Gas Sequestration and Sorption

Gas Sequestration is the capture and immobilisation of a gas, for permanent, or semi-permanent, storage. In general, the gas (or gases) to be sequestered are present in a mixture with other gases, requiring some process of separation.

The primary interest in gas sequestration is to avoid release of carbon dioxide into the atmosphere. Increases in global temperatures since the beginning of the Industrial Revolution are attributed to the trapping of heat in the atmosphere by greenhouse gases (GHG), of which carbon dioxide is the most important. Political movement towards quotas for CO₂ release, with markets which allow trading of allowances, mean that emissions become commercially important. For some industries, the quantities of carbon dioxide produced could have a major impact on profitability.

Sequestration of gases from Waste Landfills is also under research. Landfills release mixtures of gases including Carbon Dioxide and Methane, which has even stronger greenhouse properties.

Another use of Gas Sequestration is in life support systems for spacecraft, and other closed systems. Removal of carbon dioxide from the air is necessary to prevent it from accumulating to toxic levels, without requiring complete replacement of the atmosphere.

Sorption, separation and sequestration

The sorption of gases, either by adsorption onto surfaces or by absorption into the bulk material, is essential to most sequestration technologies. Sequestration may involve a number of different steps, which require understanding of various physical processes. Some examples include:

• Separation of the gas using Pressure Swing Adsorption (PSA)...
• ...or using selective permeation technologies
• diffusion of gas through the substrate
• competitive adsorption effects between the gas being sequestered and the gases already present, which can give economic benefits, by improving yield of natural gas resources (ECBM)