The CES EduPack Eco Audit Tool ? A White Paper - MAELabs UCSD

5. Case studies
An eco audit is a fast initial assessment. It identifies the
phases of life – material, manufacture, transport and use
– that carry the highest demand for energy or create the
greatest burden of emissions. It points the finger, so to
speak, identifying where the greatest gains might be
made. Often, one phase of life is, in eco terms,
overwhelmingly dominant, accounting for 60% or more
of the energy and carbon totals. This difference is so
large that the imprecision in the data and the
ambiguities in the modeling, are not an issue; the
dominance remains even when the most extreme values
are used. It then makes sense to focus first on this
dominant phase, since it is here that the potential
innovative material choice to reduce energy and carbon
are greatest. As we shall see later, material substitution
has more complex aspects – there are trade-offs to be
considered – but for now we focus on the simple audit.
This section outlines case studies that bring out the
strengths and weaknesses of the Eco Audit Tool. Its use
is best illustrated by a case study of extreme simplicity –
that of a PET drink bottle – since this allows the inputs
and outputs to be shown in detail. The case studies that
follow it are presented in less detail.
Bottled water. One brand of bottled water is sold in 1
liter PET bottles with polypropylene caps (similar to
that in Figure 8). A bottle weighs 40 grams; the cap 1
gram. Bottles and caps are molded, filled, transported
550km from Evian in the French Alps to London,
England, by 14 tonne truck, refrigerated for 2 days
requiring 1 m 3 of refrigerated space at 4 o C and then
sold. Table 1 shows the data entered in the Audit Tool.
Figure 8. A 1 litre PET water bottle.
The calculation is for 100 units.
What has the tool done? For step 1 it retrieved from the
database the energies and CO2 profiles of the materials
and the processes 3 . What it found there are ranges for
3 Data are drawn from the CES EduPack Level 2 or 3
database, according to choice.
the values. It created the (geometric) mean of the range,
storing the values shown below:
Material and primary
manufacturing process
Table 1: The inputs
Product name: PET bottle, bill of materials.
Life: 1 year.
Step 1: Materials and manufacture: 100 units
Component
name
Material Process Mass
(kg)
Bottle, 100 units PET Molded 4
Cap, 100 units PP Molded 0.1
Dead weight (100
liters of water)
Step 2: Transport
Stage name Transport
type
Transport of filled
bottles
Water 100
Embodied
energy
(MJ/kg)
Distance (km)
14 tonne truck 550
Step 3: Use phase: static mode – refrigeration i
Energy input
and output
Electric to
mechanical
Power
rating
(kw)
Step 4: Energy selected.
Usage
(hr / day)
CO 2
footprint
(kg/kg)
PET, material 84 2.3
PP, material 95 2.7
Polymer molding 6.8 0.53
Usage
(days /
year)
0.12 24 2
i The energy requirements for refrigeration, based on A-rated
appliances are 10.5 MJ/m 3 .day for refrigeration at 4 o C and
13.5 MJ/m 3 .day for freezing at -5 o C. The use energy is chosen
to give the value for refrigeration.
It then multiplied these by the mass of each material,
summing the results to give total energy and carbon.
For step 2 it retrieved the energy and CO2 profile of the
selected transport mode from a look-up table (see
Appendix A), finding:
© 2009 Granta Design Ltd. 7 MFA, 18/02/2009