<p>A full answer to your question could probably be book length, so I'll try to sum up the main arguments:</p>
<p>There are a couple of options for making non-oil-based aviation fuels. One is to grow specific crops which can yield a kind of bio-oil. This requires land, and energy for the refining process. Bio-oil crops for diesel have already <a href="https://www.theguardian.com/global-development/poverty-matters/2013/nov/26/burning-food-crops-biofuels-crime-humanity" rel="nofollow noreferrer">affected food prices</a>, and pushed further rainforest deforestation as available land for food growing is shifted. Should we be reserving vast quantities of a scarce resource for plane fuel rather than food? And if there is any spare cropland around which we don't necessarily need for food, what's the opportunity cost of not planting trees on it, with much better carbon sequestration and biodiversity benefits?</p>
<p>The other problem with biofuels is that the processing, transport, land use change and so on (everything except the burning) creates emissions. So although the premise is that by burning the crops we're just releasing CO2 already sequestered, that's not the whole picture. And processing the fuels is usually very energy intensive. For aviation in particular as well, a large chunk of emissions comes not from CO2 but from radiative forcing of high altitude emissions. So alternative fuels don't automatically fix the global warming aspect.</p>
<p>The logic of offsets isn't strong. We need to drastically reduce emissions, fast. &quot;Offsetting&quot; so overall emissions level stays the same doesn't cut it. Not to mention that offsetting schemes have mainly turned out to be scams.</p>
<p>For aviation in particular, this is all happening against a backdrop of massive inequity. Hardly anyone in the world flies, only the rich. Why should the poorest in the world (those who already cause almost no damage in emissions terms, and who have the most precarious access to food) accept the rich maintaining a massive share of cropland and energy to fund their excesses?</p>
<hr />
<p>Other alternative fuels exist, e.g. hydrogen, or waste cooking oil. But for hydrogen see the massive energy usage argument (it needs energy to generate, store, transport etc.) and there's hardly any waste cooking oil around, definitely not enough to maintain anything like the level of today's flying.</p>
<p>Flying is extremely energy-intensive. In a world in which we need to be using vast amounts of today's available energy in building renewables, why should we be making that energy sacrifice worse on something that's so inefficient and profligate?</p>

CC BY-SA 4.0
2023-12-11T13:03:34.520Z
2023-12-11T14:13:59.633Z
2023-12-11T14:13:59.633Z
thosphor
<p>I'm not an expert in the sustainable aviation fuel field, but I have a descent understanding of science and the energy sector.</p>
<p>I recently attended a conference where there were several presentations on Sustainable Aviation Fuels (SAF). As I absorbed the information, I started to form a opinion - that it might be cheaper and easier to sequester, deep underground, the raw materials used in the production of Sustainable Aviation Fuels (SAF), and then just continue to use kerosene to fuel jets. The process of converting those raw materials into SAF seems to be unnecessary and inefficient, if the goal is to reduce greenhouse gas emissions.</p>
<p>I've since learned that my alternative approach is called &quot;offsetting&quot;. Presumably, the proponents of SAF believe that they can come up with an SAF generation processes that in some way will outperform offsetting.</p>
<p>Is it probable that a fully mature SAF generation process will outperform offsetting? Or, should we deprioritize SAF and focus our research dollars on a more promising solutions?</p>

CC BY-SA 4.0
2023-12-18T22:07:01.733Z
since we don't what forms of SAF you are referring too this will be difficult to answer.  do you have a reference of some kind?
John
<climate><air-pollution><energy>
Do sustainable aviation fuels make sense?
phil1008
# Do sustainable aviation fuels make sense?

(Asked by: username_0 on 2023-12-11)

I'm not an expert in the sustainable aviation fuel field, but I have a descent understanding of science and the energy sector.

I recently attended a conference where there were several presentations on Sustainable Aviation Fuels (SAF). As I absorbed the information, I started to form a opinion - that it might be cheaper and easier to sequester, deep underground, the raw materials used in the production of Sustainable Aviation Fuels (SAF), and then just continue to use kerosene to fuel jets. The process of converting those raw materials into SAF seems to be unnecessary and inefficient, if the goal is to reduce greenhouse gas emissions.

I've since learned that my alternative approach is called "offsetting". Presumably, the proponents of SAF believe that they can come up with an SAF generation processes that in some way will outperform offsetting.

Is it probable that a fully mature SAF generation process will outperform offsetting? Or, should we deprioritize SAF and focus our research dollars on a more promising solutions?

**Tags:** climate, air-pollution, energy

> **Comments:**
> **username_1**: since we don't what forms of SAF you are referring too this will be difficult to answer.  do you have a reference of some kind?  

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## 1 answers

### Answer by username_2 on 2023-12-11. Score: 3

A full answer to your question could probably be book length, so I'll try to sum up the main arguments:

There are a couple of options for making non-oil-based aviation fuels. One is to grow specific crops which can yield a kind of bio-oil. This requires land, and energy for the refining process. Bio-oil crops for diesel have already [affected food prices](https://www.theguardian.com/global-development/poverty-matters/2013/nov/26/burning-food-crops-biofuels-crime-humanity), and pushed further rainforest deforestation as available land for food growing is shifted. Should we be reserving vast quantities of a scarce resource for plane fuel rather than food? And if there is any spare cropland around which we don't necessarily need for food, what's the opportunity cost of not planting trees on it, with much better carbon sequestration and biodiversity benefits?

The other problem with biofuels is that the processing, transport, land use change and so on (everything except the burning) creates emissions. So although the premise is that by burning the crops we're just releasing CO2 already sequestered, that's not the whole picture. And processing the fuels is usually very energy intensive. For aviation in particular as well, a large chunk of emissions comes not from CO2 but from radiative forcing of high altitude emissions. So alternative fuels don't automatically fix the global warming aspect.

The logic of offsets isn't strong. We need to drastically reduce emissions, fast. "Offsetting" so overall emissions level stays the same doesn't cut it. Not to mention that offsetting schemes have mainly turned out to be scams.

For aviation in particular, this is all happening against a backdrop of massive inequity. Hardly anyone in the world flies, only the rich. Why should the poorest in the world (those who already cause almost no damage in emissions terms, and who have the most precarious access to food) accept the rich maintaining a massive share of cropland and energy to fund their excesses?

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Other alternative fuels exist, e.g. hydrogen, or waste cooking oil. But for hydrogen see the massive energy usage argument (it needs energy to generate, store, transport etc.) and there's hardly any waste cooking oil around, definitely not enough to maintain anything like the level of today's flying.

Flying is extremely energy-intensive. In a world in which we need to be using vast amounts of today's available energy in building renewables, why should we be making that energy sacrifice worse on something that's so inefficient and profligate?


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