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> reversing that process is physically a negative yield. How energetically costly is direct atmospheric gas capture? Does sequestering flue gases look much bet

• diafygi 10y ago
  Well, from an engineering point of view, energetic cost of capture is one the inputs, not the end goal. Overall cost per unit capture is the end goal. So high energetic costs can be offset by low manufacturing costs if it results in a net overall lower cost. Anyway, yes, direct atmospheric capture is much much more energetically costly than flue gas capture. CO2 in air is 0.04% and in flue gas is 8-15%. Depending on the capture technology and the storage medium, you don't have to build nearly as much infrastructure if you tap into the 8-15% CO2 flue gas stream. Atmospheric carbon capture is literally what plants do, and the manufacturing costs for them is basically plant seeds...done. Or hell, they do that naturally anyway, so it's really just stop-clearing-forests and you've gotten your carbon capture for free. So even though atmospheric carbon capture is way more energetically costly, the manufacturing costs are basically zero, and plants are currently the cheapest solution. That doesn't stop lots of research going into trying to find something better. We found cheaper solar energy with silicon over plants (cost per watt on the grid from photovoltaics is less than biomass), so we may find something cheaper than plants for carbon capture, too.