Lightweighting is top of mind right now to aviation and transportation designers as they race to meet new CO2 emissions reduction mandates set by government regulators. Designers favor the lightweighting approach because it is a way to increase fuel economy; the less something weighs the less energy it takes to operate. But is lightweighting really the best option to reducing emissions?
While it is certainly necessary, we do think it’s a narrowly focused option. WorldAutoSteel recommends a more holistic approach for products (and we use it extensively ourselves): Life Cycle Assessment (LCA). LCA examines the complete life of a product and the energy and resources required to fulfill each life phase of that product. Just because something weighs less during its useful life (use phase) it does not mean it will be easier on the environment over its total life from manufacturing (production phase) to end-of-life recycling and disposal (end-of-life phase). Without an LCA product strategy, decisions can be made that may improve one phase of the product’s emissions, but increase emissions somewhere else along the total life cycle.
A study conducted on composite airplanes, a new materials trend in aviation, gives a fascinating example of the importance of using LCA to ensure a total emissions savings across a product life cycle, in this case a very big product. It was particularly interesting to us because the outcomes were exactly the opposite of what happens with automotive materials. The study draws these conclusions:
LCA Assessment Comparing Composite and Aluminum Airplanes
- Composite airplanes create much more GHGs in the production phase compared to aluminium (baseline) planes due to its energy intensity. But over a long lifetime, a composite plane creates up to 20% fewer CO2 emissions than its aluminium equivalent due to decreased fuel use. In fact the study states that the production phase emissions are offset “in just a few international flights.”
- Because of the significant fuel savings, composite planes offset the higher production emissions rather quickly in their lower use phase, since airplanes use such huge amounts of fuel. It’s logical—when fuel is being measured in pounds (or kilograms) per hour, a weight reduction is going to be exponentially better on emissions.
- The net result is that composite planes have a significant advantage over aluminium at the end of a rather long life.
Being the LCA geeks that we are, we couldn’t help but draw some conclusions and comparisons between our own material and aluminium in the automotive industry. Over the years, we’ve done a number of LCA case studies comparing vehicles made from Advanced High-Strength Steels to vehicles made from aluminium, using the University of California at Santa Barbara Automotive Energy and Greenhouse Gas Model. We conducted a Light Duty Truck and a Sport Utility Vehicle case study to see how material choices and significantly reduced weight affects fuel economy and life cycle emissions. Aluminium sometimes can be used to reduce vehicle weight significantly; yet there is a very different total life cycle emissions result with vehicle material choices than with the composites in the airplane study. Why? It has to do with a few things:
WorldAutoSteel LCA Assessment Comparing Aluminum and Advanced High-Strength Steel Cars
- Aluminium creates seven times more emissions in its primary manufacture than steel, even though less material is used (see the graph above).
- Even what seems like a significant vehicle weight reduction does not necessarily lead to a significant fuel savings, which means that the production phase emissions are not always offset in use phase savings, as they are in the composite plane with the giant fuel tank and flights that are thousands of miles/kilometers. For example, in our Light Duty Truck case study, a whopping 300 kg mass savings led to just 1-2 miles per gallon fuel savings over a 12-year life time, total.
- Even in cases where the increased production emissions are offset, this offset does not happen until much later in the vehicle’s life cycle, often not until the vehicle is recycled.
- Net result of all of this from a life cycle perspective is that aluminium cars, even though they might be slightly lighter, often result in higher life cycle emissions. Or, at best, they show only a minor advantage compared to Advanced High-Strength Steel cars over the total vehicle life cycle in terms of emissions savings (see example below).
There is always a “bottom line” to these kinds of stories, right? Our bottom line is: Conduct product Life Cycle Assessments in tandem with lightweighting to ensure that the decisions made are really leading to lower total life cycle emissions.
We hope you enjoy reading the full article comparing composite airplanes to aluminum planes here. For us, it’s another illustration that confirms the need for life cycle assessment to determine the right course for reducing product emissions.
By the way, most automakers are already using Advanced High-Strength Steels to lightweight vehicles and getting amazing results. Take a look at our Steel Muscle in New Vehicles page for a growing list of examples.