Reducing Carbon Emissions - To Fly or Drive? (or not eat meat?)

There is growing concern about the amount of carbon dioxide (CO2) emitted by airplanes and its contribution to global warming. I hear statements to the effect that one return flight from London to Los Angeles produces as much CO2 per passenger as driving a car for six months. As a result, some people are buying carbon offsets along with their plane tickets (more info here), others are reducing their air travel, or even stopping flying completely. All these are positive steps in the right direction. But I also hear of people who, concerned about global warming, decide to drive rather than fly. It turns out this is not necessarily any better.

To see why, let's look at some figures:

A modern jet, such as an Airbus A341 consumes 22,000 lb of fuel on a flight of 2100 miles, and carries a full load of 120 passengers.

Converting to metric units, that is about 10,000 kg of fuel for 3460 km.

Aviation fuel has a density of around 0.8 gm/cc, so 1 kg of fuel is about 1.25 litre. The fuel consumption then works out to 3 litres per passenger per 100 km. That is about 90 miles per gallon (UK) or 70 miles per gallon (US)

This is more mileage than a hybrid such as a Toyota Prius, which consumes 4.57 litres per 100 km (that's 60 mpg UK, 47 mpg US). Conventional cars get less mileage, and SUVs a lot less.

So flying is more efficient per passenger than a car with only person in it. And correspondingly less CO2 is produced

However, a second factor comes into play with flying. At high altitudes carbon dioxide has a greater warming effect. This is further compounded by the water vapor and nitrogen oxides emitted by jet aircraft, which also contribute to global warming. These factors increase the warming impact of flying by a factor of just under 2 (1.9).

Thus, overall, flying contributes about the same to global warming as a small car. But still much less than an SUV.

What is critical is the distance travelled. And that is where flying takes its toll on the environment. Flying gives us the ability to travel vast distances—distances you would probably never consider driving. You can fly San Francisco to New York, just over 2.500 miles, in five hours. Driving takes you 2 days (non-stop).

Thus, rather than replacing flying with driving, we should be reducing our long-distance travel. That is the real culprit.

But if you do choose to fly... Pray that your flight be full.

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Or... Offset your driving by becoming a vegetgarian!

Producing a kilogram of beef leads to the emission of greenhouse gases with a warming potential equivalent to 36.4 kilograms of carbon dioxide. That is about the same as driving the average European car for 250 kilometres. The production also consumes enough energy to light a 100-watt bulb for nearly 20 days. Animal Science Journal DOI: 10.1111/j.1740-0929.2007.00457.x).

Over two-thirds of the energy goes towards producing the animals' feed. The calculations did not include the impact of managing farm infrastructure and transporting the meat, so the total environmental load is even higher.

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See Also: Global Warning  |  Free Energy?—No Thanks!

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