3 ms·

> Although I'm not sure if that's any more efficient than desalination/hydrolysis for an H2 plant with fuel cells. One can make more than methane. Heavier liq

by retrac 5y ago

> Although I'm not sure if that's any more efficient than desalination/hydrolysis for an H2 plant with fuel cells. One can make more than methane. Heavier liquid fuels like methanol, which is a great gasoline analogue, can also be synthesized. Theoretically speaking, the most efficient way to split water is thermal decomposition at really, really high temperatures, with a catalyst. I've seen a variety of proposals to split water into hydrogen and fix the H2 as a hydrocarbon, with direct heating from both concentrated solar and nuclear. I don't know about the practical economics, though.

AstralStorm 5y ago
The trouble is that these hydrocarbon will just be burned like all others, causing GHG release. If you want something actually green, try ammonia via electrochemical methods, from hydrogen. This is also why these gas investments are a trap. We're already generally low on gas for winter and increasing the intake will not help, plus any operational emissions is too much and has to be optimized. 270 g CO2e is a plenty in a series of small deployments to ruin the targets.
- labawi 5y ago
  If methane is manufactured from CO₂ and H₂O, there is no net GHG release, it's just storage, same as ammonia or pure hydrogen (though large methane leaks would be a problem). IMO, methane is good, if we are actively transitioning to manufactured methane. It's a plug-in substitute with existing distribution networks, storage and consumers, easy and cheap to handle. Though efficiency is pretty bad, so it's mostly good as cheap bulk storage.
  - AstralStorm 5y ago
    Methane is not manufactured from straight gases. Usually it is either mined or steam reformed from oil or coal. You can see the problem - mining with concomitant pollution and release of previously bound CO2 when it's burned. Attempting to do pure electrochemical reforming is extremely energy intensive, and requires rare metal membranes. As well as a way to concentrate CO2 from atmosphere reliably. (The Sleipnir problem.)
    - labawi 5y ago
      I am well aware methane is not currently generated from CO₂, as we are still using fossil fuels, not generating enough surplus energy to make the reverse process economical. Do you have any numbers on synthesis energy efficiency? It is inherently energy intensive, as it is storing energy. Rare metal membranes may be current state of the art, but Nickel catalysts seem a popular alternative.

by retrac 5y ago

AstralStorm 5y ago

The trouble is that these hydrocarbon will just be burned like all others, causing GHG release. If you want something actually green, try ammonia via electrochemical methods, from hydrogen. This is also why these gas investments are a trap. We're already generally low on gas for winter and increasing the intake will not help, plus any operational emissions is too much and has to be optimized. 270 g CO2e is a plenty in a series of small deployments to ruin the targets.

labawi 5y ago
If methane is manufactured from CO₂ and H₂O, there is no net GHG release, it's just storage, same as ammonia or pure hydrogen (though large methane leaks would be a problem). IMO, methane is good, if we are actively transitioning to manufactured methane. It's a plug-in substitute with existing distribution networks, storage and consumers, easy and cheap to handle. Though efficiency is pretty bad, so it's mostly good as cheap bulk storage.
- AstralStorm 5y ago
  Methane is not manufactured from straight gases. Usually it is either mined or steam reformed from oil or coal. You can see the problem - mining with concomitant pollution and release of previously bound CO2 when it's burned. Attempting to do pure electrochemical reforming is extremely energy intensive, and requires rare metal membranes. As well as a way to concentrate CO2 from atmosphere reliably. (The Sleipnir problem.)
  - labawi 5y ago
    I am well aware methane is not currently generated from CO₂, as we are still using fossil fuels, not generating enough surplus energy to make the reverse process economical. Do you have any numbers on synthesis energy efficiency? It is inherently energy intensive, as it is storing energy. Rare metal membranes may be current state of the art, but Nickel catalysts seem a popular alternative.