“Recycling one’s rubbish is a gesture of commitment, but the
fitful efforts of individuals do not even nibble at the threat.”
The same might be applied to flying, but would that be a reasonable comparison?
A trip to Teneife is like a 1kW electric fire left on 24/7 for 100 days
I recently flew to Tenerife (for work purposes) and on the ticket it said “Calculated average CO2 emission is 559.70 kg/person”. This amount of carbon dioxide produced can be converted directly into energy consumed by using the figure for the mass of carbon dioxide emitted per quantity of energy for aviation gasoline, namely 65.78 g/MJ, to show me that my trip to Tenerife expended 2.4 MWh. This is the same as the energy expended by a 1 bar (1kW) electric fire left on 24/7 for 100 days.
The world’s electricity supply is the same energy as one return trip to Tenerife for almost everyone on the planet, once each per year
In 2012, total world electricity generation was 23 PWh (from the IEA website). This is the total energy value of the electricity produced by all means, renewable & non-renewable: coal, oil, gas, nuclear, hydro, etc. Let’s say we had a means to convert all this electricity production into aviation fuel and further that all this fuel was then expended in flying to Tenerife. This will allow us to make 23 x 10^15 divided by 2.4 x 10^6 which is 9.6 billion trips, more than one trip each per year for every person on the planet! Well, there would be a bit of a squeeze on hotel accommodation in Tenerife so we’d better count return trips instead, so that’s 4.8 billion return trips, Stansted to Tenerife, so we are not all going to get to top up our suntans once a year.
But we can’t make airline fuel from electricity – yet
But of course we can’t devote the entire electricity production of the whole world to flying, and for two reasons. First and foremost, we have better things that we need to do with electricity: heating, lighting, industrial production, powering the LHC, to name a few. Secondly, we don’t as yet have a means to efficiently convert electricity into hydrocarbon fuels like aviation fuel (basically, paraffin). What are the prospects for solving these two problems? There have been recent advances in solving the second problem (the problem of emulating photosynthesis in plants to produce energy rich hydrocarbons) and I’m confident that this problem will be solved, probably in my lifetime.
Is a nuclear energy based society a price worth paying for a suntan?
However, the theoretical maximum efficiency of this process is about 24% (and plants achieve only about half of this at best, but let’s say we can do better) so we are now down to about 1.2 billion return trips p.a. Or, one trip every four years or so, for everyone on the planet. As regards finding sufficient energy to be able to devote 23 PWh to producing aviation fuel, only nuclear, either fusion or thorium-cycle fission, or something similar, can possibly achieve this, and this is not going to happen in my lifetime, even if we believe that the development of a nuclear energy based society is a price worth paying (for a suntan).
Flying is fast and easy
Note that the intractability of this problem is not due to some particular shortcoming of flying per se: car travel, with two occupants in the car, has the same energy efficiency (kWh per mile) as flying: compared with having 1 person in a car, air travel is twice as efficient. Moving ourselves from A to B, at speed, through the air, is always going to be very costly. The problem with flying is only that it allows us to make very long journeys very easily and thus expend huge amounts of energy which we would not contemplate doing by any other means.
The only possibility is railway in partially evacuated tunnels…
What are the prospects for improving the energy efficiency of flying? Not great I’m afraid. Aeronautical engineers consider that there might be another 10% available by improvements in aircraft and engine design, and there might be another 20% to 30% available by improved air traffic control, routing and capacity management. But this will not change the fundamental fact: if we wish to have efficient, sustainable, fast, mass transit the only way is (railway) in (partially) evacuated tunnels. Theoretical studies indicate that in such tunnels speeds of 5000 km/h are easily feasible, with high efficiency, which means London to New York in 1 hour!
… but it won’t happen in my lifetime
However, this requires big advances in materials science, which are in train (forgive the pun) with the development of graphene etc, and it needs a political settlement: air travel suits the ruling elite very well because they only have to defend the airports and the airspace, which is a great deal easier than trying to defend a ground (and sea) based railway system, i.e., we all need to be happy bunnies before any of this is possible. I think we can safely assume that it won’t happen in my lifetime.
We all need to reduce our use of air travel by as much as possible
In none of this have I yet mentioned the immediate problem of global warming! Rather, this argument has just been about resource use and equity. Once you consider that at present essentially all aviation fuel derives from fossil oil reserves, and is therefore a direct (and rising) input into the increasing carbon dioxide level, then it is pretty clear that we all need to reduce our use of air travel by as much as possible.
Does this mean we should feel guilty if we choose to make frivolous flights for leisure purposes?
Err, yes, sorry
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