Why does an aircraft consume less fuel than a car?

At first glance, an aircraft with its huge engines consumes more than a car. To fight pollution, one of the demands of yellow vests is the application of a tax on kerosene, aircraft fuel. However, in reality, airplanes consume as much or even less fuel than small city cars! Here is why....

A Shell truck next to an aircraft (source:Shell Ouest)

Take the example of the A320, a 180-passenger commercial aircraft with a fuel consumption of approximately 303 litres per 100 km according to Airbus. Then take France's best-selling car in 2018, the Renault Clio 4, which consumes 4.45 litres/100 km. At first glance, the Airbus consumes 67 times more fuel than the city car.

A Renault Clio car (Source:caradisiac)

Unrealistic figures

 The reports of the European Environment Agency specify for Europe, the CO2 emissions of different means of transport.
* 14 g CO2/passenger/km for the train
* 42 g CO2/passenger/km for a small car
* 55 g CO2/passenger/km for an average car
* 68 g of CO2/passenger/km for a bus
* 72 g CO2/passenger/km for a two-wheel motorized vehicle
* 285 g of CO2/passenger/km for an aircraft

These figures seem to show that the aircraft is the most polluting, but are they realistic?  First of all, these figures are beginning to be exceeded, with the arrival of more efficient aircraft and cars. The figure of 55 g CO2/passenger/km for an average car assumes that the car is occupied by 4 people, and that the figure of 285 g CO2/passenger/km for the plane assumes 88 people as the occupancy rate. However, these figures seem far from reality: the average occupancy rate of a car in France is 1.1 people per vehicle for short journeys and 2.2 people for long journeys. On the aircraft side, occupancy rates are much higher. In March 2018, Ryanair's filling rate increased to 95%. The low-cost airline is also showing an improvement in the filling rate of its aircraft (93% compared to 91.5% at the end of 2016). Record occupancy rates also for the world, at 81.2% on average, up 0.9 percentage points compared to 2016. As a result, pollution is lower for each passenger. Knowing that the A320 consumes 3000 litres of kerosene per km and that 1 litre of fuel represents 2,580 kg of CO2. This number is then divided by the aircraft's 146 passengers. It is therefore estimated that about 53 g CO2/passenger/km of CO2 is emitted.

Pollution coming from cars (Source:20minutes)

All these figures are questionable for several reasons. 

Different factors are involved. The figures concerning the consumption of the aircraft vary according to the type, the filling rate, the weight and size of the aircraft, the engine consumption, the flight phase, the weather, the air route, the altitude, the jet stream,... Similarly for the car, it depends on the vehicle, the number of passengers on board, the mass, the maintenance of the vehicle, the road,...


According to Airbus data, each time an A320 travels one kilometre, it consumes about 3 litres of fuel, which gives precisely 303 litres per 100 kilometres (L/100) or about 1.7 litres per passenger per kilometre. So we're well below the 4 liters of the city car! Here we divide fuel consumption by the vehicle occupancy rate.

An Airbus A320 (Source: actu.fr)

The most fuel-efficient airline is Norwegian Air Shuttle with 44 pax-km/L (2.27 L/100 km[104 mpg-US] per passenger), thanks to its fuel-efficient Boeing 787-8, a high load factor of 85% and a high density of 1.36 seats/m2. Aircraft carry far more passengers than any car. While an A380 can carry up to 853 passengers, the Renault Clio can only carry 5 passengers, and this in theory.

A second parameter must be taken into account: that of distance. The plane obviously travels more than 1 kilometre in 1 hour compared to a car. Over long distances, such as Paris-Shanghai, the plane travels the distance much faster.

The plane remains polluting

Flying for short distances seems to be polluting, compared to other means of transport: train, car, bus,... In addition, the development of air transport is creating more flights and therefore more CO2 emissions worldwide. Every year, new people use the plane for trips they would never have made by car.

More environmentally friendly aircraft

New planes are coming out of the factories. They integrate ever more efficient reactors and technological innovations that reduce fuel consumption. Thus, the A320 neo, Boeing 777X, Boeing 787, Boeing 737-MAX, A350, and others reduce CO2 emissions.

Similarly, cars are also more efficient. Aircraft have reduced their fuel consumption more than cars at the same time, although improvements can be seen. Hybrid, electric, hydrogen-powered cars seem to be the future of the automobile.

An Air France aircraft using biofuel (Source:afp)

The Easyjet electric aircraft project (source: le Parisien)

Conclusion

It can therefore be said that, contrary to popular belief, airplanes consume much less fuel than cars. The total consumption of an aircraft is higher than that of a car but is distributed among all passengers. However, aircraft pollute more than cars and release more CO2 into the atmosphere. It is therefore preferable to use them to travel long distances (example: Paris-Shanghai). In the coming years, aeronautics may be able to offer more environmentally friendly aircraft, such as electric aircraft.

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— Air and Space news (@airspace_news) December 15, 2018

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