The Net Zero Game 0.4.0 Waste-heat recovery and cross-cutting energy efficiency, both coupled to the combustion that produces them: fuel that is never burned rejects no heat, so efficiency and electrification shrink the waste-heat gisement they would otherwise have recovered. Efficiency is bounded by the potential RTE identified, branch by branch, so the lever says how much of it is captured rather than how much exists. Reference scenario unchanged: 49.34 MtCO2 on the model's perimeter, 621 TWh of electricity, 77.47 MtCO2e national gross against the SNBC 3 objective of 63.