from a full lifecycle perspective:
Aluminum is produced first by the chemical refinement of bauxite, impure alumina, to pure alumina. Four tons of bauxite give 2 tons of alumina — eventually producing 1 ton of aluminum.
The pure alumina is reduced by molten salt electrolysis, using a fluoride salt to form a molten bath with the alumina. Carbon anodes are consumed in the process causing the emission of CO2, but there are also some emissions of perfluorocarbon (PFC) gases such as CF4 and C2F6 caused by process excursions. There has been significant improvements in control of the electrolytic process in recent years, still continuing, which has resulted in a 47% reduction in PFC emissions between 1990 and 1997. While the total amount emitted is small, these gases have many times the effect of CO2 as greenhouse gases.
Of the electricity consumed by the aluminum industry in smelting, over 50% is hydro generated. It is the other generation of power which is the other major source of greenhouse gases. Primary aluminum supply will be able to meet all automotive customer needs with the power mix for smelting projected to be 56% hydro, 31% coal, 8% natural gas and 5% other in 2004 and beyond — virtually unchanged from today.
The bottom line is that the overall worldwide average emissions are 14.3kg of CO2 equivalents per kg of aluminum for primary smelter metal.
…..BUT
Another of aluminum's valuable environmental benefits is its unique recyclability. In many of its product applications, studies have shown that aluminum has exceptional performance with respect to other materials when the life cycle effects of recycling are taken into account.
An important key to this is the energy savings associated with aluminum recycling. As this slide shows, the energy required to recycle the metal is only 5% of that used to produce aluminum from raw materials.
Most of the energy used to produce primary aluminum is electrical energy for the smelting process, which, in effect is an environmental investment. The energy is embedded in the metal and therefore available to used over and over again, which is why we call aluminum the "Energy Bank."
And not only does recycling reduce energy consumption, it also saves 95% of the greenhouse gases associated with primary production.
Having obtained our base aluminum, whether primary or recycled, we need to add in the emissions arising from conversion to its final state — sheet, castings or extrusions.
These are indicated here, as follows:
For sheet, we add only 0.8kg CO2 equivalents per kg to the 14.3 we started with to give 15.1. — I should mention here that, for the sake of brevity, my slides will all read CO2, but what I am really talking about are CO2 equivalents.
For secondary sheet we also add 0.8 kg of CO2 equivalents, but to just 0.7kg of CO2 equivalents that recycled metal emits, totaling only 1.5 kg per kg of aluminum.
Similarly for extrusions and castings
Here, then, is the real bottom line. Taking into account the typical mix of sheet castings and extrusions for today's cars AND today's mix of primary and secondary, we arrive at 7.18 kg of CO2 equivalents per kg of aluminum.
And now, in the final portion of my talk, let me bring all of this data to a conclusion in order to explain the environmental benefits, the pluses if you will, of using aluminum in automobiles.
Having shown how much CO2 equivalent is on the debit side, so to speak, for aluminum, now let us consider the credit side — the benefits of its use.
First of all — how much weight does aluminum in the car save?
Here we see some examples of specific weight savings.
Overall, the weight savings achieved are around 50% versus iron and steel. Or in other words, 1 kg of aluminum can replace about 2 kg of steel or iron in most automotive applications.
How does this weight saving translate into fuel savings?
The consensus from the auto industry is that every 10% weight saved yields 5 to 10% fuel savings — without compromising size or safety, and while providing improvements in driving performance and end-of-life value.
For the purpose of the calculations to follow on the next few slides, let's call it a 7% fuel savings, which we believe is very conservative by the way.
The actual figure we use is 0.46 liters per 100kg mass saved per 100km traveled (or .000046 liters per kg per km)
For every litre of fuel saved we take the, I think, reasonable figure of 2.85 kg of CO2 per litre of fuel.
Before I get into my worked examples, it is worth noting that, through all the many steps in these assessments, assumptions have to be made. I have put together a list of all these assumptions in the paper handout — I encourage you to analyze them and come up with your own conclusions on the overall benefits that I am claiming. Put your own assumptions in. I guarantee that you will show a sizeable CO2 credit at the end of the car's life
So, now we get to the fun part, where we take all of the preceding and work on three cases.
The first one is for today's typical car in North America:
It contains 113 kg of aluminum, replacing some 226 kg of iron and steel.
The environmental "burden" for the aluminum is 811 kg of CO2 equivalents. (113x7.18)
The CO2 emissions from 226 kg of ferrous would be 407 kg. (226x1.8)
The net "burden" for aluminum is 404 kg CO2 equivalents. (811-407)
Fuel saved for 113 kg weight saved would be 1004 litres (113x0.000046x193000) over the 12 year 193,000 km life.
CO2 savings from this fuel saving is 2861 kg (1004x2.85)
Net benefit over the life of the car 2457 kg CO2 equ. (2861 - 404)
Crossover time to zero net CO2 is about 20 months
I have plotted this all here assuming linear annual mileage accumulation.
The next example — Case 2 — Here we are looking, actually at the GM Olds Aurora with 204 kg (450lbs.) of aluminum.
The same process as before — in this case, more aluminum simply means a bigger deficit on day 1, but also a bigger "credit" by the nominal end of life — some 4433 kg of CO2 equivalents savings in this case compared to the all-ferrous version.
So this could be looked at as "the more aluminum substitution, the greater the CO2 credit." The crossover in this case is the same at 20 months.
204 kg of aluminum content, replacing some 408 kg of iron and steel
The "burden" for the aluminum is 1465 kg of CO2 equ.(204x7.18)
The CO2 emissions from 408 kg of ferrous would be 734 kg (408x1.8)
The net "burden" for aluminum is 731 kg CO2 equivalents (1465-734)
Fuel saved for 204 kg weight saved would be 1812 litres (204x0.000046x193000) over the 12 year 193,000 km life.
CO2 savings from this fuel saving is 5164 kg (1812x2.85)
Net benefit over the life of the car 4433 kg CO2 equivalents (5164 - 731)
Case 3 is somewhat different.
Here, we are considering what we would call a full AIV — an aluminum intensive vehicle, where all of the structure and all of the skin is aluminum.
Obviously there is now even more aluminum, 340 kg (748 lbs) but now we assume that the weight savings are a little less (only 45% for the structure) and that the structure material is all primary not secondary. Rather than 40% prime.
This simply reflects the fact that there would not be enough scrap available at least until these vehicles start coming around for recycling — 12 , maybe 15, maybe more years later.
In this case, the lifetime "credit" is even higher at nearly 5000 kg, 5 tonnes.
And would be higher with a longer lifetime.
So, in this case, the CO2 debit is 3946 kg (190x15.1)+(150x7.18)
Take away 1162 kg CO2 for the 645 kg of ferrous replaced (645x1.80) = 2784kg
Fuel saved over 12 years = 2713 litres (645-340)x0.000046x193100
CO2 saving from fuel saving 7733 kg (2713 x2.85)
Net "credit" is 4949 kg CO2 ( 7733-2784)
Time to "CO2 net zero" = 52 months or 70,000 km (43,000 miles) of driving.
Hopefully, I have illustrated for you the merits of lightweighting with aluminum, but just before I wrap up my presentation, I'd like to show you a new emerging technology that will enhance the recyclability of automotive aluminum.
This new technology is called "LIBS"— laser-induced breakdown spectroscopy — and it is being developed to allow separation of aluminum shreds by alloy.
Already today 95% of automotive aluminum is recovered by disassembly or by separating aluminum shreds. But most of that recovered metal goes back into castings and is somewhat downgraded.
This new technology will allow full closed-loop recycling of the wrought alloys — that is to recycle them back into the same products from which they came, as we do today with aluminum beverage cans.
The idea involves shredding as per normal, followed by shred shape recognition and laser OES of each shred such that it can be diverted into the appropriate bin.
LIBS is being developed by Huron Valley Steel in Detroit with support from the Auto Aluminum Alliance — an alliance of automakers and aluminum companies.
To see the benefit of this … If we now put 60% recycle into the AIV in the Case 3 example we just saw, we would increase the CO2 "credit" per car to 6454 kg and reduce the "crossover" to just 20 months.
The conclusions, then;
Aluminum can replace iron and steel in automobiles with weight savings of 45 to 50% with gains in performance and no loss of safety.
Fuel savings deriving from the weight saving balance the net CO2 emissions typically within the first few years of vehicle service. And, over the life of the vehicle, a substantial CO2 "credit" is created.
The advent of alloy sorting from end-of-life vehicles will lead to closed-loop recycling of auto aluminum and even greater environmental gains from the use of aluminum in vehicle construction.
And lest you think that this is just an aluminum industry sales pitch, let me assure you that we are not the only ones that recognize the valuable contribution that aluminum can make...
Will Boddie, VP Research & Vehicle Technology for Ford Motor Company, recently stated ...
"High-volume application of lightweight materials, including aluminum, is a key to increasing fuel economy and decreasing emissions to address global environmental concerns."