long-term strategies for increased recycling of automotive aluminum and its alloying elements. Environmental Science and Technology 2014 ;Volum 48.(8) s. 4257-4265 http://dx.doi.org/10.1021/es405604g Copyright © 2014 American Chemical Society

Paper 5: Modaresi, Roja; Pauliuk, Stefan; Løvik, Amund Nordli; Müller, Daniel Beat. Global Carbon Benefits of Material Substitution in Passenger Cars until 2050 and the Impact on the Steel and Aluminum Industries. Environmental Science and Technology 2014 ;Volum 48. s. 10776-10784 http://dx.doi.org/10.1021/es502930w Copyright © 2014 American Chemical Society
Doctoral thesis at NTNU;2015:116


Roja Modaresi

Norges teknisk-naturvitenskapelige universitet


Annan naturresursteknik





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