Direct Flue Gas and CO<sub>2</sub> Injection for Simultaneous Energy Recovery and CO<sub>2</sub> Sequestration in Ocean: Feasibility Analysis and Perspective
Yogendra Kumar, Jitendra S. Sangwai
Abstract
Addressing rising energy demand and making industrial clusters carbon neutral are crucial for sustainable energy transition. Large-scale CO 2 capture from flue gas can be a costly affair, and hence directly injecting flue gas under subsurface offshore reservoirs can be an economical solution. In this pursuit, methane production from natural gas hydrate (NGH) reservoirs using CO 2 sequestration can offer a simultaneous solution for energy transition and achieving net zero. This review delves into the intricate engineering considerations and begins with hydrate thermodynamics and kinetics discussion and subsequently provides a comprehensive analysis of technical factors including porous media characteristics, the state of gas injection, and the assessment of hydrate stability under various conditions of flue gas injection in ocean environments. While the depth required in the ocean for stable CO 2 hydrate formation increases with the decrease in the CO 2 fraction in the flue gas mixture, the depth for hydrate formation in subsea sediments reduces as the CO 2 fraction in the injected flue gas stream decreases. Even though the hydrate formation from flue gas and pure CO 2 in ocean is possible at a depth of 500–2000 m based on CO 2 concentration, which is not necessarily favorable environmentally, the best possible location for flue gas injection (10–20% CO 2 ) is under seabed sediments where it can form hydrates at a maximum depth of 100–150 m from the seabed. The paper helps in exploring the possibilities of direct flue gas and CO 2 sequestration in the ocean for simultaneous energy production and long-term, large-scale CO 2 sequestration.