Energy and Infrastructure Requirements for Large-Scale Carbon Capture, Utilization, and Storage: Heat Supply, Capture Mix, and Carbon Fate

Capturing carbon dioxide at a climate-relevant scale is an energy supply problem as much as a separation problem. We developed a linked scenario model that follows capture mix, heat supply, and carbon fate through one balance of heat, electricity, generation, storage, land, and retained carbon. An illustrative 10 Gt CO2/year portfolio with 55% flue-gas capture, 25% already separated CO2, and 20% direct air capture (DAC) needs 30.25 EJ/year of process heat and 10.06 EJ/year of direct electricity. On an annual energy basis, dedicated wind and solar supply requires 5.37 TW of nameplate capacity with electric boilers, and 2.64 TW with heat pumps at a coefficient of performance of 3. Losing the already separated streams and drawing heat from a heat-pump source at 20 °C raises the requirement to 4.12 TW. Complete electrochemical DAC must use less than 3.47 GJ/t of precompression electricity to beat thermal DAC with heat pumps, and diverting 1 Gt/year of DAC CO2 to methanol more than doubles portfolio electricity while halving the atmospheric CO2 reaching geological storage. The results are scenario-dependent and identify heat integration, source availability, and carbon fate as screening criteria for process development and deployment planning.