In 500 words or Less: Sustainable Aviation Fuel
Climate complexity condensed in 500 words or less
Hi there! Welcome to another edition of Living In A Greenhouse. As a part of my planned newsletter revamp, here is another format. I hope you like it.
Given it is a fairly self-explanatory title, I will get right to it.
In absolute numbers, commercial aviation accounts for nearly 5% of global emissions. That’s not a lot but the thing about aviation is, despite the relatively lower carbon footprint, it is a very ‘visible’ polluter given the discretionary nature of flying.
While we may possibly have hydrogen-powered commercial aircrafts or those that run on batteries in the near-future, we are currently a little ways from that.
What we do have right now is Sustainable Aviation Fuel, a synthetic type of kerosene, that is not extracted from fossil fuels.
Sustainable Aviation Fuel (or SAF) typically produces ~80% lesser emissions than conventional jet fuel, and this can go as high as near-zero depending on the technology. (Yes, I said near-zero and aviation in the same sentence).
For the sake of convenience and clarity, there are broadly two types of SAF:
The first type is biofuels-based.
This may be surprising, but this type has been around for over a decade now. Virgin Atlantic flew the first biofuel flight in 2008. The first-generation aviation fuel from corn, sugarcane, palm oil etc., is considered mature technology, while the 2nd generation accepts vegetable oil wastes, algae and others.
Despite being the only viable and the widely-used alternative-fuel currently, it is not a perfect solution.
Scale is dependent on the feedstock. Any increase in supply of raw materials, if done irresponsibly, might result in biodiversity loss and deforestation in high carbon stock areas. Further, the same feedstock has multiple end-uses and faces competing demand.
The second type is either gas-based or liquid-based hydrocarbons
Gas hydrocarbons use the same feedstock as biofuels, plus municipal solid waste. This gets converted into a mixture of hydrocarbon gases (through a process that gave Germany the edge in WW II. Read here for a short history lesson).
The most sustainable option out there is to produce (the currently expensive) ‘green’ hydrogen using renewable energy, synthesise it with carbon from Direct Air Capture (also, very expensive), and produce liquid hydrocarbons using the same process that the Germans deployed in unsuccessful pursuits way back then.
(Here’s a quick primer on the many colours of hydrogen from last week’s edition)
Both these technologies are promising, but is currently not available at-scale.
However, with a higher emphasis on ramping up green hydrogen infrastructure (read last week’s post), we can expect liquid hydrocarbons to be used in commercial aircrafts by 2030.
The last word.
The best thing about SAF is that it is ‘drop-in’. In other words, you don’t have to make changes to aircrafts or engines or the distribution infrastructure to utilise this fuel.
But current annual production is nowhere near where it must be at. We produced 100 million litres of SAF last year, or less than 1% of overall aviation fuel demand. By the year 2050, we will need about 450 billion litres of SAF to meet 2/3 of global aviation fuel demand.
Higher prices certainly don’t help. Jet biofuel costs 3-5 times more than conventional jet-fuel.
That’s why it’s imperative that investments improve the economics of SAF. Besides the focus on advancing research in the technology itself, independent measures must be taken to make SAF cost-competitive.
One way is to deploy policy levers that enable responsible supply chains for feedstock, resulting in higher cost efficiencies. Another alternative, (and a personal favourite), is to tax conventional jet fuels with a carbon price that will reflect its true cost. The EU has already tabled a proposal for carbon taxes on intra-EU flights, much to the dismay of the airline operators.
Here’s to hoping more follow suit.
Bonus
What do whales do for Carbon Sequestration
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Banter
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