It doesn’t really matter whether you’re producing biodiesel or SAF; it’s a slightly different length of carbon chain coming out of the refinery.

The difference isn’t the slight variation in chemical structure of the molecule between the two products, its the drastic difference in the applicable use case of the resulting product, and the economic incentives to produce one vs the other. These are what make the SAF and biodiesel gigantically different product with hugely different economic, climate and geopolitical implications.

No amount of B5, B20 or B100 grades of biodiesel are going to enable carbon neutral air travel where SAF can. However, alternate fuels or methods of ground transportation can offset or replace diesel or biodiesel. With today’s technology only a number of small electric prop planes (certainly no commercial jets) can operate with anything close to carbon neutrality without SAF. Commercial aviation is a reality in our world and we can choose to find carbon neutral alternatives or embrace its carbon rich nature and try to make drastic carbon cuts elsewhere. I believe the latter is much less likely than the former. Alternatively we can simply turn a blind eye to our climate and reap the consequences. I’m not ready to throw in the towel and embrace that yet.

The same problem of competing with food is there because that’s where you’re sourcing carbon and hydrogen from.

Even if a portion of input feedstocks that go into producing SAF today are food or competing with food, how are you holding the position that municipal waste, used cooking oil, and agricultural waste are sources of food? I’ve posted sources that show the alternates available and possibly upcoming that would enable more non-virgin SAF. Are you holding the position that humanity will simply never achieve anything except fossil based fuel for aviation or something else I haven’t understood of your position yet?

Further yet, what is the connection you’re making a food supply with regard to hydrogen? Are you referring to fertilizer?

First, that is a great link. I don’t follow biodiesel efforts very closely and always appreciate the data from a real world execution perspective.

That said, while the article contains a number of criticisms you’re pointing out, the article is mostly focused on biodiesel and not necessarily SAF, and even less applicability to California where the majority of North American SAF is produced. The article even called this out with the distinction that biofuels (SAF in this case) from virgin feedstocks doesn’t qualify for the Low Carbon Fuel Standards (LCFS) laws in California that make SAF economically viable. Meaning there is far lower incentive to try to produce SAF from virgin feedstocks, which I believe is your primary criticism of SAF.

“Additionally, the Producer’s Tax Credit, coupled with the California LCFS, will heighten the demand for lower carbon-intensity feedstocks like tallow, UCO, and corn oil. Under the LCFS, west-coast market demand is stronger for feedstocks that provide greater carbon-emission reductions than virgin vegetable oils like canola and soybean oil. These policies will continue to pull available global feedstocks into the California renewable diesel market, and boost U.S. import demand for feedstocks that make lower carbon-intensity biofuels that generate additional credits in the California market.”

from your provided source

The other point your article highlighted was the bottleneck to using less virgin sources was the need to increase the non-virgin sources of feedstocks. As in, the market is demanding more biofuel from non-virgin feedstock than can supplied. This is important as it goes back to the work identifying and introducing further non-virgin feedstocks that I linked in my other post on this topic here.

Food. Food oils in particular.

While certainly possible technologically, for the main efforts in North America you are incorrect on the use of food (meaning something humans can eat) for SAF.

The largest producer of SAF in the USA is in California (and partially fuels LAX airport, BTW). This operation is using waste from other processes and not food that would otherwise be eaten.

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That is a very important question. SAF is a name for a bunch of different fuels produced from sustainable sources. I posted a larger reply to the main article that details some of the input feedstocks which answers your question here.

I’ll preface this by saying that SAF by itself isn’t a silver bullet that solves all problems with carbon use in aviation. It can, however, be an important piece of a larger solution. Additionally, even in isolation without a larger plan it has a net benefit on carbon reduction which is a win in the battle against climate change.

The basic problem is that “sustainable” aviation fuels, if based on biofuels, would substantially compete with food production.

Certainly possibly, but not absolutely.

Virgin feedstocks (the stuff needed to feed in to make SAF) would support your position because the plants grown specifically for harvest to be turned into SAF would displace food crops, or possibly support destruction of other non-agricultrual land to grow net more crops. I agree with you that both of these situations would be a net negative to SAF.

However, virgin feedstocks aren’t the only nor even most desired feedstocks for SAF. There are many ways to produce the fuels that fall into the definition of SAF. Things that we would otherwise consider waste streams can be SAF feedstocks such as the following:

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There are other pathyways being explored too such as the waste water runoff from dairy farms and beer breweries:

“To that end, the Argonne Lab scientists look to using carbon-rich wastewater from dairy farms (and breweries, for other reasons) as feedstock for SAF production. The study author at Argonne, Taemin Kim, said that the energy savings come in two ways. “Both [dairy farms’ and breweries’] wastewater streams are rich in organics, and it is carbon-intensive to treat them using traditional wastewater treatment methods. By using our technology, we are not only treating these waste streams, but [also] making low-carbon sustainable fuel for the aviation industry.””

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Unless we as a global society choose to simply eliminate air travel for people and cargo, we have to accept that a better approach to energy used for air travel is needed to meet reality. SAF is an important part of that in my mind.

Yes, I’m one.

Like most things, not one thing will fix a problem. SAF is one piece that measurable makes our situation better. The fact you can possibly fly on a plane today partially with SAF is an amazing achievement and the result of lots of hard work by lots of people trying to make a positive difference.

What it looks like this company is building would be partially compatible with that approach.

For the Haber-Bosch process needs input H2 (plus the atmospheric Nitrogen). 33% of what this company is building is an electrolyser. Further, the Sabatier reactor they’re using (another 33% of their process) could possibly be swapped out for a Haber-Bosch reactor.

I don’t know enough about the environmental conditions needed for handling ammonia vs methane to understand if there are any “gotchas” to creating ammonia in situ.

What are the other options you see for the excess electricity that would be more feasible than this methane approach?

This has the same problem as CO2 capture technologies, that is the relatively low CO2 concentration in the air.

You’re correct that the CO2 concentration in atmospheric air is low: 0.04%. Consider the following:

• Each molecule of C02 has a single carbon atom.
• Each molecule of methane also has a single carbon atom.
• So we could say that atmospheric air has 0.04% of methane production capacity.

I would agree with you this would be a waste of time if the goal was CO2 sequestration, but it isn’t. The goal is to use otherwise 100% wasted electricity to produce something useful that can be stored long term that there is a market for, in this case methane.

The only way to make this even remotely feasible

What is your definition of “feasible” here? Economically compared to fossil based methane? Volume of production?

… are end of pipe solutions where you directly capture the exhaust of a fossile fuel combustion process. But that in turn is at best a temporary band aid.

The company agrees with you. They called out that being able to direct capture pure CO2 from an industrial application would be ideal, but as they also concluded, thats not where the excess electricity is that is really the primary economic driver of this technique.

LFP

Thank you for that.

Its odd calling LFP “new” and “a change is coming”. The first production EV to ship in the USA with an LFP was in late 2021 I think.

I would have thought this might be talking about cheaper chemistry Sodium Ion batteries, which are already on the road in small quantities in China.

Now, what ever happened to regularly riding horses around?

Besides the issue with horse excrement, other issues occurred (Hayden, 2016):

Dead horses often clogged city streets;
In New York City in 1880, 15,000 horses died on the streets, or 41 dead horses a day (which had to be removed);
Some place to stable the 100,000+ horses that operated within New York, and food to feed them;
On a per capita basis, 19th century horse-drawn vehicle accident rates were similar to those of the automobile in the 20th century.

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Guess you’ve never heard of a fistulated cow before, they can totally connect tubing or pipes to cows to harvest methane straight out of their intestines.

And the cost for fistulating each cow? And how much methane will such a cow produce? How contaminated will the methane be? What methods would be required to refine it to pipeline grade? Further, can you feed a cow with the output overproduction of a PV solar panel?

This is what I meant when I said cows wouldn’t be economically viable sources of methane from electricity. If you think cows are they, then I won’t stop you though.

Confused, how is this useful?

There are many MANY useful applications of carbon neutral methane. The most beneficial and obvious to me are:

• Useful method of storing excess generated solar and wind power
• Entire industries, markets, and infrastructure already existing for the storage, transportation, and consumption of methane

You can get methane out of a cow’s ass all day long

You cannot get pipeline grade methane out of cows ass, and even if you could, you wouldn’t have the technology to capture it for use in the marketplace in any quantity that would be cost effective against fossil fuel based methane. As in, even if you could (and you can’t), it would cost so much that no one would buy it and instead just pull more out of the ground. The solution proposed here is on the path to being worth skipping the fossil fuel route for methane and using this instead.

and methane is a greenhouse gas,

So is the CO2 that is being used as the feedstock to create the methane. This would be reducing atmospheric CO2, which I hope you would agree is a useful element when directly combating climate change from C02 emissions.

I thought we wanted less methane, not more.

This wouldn’t be producing net more methane. The market is already consuming all of methane it demands. This would replace some of the supply that is currently being fulfilled by carbon positive fossil fuel sources.

I didn’t see anything in the article at all regarding speculation or futures markets of electricity with the one exception being a mention of some industrial operators signing long term contracts to buy oversupply.

Can you refer me to the section of the article you’re responding to?

I’ve seen this in the USA too. A local water co-op put a 1.2MW array floating on top of one the municipal water reservoirs. Along with carport and building PV arrays, they offsets 50% of the electricity consumed by the facility.

Their floating array also offsets some water lost to evaporation, but its too early for measurable numbers on that front so far.

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