Ford LCA harmonization study clarifies benefits of lightweighting for vehicle life cycle energy use and GHG emissions
29 May 2013
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| Correlation between weight reduction and life cycle primary energy demand for (a) component and (b) total vehicle scenarios. Credit: ACS; Kim and Wallington. Click to enlarge. |
While reducing vehicle weight (lightweighting) by replacing steel and iron with alternatives such as aluminum, magnesium, and composites decreases fuel consumption and greenhouse gas emissions during vehicle use, it can increase energy consumption and GHG emissions during vehicle production.
Hyung Chul Kim and Timothy J. Wallington at Ford Motor’s Systems Analytics and Environmental Sciences Department set out to clarify the lifecycle benefits of vehicle lightweighting in a meta-analysis of previously published life cycle assessments (LCAs). While numerous studies assay the benefits of lightweighting, the wide variety of assumptions used makes it difficult to compare results from the studies, the pair noted in their paper, published in the ACS journal Environmental Science & Technology.
Using lightweight materials (e.g., aluminum, magnesium, or composites) to replace conventional materials (e.g., steel, iron) decreases the energy consumption and hence GHG emissions during vehicle use. However, the production of lightweight materials generally requires more energy and generates more GHG emissions than the production of conventional materials. Life cycle assessments (LCAs) must be performed to determine the net energy and GHG benefits of using lightweight materials. Vehicle lightweighting is an area of current interest, and this has led to a large number of LCA studies.
Unfortunately, a wide range of initial assumptions such as recycling rates, vehicle lifetime, and material substitution factors have been assumed, and it is difficult to compare the results from the different studies. To provide clarity in discussions of the energy and GHG benefits of vehicle lightweighting we present a comprehensive review of the results from the published studies. To facilitate a direct comparison of results from the various studies we adjusted the LCA results in two steps. First, the results were normalized by dividing the lightweighted results by the baseline results. Second, the results were harmonized to reflect a common set of input assumptions for key parameters.
—Kim and Wallington
They reviewed 43 available studies on the benefits of lightweighting, and selected the GHG emissions and primary energy results from 33 studies (and 119 scenarios) that passed a screening process. Eleven studies and 40 scenarios were of total vehicles; 22 studies and 79 scenarios were of vehicle components.
Of the 79 component scenarios, 70 addressed substitution of steel or iron used in body or engine with lighter materials; 5 scenarios compared aluminum with other materials for powertrain components; and 4 scenarios addressed mixed materials.
They then harmonized the results from these 33 studies using a common set of assumptions (lifetime distance traveled, fuel-mass coefficient, secondary weight reduction factor, fuel consumption allocation, recycling rate, and energy intensity of materials).
Vehicle LCAs. Across the range of the total vehicle LCAs, the use phase accounts for 63−92% of the life cycle energy consumption; materials production 8−32%; manufacturing and assembly 1−4% and the rest <4%. The upper bound of lightweighting and associated life cycle energy savings for the total vehicle LCA is ∼40% and ∼25%, respectively, much smaller than those for component LCA.
All the lightweighting scenarios of total vehicle that describe intensive use of aluminum, magnesium, or composites resulted in reduced life cycle energy; the energy reduction per weight saving during the use-phase is much smaller than for the component level scenarios. This stems from the fact that vehicle weight accounts for only part of the use-phase fuel consumption in total vehicle LCAs with the balance being related to aerodynamic factors, the authors noted. Weight reduction thus results in a less than proportional energy consumption reduction during the use-phase. In component LCAs, on the other hand, the fuel consumptions related to aerodynamic factors are not accounted for in the use-phase.
Component LCAs. In the reviewed studies, the use phase dominates the life cycle energy demand for the baseline steel components accounting for 66−97% of the total, followed by the materials production phase contributing 3−20%. In the lightweighting scenarios, material production accounts for 3− 55% of total life cycle energy demand, while manufacturing and assembly account for 1−16%.
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Life cycle energy benefit of lightweighting components before and after harmonization for common lightweight materials with steel as the baseline material. Values below 1 indicate that lightweighting decreases the life cycle energy use. (CFRP = carbon-fiber reinforced plastic, GFRP = glass-fiber reinforced plastic, HSS = high-strength steel, c = fuel-mass coefficient). Credit: ACS; Kim and Wallington. Click to enlarge. |
Among their findings and conclusions from the study:
LCA results of lightweight vehicles or vehicle components should be carefully interpreted as the results are sensitive to the methodology used, and values assumed for parameters and a wide range of values and choices have been used. In particular, they noted, component-level LCAs present often inconsistent conclusions across studies regarding the life cycle benefits of lightweighting materials.
Harmonization of each parameter highlights significant uncertainties in the life cycle benefit of lightweight materials. Depending on the materials production method (the Pidgeon or electrolytic process), recycling rate, and to a lesser extent on data source, the available studies indicate that the primary energy demand from magnesium production and recycling is 39−360 MJ/kg, while energy demand for the same phases of aluminum ranges from 26−249 MJ/kg.
The primary energy demand from steel for these phases ranges less widely: 12−54 MJ/kg. Magnesium and aluminum can substitute for steel at a ratio of 0.3−0.6 and 0.4−0.8, respectively. Hence, the authors point out, the energy demand for combined materials production and recycling phase for these metals would be essentially the same as for steel when the lower bound of energy demand is used.
Therefore, choices of material source can eliminate the disadvantage of these metals associated with high energy intensity during materials production, although such choices are often limited by quality or process constraints, they conclude.
We note that the substantial database of LCA studies shows that all the lightweight materials discussed here have a significant potential of reducing life cycle energy when avoiding energy-intensive material production processes. In particular...using aluminum, glass-fiber reinforced plastic, and high strength steel to replace conventional steel was found to significantly decrease the vehicle life cycle energy use in all studies after harmonization to a common set of assumptions. The same conclusions are drawn for GHG emissions after normalization and harmonization...as fossil fuels are the dominant energy source for vehicle operation in the reviewed studies. Further investigations would be needed to reduce uncertainties around the life cycle environmental benefits of using magnesium alloys and carbon-fiber reinforced plastics in vehicles.
The current harmonization shows that whether lightweighting reduces life cycle energy demand and GHG emissions depends on material source and process type or inventory data source for these materials. Given the flexibility in options implied by the variety of materials available and the broad consensus that they have energy and emissions benefits...we conclude that lightweight materials (particularly Al, GFRP, and HSS) are likely to see increased use in automobiles.
—Kim and Wallington
Resources
Hyung Chul Kim and Timothy J. Wallington (2013) Life-Cycle Energy and Greenhouse Gas Emission Benefits of Lightweighting in Automobiles: Review and Harmonization. Environmental Science & Technology doi: 10.1021/es3042115
The same firm claimed, not too long ago, that HEVs could not be built competitively. Their new Lincoln MKZ Hybrid 2013 sells for the same price as the non-hybrid version? What a change of mind in a very short time?
Cars made with recycled aluminum have lower energy and pollution foot prints, weight 35+% less and will soon be mass produced at the same price as the steel units.
New Aluminum made with clean Hydro electricity also has lower emission foot prints than most steel.
Future light composites will also become very competitive.
Posted by: HarveyD | 29 May 2013 at 02:20 PM
Harvey,
I admire your optimism but not your realism.
Any new car chassis will be increase demand for new aluminium with the same amount. There is no spare recycled aluminium in the market!
There is also no spare clean hydro power in the market just waiting be used for bauxite conversion.
when all the hydro/solar/wind/nuclear power has been used, where do you get incremental power for incremental new aluminium?..
You offer your predictions about the future 'free of charge'. I suppose that means that you also accept no liability, should you be wrong? ;-)
Future light composites may become competitive. Who knows? Currently they cost 40 times as much as aluminium, according to Dr Harald Ludanek of VW, said about the CFRP used for the VW XL1 prototype at its unveiling in 2011.
Posted by: Thomas Pedersen | 30 May 2013 at 07:07 AM
TP...
The same comments were used against aluminum/magnesium wheels versus steel wheels not so long ago. Many new cars currently come with alum/mag wheels as standard equipment. More and more car owners use Mag wheels as summer wheels and keep the steel units for winter. Price wise: Mag = $99 and Steel = $69 or about an extra $120 for four. That is not much extra on a $30,000+ car?
we have 6 large aluminum plants and have enough hydro energy for at least 10+ more. Each plant can produce 200,000 to 400,000 tonnes/year. Golf States and Russia could produce even more with their excess NG. The price of aluminum is relatively stable.
A new process can extract 7 B lbs of aluminum + other minerals from a single local clay site. Raw materials to produce aluminum are not rare.
Oceans and land fills are being covered with used aluminum and plastic cans instead of recycling. Many vehicles could be built with waste materials if 95+% were recycled.
The price of most composites will go down like the price of EV batteries with mass production.
Please do not fall to manufacturers PR and financed studies too easily.
Posted by: HarveyD | 30 May 2013 at 08:54 AM
New ultra strong fibers and nano fibers such as artificial spider fiber, may be used to created very strong composites in the not too distant future.
Three D printers operating 24/7 will produce much lower cost complex precision composites parts for future much lighter ground vehicles.
Of course, the steel industry and supporters of huge heavy vehicles will fight evolution for decades. Resistance to change is inevitable
Lately, pipelines and Tar Sands industries are flooding the areas with news about how 'blue' and 'white' the future would be by replacing imported light Oil with heavy Tar sand Oil.
Not a word about the disposal of highly polluting Petroleum Coke and the extra 17% emissions for heavy Oil.
Detroit heavy oil (from Tar Sands) refineries (and adjacent areas) are faced with Petroleum Coke stock piles problems now and it is nasty. China is not too eager to buy that junk.
Posted by: HarveyD | 30 May 2013 at 09:33 AM
HarveyD has a point.
Material science has made huge strides. Nano processes and glass-fiber reinforced plastic could make huge improvements.
Sad thing is, some 1960's cars weighed under 2000 lb., simple 1980's Hondas were getting 50 mpg, yet they disappeared.
Posted by: kelly | 30 May 2013 at 09:40 AM
Kelly,
Have a look at fueleconomy.gov. 1980s Honda Civics got roughly the same fuel economy as 2013 Honda Civics, and that's not even taking into consideration the Civic Hybrid. The difference is that the rating system has been refined, so the claimed numbers are much more representative of average use. Current Civics would get 50+ mpg under the old system.
New Civics are also much bigger and safer than they were in the 1980s, and they emit a lot less HC, NOx.
Posted by: Bernard | 30 May 2013 at 11:53 AM
@Bernard, http://www.mpgomatic.com/2007/10/16/honda-civic-gas-mileage-1978-2007/
Read um 'n weep. There are over ten, >50 mpg 1980's Honda's listed.
"..the rating system has been refined" actually means auto makers can cover a failing trend.
Posted by: kelly | 30 May 2013 at 12:44 PM
kelly,
Go back to the source (fueleconomy.gov). They've converted the old ratings to the new system, and also provide the option of seeing what the old sticker said (click on "View Original EPA MPG").
The link that you provide confuses the two rating systems, and it also confuses the CRX (two seater) with the Civic (small family car). The corrected figures for the CRX HF are below 50mpg, by the way.
In other words, cheer-up. You are pining for good old days that never existed, when in fact you are living in the real good old days.
Posted by: Bernard | 31 May 2013 at 05:33 AM
Recycled aluminum uses only 5% of the energy to make new aluminum. The Tesla Model S has an aluminum chassis and body that saves weight.
All those big brown UPS trucks were aluminum and fiberglass so that they could carry lots of packages and not weigh a lot. Combine that with diesel, or better yet diesel hybrid like the 1999 PNGV cars and you get improved mileage with less oil usage.
Posted by: SJC | 31 May 2013 at 05:54 AM
Bernard,
I went back to fueleconomy.gov samples and beyond:
http://www.fueleconomy.gov/feg/calculatorCompareSideBySide.jsp?column=1&id=5262
multi-multi-multi-level drill down by model
http://www.mpgomatic.com/2007/10/16/honda-civic-gas-mileage-1978-2007/ all models clearly listed
http://www.cargurus.com/Cars/1989-Honda-Civic-CRX-Specs-c9086 all models clearly listed
The government obscured it's own screwed-up altered mpgs, then obscured those screw-ups with compound level drill-down screw-ups to specific model mpgs that don't match actual test drives and reviews of the time.
It's called government OBFUSCATION - the hiding of intended meaning in communication, making communication confusing, willfully ambiguous, and harder to interpret.
The sample mpgs vary from 24 to 56. With the effort the EPA put into 'clouding' the info - just accept the readable, non-government(more honest) mpg listings.
The only significant increase between the 1980s and 2000s Honda(non-hybrid ICE cars) is overweight, NOT mpg.
Posted by: kelly | 31 May 2013 at 06:54 AM
kelly,
You are correct. This conspiracy runs deep!
It's so bad that even GCC recently ran an article claiming that EPA "adjusted" figures are well within 10% of user-reported figures (as opposed to EU figures which are 25% off).
greencarcongress.com/2013/05/icct-20130529.html
Thank you for alerting the community to this government obfuscation. I hadn't yet realized that 30 year old mpg figures played such a key role in the conspiracy! I have now been enlightened, although I must admit that the obfuscation is working, since I'm not fully convinced that you are not a part of the conspiracy.
Some of what I wrote above is in jest, but even I don't know what part. The conspiracy is so deep that I can't trust myself!
Posted by: Bernard | 31 May 2013 at 07:55 AM
Bernard, trust the physics. If the car is over 20% heavier, but with still basically the same small ICE engine - mpg will decrease.
Posted by: kelly | 31 May 2013 at 09:21 AM
Bernard and Kelly...most gains in fuel consumption reduction are very recent (last five years or so). We may have Toyota (HEVs and copy cats), the current US's Administration and higher Oil price to thank.
The near term arrival of many more HEVs, PHEVs, BEVs, lighter, more efficient ICEVs and electrified buses-light trucks-taxis will further reduce fuel consumption in the next five years.
Posted by: HarveyD | 31 May 2013 at 09:25 AM
I'll mention a 2013 EPA non-ICE example.
WITHOUT altering the original years old battery, through 150 lb. weight loss and motor/system tuning, Nissan improved the Leaf range by 15% in just two market years.
This is known throughout the 96% of non-US humanity.
EPA stumbles in, changes its rules, and the EPA sticker range only improves from 73 to 75 miles - LESS THAN 2%, which is totally misleading.
Maligning the EV range progress rate is criminal at this early EV stage.
Posted by: kelly | 31 May 2013 at 09:53 AM
..LESS THAN 3%,
Posted by: kelly | 31 May 2013 at 10:06 AM
Sorry Bernard, some **** deleted the EPA Leaf mislabeling.
Posted by: kelly | 31 May 2013 at 10:08 AM
"criminal"
Add the rule of law to things kelly does not understand.
Posted by: Kit P | 31 May 2013 at 04:02 PM
Misleading sales information is often called fraud - something you/your industry is quite familiar with.
Posted by: kelly | 31 May 2013 at 06:40 PM
kelly,
EPA testing protocols are published and well known. Nissan isn't contesting the EPA results, but you can go ahead and do that. The great thing about science is that it's reproducible.
Highway mpg (which is what you've mentioned exclusively so far) doesn't have that much to do with weight. It has to do with friction, aerodynamics, and combustion efficiency. Huge advances have been made in all three of these areas in the past 30 years.
Take aero for instance. Drag coefficient maps almost directly to fuel use at speed. So, for instance, reducing drag from .40 to .30 will reduce fuel use by 1/4 at highway speeds.
Combustion efficiency is another big factor. Your beloved mid-80s Civic used a carb and two-valve heads with fixed camshaft timing. It didn't have knock sensors, so it was tuned from the factory for the lowest quality gas. The carb couldn't measure air mass, so the mixture was extremely conservative. It was set-up to work in Miami (sea level) and Denver (mile high), Phoenix and Anchorage, all at the same time.
Friction isn't as glamorous as the other two categories, but think about what motor oil was available in 1985 (10W30) and what Honda uses now (0W20). Compare old and new piston rings and cylinder wall finishes. Look at how bearings are designed and manufactured. A lot has happened in 30 years.
Most of these advances are chronicled right here on GCC. I am disappointed that someone who is such a prolific commenter on the site is substantially unaware of technical progress in the automotive industry.
Posted by: Bernard | 01 June 2013 at 05:58 AM
@Bernard, part of this discussion is not technical nor really debatable:
The EPA changes it's mpg testing rules. The public is left comparing apples and oranges.
You did not drill the many levels down to each model year and variant on fueleconomy.gov and compare to the clear site Honda mpg lists I provided - WHY?
Because you would still be working on it and, as you say, "I must admit that the obfuscation is working."
Being consistent, the 2013 Leaf EPA range would be 82 miles, not from 73 to 75. What can Nissan contest as the EPA rates ALL their future cars as well?
Eight(8)% annual improvement is vastly better than almost 3%.
Which percent will people put their money on?
"It has to do with friction, aerodynamics, and combustion efficiency. Huge advances have been made in all three of these areas in the past 30 years."
And the article is about "..clarifies benefits of lightweighting", yet - despite the 'friction, aerodynamics, and combustion efficiency. Huge advances' - where's the "Huge advances" in MPG.
Perhaps one shouldn't gloat about automaker "friction, aerodynamics, and combustion efficiency.. Huge advances.."
The fastest 'aerodynmics, etc' advances are on a Blackbird Mach 3+ jet first flown in 1962.
Posted by: kelly | 01 June 2013 at 10:02 AM
It takes a certain dose of courage and bravery to admit that we have been had for decades by PR campaigns from the Big-3.
The real facts are, that most of their products got progressively worst or did not improve for about five decades or up to 2008 or so.
My last US car was a 1990 Buick. I got tired of replacing-repairing the A/C unit every year, generator, starter, etc and was happy to dump it while it still 'looked' like new. The original tires were awful and lasted less than 25,000 miles.
By mid-1990 I did like my wife and I switched to Nissan Maxima and Toyota Camry with 'M' tires and I enjoyed trouble free driving since. I have to admit that I'll copy cat my wife again and go for a Camry HEV very soon. She's very satisfied with her Prius III.
Posted by: HarveyD | 01 June 2013 at 10:09 AM
@Bernard, perhaps part of this discussion is not technical nor really debatable:
The EPA changes it's mpg testing rules. The public is left comparing apples and oranges.
You did not drill the many levels down to each model year and variant on fueleconomy.gov and compare to the clear site Honda mpg lists I provided - WHY?
Because you would still be working on it and, as you say, "I must admit that the obfuscation is working."
Posted by: pat | 01 June 2013 at 10:27 AM
If consistent, the 2013 Leaf EPA range would be 82 miles, not from 73 to 75.
What can Nissan contest as the EPA rates ALL their future cars as well?
Eight(8)% annual improvement is vastly better than almost 3%.
Which percent will people put their money on?
"It has to do with friction, aerodynamics, and combustion efficiency. Huge advances have been made in all three of these areas in the past 30 years."
And the article is about "..clarifies benefits of lightweighting", yet - despite the 'friction, aerodynamics, and combustion efficiency. Huge advances' - where's the "Huge advances" in MPG.
Perhaps one shouldn't gloat about automaker "friction, aerodynamics, and combustion efficiency.. Huge advances.."
The fastest 'aerodynmics, etc' advances are on a Blackbird Mach 3+ jet first flown in 1962.
Posted by: pat | 01 June 2013 at 10:29 AM
"The public is left comparing apples and oranges."
Actually, all cars available in the US since 1984 have been re-rated using the new, more accurate system. As noted earlier, you can also view the original ratings by clicking on a clearly labelled link. It really could not be easier, even if you clearly do not like the results that you get.
I trust that you actually understand that aerodynamics above the speed of sound (and actually, a little below) are completely irrelevant to mass-produced automobiles. If not, I can't help you.
Posted by: Bernard | 01 June 2013 at 01:29 PM
Title: "Ford LCA harmonization study clarifies benefits of lightweighting for vehicle life cycle energy use and GHG emissions"
In other words, more vehicle weight requires more energy use, which leads to fewer miles per gallon(MPG).
Re-rating EPA MPG figures obscures trends.
Your help doesn't alter the above facts.
Posted by: kelly | 01 June 2013 at 01:54 PM