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> 0.3% of the Iron-oxide becomes nanoparticles which cannot be converted back into Iron. At that rate, 50% of the initial iron will be gone in 333 cycles of ir

> 0.3% of the Iron-oxide becomes nanoparticles which cannot be converted back into Iron. At that rate, 50% of the initial iron will be gone in 333 cycles of iron -> iron oxide -> iron. This a hard type of energy source to reason about: 1. It's not a pure fuel and acts like a battery most of the time, but it's also not renewable 2. Iron is extremely abundant on Earth, but it requires mining and processing to extract 3. Iron oxide in nanoparticle size would likely be a pollutant and hazardous to human health, not something that will break down quickly and harmlessly. The high fuel density and low explosiveness may make it a good use case in some niches, but I imagine it's actually more scalable and healthy to burn jet fuel and reproduce it from renewable powered carbon capture, where density is needed.

proto-n 3y ago
Is iron oxide magnetic in nanoparticle size? Because if it is, then we can probably very efficiently filter it before releasing it into the atmosphere.
- juujian 3y ago
  The article mentions a HEPA filter.
  - sudhirj 3y ago
    That’s still a mess, if the particles are magnetic a magnet will be a way cleaner and more effective filter.
    - sacnoradhq 3y ago
      Unfortunately, you're mistaken. In practice, iron(iii) oxide is barely paramagnetic and the particles are likely well above the Curie point and possibly at the melting point.
- thsksbd 3y ago
  iron oxide magnetic properties depend on its oxidation state, temperature and particle size.
  - 13of40 3y ago
    Not sure why this is dead, but AFAIK magnetism in iron and steel is dependent on "domains" of iron molecules that are aligned in a crystal structure so the magnetic effect isn't just scattered to all directions. That's why some kinds of stainless steel aren't magnetic - the adulturant elements break up the crystal structure. In this case I think the question would be whether these particles are big enough to form a "domain" and become magnetic.
    - thsksbd 3y ago
      at nanoscale many (all?) iron oxides become super-paramagnetic. If anything, they're even more attracted to magnetic fields.
    - pixl97 3y ago
      If the output is iron oxide, no it is only very very weakly magnetic.
      - sacnoradhq 3y ago
        And if iron(III) oxide is near the melting point, it's unlikely to be magnetic and may not even be paramagnetic. This would be an interesting lab experiment: heat a sample to 1500 C exactly and test for paramagnetic properties.
- idiotsecant 3y ago
  Even if it isn't we are very good at filtering materials from exhaust gasses. Something like a wet electrostatic precipitator is probably overkill, but would do the job without having to care about magnetic properties.
- nabla9 3y ago
  Traditional methods or their combination: wet scrubber, electrostatic precipitator or bag filters will do the job.
juujian 3y ago
Might be possible to create a completely closed system to address the loss? I am more concerned/confused by the fact that they use hydrogen to reduce the iron. That seems like a very convoluted process, why not use the hydrogen generate heat instead? Yes, it has much lower density, but it has advantages to make up for it, for instance the fact that you don't need to worry about evaporation, leakage, filters, all that at all.
- PaulHoule 3y ago
  Hydrogen is devilishly hard to transport and store. Hydrogen packs a lot of energy per gram, but the density is so low. You need a huge tank if you compress it as a gas, you can liquefy it but the density is still not great, it takes a lot of energy, and you have to deal with this: https://en.wikipedia.org/wiki/Spin_isomers_of_hydrogen https://en.wikipedia.org/wiki/Spin_isomers_of_hydrogen freshly liquefied hydrogen contains a lot of stored energy in that form which will be released over time and cause quite a bit to vaporize, for long term storage you have to release that energy. Thus people have looked at all sorts of schemes for storing hydrogen such as absorbing it in metals like palladium, metal hydrides, chemical carriers such as ammonia, methane, etc.
  - kaliszad 3y ago
    Sodium would be a much better proposition. With NaOH, you can create a closed cycle. The electrolysis of NaOH is the well known Castner process, a consumable metal anode fuel cell with sodium is also well known (expired Patent: US3730776A by Lockheed) More details and overlap with other approaches: https://orgpad.com/s/5BfLP-cxj-7 https://orgpad.com/s/5BfLP-cxj-7 Sodium has higher energy density (3.5 kWh/L) than liquid hydrogen, there is no energy needed to store it and no catalyst is needed for the fuel cell because sodium is so reactive with water. The fuel cell is rather easy to construct (I know somebody, who has done it in a garage). NaOH solution is very caustic but also neutralizes well naturally without long term effects at least in comparison to crude oil that seems to be the better proposition. And of course sodium is everywhere, where NaCl - table salt is.
umvi 3y ago
> The nanoparticles are not emitted in the atmosphere but captured in a HEPA filter. If that's true, your point #3 is moot. And if the nano particles can be captured by a filter, maybe we could design filters specifically for iron oxide nano particles that would allow the nano particles to be extracted > but I imagine it's actually more scalable and healthy to burn jet fuel and reproduce it from renewable powered carbon capture, where density is needed. You're saying capture carbon from CO2 and turn it into kerosene? I tried googling around and everywhere I look it seems like this is currently way more difficult than renewable iron fuel (https://www.planet.veolia.com/en/how-produce-kerosene-co2 https://www.planet.veolia.com/en/how-produce-kerosene-co2).
- a3w 3y ago
  Cherry-picking the fuel for jets example makes sense, since somehow we don´t expect aviation to transition completely to airscrews. As for the disposal of HEPA filteres loaded with air-stable inorganics, that still is pollution, only the kind of waste you store safely, and if not give people cancer, but highly localized so.
jerf 3y ago
To a first approximation, Earth is a big ball of iron, so losing 50% of the iron in 333 cycles doesn't seem like that big a deal. Getting more iron is an energy issue rather than an availability issue. I'm also somewhat concerned about the nanoparticle's effect on living things. It is likely that it is only a question of local exposure, as in general once they get out they should still rust in some relatively short period of time, and as Earth is the aforementioned big ball of iron, a bit of rust in the environment is quite unlikely to hurt anything because if it could hurt a thing that thing would already be dead, but locally nanoparticles would be something weird and I could see breathing them could be problematic. It is also entirely possible that it is safe up to surprisingly absurd levels too (your body is familiar with iron, and while there are toxic doses of iron you're not getting to them with nanoparticle exposure any time soon), it would just be something that would need some study.
- rsaesha 3y ago
  >Earth is a big ball of iron. No it's not. Inside the crust both Si and Al are more common. There is plenty of Fe, which is all in oxide form. Mining and processing required.
  - dredmorbius 3y ago
    Shrug. Iron is abundant on Earth, including within the crust, where it's the fourth most abundant element (after Oxygen, silicon, and aluminium), roughly 5% by mass. And yes, considerably more prevalent in the core. Iron and oxygen account for roughly 32% of Earth's total mass, each, the largest proportion of any element. <https://en.wikipedia.org/wiki/Earth_mass https://en.wikipedia.org/wiki/Earth_mass> Sure, not as abundant as silicates. But nowhere near as rare as gold, platinum, and rhodium. Or even copper, silver, or lead. <https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...> There's even a fair bit of it flowing though your veins and arteries right now. And yes, the major ore deposits are old. Most are BIFs (banded iron formations), and date to 1 bya or 3.5 bya, laid down by early oceanic algae for the most part. Sometimes it's more than fine to allow a slight exaggeration to pass without litigating it to death.
jjk166 3y ago
The nanoparticles can't be converted back to iron in this process, but they can still be turned back into iron by other processes. No system is truly closed loop, but this is more closed loop than any other energy-to-fuel system. You need to extract the feedstocks for any energy-to-fuel system. Iron is cheap and simple to extract, compared to say carbon from the atmosphere. The nanoparticles do not get released to the environment. Emissions from burning carbon based fuels also include pollutants that are hazardous to human health.
- idiotsecant 3y ago
  > Emissions from burning carbon based fuels also include pollutants that are hazardous to human health. Which do get released into the environment in quite large quantities!
mirekrusin 3y ago
Can't you just make pulsating/spinning magnet to capture it?
- sacnoradhq 3y ago
  What half-bakery are you imagining? This won't work with blazing hot rust nanoparticles.

proto-n 3y ago

Is iron oxide magnetic in nanoparticle size? Because if it is, then we can probably very efficiently filter it before releasing it into the atmosphere.

juujian 3y ago
The article mentions a HEPA filter.
- sudhirj 3y ago
  That’s still a mess, if the particles are magnetic a magnet will be a way cleaner and more effective filter.
  - sacnoradhq 3y ago
    Unfortunately, you're mistaken. In practice, iron(iii) oxide is barely paramagnetic and the particles are likely well above the Curie point and possibly at the melting point.
thsksbd 3y ago
iron oxide magnetic properties depend on its oxidation state, temperature and particle size.
- 13of40 3y ago
  Not sure why this is dead, but AFAIK magnetism in iron and steel is dependent on "domains" of iron molecules that are aligned in a crystal structure so the magnetic effect isn't just scattered to all directions. That's why some kinds of stainless steel aren't magnetic - the adulturant elements break up the crystal structure. In this case I think the question would be whether these particles are big enough to form a "domain" and become magnetic.
  - thsksbd 3y ago
    at nanoscale many (all?) iron oxides become super-paramagnetic. If anything, they're even more attracted to magnetic fields.
  - pixl97 3y ago
    If the output is iron oxide, no it is only very very weakly magnetic.
    - sacnoradhq 3y ago
      And if iron(III) oxide is near the melting point, it's unlikely to be magnetic and may not even be paramagnetic. This would be an interesting lab experiment: heat a sample to 1500 C exactly and test for paramagnetic properties.
idiotsecant 3y ago
Even if it isn't we are very good at filtering materials from exhaust gasses. Something like a wet electrostatic precipitator is probably overkill, but would do the job without having to care about magnetic properties.
nabla9 3y ago
Traditional methods or their combination: wet scrubber, electrostatic precipitator or bag filters will do the job.

juujian 3y ago

Might be possible to create a completely closed system to address the loss? I am more concerned/confused by the fact that they use hydrogen to reduce the iron. That seems like a very convoluted process, why not use the hydrogen generate heat instead? Yes, it has much lower density, but it has advantages to make up for it, for instance the fact that you don't need to worry about evaporation, leakage, filters, all that at all.

PaulHoule 3y ago
Hydrogen is devilishly hard to transport and store. Hydrogen packs a lot of energy per gram, but the density is so low. You need a huge tank if you compress it as a gas, you can liquefy it but the density is still not great, it takes a lot of energy, and you have to deal with this: https://en.wikipedia.org/wiki/Spin_isomers_of_hydrogen https://en.wikipedia.org/wiki/Spin_isomers_of_hydrogen freshly liquefied hydrogen contains a lot of stored energy in that form which will be released over time and cause quite a bit to vaporize, for long term storage you have to release that energy. Thus people have looked at all sorts of schemes for storing hydrogen such as absorbing it in metals like palladium, metal hydrides, chemical carriers such as ammonia, methane, etc.
- kaliszad 3y ago
  Sodium would be a much better proposition. With NaOH, you can create a closed cycle. The electrolysis of NaOH is the well known Castner process, a consumable metal anode fuel cell with sodium is also well known (expired Patent: US3730776A by Lockheed) More details and overlap with other approaches: https://orgpad.com/s/5BfLP-cxj-7 https://orgpad.com/s/5BfLP-cxj-7 Sodium has higher energy density (3.5 kWh/L) than liquid hydrogen, there is no energy needed to store it and no catalyst is needed for the fuel cell because sodium is so reactive with water. The fuel cell is rather easy to construct (I know somebody, who has done it in a garage). NaOH solution is very caustic but also neutralizes well naturally without long term effects at least in comparison to crude oil that seems to be the better proposition. And of course sodium is everywhere, where NaCl - table salt is.

umvi 3y ago

> The nanoparticles are not emitted in the atmosphere but captured in a HEPA filter. If that's true, your point #3 is moot. And if the nano particles can be captured by a filter, maybe we could design filters specifically for iron oxide nano particles that would allow the nano particles to be extracted > but I imagine it's actually more scalable and healthy to burn jet fuel and reproduce it from renewable powered carbon capture, where density is needed. You're saying capture carbon from CO2 and turn it into kerosene? I tried googling around and everywhere I look it seems like this is currently way more difficult than renewable iron fuel (https://www.planet.veolia.com/en/how-produce-kerosene-co2 https://www.planet.veolia.com/en/how-produce-kerosene-co2).

a3w 3y ago
Cherry-picking the fuel for jets example makes sense, since somehow we don´t expect aviation to transition completely to airscrews. As for the disposal of HEPA filteres loaded with air-stable inorganics, that still is pollution, only the kind of waste you store safely, and if not give people cancer, but highly localized so.

jerf 3y ago

To a first approximation, Earth is a big ball of iron, so losing 50% of the iron in 333 cycles doesn't seem like that big a deal. Getting more iron is an energy issue rather than an availability issue. I'm also somewhat concerned about the nanoparticle's effect on living things. It is likely that it is only a question of local exposure, as in general once they get out they should still rust in some relatively short period of time, and as Earth is the aforementioned big ball of iron, a bit of rust in the environment is quite unlikely to hurt anything because if it could hurt a thing that thing would already be dead, but locally nanoparticles would be something weird and I could see breathing them could be problematic. It is also entirely possible that it is safe up to surprisingly absurd levels too (your body is familiar with iron, and while there are toxic doses of iron you're not getting to them with nanoparticle exposure any time soon), it would just be something that would need some study.

rsaesha 3y ago
>Earth is a big ball of iron. No it's not. Inside the crust both Si and Al are more common. There is plenty of Fe, which is all in oxide form. Mining and processing required.
- dredmorbius 3y ago
  Shrug. Iron is abundant on Earth, including within the crust, where it's the fourth most abundant element (after Oxygen, silicon, and aluminium), roughly 5% by mass. And yes, considerably more prevalent in the core. Iron and oxygen account for roughly 32% of Earth's total mass, each, the largest proportion of any element. <https://en.wikipedia.org/wiki/Earth_mass https://en.wikipedia.org/wiki/Earth_mass> Sure, not as abundant as silicates. But nowhere near as rare as gold, platinum, and rhodium. Or even copper, silver, or lead. <https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...> There's even a fair bit of it flowing though your veins and arteries right now. And yes, the major ore deposits are old. Most are BIFs (banded iron formations), and date to 1 bya or 3.5 bya, laid down by early oceanic algae for the most part. Sometimes it's more than fine to allow a slight exaggeration to pass without litigating it to death.

jjk166 3y ago

The nanoparticles can't be converted back to iron in this process, but they can still be turned back into iron by other processes. No system is truly closed loop, but this is more closed loop than any other energy-to-fuel system. You need to extract the feedstocks for any energy-to-fuel system. Iron is cheap and simple to extract, compared to say carbon from the atmosphere. The nanoparticles do not get released to the environment. Emissions from burning carbon based fuels also include pollutants that are hazardous to human health.

idiotsecant 3y ago
> Emissions from burning carbon based fuels also include pollutants that are hazardous to human health. Which do get released into the environment in quite large quantities!

mirekrusin 3y ago

Can't you just make pulsating/spinning magnet to capture it?

sacnoradhq 3y ago
What half-bakery are you imagining? This won't work with blazing hot rust nanoparticles.