One of the more compelling geoengineering strategies I've seen discussed has been Olivine weathering:
Given that formulation I assume that the amount of olivine needed is the same order of magnitude as the 1 liter of oil to produce the CO2.
The world is consuming 97 Mio barrels of oil per day [2]. I doubt we can mine that amount of olivine on a daily basis. Is it even available in that quantity?
How is olivine considered an adequate option to reduce the CO2 in the atmosphere?
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[1] that Wikipedia article above.
In energy-tech, a useful metric is energy-return-on-energy-investment -- a saudi oil well returns 40 units of energy for each unit of energy required for extraction, tar sands are something like 3:1, solar panels are something like 5:1.
Taking that mindset, what's the ratio of CO2-sequested-for-CO2-required-to-mine? Yes, we can get better numbers if we electrify all the heavy machinery and power it with solar, but given that heavy mining trucks are largely fossil fuel powered, where are we today?
So we need to go olivine mining at a greater rate than we have done oil extraction... Will there be millions of olivine rigs, olivine pipelines, olivine wars?
Somehow I don't think it's gonna happen...
Something a little more simple and using abundant resources.