[Manuel_D]

Synthetic fuel has a lot of difficulties. One, it requires hydrogen as an input which is typically produced through steam reformation [1], a process that emits CO2. Electrolysis is less efficient and hard to scale as equipment is subject to intense corrosion.

Second, CO2 is at very low concentrations in the atmosphere. Direct atmospheric carbon sequestration is expensive and slow. The biggest startup in the synthetic fuel business is behind schedule and is struggling to solve these two main challenges [2].

1. https://en.wikipedia.org/wiki/Steam_reforming

2. https://www.technologyreview.com/2022/04/25/1050899/promethe...

[p1mrx]

We need to massively scale up green hydrogen production under basically any scenario where climate change is avoided. Hydrogen is an input for many industrial and agricultural processes.

[jasonwatkinspdx]

Biofuels do not require hydrogen or atmospheric CO2 capture, well beyond growing plants.

Also something I learned recently is that the idea that biofuels are a no go because they compete with food is a simplistic deflection. Looking at Brazil as an example the biofuel crops like sugarcane and groundnuts are grown in marginal land in the south that wasn't being used for agriculture. The main driver of Amazonian deforestation is cattle ranching.

[Manuel_D]

Biofuels produced by growing plants is limited by the available biomass. Brazil powers it's automobiles with biofuel, but not ships. And more importantly, Brazil is a huge country with massive amounts of arable land.

[xorcist]

Ammonia?

[Manuel_D]

Ammonia also requires hydrogen as an input. Ammonia is essentially a storage mechanism for hydrogen, eliminating the need for cryogenic or compressed storage. Basically, you need to find a carbon-neutral alternative to the Haber process [1] to produce ammonia as fuel.

1. https://en.wikipedia.org/wiki/Haber_process

[KMag]

The Haber process only produces CO2 if you consider the steam reformation to generate the feed hydrogen to be part of the Haber process. Technically, the Haber process itself is carbon-neutral, it's just that the hydrogen feedstock is almost never carbon neutral at the current time.

[xorcist]

In the context of hydrogen storage, was it not obvious what "ammonia" refers to?

We do not need an alternative to the Haber process, the idea is to use electrolysis to produce hydrogen from sea water. There is room for improvement in the process but the technology is old and well understood.

There are other ways to store hydrogen, and it's far from certain ammonia will win out in the marketplace, but there are no serious alternatives to hydrogen as an energy carrier in the long term for this application. Everything else is just impractical and even more expensive.

Just like flight fuel, it has seen little change because it is quite heavily subsidized in its current form. The day we collectively stop and start taxing it like other fuels, the market will change overnight.

[hef19898]

Which we have already. And that wouod be a great solution to the problem of storing electricity / energy. And it could even use, partially, existing gas infrastructure. Green hydrogen absolutey is a thing, bow we just need to deploy it at scale.

[Manuel_D]

No, almost all of our ammonia is produced via the Haber process which emits carbon dioxide. Less than a tenth of one percent of our hydrogen is produced via green hydrogen:

> As of 2021, green hydrogen accounted for less than 0.04% of total hydrogen production. Its cost relative to hydrogen derived from fossil fuels is the main reason green hydrogen is in less demand. For example, hydrogen produced by electrolysis powered by solar power was about 25 times more expensive than that derived from hydrocarbons in 2018.

https://en.wikipedia.org/wiki/Green_hydrogen

[hef19898]

I said we mist roll it out at scale, didn't I? The tech is there, and it works, now we have to build it.

You know, like Musk did with EVs and charging networks.

[Manuel_D]

And as per the article, it's 25 times more expensive than existing hydrogen sources.

By comparison, the economics nuclear powered ships are not that much worse than conventional propulsion: https://en.wikipedia.org/wiki/NS_Savannah#Economics_of_nucle...

[g8oz]

Yes and while it may be early days for green hydrogen, it once was for solar and wind as well. And as it did with solar the European Union is leading the way in developing policy frameworks that will grow the industry.

https://energy.ec.europa.eu/topics/energy-systems-integratio...