What happens to CO₂ after capture: utilisation pathways and their energy cost

A capture system is only as useful as the destination of its output. This note classifies the destinations for captured CO2 — geological storage, mineralisation, direct use and conversion to chemicals or fuels — and applies a single governing metric to conversion: energy consumed per unit of product divided by the energy content of that product. Because CO2 is the fully oxidised end state of carbon, that ratio exceeds one for any fuel, so CO2-to-fuel is an energy carrier rather than an energy source. The conditions under which conversion is nonetheless worthwhile are identified, the case for mineralisation in distributed urban capture is made, and the elements of a checkable utilisation claim are listed. An earlier version of this note was published on the author's blog: https://hrohera27.blogspot.com/2026/09/what-happens-to-co2-after-you-capture.html