Targeting the preindustrial level of atmospheric CO2 is such an ambitious target, trying to undo 300 years of emissions. Then again, it’s not like we’ve stopped emitting.
If we instead try to calculate the energy requirements to simply offset the average emissions of that particular year, using this formula of 652 kJ/kg CO2, and average annual CO2 emissions, against the current numbers of about 37 billion tonnes, or 37,000,000,000,000 kg, we have 2.4 x 10^16 kJ, or 2.4 x 10^19 joules. Which converts to 6.7 x 10^12 kWh, or 6,700 TWh.
Total annual US electricity generation is about 4700 TWh per year.
Global electricity generation is about 25000 TWh per year, about 40% of which is from low or zero carbon sources.
So basically if we’ve got 6700 TWh of clean energy to spare, it would be more effective to steer that into replacing fossil fuels first, and then once we hit a point of diminishing returns there, explore the much less efficient options of direct capture for excess energy we can’t store or transport. Maybe we’ll get there in a decade or two, but for now it doesn’t make any sense.
