Review on CH4-CO2 replacement for CO2 sequestration and CH4/CO2 hydrate formation in porous media.

• A review on the encapsulation of carbon dioxide using gas hydrates was performed. • The effect of additives in CH 4 and CO 2 hydrate formation were studied. • Gas hydrate formation mechanisms on porous media with CH 4 /CO 2 were studied. • The use of gas hydrates as a mechanism for energy storage is explored. • Effect of porous media in energy storage, as well as methane release, were studied. Adverse effects of excess greenhouse gases in the atmosphere emanating from fossil fuels have prompted intense research on clean energy sources as replacements and carbon capture. Research on natural gas hydrate has intensified in the past century due to the occurrence of natural gas hydrate in numerous places around the world on the sea beds and in permafrost regions. Due to its energy value and ability to form a clathrate hydrate with water, the methane molecule has proven to be useful as both a viable energy store and a means of carbon dioxide sequestration in natural gas hydrates. Methane can be produced from natural gas hydrates while controlling carbon dioxide emission, by replacing methane molecules with carbon dioxide from its crystalline structure. This review focuses on the encapsulation of carbon dioxide by a replacement reaction of methane from natural gas hydrates, with methane-carbon dioxide replacement models presented and discussed. Experimental variables affecting the CH 4 -CO 2 replacement process along with reported theoretical findings were reviewed. These are discussed along with the challenges and limitations in the replacement process. In addition, the fundamentals of hydrate formation mechanisms on porous media are detailed. Finally, an extensive discussion and comparison of the experimental studies of hydrate formation involving various porous media materials such as activated carbon, glass beads, solid and hollow silica in the presence of chemical additives and nanoparticles, with carbon dioxide and methane gas molecules are presented. Climate change mitigation strategies in minimising CO 2 emissions while harnessing energy by replacing methane with CO 2 from the hydrate structure. [ABSTRACT FROM AUTHOR]