Could Air Travel be Greener?

Yes it can. Automologist MAC tells us how…

In all honesty, air travel is really a minor contributor to greenhouse gases. Emissions from aircraft amount to just over 2% or so of the world’s total, so there probably are much bigger fish to fry. Current air travel is running at about two-thirds of pre-Covid levels, but as the post-Covid apocalyptic world gets back on the move and emissions climb, the dirty profile of air travel will undoubtedly be on the rise again. Meanwhile, all those hemp-trouser-wearing do-gooders will continue their efforts to spoil yet another one of my guilty pleasures. Can we make air travel green(er)? It turns out that making air travel greener is probably easier than we think and may be just around the corner.

There have already been some attempts to get battery-powered craft into the air and for real short-haul flights, this may be a doable solution. But batteries are heavy and when you take them up to the heights where long-haul planes normally operate, the batteries’ performance is reduced by the cold temperatures. We have seen techno-fantasy for compressed hydrogen planes and nuclear planes or even a return to last century’s airship technology . But all of these are more likely to remain a fantasy for a very long time to come.

So, the idea of sustainable aviation fuel is being mooted. The stuff of legends and apothecary magic could be created to match current fuel specifications and be a quick ‘drop-in’ replacement for the dirty old kerosene currently being used at 40,000 feet. No need to change the infrastructure or engines or even design of the planes. All you need to do is manufacture it directly from the Carbon Dioxide currently in the air. Easy right?

As this ‘unicorn’ of fuels uses CO2 that comes directly from the air, it is still green as there will be no increase in net CO2 after burning. Or, hey, here is an idea—put some great big air scrubbers on the smoke stacks of polluting industry and stop it going into the air in the first place. Assuming that you can do this at a competitive price compared to the stuff from an oil field, the rest would be history as they say.

Well, airlines are already using what they call SAF as a part of their fuel strategy and it has thus far been used in about half a million flights. As a whole, the industry aims to be carbon neutral by 2050 and for now SAF is the only option being considered to seriously get them there. Of course, it isn’t going to be easy to get enough of the fuel manufactured to have the entire airline industry compliant.

Manufacturing SAF is not easy. Essentially you are saying I am going to take the stuff that just came out the back of the plane and turn it into something that is the same as what went into the plane in the first place. This takes gluing the carbon from the carbon dioxide into a big energy rich molecule like hydrogen. Presently, the cost to do this is about three times the cost of existing sources of aviation fuel.

That is because the current method uses photosynthesis to fix the carbon as it is related to discarded cooking oils, which are of course triglycerides. This is then hydro-treated to create propane, which in turn can be processed into a drop-in energy source, such as SAF. Nearly all current SAF is manufactured using reclaimed cooking oil from the catering industry. It is great that this can be done but to reach the volume we need, there will be a need to get the oil direct from the plantations. This will encourage the spread of oil plantations and the destruction of the very eco-systems we need to keep producing oxygen and will, of course, upset those that wear hemp trousers…

There are any number of European companies that are looking at producing bio-fuels from thin air and water—ie. using electrolysis to split the hydrogen from oxygen in water and splitting the carbon dioxide to carbon monoxide from the air we breathe. A Swiss company called Synhelion already has scaled up the process using mirrors in an array to concentrate the rays to produce temperatures of 1500 centigrade. Sure, for now they can only operate whilst the sun shines, but hey it is a start. This tech cleans the air of carbon and reduces sea levels all at the same time. Okay, the sea level bit is a bit of a stretch…

I do have a question: if all of this tech is currently available, why are we still considering a mass migration to electric vehicles which will at least in the short term put loads of Carbon Dioxide into the atmosphere as coal is used to produce the electric for the batteries? I don’t know the answer to that, but if there are some clever wags out there who could let me know, there is a comments section just below.