Low-cost negative emissions by demand-side management for adsorption-based direct air carbon capture and storage

Limiting anthropogenic climate change to below 2 °C requires substantial and rapid reductions in greenhouse gas emissions. Additionally, carbon dioxide removal technologies are essential to compensate for hard-to-abate emissions and counteract overshooting the earth’s carbon budget. One prospective technology is direct air carbon capture and storage (DACCS), but its energy intensity and costs limit large-scale deployment. Flexible DACCS operation seems promising for cost reduction but yet remains underexplored. This study explores the economic benefits of flexible operation of adsorption-based DACCS, considering fluctuations in both electricity prices and greenhouse gas emissions from the electricity supply. To increase the feasibility of flexible DACCS operation, the typical steam-assisted temperature vacuum swing adsorption cycle is enhanced by introducing two break phases and variable air and steam mass flows during adsorption and desorption. The benefits of flexible operation are comprehensively evaluated using a DACCS system model integrating a detailed dynamic process model with life-cycle greenhouse gas emissions and economic data. The flexible operation allows each cycle to be adjusted to optimally address the time-varying greenhouse gas emissions and costs from electricity supply. A rolling horizon algorithm combined with particle swarm optimization is used to optimize the DACCS cycles in flexible operation mode over one week. The case study focuses on the future German power grid and a DACCS system using amine-functionalized sorbents. Results indicate that flexible DACCS operation can significantly reduce net carbon removal costs by up to 20 % compared to a steady-state operation. These findings highlight the potential of flexible DACCS operation to support carbon neutrality efforts by enabling cost-effective carbon dioxide removal through integration with volatile renewable energy systems.