Environment

Oil Point example: "Sweaters"

In this example, two sweaters of different materials are compared using the Oil Point Method. The sweater materials are "pure primary PET" (polyester) and "pure cotton".

The comparison is done in three steps: 1. Focus, 2. Evaluate and 3. Interpret.

1. Focus

FUNCTIONAL UNIT
The Functional Unit, or "service", can be defined as "Provision of a clean, non-coloured knitted sweater of 1 kg weight, to be used washed and tumble-dried 75 times in Denmark".

2. Evaluate
(PET sweater)

  OP/kg OP/product

Material:
1.2 kg (processing)


1.3

1.56
Manufacturing:
1 kg yarn & knitting

2.8


2.8

Transport:
1 kg* 1000 km
= 1 tkm
0.01 OP/tkm 0.01
Use:
75 x
- washing at 60 C,
- light drying,
- detergent


0.05
0.15
0.012


3.75
11.25
0.9
End-of-life:
inciner., 0.75 kg
landfill, 0.25 kg

0.9
0

0.675
0
Total:
Total per year
:
18.2
6.1
2. Evaluate
(Cotton sweater)
  OP/kg OP/product

Material:
1.2 kg
processing
feedstock


0.6
-0.1

0.72
-0.12
Manufacturing:
yarn, knitting & cleaning


4.4



4.4

Transport:
1 kg* 1000 km
= 1 tkm
0.01 OP/tkm 0.01
Use:
75 x
- washing at 60 C
- intensive drying
- detergent


0.05
0.2
0.012


3.75
15
0.9
End-of-life:
inciner., 0.75 kg
landfill, 0.25 kg

0.1
0

0.075
0
Total:
Total per year
:
24.7
8.3

Results: The cotton sweater scores about one and a half times as many Oil Points as the PET sweater. The highest impact in both alternatives results from the tumble-drying in the use stage. Here, cotton requires more intensive drying, probably due to its higher capacity to absorb water.
3. Interprete

UNCERTAINTIES
Uncertain are the processes in the stages transport, use and end-of.life. Neither transport nor end-of-life processes have significant influence on the overall result. In the use stage, however, natural drying instead of tumble-drying would lead to a more or less equal environmental performance of cotton and PET.

HOLISTIC CONTEXT
Seen in a holistic perspective, even minor improvements would make sense as sweaters are mass products. Most influencial, however, is the use pattern of the owner.

IMPROVEMENT POTENTIALS
Improvement potentials lie primarily in the washing and drying properties of the sweaters. For example, fibres could be treated in order to absorb less water. More challenging would be to rethink the use situation of the sweaters. Why are they washed every second week? Is it possible to stimulate the user to wash the sweater with longer intervals, e.g. by changing the design?

References

Details on the example:
Niki Bey: "The Oil Point Method", 2000

Links:
Zanussi Denmark
National Concumer Agency of Denmark

Image Thomas Nissen
Copyright © 2001 Torben Lenau, Niki Bey
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