Price support mechanisms
There is, shock horror, an alternative - to tax aviation fuels in the same way as other fossil fuels and maybe offer a discount for something greener. I suspect that would be a more urgent incentive.
A Virgin Atlantic 787 took off this morning from London Heathrow bound for New York in what was billed as the world's first example of a long-haul commercial flight powered entirely by sustainable aviation fuel (SAF). VS100, aka Flight100, left the UK capital at 1130 GMT and, as of writing, is a little less than half way …
There are potential adverse incentives to this if taxation isn't imposed universally. Planes may be flown with brimmed tanks if entering a country with a higher tax rate and may perform detours to fill up in cheaper locations. Both of these would drastically increase emissions.
Not to dismiss the idea out of hand, just to help you understand the complications.
This is the traditional excuse, though the real problem seems to be a lack of will, probably linked to a fear of the political consequences of putting up the cost of summer holidays.
The same perverse incentives could equally arise from "price support" and any mechanism found to deal with one would also apply equally to the other.
"The same perverse incentives could equally arise from "price support" and any mechanism found to deal with one would also apply equally to the other."
I agree but, looking more broadly, if they're extra emissions from low net carbon (lest someone jumps down my throat for calling them carbon neutral) fuels, even due to tankering, then that has less impact. Further, if that perverse incentive results in extra SAF being produced, that could help lower the price through efficiencies of scale.
If all the waste cooking oil in the US was used this way it would power 1% of US air travel. The cooking-oil supply is notoriously unregulated with 'recycled' often being adulterated with fresh palm oil.
Every time something is grown for fuel it puts pressure on food-growing and hence land use. In this situation it means more jungle being destroyed and increased food prices, often in countries where food for everyone is already in short supply.
As for the 'hardly any CO2' claim that's bullshit bookkeeping. Burning vegetables still puts C02 into the atmosphere.
"Burning vegetables still puts C02 into the atmosphere."
It puts into the atmosphere the CO2 that was taken out by the growing vegetables. That's a net zero at that level. However transport and processing have to be considered so if they used fossil fuels there's addition of some CO2 as a second order effect. If this is genuine waste then it's not a case of plants being grown for fuel. However destroying forest to grow cash-crops, even where those cash-crops are food, is a concern.
"It puts into the atmosphere the CO2 that was taken out by the growing vegetables. That's a net zero at that level."
Only if we consider absolute volume regardless of time scales. There is an argument that if it takes, say, a year to grow the corn that is converted to fuel consumed in a day or less of flying, that isn't really net zero overall. This has much in common with the recognition that planting lots of trees has only a very long term contribution to carbon capture because they take years to sequestrate any significant amount of carbon.
As usual, the reality is a lot more complicated than the factoids presented to most of us from both sides of the net zero argument.
It puts into the atmosphere the CO2 that was taken out by the growing vegetables.
and where do you think the carbon in the hydrocarbon "fossil" fuels comes from?
answer is it all came from the atmosphere albeit a very long time ago.
our current understanding of the carbon cycle
photo synthesis removes carbon from the atmosphere and is stored in the plant/tree/vegitations structure
plant falls apart & dies or is eaten etc and the carbon containing bits eventually get deposited on the ground, after a very long time it ends up quite deep as other things go on top.
heat & pressure convert he hydrocarbon containing deposits & forms oil & gas we refine into fuel.
The point being that carbon in "fossil" fuels originated from the atmosphere.
"Every time something is grown for fuel it puts pressure on food-growing and hence land use."
Just reclaim that land from golf Courses.
That will peak the interest of those who like to spoil a walk by getting frustrated hitting a small round white ball. That group has significant intersection with the group that are the most frequent fliers, I would suggest.
Anon, but I'm already wearing my flame proof pants as I had a curry last night!
On a serious point, what we should be really alarmed by is the amount of totally avoidable gas flaring. About 140 billion cubic meters per year, which is enough to power the whole of sub-Saharan Africa and contributes 40 percent of the annual black carbon deposits in the Arctic.
When the total effects are calculated the annual CO2 emissions from flaring is around 126 million tonnes.
For reference the total effects of aviation was 785 million tonnes in 2019.
"We have enough trouble feeding people as it is"
But is that a problem of production or of supply?
My understanding is that there is more than enough food in the world for everyone, but shortages (famines) are caused by a combination of localised crop failures and lack of local distribution capability (often due to war or similar).
Also, we could at least initially repurpose agricultural land that isn't being used for food crops - crops for SAF production might be viewed as having more social and economic benefit that tobacco, perhaps?
This isn't so desperately different from the availability of HVO as a diesel substitute.
It is cleaner, but it's pricier and throwing production chains at making lots of it is highly questionable. For niche applications in diesels that run infrequently (and therefore fail because of mandated bio-content leading to dieselbug growth in retail diesel) ; HVO has advantages.
Unfortunately in aviation the bulk nature of affairs means that short of redirecting say, the mass of grain thrown at producing beer, vodka, gin, etc. the kind of quantities of fuel needed aren't likely to ever be kept up with by "alternative, fringe" means.
Aviation and Hydrogen seem to be by far the best match of technologies (don't mention the Hindenburg) as far as being able to be done in both bulk and with green credentials. Very strong argument for building lots of offshore nukes combined with electrolysis plants to fuel the supply chain.
Or we can just carry on digging up old fossils; though there comes a point where one gets sick of spoon feeding the Saudis ludicrous amounts of cash.
I've not seen it written down, but wouldn't the amount of Hydrogen required by a plane, actually be a significant advantage (lighter than air) when it comes to take off, and this diminishing as it requires to come back to earth will also be an advantage.
My guess is that the buoyancy of the Hydrogen will be far less than the mass of the plane and passengers. Maybe someone has some figures on whether it will actually be a measurable advantage?
The headache with hydrogen is that it's much less dense than a liquid fuel like kerosene. The tanks you need to cart Hydrogen around in decent quantities and high pressures will be big and heavy constructions.
Energy released per kg is an advantage to hydrogen and so I'm surprised that there haven't been efforts to put a hydrogen engine onto a fighter jet for performance reasons; one can only assume it hasn't happened because the weight penalty is more severe than the gain.
In order to provide all that used cooking oil, we're all going to have to eat more chips (fries for left-pondians). But then the planes will be able to carry fewer people because we'll all be morbidly obese, so we'll have to eat more chips again to provide extra oil, then the planes will carry even fewer people, so then .....
There were some fuel problems that led to reformulations of JET-A that happened only under specific conditions. It took some time to pinpoint the problem as it was due to icing in the fuel which would lead to a crash or the problem would "melt away" before anything could be found. IIRC, a fast decent after a long cold soak would cause ice crystals to form and clog up the plumbing. A fast decent isn't common, but not terribly unusual depending on traffic, jet streams and so forth. It can be more uncomfortable for passengers if they can't equalize their ear canals quickly enough so passenger jets descend at a moderate rate for comfort and it makes ATC job easier.
Using a 787 is not likely the best test platform for fuel testing. A narrow body jet will be far less thirsty but can still fly all of the different flight profiles that are common in all sorts of weather to see how stable the alternative fuel is across the board.