An experiment-based assessment of the feasibility of the CO₂ geological storage in unexploited coal beds in northern Spain

The storage of CO₂ in unused coal mines is a viable option for reducing emissions of CO₂, whose accumulation in the atmosphere is one of the main contributors to global warming. Understanding CO₂ behaviour and storage capacity of the coal is an important first step before injecting the CO₂. We used experimental equipment to extract coal from a mine and to obtain a representative sample of both its internal structure (in terms of cleats, macropores, mesopores and micropores) and occluded gases. Storage capacity was studied in terms of variations in gas pressure. The adsorption isotherm was experimentally obtained applying a procedure specifically designed to avoid altering the coal. An unused coal bed was selected to determine how much CO₂ it could adsorb and to study the feasibility of storing power plant CO₂ in this kind of mine.