Archive for the ‘aviation’ Tag

Sustainable Aviation Fuel (SAF) and airport expansion

Posted February 12, 2025
Filed under: Environment, Transport, Travel, UK | Tags: , , , , , , ,
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Decarbonising aviation is very difficult. It is a good example of why oil-based fuels have been so important in the development of modern society. Nothing quite matches the energy intensity of oil, with the exception of nuclear. Sustainable Aviation Fuels (SAF) are trumpeted as the solution to aviation’s sustainability problem.

I am grateful here to Ben Purvis, Research Associate, Sustainability Assessment, University of Sheffield, for his contribution to the The Conversation for the content here. Purvis notes that there are so-called pathways for creating sustainable aviation fuel. These are:

  • Oils or fats, including used cooking oil or tallow.
  • Municipal solid waste, agricultural residues and sewage
  • Hydrogen and captured carbon using renewable electricity.

It might seem that used cooking oil processing into aviation fuel is a win-win. But with the best will in the world, there is just not enough to go round. At the moment it is around 2 per cent of all aviation fuel. There is a UK mandate to increase this to 7 per cent by 2030 and 22 per cent by 2040. That is still only 1/5 or there about. To meet the current demand the UK imports 92 per cent of its used cooking oil from China and Malaysia (with its own carbon footprint). Currently the UK has one facility converting used-cooking oil to aviation fuel. That is the Phillips 66 Humber Refinery.

A recent report from the Royal Society notes that the 12.3 million tonnes of jet fuel per year needs 42.4 million tonnes of rapeseed biomass per year. In land terms, that is 68% of the UK’s agricultural land or 6.2 to 10.3 million hectares (see Innovate UK). The aviation industry’s own sustainability roadmap, CORSIA, precludes use of agricultural land for “fuel” crops.

The UK Chancellor of the Exchequer said on the 30 January 2025 (BBC radio 4, Today, c0815) that SAF could reduce aviation’s GHG emissions by 70 per cent. “Engines have become much more efficient. And, just at the beginning of this year, this government introduced the mandate for sustainable aviation fuel, which can reduce carbon emissions from flying by 70%. And of course, there’s going to be much more progress on that in the years to come.” (Quotes taken from the Guardian)

Equally there is global competition from both the EU and the USA (the latter now depends on the airlines rather than the state as burning fossil fuels now seems to be a US citizen imperative). Whilst it is clear that production could be increased with more investment, there is little confidence that it would be profitable; moreover, there is the small problem of cost – whichever pathway is taken, SAF costs more to manufacture than does aviation fuel (kerosene). That is £s on each ticket.

Surely there is enough municipal solid waste and sewage to go round? Well maybe, but the technology is in its infancy or not yet approved (see below) and no commercial facilities are producing it as yet. As for hydrogen, first it is packed with carbon if fossil fuels are the source of energy for the electrolysis necessary to produce it. Electrolysis by electricity from renewables remains distant. There is a long way to go before the UK grid is totally decarbonised. And now the British Government has added data centers to the mix, which means electricity supplies more generally are under pressure. Hence the Government’s latest endorsement of nuclear power and another un-tested technology, Small Modular Reactors (SMRs).

Not only manufacturing is a challenge, but the infrastructure to store hydrogen at airports or other facilities is just not in place. Hydrogen is also explosive and there are examples of denial of licences for users to store it, for example bus companies. It would require a major change to planning laws for widespread storage.

One UK company is undeterred: Logan Air. Logan Air has announced (12 February 2025) a plan to launch the world’s first hydrogen-fuelled commercial service by 2030. The company does not reveal the identity of the manufacturer of the aircraft that they will use for their point-to-point service (also as yet not stated). This against the backdrop of Airports Council International backtracking on its hydrogen ambitions in favour of scaling SAF, better air traffic management and improving aircraft engine efficiency.

Photo: Airbus

There remains, therefore, the central question of actual aeroplanes. There was some succour in that Airbus was developing hydrogen planes (the A380 Airframer). This aeroplane was going to be a 100-seat 1850km range aircraft (right). But as recent as 6 February 2025 the Force Ouvriere trade union was informed that the launch date has been put off by between 5 and 10 years with an additional budget cut of 25 per cent. The company has identified the lack of available green hydrogen as one of the reasons for the delay. Another, less explicit but particularly troubling reason, is the company’s intention to replace its popular A320neo with a newer and more efficient conventionally-fuelled aircraft. The end of fossil-fuelled aircraft is nowhere in sight. The only option then, for sustainable aviation, is SAF from vegetable oils, tallow or waste.

Pic: By Peter Bakema

There is a need, therefore, to clarify whether SAF is actually sustainable. In theory, because the things that it is made of already exist or are grown, burning it does not add to overall CO₂ levels. (Hydrogen, even more so, because it is derived from water and the emissions are just water.) So, aeroplanes still emit CO₂ when we really need to be capturing it and locking it into plants such as trees to generate negative emissions. Equally, it assumes that the crops and the waste had it not been for SAF would have degraded and decomposed releasing greenhouse gases in any case. The reality is that the area being used to cultivate crops to be turned into SAF would in actual fact be used either for food consumption or some form of rewilding. Essentially growing crops to fly planes (at least part of the way to their destinations) would displace food production. This would be a major distortion of land use.

The reason that SAF is so topical is because the British Government seeks to make the case that not only can we continue to fly at current levels, but that airport expansion is possible because the emission reductions from SAF rollout will offset increased flights (all in the name of growth). The above argument challenges that proposition. The calculation also needs to factor in the carbon emissions generated by constructing new runways. It is not trivial.

Here is Mike Berners-Lee discussing SAF.

Michael O’Leary is right and very wrong, mischievously so

Posted December 29, 2023
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Michael O’Leary (left) is the boss of RyanAir. He has spent much of his life at the helm and took it from limping Irish airline to Europe’s biggest. As he says himself, RyanAir was early into the low cost business after the skies were deregulated and have kept the advantage over rivals. He’s fabulously wealthy off the back of that success.

So, on 26 December 2023 O’Leary proclaims that there is not enough used cooking oil in the world to fuel the world’s airlines for one day, let alone a year. on that he is right. But he has made many other claims that are not defendable with even a cursory analysis. Let’s take them one by one.

O’Leary argues that air travel contributes just 2pc of carbon dioxide. Ships contribute 5pc, but no-one is shouting about global supply chains. Here are 10 points to consider.

  1. We do not measure greenhouse gases as a percentage, we measure in absolute terms. That 2pc is equivalent to 800 Mt CO2 per year. If we are to get anywhere near even 2 degrees of warming (let alone 1.5 degrees), all GHGs have to be eliminated, Even a fraction of 1pc is too much. In meeting the 1.5 degree Celsius target, the atmosphere can absorb, calculated from the beginning of 2020, no more than 400 gigatonnes (Gt) of CO2. Annual emissions of CO2 are estimated to be 42.2 Gt per year, the equivalent of 1,337 tonnes per second (https://www.mcc-berlin.net/en/research/co2-budget.html). At this rate, at the time of writing, we have 23 years before that budget is used up at current levels, but we have seen clearly how projections are changing – climate change is happening faster than expected. The models are being revised. And we continue to grow demand for fossil fuels whilst destroying carbon sinks such as oceans, forests, bogs, etc. For something most of us do not need, flying is disproportionately expensive in terms of carbon budgets.
  2. Whilst O’Leary might say that 2pc is not much, carbon emissions overall have doubled since the mid-1980s. Aviation has just kept up with the average increase in emissions across the board. Absolute emissions from aviation are increasing.
  3. Carbon generated by aeroplanes is not the same as that emitted by land-based activities. Indeed, if we consider aviation’s full impact it is more like 3.5pc. Aviation emits other greenhouse gases, and the release of water vapour at altitude significantly increases its warming impact. Accounting for this, its contribution increases by around 70%.
  4. CO2 emissions arising from aviation are not globally fair (equitable). It is the relatively rich who fly. 1 per cent emit half of GHG emission from aviation. Business class is more carbon intensive than economy. Private jets…let’s not go there. Most people on the planet have never flown (estimated between 80 to 90pc) and have not contributed to aviation-generated carbon emissions. Put another way, only 5pc of people fly in any one year (less than that for international travel). The average air traveller takes just over 5 flights per year (1).
  5. We do not adequately count all emissions. Domestic flights are ok – they are factored into national emission-counting, but international/long haul belong to no one (though airlines to count them). Incentives are not in place to reduce emissions from long-haul flights. This we must get to grips with, but recent stunts like those from Branson do not help.
  6. O’Leary seeks to distract attention – forget aviation, much better and easier to electrify cars and vehicles. Vehicular emissions are 20pc of the total with cars alone producing 3bn Mt CO2e annually. Another diversion – Air Traffic Control – if they could be more efficient there would be no need to spend hours circuling airports in stacks (the fact that there may be too many planes in the air is not considered).
  7. There is the technological fix – O’Leary has them all up his sleave. Seemingly he is “generally a believer that technology and human ingenuity will overcome climate change”. He goes on “I have no doubt that we will not decarbonise because we tax people more” So belief will get us there; though at this point in time, there are no viable electric planes in sight. Or any other fuels, for that matter.
  8. O’Leary argues that “[p]eople will absolutely not stop flying because of concerns about climate change”. This may, of course be true, but that is why we have Governments, regulations and tax to provide the incentives. What O’Leary is doing at RyanAir is expand capacity with the purchase of new fuel-efficienter aircraft. But they are not sustainable.
  9. So. let us look at the low cost base and the subsidies airlines get to maintain them. Fuel (tax) is a huge subsidy not open to land-based services. Some old data – but in 2012 the lack of tax on fuel amounted to an annual subsidy of £5.7bn. No VAT on tickets add 4bn to the total. In the UK, the Government actually reduced air passenger duty on domestic flights. Seemingly there is another £200m subsidy to the industry. And then there is the infrastructure provided by the state such as roads and rail links. Did Heathrow really need a fourth rail link to the airport with CrossRail?
  10. And on ships, there is a lot of discussion both amongst engineers, campaigners and industry about decarbonisation. Try these:

Pictures:

Michael O’Leary, World Travel & Tourism Council

RyanAir Boeing 737, By Dylaaann – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=114958876

References:

(1) Stefan Gössling, Andreas Humpe, The global scale, distribution and growth of aviation: Implications for climate change, Global Environmental Change, Volume 65, 2020;