Carbon capture is of course less efficient than not burning fossil fuels to begin with, so the first goal must be to no longer emit new carbon. Then it may make sense to capture some carbon and turn it into synthetic fuels for certain applications because of the energy density and ease of storage. Maybe even for plastics and similar stuff. After that, undoing a century of emissions, that is a monumental challenge. Depending on how exactly we want to store the carbon, we might need more or less the same amount of energy that we got out of fossil fuels over the last century. Double our renewable energy generation capacity and then use half of it for half a century - roughly taking into account the increase in emissions over the past century - to capture carbon.