Cleaning up plane pollution for the future

30 July 2019

Interview with 

Hector Pollitt, Cambridge Econometrics


A Rolls-Royce Trent900 Jet Engine


While electric propulsion remains in development, liquid fuel reigns supreme which is not good news for air pollution emissions. A 747 burns on average 5 gallons of fuel per mile! Multiply that by several hundred miles a flight and then by several million flights a year, the emission toll adds up quickly. To find out how much of an impact this has on the environment and if there is a solution Adam Murphy and Izzie Clarke spoke with Hector Pollitt, director and head of modelling at Cambridge Econometrics.

Hector - We look up into the sky and we see aeroplanes with vapour trails and we think oh, this must be causing a lot of pollution. To some extent this is true; however, at the moment the aviation sector accounts only for 2% of global emissions. The concern is that whereas most of the other sectors in the economy are starting to decrease emissions, in aviation we're very much seeing the opposite going on, and it's predicted that in the coming decades overall emissions from aviation could triple.

Adam - So where is this increase coming from? Why are we seeing it going up?

Hector - Yeah in summary we're seeing more flights overall, more aeroplanes taking off and landing, so more fuel being burnt and more emissions resulting. In the UK, there's this constant debate about the expansion of Heathrow in the southeast; and the airport capacity, of course, that is another way of enabling more flights. Even more important than that is the growing size of the middle-class in the developing world and all of these people with their newfound wealth who want to go to other countries, other continents, and see other parts of the world for themselves.

Adam - Now we heard about the issues and challenges behind electric flight, but are there any other solutions being tested or implemented right now that can help?

Hector - Yeah. And I think when it comes to climate change we're always looking to technology for the solutions. We heard about electrification as one possibility in aeroplanes. There are also potential biofuel options that are out there in the future. Again these are still under development and we don't know how that will go, but they may be something that's a bit more realistic in the shorter term. Also there are some specific short run measures that would improve efficiency in aeroplanes. One option would be even getting the airlines to use the latest flight planes available to improve efficiency. Also reducing taxiing on runways, for example - planes could be pulled up rather than operating under their own thrust in the airports. And a more rational flight path through the air traffic control services, and that could reduce overall distance per flight which would help a bit. But these are only short run solutions.

Adam - You mentioned biofuel, what exactly is that and what state is that in?

Hector - It's an area where there is a lot of research going into at the moment. It hits some of the same issues that we heard with the electrification about the power-to-weight ratio in the planes. I suspect at some point we will start to see a blended fuel coming in, a bit like we have in petrol in our cars, so you'll start to see an increasing proportion of jet fuel kerosene being mixed with biofuels. It's still at a reasonably early stage though, we can't say anything for sure on this topic.

Izzie - What actually would they be mixing in with kerosene?

Hector - Yeah, that's a good question and I suppose it really depends on how the technology will go. We hear quite a lot about algae-based research and next-generation biofuels, so it's something that's a bit different to the corn that's grown and converted into biodiesel that we put in our cars at the moment.

Adam - What's the future here? Do we see an end to this problem?

Hector - It's going to be very difficult to stop people from flying I think, particularly in the developing world. I think when it comes to climate change though, the state we’re at now, and not least we're seeing the record temperatures last week, I think we really need to throw everything that we can at the problem, so I would propose a multi-pronged approach. Yes, let's try to reduce our own flying a bit. Putting a tax on aviation fuel which is currently pretty much tax-free at the moment would certainly help with that. Consider airport capacity, whether it’s really necessary going forward. Let's use the most efficient planes that are available. Let's put in these other efficiency measures as well and do the best that we can with that. Let's see where we can go with these new technologies as well - just throw research resources into it and maybe something will pay off in the long run.


To expand on the comments about aviation biofuel see the online library on this subject put together by a nonprofit educational organization: There is not only research going on, but there are regular commercial flights on United Airlines between Los Angeles and San Francisco that use biofuel blends. See also articles about use of aviation biofuel in commerical flights in the Nordic countries. There have been other demonstration flights and occasional commercial flights, also.

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