ICCT Study Finds Commercial Aviation Efficiency Improvements Have Stagnated Over Last Two Decades; Need for Comprehensive CO2 Standards for Aviation
28 November 2009
| Aircraft efficiency, measured in terms of both passengers alone (passenger-km) and passengers plus cargo (ton-km), has doubled since 1960. But little improvement has come in the past two decades. Source: ICCT. Click to enlarge. |
An analysis of sales- and activity-weighted fuel efficiency for new jet aircraft from 1960 to 2008 shows that while aircraft efficiency has doubled since 1960, advancements in the efficiency of commercial aircraft have stagnated in the last two decades. Without an effective carbon dioxide emission standard, fuel prices alone are unlikely to spur large improvements, suggests the study by researchers at the International Council on Clean Transportation.
ICCT researchers modeled the fuel consumption of more than 25,000 planes produced and delivered over the past 50 years. Fuel burn was simulated for full loads over design-range routes, and calculated on the basis of both seat-kilometers (i.e., passengers alone) and ton-kilometers (passengers plus cargo).
The analysis found that fuel efficiency increased 80% from 1960 through the end of the 1980s, with most of the progress coming during the arrival of wide-body aircraft in the late 1960s, and with the development in the 1980s of more efficient mid-range aircraft such as the Boeing 757 and 767.
During the 1990s however, efficiency gains dropped to less than one percent annually. On average, fuel efficiency has remained flat on a seat-km basis and improved only 0.29% annually on a ton-km basis since 2000. However, fuel costs rose dramatically from about 10% of operating expenses in 2004 to peak at more than one-third in 2008.
Conventional wisdom holds that fuel prices drive constant improvements in new aircraft efficiency, but this analysis suggests efficiency improvements actually tend to come with the introduction of new designs, which are much less common today.
—ICCT senior researcher Daniel Rutherford, who co-authored the study with researcher Mazyar Zeinali
In the two decades that efficiency has stagnated, the introduction of new aircraft designs has slowed considerably. The lack of new designs has approximately tripled the average age of operating aircraft production lines since 1990. Efficiency improvements by manufacturers may be going more to improving performance, range and customer amenities rather than reducing fuel consumption.
These improvements impose a fuel efficiency penalty, particularly on a seat-km basis, on passenger aircraft by boosting empty aircraft weight and drag during cruise. These trends suggest that aircraft manufacturers reacted to low fuel prices by devoting an increasing share of component efficiency improvements to boosting the performance of passenger aircraft instead of reducing fuel burn and emissions.
Such a development would be consistent with Peeter et al.’s (2005) finding that other performance attributes, notably speed and range, were prioritized over fuel efficiency during the transition from piston-driven to jet aircraft during the late 1950s and early 1960s.
—Rutherford and Zeinali
Applying a carbon dioxide standard only to new production lines, as the UN’s International Civil Aviation Organization (ICAO) has proposed, could actually prove counterproductive by encouraging manufacturers to delay the introduction of more efficient designs in favor of older, unregulated models, the study suggests. To avoid such an outcome, the ICCT study concludes that a standard covering aircraft from both new and existing lines would be most effective.
Commercial aviation currently accounts for about 12% of carbon dioxide produced by the transportation sector. That figure will grow to 19% in 2050, according to International Energy Agency projections.
Resources
Daniel Rutherford and Mazyar Zeinali (2009) Efficiency Trends for New Commercial Jet Aircraft, 1960 to 2008
"Efficiency improvements by manufacturers may be going more to improving performance, range and customer amenities rather than reducing fuel consumption."
This is hard to swallow. Commercial jets fly about the same speeds now as they did back in 1960; about Mach .89 on average. Improved range is mainly a by-product of efficiency and customer amenities are going to make a difference if they add weight although I'm not sure what is meant by this. In the case of an airline like Jet Blue surely the weight of video screens installed in every seat is countered by the minimal food and preparation equipment carried on board.
What I think we really see here is the three dacade long transition from the turbo-jet to the far more efficient turbo-fan engine. This was relatively low-lying fruit for the industry as the technology was basically paid for by the US government. The next breakthrough in efficiency is surely to be difficult to achieve as we are witnessing in the painful development of the Boeing 787.
Posted by: RD | 28 November 2009 at 08:19 AM
One of the major efficiency improvements over the past two decades has been the increase in load factor. The incremental airplane fuel use of going from 65% full to 100% full is fairly small. The per passenger mile fuel use is reduced by about 25%.
This source of improvement is nearing its limits as the scheduling and booking systems are now routinely getting over 90% load factor for airline averages. The next such major external improvement source will be through more direct and efficient flight routing. This requires major overhaul of older aircraft navigation systems and redesign of air traffic control systems and procedures. The results from early deployments indicate that this will be a smaller improvement that is in the 5-10% range.
Posted by: fairhavenhorn | 28 November 2009 at 08:38 AM
As the world's standard of living rises and air transport grows, it is not feasible that further efficiency improvements alone can usefully limit CO2 emissions. Barring electric airplanes we will have to use carbon-neutral artificial fuels made from atmospheric CO2; better to start that sooner than later.
Posted by: richard schumacher | 28 November 2009 at 09:55 AM
Significant improvements in efficiency can be accomplished by using pulse detonation engine technology. This is being developed by major engine manufacturers such as Rolls, Pratt, and GE.
Posted by: Mannstein | 28 November 2009 at 03:49 PM
Or, we could reserve biofuels for aviation use, and promote only biofuel programs which have a low carbon footprint. General commuter transportation would use EV's, and long haul trucking would use fuel cells and hydrogen refined from natural gas, along with carbon sequestration at the site of stripping.
Posted by: Mark_BC | 28 November 2009 at 05:21 PM
Who makes the carbon neutral jet fuel? Is that much the same as clean coal burning power plants?
Where are those two technologies used?
Posted by: HarveyD | 29 November 2009 at 07:46 AM
Mark,
You may be on to something. If the biofuels can be used for planes, EVs for cars and DME for trucks, we can reduce imported oil and net carbon emissions.
Posted by: SJC | 29 November 2009 at 09:24 AM
I don't know, but different feedstocks can have dramatically different footprints. Waste cellulosic or algae sources come to mind. Can these be relatively easily converted into aviation fuel?
Posted by: Mark_BC | 29 November 2009 at 10:23 AM
Nobody makes carbon-neutral jet fuel commercially today, just as nobody yet builds jet engines with twice today's energy efficiency. But we do know that carbon neutral fuels can be made; see
http://www.greencarcongress.com/2008/02/los-alamos-deve/comments/page/2/
The fuel is relatively expensive, but it's easy to foresee a time when jet fuels costs more than $5 per gallon even without including the indirect costs of CO2 pollution. Include those, or apply a fossil carbon tax, and artificial carbon-neutral fuel becomes very attractive. More efficient engines would complement this by reducing overall costs.
Note that nuclear power is not required for the process; any carbon-free energy source can be used.
Posted by: richard schumacher | 30 November 2009 at 08:22 AM
Note also that this is not a biofuel. Biofuels sound good, and they certainly can be made, but because of the collection area required they may never be more than a minor contributor to carbon-neutral energy.
Posted by: richard schumacher | 30 November 2009 at 08:26 AM
To me, a fuel made from biomass is a biofuel, whether fermented or synthesized. I generally refer to biofuels as those made from biomass gasification and fuel synthesis. You can make alcohols or petroleum fuel synthetic equivalents, but it is my impression that it is not done because oil derived fuels are and have been cheaper.
I guess semantics is a big part of the discussion. You can make synthetic fuels from coal and natural gas, but I do not call those biofuels. Fermentation takes a lot of water and is a relatively slow process, but has gained favor. With gasification and synthesis of biomass, you can make whatever fuels you want and make them more carbon neutral.
Posted by: SJC | 01 December 2009 at 06:11 AM