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Blog on “carbon footprint” from World Bank Group staff air travel

Jon Strand's picture
The World Bank Group (WBG) has highlighted climate change as a critical challenge for sustainable development and poverty reduction in the 21st century.  As part of its own corporate responsibility efforts, the WBG is taking steps to more accurately measure, reduce, and offset its greenhouse gas emissions (in other words, its “carbon footprint”). 

The measurement of the carbon footprint from business air travel is crucial, as it constitutes by far the largest part of the institution’s carbon footprint (at least 55%, and perhaps as high as 70%). Current internationally accepted methods used by the WBG for assessing the carbon footprint due to air travel consist of two steps: First, passenger miles flown by WGB staff are calculated, as a share of global flight activity. Secondly, fuel consumption for WBG air travel is taken to be the same share of global airline fuel consumption.

This calculation however does not account for systematic differences in footprints per traveled distance by travel class, with higher footprints for premium (business and first) classes than for economy class. This may appear surprising: “A passenger is a passenger”, one might say; travel class shouldn’t matter for how much fuel an aircraft burns. The problem with this argument is that the “footprint” of a passenger on a commercial flight depends more on the space taken up by the passenger in the aircraft, and less on how much the passenger (and her or his luggage) weighs. It is true that aircraft fuel consumption largely depends on aircraft weight. But passenger weight is only a relatively small fraction of total aircraft weigh (15-20%). Also, spacing of passengers is very important for how many passengers can be carried. As a result, with more passengers on a given flight, the “footprint” per passenger drops. 

The space taken up by an average traveler is larger in premium travel classes than in economy class, in some cases much larger. Two factors are behind this. First, in premium classes seat spacing is more dispersed. Secondly, load factors (the fraction of available seats that are actually occupied) are in most cases lower in premium classes than in economy class. Our calculations show that a business class passenger takes on average up 2.5 – 3 times as much space in an aircraft as an economy class passenger. The ratio of first-class to economy-class space occupied per traveler is even higher, in some cases 6 or more.

We have recalculated the WBG footprint from data on headquarters-based staff air travel for 2009, based on these premises. Our best assessment is about 225,000 tons CO2, about twice the prevailing estimate, due to the higher “footprint” in business class (64% of all WBG air travel in 2009), and even higher in first class (5% of travel). We have also made some tentative calculations for 2012, and found that this footprint seems to have fallen by about 14%. This reduction is due mainly to two factors: the share of premium-class travel fell from 69 to 66%, and more importantly, first class travel had been virtually eliminated for WBG staff by 2012. The latter reduced the WBG’s air travel carbon footprint by almost 10%. There was also a slight reduction in the overall travel volume of the WBG, by 1-2%.

The costs to offset emissions while accounting for the impacts of different travel classes are not very high. To take some examples, for round-trip travel to London or Frankfurt the Bank’s offset cost, at a carbon cost of $25 per ton CO2 (corresponding, perhaps, to estimated long-term damages from emissions but far higher than current offset market prices), would be about $40 in economy class, and about $80 in business class; and for round-trip travel to Delhi, twice this amount. This constitutes only a few (2-3) percent of basic ticket costs. 

A further step to consider would be to allocate carbon offset payment costs to individual Bank travel budgets, rather than paying them from a central budget as is customary today. This could lead to further awareness on the part of all Bank staff and managers of the carbon footprint of the institution’s air travel.


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