Subsurface sequestration of carbon dioxide — an overview from an Alberta (Canada) perspective

To stabilize the atmospheric concentration of greenhouse gases (GHG), a huge reduction of carbon dioxide (CO₂) emissions is required. Although some people believe that this necessitates a considerable reduction in the use of fossil fuels or fuel switching, other options are available that allow the use of fossil fuels and reduce atmospheric emissions of CO₂. Sequestration of CO₂ from fossil fuel combustion in the subsurface could prevent the CO₂ from reaching the surface for millions of years. Geological sequestration of CO₂ in deep aquifers or in depleted oil and gas reservoirs is a mature technology. Despite the huge quantities of CO₂ that can be sequestered in this way, this approach does not provide any economic benefit. This paper discusses a third option, which consists of injecting CO₂ in deep coal seams to sequester the carbon and enhance the recovery of coalbed methane (CBM). Waste CO₂ from CBM-fueled power plants could be injected into CBM reservoirs to produce more methane (CH₄) for the power plant. The 2:1 coal-sorption selectivity for CO₂ over CH₄ supports the feasibility of operating fossil-fueled power plants without atmospheric CO₂ emissions. Other CO₂ sequestration technologies, such as ocean disposal and biofixation, are briefly discussed and the suitability of these approaches is evaluated for use in Alberta, Canada.