Life Cycle Assessment
Audi looks one step ahead
Life cycle assessment –
the concept
Times change. Raw materials are becoming scarcer, emissions are on the
increase and many cultures in various parts of the world are undergoing
major changes. Against this backdrop, careful use of resources is gaining
in importance all the time.
Audi is helping to make this change – true to the technical leadership
implied in its classic motto 'Vorsprung durch Technik'. Modern technologies, new materials and highly efficient components are available to
optimise vehicle design. For Audi, as a pioneer in vehicle development,
progress in the careful use of non-renewable resources is a task that
involves every area of its activities.
Life cycle assessments (LCA) are important procedures that can help to
reduce the motor vehicle's impact on the environment. Audi not only
assesses the vehicle while it is in use, which mainly concerns its fuel
consumption, but the entire life cycle from production to recycling.
Audi looks one step ahead.
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Life cycle assessment –
what's involved
The life cycle assessment analyses the effects of a product on the
environment during its entire existence, from production to its period
of use and its end-of-life recycling. It is a quantitative evaluation of
ecological aspects such as the emission of greenhouse gases (including
carbon dioxide [CO2]), energy consumption, acidification or 'summer
smog'. Audi compiles its life cycle assessments according to the
procedure laid down in the international ISO 14040 series of standards.
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Assessment of a vehicle’s
complete life cycle as a major
contribution to more
sustainable treatment of the
environment.
•
•
•
•
Development phase:
Production phase:
Use phase:
Recycling phase:
assessment of materials and semi-finished product manufacturing chains
assessment of components and complete vehicles
assessment of fuel/electricity (including production)
assessment of process chains of valuable materials
Stages in motor-vehicle life cycle assessment
Materials
and production
Production components
(depending on manufacturing concept)
Recycling
Input
Energy
Raw materials
Output
Emissions
Waste
Use
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Life cycle assessment –
the boundaries
Before a life cycle assessment is compiled, its boundaries must be defined
by deciding which processes should be examined. The available means,
the time framework and data availability all have to be taken into account.
Audi has laid down broad limits for its complete-vehicle life cycle
assessments.
The examination starts with the manner in which raw materials are
obtained, and how individual components are manufactured. Even during
the first new-model development stages the engineering teams have to
take decisions that have major effects on in-house production and the
entire supply chain.
Audi's experts assume for assessment purposes that vehicles will cover
a distance of 200,000 kilometres. They not only take into account the
emissions caused when the vehicle is being driven, but also those that
occur when the fuel is produced. Recycling at the end of the vehicle's life
and the use of secondary raw materials are also included in the life cycle
assessment.
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System boundaries of vehicle LCA
Manufacture
Raw material extraction
Semi-finished product
manufacture
Supply → pipeline
Transport → refining
provision of fuel
Recovery of energy
and raw materials
Component manufacture
Production
Use
Recycling
= product system
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Life cycle assessment –
effect categories
The result of the inventory analysis is converted into effect indicators
and these in turn are grouped into effect categories which describe the
principal environmental problem-areas: the 'greenhouse effect' (global
warming potential), eutrophication of water and soil, 'summer smog',
acidification and damage to the ozone layer. When evaluating the
greenhouse effect, which is a major indicator, the Audi LCA specialists list
the effects resulting from all gases that influence the climate. The gases
are included in the LCA according to their effect in relation to CO2, but the
importance of other effect categories as well as the greenhouse potential
is not disregarded.
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Effect of substances on the environment
Inventory analysis
Effect
indicators
Estimated effect
CO2
Global warming potential
Extraction of raw materials
CH4
Eutrophication
Manufacture
SO2
Photochemical smog
Production
Utilisation / transport
NOx
Acidification
HC
Ozone breakdown
R11
Recovery / Recycling
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Life cycle assessment –
questions
The central factor that has to be considered in Audi life cycle assessments
is the effect that possible optimisation will have in the various phases of a
vehicle's life.
For example, the use of lightweight materials usually leads to additional
effort or complexity in component manufacturing. On the other hand, the
vehicle weighs less and therefore consumes less fuel in the subsequent
operating phase. For Audi, environmentally acceptable lightweight
construction means that the savings during vehicle operation must be
greater than the additional effort and expense caused in the production
phase.
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Environmentally acceptable lightweight construction
Additional environmental
burden caused
by manufacture of
lightweight materials
0
Reduced environmental
burden during vehicle
operation as a result of
lightweight construction
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Life cycle assessment –
the influencing factors
LCA is a tool that enables Audi to evaluate the effects of strategic
decisions when new vehicle concepts are being developed. This concerns
in-house processes and also those used by outside suppliers.
Even a single modification can have a negative effect on one of the phases
in the life cycle, but if the drawbacks are more than compensated for in
another phase, the balance is then positive. In practice this means that
the extra effort and expense involved in using lightweight materials is
made good by reduced consumption in the vehicle's use phase, so that
there is an advantage below the line compared with a conventional
concept.
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LCA of different vehicle concepts
Greenhouse gases [in t CO2 equivalent]
Materials
and production
Recycling
Use
Additional
burden by
lightweight
design
Net
reduction
of greenhouse gases
Break-even
Depreciation distance
0 km
200.000 km
Influencing factors (examples)
•Materials
•Component concepts
• Degree of weight saving
•Production
• Processes
• Energy sources
• Electricity mix
•Weight of vehicle
•Power unit
• Type of fuel
• Drivetrain efficiency
•Production of fuel type
• Processes
• Energy sources
• Electricity mix
•Recovery of valuable materials
Conventional construction
Environmentally acceptable
lightweight construction
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Lightweight construction –
choice of materials
The choice of materials has a decisive effect on the CO2 emissions that
occur in component manufacturing. The range is wide, in view of the many
different manufacturing and recycling methods involved. Due to the
production process and the nature of the energy source, primary
aluminium gives rise to higher emissions than occur in the production of
primary steel. If on the other hand recycled aluminium can be used, the
effort and expense are at a lower level, comparable with recycled steel. At
Audi the recycling process starts in the production phase, when trimmings
from the presses are collected and returned for recovery.
Production recycling makes a significant reduction in CO2 emissions possible.
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Greenhouse gas emissions for various materials [kg CO2 eq. / kg component weight]
Steel
Aluminium
Magnesium
CFRP*
0
5
10
= Process-dependent scatter
*Carbon fibre reinforced polymer
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20
25
30
35
40
45
•The scatter bandwidths for the various materials result
from the different manufacturing and recycling processes
that can be used.
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Lightweight construction –
component concepts
If a vehicle's use phase is considered in isolation, then lightweight
materials are extremely attractive. The chart shows the potential weight
saving for components with identical functions if a modern lightweight
material is used instead of conventional steel.
Aluminium is about two-thirds lighter than steel, but metal of slightly
heavier gauge has to be used for a vehicle body. An aluminium body
built according to the Audi Space Frame (ASF) principle weighs about
40 percent less than a comparable steel body.
Magnesium is about a third lighter than aluminium. At the moment it is
mainly used in the form of castings.
Carbon fibre reinforced polymer (CFRP) – a composite material
containing about 50 percent woven carbon fibre in a resin matrix – is even
lighter than magnesium, but offers a similar overall weight saving. Its
production is still extremely intensive in terms of energy consumption.
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Lightweight potential of components (identical functions)
100 %
Weight-saving potential,
depending on material and
manufacturing processes
(compared with steel):
75 %
100 %
~ 40 %
~ 55 %
~ 55 %
~ 40 % for aluminium
~ 55 % for magnesium
~ 55 % for CFRP
50 %
25 %
0 %
Steel
Aluminium
Magnesium
CFRP
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Lightweight construction –
secondary effects
The weight reduction that Audi achieves by using lightweight materials
permits welcome secondary effects in other areas of the vehicle.
Lower body weight initiates a downward turn in the weight spiral, which
permits chassis and drivetrain components to be downsized, for instance
by reducing the size of the brakes. Weight-saving potential is possible in
every technical area. In the life cycle assessment these savings help to
compensate for the additional effort and expense incurred in the manufacture of lightweight materials.
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Reversing the weight spiral
Downsizing of
engine
Lightweight body
construction
Secondary effects,
e.g. transmission
Secondary effects,
e.g. chassis, brakes
A smaller fuel tank
Detailed lightweight
construction in all areas
Lightweight construction is the starting point for a reversal of the weight spiral.
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Audi A6 –
the life cycle assessment
Audi has compiled a detailed LCA for the new A6. For comparison, the
engineers chose the top-selling model from previous generation, the A6
3.0 TDI with automatic transmission.
A notable achievement on the new model is reversal of the weight spiral:
the new Audi A6 3.0 TDI quattro is 80 kilograms lighter. This is due to
more intensive weight-saving measures applied to the body, engine,
drivetrain and chassis. The chart shows all the areas that contributed
significantly to this reduction.
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MMI 3G system
integration
Aluminium module
cross-member
Engines and transmissions
optimised for weight
saving – adoption of
lightweight materials
for functional integration
Use of high-end steel
grades in the bodyshell,
including form-hardened
grades and tailored
blanks
Aluminium rear shelf
Aluminium boot lid
Cast aluminium
suspension strut domes
Aluminium
bonnet
Lightweight
forged wheels
Aluminium doors
Neodymium speakers
Aluminium
bumper system
Aluminium pipes
Aluminium axle
components
Aluminium fender
quattro drivetrain optimised
for weight saving
Lightweight composite
brake discs
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Audi A6 – materials
The materials used for the product have a significant influence on the
LCA. According to the material classification in VDA directive 231–106,
the proportion of lightweight metals in the new Audi A6 3.0 TDI is about
19 percent of the car's curb weight, three percentage points more than in
the previous model. By contrast, the proportion of steel and other ferrous
metals went down by 5 percent. Audi has extensively replaced steel with
aluminium.
Previous Audi A6
4 %
New Audi A6
6 %
5 % 5 %
2. Light metals
16 %
55 %
3%
17 %
4 %
16 %
1. Steel / iron
19 %
50 %
3. Non-ferrous metals +
4. Special-purpose metals
5. Polymers +
6. Process polymers
7. Other materials +
8. Electrics / electronics
9. Fuels and
auxillary means
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Audi A6 – the results of
the life cycle assessment
The new Audi A6 contains a higher
proportion of light metals than the
previous model, and in most cases
more energy is consumed in their
production. Despite this, the
break-even point is reached before
the first 5,000 kilometres have
been driven, and from this point on
the new car's much lower fuel
consumption makes the balance
more positive with every successive
kilometre.
Although the previous model emitted scarcely 53 metric tons of CO2
equivalents during its complete life cycle, the new Audi A6 has distinctly
less impact on the environment: 46 t of CO2 equivalents. In other words,
Audi has succeeded in reducing greenhouse gas emissions by 7 metric
tons of CO2 equivalents or 13.2 percent. In all other relevant effect
categories too, the new model records better results than its predecessor.
Reduction of all examined effect categories
Global warming potential
Photochemical ozone creation potential
-4 %
Acidification potential
-3 %
Ozone depletion potential
Eutrophication potential
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-13 %
-0,5 %
-3 %
60.000
Materials and production
Use
Recycling
Audi A6 3.0 TDI
quattro tiptronic
(previous model)
7.1 l / 100 km
40.000
30.000
Audi A6 3.0 TDI
quattro S tronic
(new model)
6.0 l / 100 km
20.000
Audi A6 3.0 TDI quattro tiptronic (previous model)
Audi A6 3.0 TDI quattro S tronic
10.000
200.000
180.000
160.000
140.000
120.000
100.000
80.000
60.000
40.000
20.000
0
0
[kg of CO2 equivalents]
50.000
Fuel
consumption:
Distance covered [km]
The additional burden caused by more intensive lightweight construction
and drivetrain optimisation is written off during the first 5,000 kilometres.
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Life cycle assessment –
electromobility
Electrically propelled vehicles such as future e-tron models from Audi
have a highly efficient drivetrain and cause no local emissions. Of course,
responsibility does not end at the electric power socket. In the use phase,
the complete 'well-to-tank' CO2 emissions caused by the generation and
supply of electric power have to be included in the LCA.
As the chart shows, there are immense differences between the various
regions of the world, depending on the local electricity mix. In China most
electricity comes from coal-fired power stations with intensive CO2
emissions, whereas in Norway clean hydroelectric power predominates,
and emissions of CO2 equivalents (in grams per kWh) there are lower than
in China by a factor of 25.
The chart on page 28 shows the effect of the electricity mix on the
operation of a compact-class electric car. In China its emissions of
greenhouse gases total 171 grams per kilometre, in Norway a mere
7 grams. For this reason Audi plans for its future e-tron models to be
operated exclusively on electricity generated by ecological means. With
its e-gas project, Audi will be playing an active part in the development of
regenerative electricity production.
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A similar picture is revealed if the production and recycling phases are
Greenhouse gas emissions caused by
electric power generation / well-to-tank
added to the use phase. An electric car has a much better overall balance
(selected countries)
than a conventional vehicle powered by a petrol engine in Norway,
whereas in China the balance is worse. The chart on page 29 also shows
that the production of a conventional car accounts for about 20 percent of
total emissions, and that this proportion is higher for an electric vehicle
because production of the batteries consumes a large amount of energy.
China
1140 g
g CO2 eq. / kWh
EU 25*
560 g
1 %
Coal
Nuclear power
Norway
46 g
19 %
23 %
Hydroelectric
Others
77 %
77 %
39 %
32 %
99 %
10 %
*Electricity mix of EU 25-Members (2007)
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Greenhouse gas emissions from electric vehicles in relation to the electricity mix
Greenhouse gas emissions g CO2 eq. / km
Assumption:
battery-electric vehicle,
compact class
consumption: 15 kWh / 100km
200
171
150
100
84
50
7
0
China
28
EU
Norway
Greenhouse gas emissions balance in relation to electricity mix
Internal combustion engine
Materials and production
~ 20 %
~ 80 %
< 1 %
Use (well-to-wheel)
Recycling
Electrically propelled
► Electricity mix as in China
~ 25 %
~ 1 %
~ 75 %
► Electricity mix as in Europe
~ 45 %
~ 55 %
~ 2 %
► Electricity mix as in Norway
~ 90 %
~ 5
%
~ 5 %
Better
Assumption:
compact class car, distance
200,000 km, consumption: internal combustion engine:
5.5 l fuel / 100 km
electric drive: 15 kWh / 100 km
Poorer
than reference vehicle with
internal combustion engine
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Life cycle assessment –
conclusion
The public today tends to judge cars to a large extent by their fuel
consumption. Here too, Audi looks one step ahead. Its life cycle
assessments analyse effects on the environment for the vehicle's entire
lifetime. The use of sustainable materials and manufacturing processes
can greatly reduce these effects.
The LCA that Audi has compiled for its new A6 shows on the one hand that
the new saloon model is superior to its predecessor in all environmentally
relevant criteria. In addition it is sound evidence that the lightweight
design measures Audi has adopted quickly pay for themselves during the
use phase, despite the higher energy consumption they entail. The weight
advantage soon makes itself felt as a worthwhile reduction in CO2
emissions – an admirable example of environmentally acceptable lightweight design as Audi understands it.
Although electric vehicles are locally emission-free, a 'well-to-tank'
assessment is essential if their potential environmental benefit is to
be correctly estimated. Considerable differences occur according to the
regional electricity mix. No ecological benefit is obtained unless renewable
energy is used. Audi is now helping to develop it.
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Impressum:
AUDI AG
Total Vehicle Development and
Product Communications
85045 Ingolstadt
Tel:+49 841 89-32100
Fax+49 841 89-32817
Status: 05 / 2011