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What a stupid idea[0]. Massive distributed capital expenditure for the express purpose of collecting CO2 for an uneconomic (but technically feasible) conversion

What a stupid idea[0]. Massive distributed capital expenditure for the express purpose of collecting CO2 for an uneconomic (but technically feasible) conversion to methane. If converting CO2 to methane made sense in any form[1], it would happen first at point sources (e.g. breweries) long before this Rube Goldberg-esque inanity. [0] No really, it's awful. Might as well try and collect the water cars emit to try and reduce our dependence on bottled water. [1]It, as a rule, doesn't per thermodynamics and Coloumb's constant.

adrianN 7y ago
Converting CO2 to Methane makes a lot of sense if you want to store large amounts of power. Every country already has the infrastructure for storing and distributing gas and turning it into electricity and heat.
- thereisnospork 7y ago
  Not compared to doing pretty much anything else with that power. Which includes easy things like pumping water uphill, charging lithium batteries, or just making H2 and distributing that into the gas grid directly. To make CH4 from CO2 takes 8 electrons at (near enough) 2V, giving 1 / (96450 * 8) moles CH4 per amp second. Per tonne, that works out to roughly 1000$/tonne CH4 or 2900$/tonne CO2. Assm 4c/kwh. So with an exceptionally efficient process requiring negligible capital expense or labor it is possible to convert 3000$ and one tonne of CO2 into 200$ of natural gas. Short of making rocket fuel on Mars, I'm not smelling even the slightest whiff of an application: which is why I am so derisive of the article's proposal - charitably it is at best proposing the equivalent of solar roadways.
  - adrianN 7y ago
    Hydrogen is a lot harder to store than Methane, and afaik you can't substitute 100% Hydrogen for natural gas without changing large chunks of the heating infrastructure. But you're of course right that making hydrogen has a much better efficiency.
    - thereisnospork 7y ago
      Britain is/was looking into just that with some moderate seriousness[0]; a quick google suggests as much as 30% enrichment. Though as I recall they wanted to use SMR/ATR on natural gas and bury the resulting CO2 in the north sea as opposed to electrolysis. [0] https://www.sciencedaily.com/releases/2018/06/180611133412.htm https://www.sciencedaily.com/releases/2018/06/180611133412.h...

adrianN 7y ago

Converting CO2 to Methane makes a lot of sense if you want to store large amounts of power. Every country already has the infrastructure for storing and distributing gas and turning it into electricity and heat.

thereisnospork 7y ago
Not compared to doing pretty much anything else with that power. Which includes easy things like pumping water uphill, charging lithium batteries, or just making H2 and distributing that into the gas grid directly. To make CH4 from CO2 takes 8 electrons at (near enough) 2V, giving 1 / (96450 * 8) moles CH4 per amp second. Per tonne, that works out to roughly 1000$/tonne CH4 or 2900$/tonne CO2. Assm 4c/kwh. So with an exceptionally efficient process requiring negligible capital expense or labor it is possible to convert 3000$ and one tonne of CO2 into 200$ of natural gas. Short of making rocket fuel on Mars, I'm not smelling even the slightest whiff of an application: which is why I am so derisive of the article's proposal - charitably it is at best proposing the equivalent of solar roadways.
- adrianN 7y ago
  Hydrogen is a lot harder to store than Methane, and afaik you can't substitute 100% Hydrogen for natural gas without changing large chunks of the heating infrastructure. But you're of course right that making hydrogen has a much better efficiency.
  - thereisnospork 7y ago
    Britain is/was looking into just that with some moderate seriousness[0]; a quick google suggests as much as 30% enrichment. Though as I recall they wanted to use SMR/ATR on natural gas and bury the resulting CO2 in the north sea as opposed to electrolysis. [0] https://www.sciencedaily.com/releases/2018/06/180611133412.htm https://www.sciencedaily.com/releases/2018/06/180611133412.h...