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For an airline, what is the decrease in fuel burned with a 1kg decrease in passengers/luggage?
Hello and thanks for your question regarding the decrease in burned fuel associated with a 1kg decrease in passengers and/or luggage. The most helpful sources I found were from How Stuff Works, The Calculator Site, and GS Clean Energy. Unfortunately, this question cannot be given a straightforward answer as it is contingent on several variables. But I have provided a formula from which you should definitely be able to justify encouraging weight reduction on board commercial flights.
METHODOLOGY
As previously stated, specific numbers depend heavily on variables, such as aircraft type, passenger weight, weight of carry-on's and luggages, distance of flight, how much fuel is on board (and weight thereof), fuel efficiency of the specific aircraft, etc. Having said that, most of the research on this subject looks at the Boeing 747, as that is the most common aircraft in the world and your request encourages the nomination of a standard aircraft by which we can judge fluctuating fuel efficiencies. I thought the most straight forward way to frame this answer would be to use what data I found regarding the fuel efficiency of a Boeing 747, and the figures for average fuel burned per passenger per mile. I used the average body mass of a airplane passenger and his or her in kg to ascertain an informed estimation for the amount of fuel burned at the rate of a single kg. I began the report by provided some general facts and figures pertaining to the Boeing 747 consumption and average passenger weights. I then inputted some of those figures into a formula which would help us figure out about how much fuel is burned per kg per mile. It should be noted that some of these articles are older than 2015--that is because the data hasn't been updated on any kind of a regular basis. However, weight of aircrafts have not changed drastically since 2013. Thus, these numbers are still relevant and applicable.
BOEING 747 WIEGHT AND STATISTICS
At a glance, "the Boeing 747 burns approximately 10 to 11 tonnes of fuel an hour when in cruise. This equates to roughly 1 gallon (approximately 4 litres) of fuel every second. It can carry up to 238,604 liters of fuel. It has a range of about 7,790 nautical miles."
A recent article on the mathematics of airline luggage and fuel costs indicated a few key points about fuel ratios and weight. First off, the maximum takeoff weight for a Boeing 747-100 is 333,390 kg. Of that, only 162,400 kg is the air-frame weight. The weight of fuel is 23,552 more, and then about 240 kilos for the weight of the 3-man crew. Insofar as the average weight for a passenger is concerned there is "a basic rule of thumb of 79 kg per male and 57.6 kg per female." The article also notes that the average for checked luggage is 30 kg and an average of 7 kg for carry on luggage.
In another article there is a chart which breaks down the rate of kg worth of fuel burned, number of seats, and a how much fuel is burned per passenger. For B747-400, the burn-rate is about 102.4 kg per passenger. It varies by type of plane, number of seats, how much fuel the craft can hold, etc. This statistic is based on the burn rate of trip from New York (JFK) to Los Angeles (LAX).
CO2 offset research indicated that only "on ce total emissions for a flight are known, emissions per passenger can be calculated. It is important to note that calculators differ in how they take into account cargo versus passenger load, seat occupancy rate, and seat class." Basically, a hard and fast answer cannot be provided preemptively or generally. Exact numbers will vary by type of aircraft, amount of fuel, number of passengers/crew members, etc.
Further emissions research concluded that 145,000 pounds is the total carbon emission of a roundtrip flight from New York to Phoenix. Furthermore, "carbon emission per passenger: 145,000 ÷ 180 = 806 pounds. Carbon emission per passenger per mile: 806 ÷ 4,300 = . 19 pounds. Carbon emission per pound of airplane weight per mile: 145,000 ÷ 155,000 ÷ 4,300 = .0002 pounds."
An explanation on How Stuff Works provided a concise breakdown of the Boeing 747 fuel costs. Essentially, a Boeing 747 burns 1 gallon of fuel per second, totaling about 36,000 gallons in a 10-hour flight. This flight can carry 568 people, but the article estimates per 500 people (since flights generally aren't filled to capacity). Based on this, the plane is burning .01 gallons per person per mile, including luggage.
In light of these figures, the calculation based on a 1,000 mile trip is as follows:
Average weight of a passenger is 116 kg (based on a male, with one carry on and one checked bag 79+30+7= 116 kg)
Broken down to a single kg, the plane burns ~0.00009 per mile (.01 gal divided by 116 kg)
Thus, a Boeing 747 would burn roughly .09 per kg on a 1,000 mile trip
(0.00009 x 1,000)
SUMMARY
As this is a very complex question, subject to change as a long list of variables fluctuate, I provided a concise formula to estimate the amount of fuel burned per kg per mile in the best way possible. With this formula you can feasibly plug in different mileage counts and flight itineraries to estimate the amount of fuel burned per kg for specific flights.
Thanks for choosing Wonder!