Life-Cycle Assessment in the automotive industry
Gregory Launay, translation by Audrey Brousseau - Last update: August 25th, 2012
What’s the life-cycle assessment of a vehicle?
Today we are quite aware of the issue of greenhouse effect gases and CO2 release in the automotive sector.
Let us face it, this acknowledgement is mainly due to the effects on our wallets. The price you pay when you’re filling up your tank is highly representative! It is a short step to making the link between the vehicle consumption and CO2 emissions, as figures are published in many specialized magazines.
But the latter only refer to the last layer of CO2 emissions, known as “tank to wheel”. In other words, they refer to the direct CO2 impact of car use.
But we must admit that gas has not miraculously ended up in stations. Energy was needed, and thus CO2, to extract, transport, refine it. If those emissions are added to the previous ones, this is “from wheel to wheel” reasoning, which is a telling image.
The same remark could be made concerning car manufacturing, as it needs energy consumption along with CO2 emissions.
This takes us to the notion of Life-Cycle Assessment (LCA) which precisely aims at answering this question: “What is the environmental impact of a vehicle when all phases of its life are taken into account”.
The goal of this logic, as it clearly appears, is to recognize the various impacts of a product on the resources and the environment over its lifespan, from extraction of raw materials to processing at the end of its life (landfill of waste, incineration, recycling). This cycle is often referred to as “cradle to grave”. Therefore, several types can be identified when referring to the use of a mass-market product:
- The impact linked to the production of raw materials: extraction, transportation, processing of basic raw materials. The extraction of iron ore, for example, its transportation, then its processing into cast iron or steel and finally coated sheet or blocks.
- The impact linked to the manufacturing and the assembly operations of the object: for example, the pressing of coated sheets, then the assembling of the various parts composing the final object.
- The impact linked to inbound logistics, in other words the transportation of raw materials and parts between the various manufacturing and/or assembly plants. For example, most parts of an engine are now manufactured in various specialized supplying plants and then delivered to the car manufacturer’s assembly plant.
- The impact linked to outbound logistics, in other words the delivery of the finished product to the outlets and to the final customer if necessary.
- The impact linked to its use (gas consumption)
- Eventually, the impact linked to the vehicle’s end of life: dismantling, recycling, shredding
The different steps in the life-cycle of a car
But what lies beneath the word ‘impact’? The following areas can be explored by what is termed LCA:
- Climate change potential: quantification of emitted greenhouse effect gases (CO2, CH4…)
- Acidification potential: quantification of the acid potential (how obvious it is!) and its impact of acid rains for example.
- Ozone potential: quantification of polluting ozone that provokes breathing problems (which is different from the ozone layer, the notorious hole)
- Natural resources depletion: quantity of consumed raw materials
From now on, we’ll only focus on the global warming issue. We can eventually mention that this approach appeared some forty years ago, and that a standard sometimes comes up from it, like in France with the ISO 14010 standards.
LCA applied to the automotive
Now that we have understood the notion, let’s move on to practical work: what does my car have to do with all this? Let’s focus on gas production first. All the figures that have been published are of the same order and show 80% to 90% efficiency for fuel refining and transportation. The real figure is different according to what type we’re talking about: gas oil, unleaded petrol, from Saudi or Canadian crude oil…Of course we’ll only focus on the order of magnitude, and we’ll consider the 87% average as it was produced by the ADEME.
What does it mean exactly? Well, very simply that when we buy 1 liter of fuel at the station, about 1,15 liter (1/0.87) was extracted in energy equivalent, and thus 0.15 was consumed in order to provide the remaining liter to whoever wants to buy it.
In terms of CO2 emissions, it means that whereas a car is supposed (according to regulations) to emit 153 grams of CO2 per km (about 6 liters of fuel per 100 kms, like the average car sold in Europe in 2008), it actually emits about 176 grams (153/0.87), once fuel processing and transportation have been taken into account.
Let’s focus now on car manufacturing: raw materials extraction, manufacturing / assembly, logistics. We may look through reference studies dealing with this issue in order to know more about CO2 emissions in each step. We’ll mention three studies.
The latest (as far as I know) was conducted by the European Commission (driven by its research center, the Joint Research Center). Its conclusion gives greenhouse effect gases emissions in a range of 5 - 5.5 tons of CO2 equivalent.
Concerning the American market, a study conducted by a university in California (Reducing Greenhouse Gas Emissions with Hybrid-Electric Vehicles: An Environmental and Economic Analysis, May 2005) gives a 7-10 ton range.
Finally in Japan, last of the three big international markets, Hiroshi Komiyama gives about 10 tons (Vision 2050, Roadmap for a Sustainable Earth, May 2008).
Greenhouse effect gases emissions (in CO2eq) linked to car manufacturing – Synthesis from the author.
The results may vary by almost twice as much. Those differences can be explained by the assumptions included in the studies: specific definition of the limits of the study, emission factors used for raw materials, CO2 equivalence for other greenhouse effect gases (CH4, NH3…).
But they also illustrate the specificities of the various car markets. For example, the vehicle mass is different from one market to another. The same thing can be said for the logistics in the transportation of raw materials and parts of the finished product. This aspect is directly linked to the location of industrial plants, as further distances are covered in North America than in Europe. Another example: Japan imports most of its raw materials, unlike North America and Europe. And last, Japan and North America have automatic transmission in their vehicles, those gearboxes being by nature more complex, heavier, and thus more energy consuming. It would also be interesting to compare the different resources that are used (oil, coal, gas) in various industrial processes, as different emissions may thus be produced for the same task.
Let’s focus on the vehicle mass for a moment. European and Japanese markets consist in quite small cars (everything being relative of course).
Average mass of passenger cars sold by the 14 biggest car manufacturers in the EU15 – Source: ACEA, 2008 figures
This graph shows us the average mass of passenger cars sold by the main manufacturers in the EU 15 along with the volumes involved. In weight average, the average vehicle mass calculated is 1262 kg.
The same calculation could be made concerning the American market. The following graph shows the top 10 vehicle sales in the USA and the corresponding masses. The weigh average is here 1820 kg!!
Average mass of the 10 most commonly sold passenger cars in the USA – Source: IOCA, 2008 figures
We’re still focusing on the order of magnitude here. In light of what has just been said, 8 tons CO2eq is not an absurd figure to consider. Let’s connect this to the general life-cycle of a car. The three studies that we have already mentioned enable us to draw the following graph:
Contribution of the different items in the CO2 emissions of a vehicle under Life-Cycle Analysis – Synthesis from the author
Here again, we can observe significant differences between the studies. Those differences are also linked to the assumptions under consideration. First, the average distance covered by a car each year and its service lifespan. Figures vary from 15.000 to 20.000 kms a year (the global average being 15.000 kms) for a lifespan of 12 to 15 years. The total covered distances are between 210.000 and 250.000 kms.
Then, the average consumption under consideration (the consumption declared under certification driving cycle in the country or the estimated consumption which would be more realistic than the actual consumption of the average customer). Finally, refining efficiency of which values vary from 80% to 90%.
What synthesis should we consider?
If we consider our average global car covering 15.000 kms a year in 15 years, and consuming 9 liters per 100 kms (225 grams of CO2 per km), we obtain the following orders :
- 8 tons of CO2 for its manufacturing
- 0.5 tons of CO2 for its maintenance and its recycling
- 50.6 tons of CO2 for its use
- 6.6 tons to process the fuel needed for its use
Evaluation of greenhouse effect gases (in tons of CO2eq) under the cycle analysis of the average global car – Synthesis from the author
Manufacturing thus represents 1/6 the car use (fuel production set-aside), that is to say about 35.000 kms.
What about annual flow?
Let’s go back now to the traditional method of counting greenhouse gases emissions: annual flow. In national statistics, transport (and thus the automobile) is a full item which takes the fuel used annually into account.
In this counting method, the use of the automobile is accountable for about 7% of human-induced greenhouse effect gases emissions, in other words 3.4 Giga tons of CO2 equivalent (or Gt CO2eq).
Now we can add the part linked to oil processing, that is to say 0.5 Gt CO2eq (3.4 * (1-0.87)) and the emissions linked to annual industrial manufacturing (about 70 million vehicles), that is to say about 0.6 Gt CO2eq (8 tons per 70 million).
This gives us an annual total figure linked to the automobile equal to 4.5 Gt CO2eq, considering full life-cycle producing 9% of the greenhouse effect gases emissions.
Global greenhouse effect gases emissions by sector - Source: GIEC, 2007- 2004 figures
What about the electric car?
To date, there is no detailed public study under Life-Cycle Assessment for an electric vehicle. Such studies are still in progress and the first ones should be published in 2012 (by the ADEME in particular).
But some elements have just been made public by British organization LowCVP. They compare CO2 emissions from a gas vehicle, a hybrid, an electric and a plug-in hybrid. Here are the results:
Comparison of CO2 emissions under Life-Cycle Assessment of various electricity-powered vehicles – Source: LowCVP, June 2011
The study took into account a “2015 vehicle” covering 150.000 kms during its lifetime, a fuel containing 10% bioethanol and CO2 content of electricity of 500g per kWh, a figure which is quite close to the European average.
Focusing on a 2015 new vehicle that doesn’t drive a lot gives total figures that are quite far from what we have established previously for our global average vehicle (25 tons instead of 65), but this is not what matters most.
First, those results confirm that, concerning use, the electric car certainly induces fewer emissions than the combustion vehicle (see details here). The study also underlines the fact that production induces more emissions when it implies electric cars, probably because of battery processing.
In short, those are quite favorable results for electric cars: 19 tons of CO2 instead of 24, that is to say 20% less.
In addition to those results being only relevant in Europe, we have to keep in mind the challenge we have to face: the global vehicle fleet has to produce three times fewer emissions while it’s doubling…
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