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.
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:
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.”"
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.
We have the excess electricity already, but I’m not yet at the legally required amount of solar panels.
At work we are investing in energy storage, both batteries and heat storage and looking for more solutions.
For any but the largest commercial solar/wind providers, batteries and heat storage (or cold storage actually too!) are the best uses of overproduction of electricity. Batteries at your location are 90%+ efficient round trip, meaning for every 1kWh you shove into the battery, even after all the conversion and storage costs, you'll be able to get 900Wh or more out of the battery when you have a use for it. Many PV tied batteries are upwards of 97% efficient even!
Heat storage is another great use, whether in water (to mitigate need for new energy expenditure to heat water for use), or in thermal batteries for space heating. Although the biggest downside to thermal batteries are their size. If you've got spare space then they can be effective in a home or business.
I’m looking at hydrogen, because it’s known tech and I dream of finding a way to use it in a more stable chemical form for storage.
I did the same looking at Hydrogen, and its pretty bleak. Not only is creating hydrogen safely (from electrolysis) difficult, but storage is a nightmare. Any kind of gaseous storage is incredibly difficult because of how small a molecule H2 is, and if you're storage is inside a building that leakage creates explosion risks.
The safest way I saw to store and consume hydrogen is absorbed into a metal hydride. The problem there is that fillers (because of pressure) are expensive $2k for the cheapest one I saw, and you need many metal hydride cylinders to store any appreciable amount of hydrogen. So they end up being large, heavy and bulky or relatively little energy storage.
For home use, a regular lithium battery is so much more efficient and safe.
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:
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.
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.
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.