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Comparative Life Cycle Assessment of Car Disc Brake Systems: case study results and methodological options for comparative LCAs
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). (Ecodesign)ORCID iD: 0000-0001-7401-4550
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). (Ecodesign)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Purpose

Two Life Cycle Assessment (LCA) studies comparing a new low-particulate- matter-emission disc brake and a reference disc brake are presented. The purpose is to identify the difference in environmental impacts due to a material change in the new disc brake parts. Additionally, the validity of the simplification called comparative LCA with an omission of parts is investigated. This is done by comparing results between the simplified and the full LCA model.

Methods

The two disc brakes, new disc brake and reference disc brake, are assessed according to the LCA ISO standards. The ReCiPe 2016 Midpoint (Hierarchist) impact assessment method is chosen. Simplifying a comparative LCA is possible. All of the LCA parts that are identical between the two compared products can be omitted, and only the ones that differ need to be assessed. In this paper, this simplification is called comparative LCA with an omission of parts and is defined as an isolated model of the full LCA system. The epistemology is borrowed from economics research on models and adapted to LCA models. An objective is to support discussions around the methodology of the simplification that is lacking in published LCA research.

Results and discussion

The comparative impacts are analysed over seventeen impact categories. The new disc brake alternative uses more resources during the manufacture of one disc compared to the reference disc brake alternative. The shorter life length of the reference disc demands a higher number of spare part discs to fulfil the same functional unit, but this impact is reduced due to material recycling. The new disc brake contributing impacts are connected primarily to the coating and secondly to the pad manufacture and materials. The external validity of the isolated LCA model is investigated by comparing the results of the two LCA models. The impact differences are identical independent of the LCA model. Hence, the purpose of the study can be fulfilled, and the isolated model is valid.

Conclusions

Both LCA models, simplified and full, reveal that the new disc brake has limited environmental advantages. The omission of identical parts makes it more difficult to determine if an impact is significant or insignificant. There are no arguments that point to that the external validity is compromised for the ‘comparative LCA with omitted parts’, compared to the full LCA. The simplification seems to be reasonable from a short-term perspective

Keywords [en]
disc brake, particulate emissions, external validity, comparative LCA, LCA methodology, material choice impacts, isolated model
National Category
Other Mechanical Engineering Vehicle Engineering
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:kth:diva-244168OAI: oai:DiVA.org:kth-244168DiVA, id: diva2:1289398
Projects
Lowbrasys
Funder
EU, Horizon 2020, 636592
Note

Submitted, under review round 2, to International Journal of Life Cycle Assessment, August 2018.

Available from: 2019-02-18 Created: 2019-02-18 Last updated: 2019-03-27Bibliographically approved
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Tasala Gradin, KatjaHedlund Åström, AnnaRitzén, Sofia
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