From a purely thermodynamic standpoint, you actually _can_ be net-energy-positive. You're gaining a lot of energy going from CH4/etc + O2 to H2O + CO2. You're

From a purely thermodynamic standpoint, you actually _can_ be net-energy-positive. You're gaining a lot of energy going from CH4/etc + O2 to H2O + CO2. You're then directly sequestering CO2 (usually in solution in a deep brine), rather than C. You need to expend energy to concentrate the CO2, but it's less than you gain from combustion. In practice, it's more difficult to come out energy positive overall if we're capturing CO2 at atmospheric concentrations rather than from flue gases/etc at the time of combustion. Regardless, though, "driving roads in reverse" is not a good analogy. We don't need to expend anywhere remotely as much energy as was generated from the original combustion.