Assuming a totally steady-state biosphere, and that zero-carbon energy and carbon capture are mutually exclusive, which are not a valid assumptions. Almost ever

Assuming a totally steady-state biosphere, and that zero-carbon energy and carbon capture are mutually exclusive, which are not a valid assumptions. Almost every first-world country's biosphere is limited by human action, so a country running on "zero carbon" energy can allow the biosphere to capture carbon at effectively the same rate as the biofuel country, and not release the carbon back into the atmosphere.