Life Cycle Engineering and Assessment
O.Jolliet, Y.Leterrier
Case Study of Automotive Components
Introduction
This case considers a hypothetical structural component developed for transportation
applications such as the front end of a car. This case is intended to illustrate the tradeoffs which arise when optimizing both technology and environmental impacts. Most of
the data used in the inventory analysis were found in studies of Renard et al. (1994) and
Young and Vanderburg (1994).
Materials selection and basic assumptions
A supplier to the automotive industry faces a decision regarding the choice of material
for a new structural part. The development department of the company has selected
three materials that could satisfy the functional and production requirements. The three
materials selected are steel, aluminum and a thermoset composite (polyester-based
SMC, for sheet molding compound), as specified in Table 1. The steel component is
considered to be the reference material, and is attributed a weight of 10 kg. The
corresponding weight of the component was calculated for the other two materials, with
the criteria of constant equivalent bending stiffness per weight of material, E1/3/ ,
where E is the Young's modulus and  the density (Ashby, 1992). Table 1 further
specifies the recycling potential for each material type, as well as a typical market cost.
The recycling potential represents the fraction of regrind that is incorporated in the
virgin material to produce a new part, according to the technical state-of-the-art (Furrer,
1995; Kelderman, 1995).
The production yield for both the steel and the aluminum parts is considered to be equal
to 0.65 (i.e., the weight of raw materials is 10/0.65 = 15.4 kg for the steel part), and to
be equal to 1.0 in the case of the composite part. The fuel consumption per marginal
weight change is further assumed to be equal to 0.00004 l/kg.km.
Two alternative scenarios are considered for each material, that are a non-recycling
option and an hypothetical 100 % recycling option.
Table 1. Material selection for the Life Cycle Assessment of a structural component
Density Young's E1/3/  Final Required Recycling
Price
Modulus
weight raw mat. potential

E (GPa)
(kg)
(kg)
(%)
(USD/kg)
(kg/l)
Steel sheet
7.87
200
0.74
10
15.4
90
0.8
SMC
1.5
4.0
1.06
7
7.0
20
4
Aluminum
2.7
72
----5.9
90
2.5
3.8*
Material
*real optimised industrial value
Life Cycle Engineering and Assessment
O.Jolliet, Y.Leterrier
1. Goal definition
The production unit is one component, and is expressed in terms of its final weight. The
main function is transport over the whole car life cycle (overall service of the car of
200'000 km), ensuring a similar stiffness for the different materials. The functional unit
is therefore one component of equivalent stiffness for a given service of 200’000 km
(Table 2).
1a) Complete table 2 by giving the functional unit and reference flows (the required
basic inputs to ensure the defined functional unit) for SMC and aluminum in term of
total raw material required and gasoline consumption. Use data in table 1.
1b) Identify key environmental and technological parameters, already at this basic stage.
Table 2: Definition of product function, functional unit and reference flow
Products
Main function
Secondary functions
scenario 1, 2, 3
Transport of persons
Ensure required stiffness
automobile component
Product or Functional
system
unit
Reference flows
scenario 1
Steel
Steel raw material(kg):15.4
Required gasoline (l):
Production:
scenario 2
SMC
SMC raw material(kg):
…..
Required gasoline (l):……. Use phase:
Alu raw material(kg): …..
Required gasoline (l):…….
scenario 3
Aluminum
Key
environmental
parameters
2. Inventory: energy and CO2 balance
As a first screening, the primary energy balance will be performed for the different
scenarios. The detailed calculation will be performed for aluminum only and then
compared to results for steel and SMC.
2a) On the basis of table 3, calculate the total energy requirements for the aluminum
(0% recycling) component, without and with a transport of 200000 km. Determine it
also for aluminum 100% recycled.
2b) Introduce aluminum results in table 4 and discuss them in comparison with steel
and SMC. For which scenario will recycling bring the highest improvements ?
2c) Sensitivity study: complete figure 1 with the two aluminum scenario and discuss the
interaction between materials and transport distance.
2d) On the basis of the ETHZ database, calculate the overall CO2 emissions for the
Aluminium 0% recycled scenario
Life Cycle Engineering and Assessment
O.Jolliet, Y.Leterrier
3. Impact assessment
3a) Evaluate the overall characterisation score for greenhouse effect for aluminium.
Compare it with steel and SMC. What is the dominant pollutant for this effect class.
4. Interpretation
4a) On the basis of the evaluation results from critical surface-time 95 and ecoindicator
99 (figure 2 and 3: Jolliet and Crettaz, 1997; Goodkoep and Spriensma, 1999), discuss
the best alternative from an environmental point of view. Describe the influences of
logistic.
References
M. F. Ashby, 'Materials Selection in Mechanical Design', Pergamon Press, Oxford,
1992.
P. Furrer, in 'Proc. R'95', Geneva, Feb. 1-3, 1995, pp. II-7-12.
M. Goedkoop, 1995; Eco-indicator 95, weightening method for environmental effects
that damage ecosystems or human health on a European scale, Final report; RIVM
Jolliet O. and Crettaz P., 1997. Critical surface-time 95, a Life Cycle Impact Assessment
methodology, including exposure and fate. Workshop of the EU concerted action on
harmonization of Life Cycle Assessment in agriculture, Lyngby, DK, 15-19 January
1996. EPFL-HYDRAM, CH-1015 Lausanne.
H. Kelderman, in 'Proc. R'95', Geneva, Feb. 1-3, 1995, pp. I-324-331.
H. Renard, D. Meillassoux and P. Trassaert, in 'Proc. JEC'94', Paris, April 20, 1994.
S. B. Young and W. H. Vanderburg, JOM, 1994, 46, 22-27.