Figure 1

NGH production method using air and CO₂/air.

(a) Schematic illustration of the described air (or CO₂/air) driven NGH production method composed of two distinct steps: NGH decomposition caused by injected air (or CO₂/air); subsequent decomposition driven guest exchange process. (b) Discovery of the concept of critical methane concentration (CMC) depending on the molar ratio between CH₄ and injected air and CO₂/air. (c) Methane hydrate at 288.15 K and 200 bar before air injection (top) and mixed hydrate crystals coexist with water at 288.15 K after air injection above the critical concentration (bottom).