CO₂ Storage in Shallow Underground and Surface Coal Mines: Challenges and Opportunities

Abstract

Effective storage of CO 2 requires a better understanding of coal and minerals such as clays to develop new sorbent materials and sequestration technologies.The looming global energy and environmental crises underscore a pressing need for the revision of current energy policies. The dominatingsalbeit somewhat optimisticspublic perception is that hundreds of years' worth of coal available for power generation will offset the decline of oil and gas reserves. Although use of coal accounts for half of U.S. electricity generation and for a quarter of world energy consumption, it has been perceived until recently as an unwelcome guest "from the era and pages of Charles Dickens" by environmentalists and legislators (1). For coal power generation to be properly considered, CO 2 and other greenhouse gas (GHG) generation and deposition must be addressed to assuage global climate change concerns. The ongoing development of a "pathway to stabilization" of CO 2 emissions championed by the U.S. Department of Energy (DOE) (2) is an integral part of the global response to these challenges. Capturing and sequestering CO 2 emissions is one of the principal modes of carbon management. The current strategies are geared toward implementation of various sequestration options, including terrestrial (via improved management of forests, range-, wet-, and agricultural lands), geological sequestration, and advanced biological and chemical approaches (2, 3).One of the carbon storage opportunities is sequestration in deep (>1.5 km) coal seams that are not suitable for mining. In this option, CO 2 injected into a coal bed becomes adsorbed onto the coal's surface and is immobilized. The main difficulty of this method is maintaining injectivity as the coal matrix imbibes CO 2 and swells (4). Furthermore, delivery of the captured GHG emission from the point of power generation to the remote sequestration site involves dealing with logistical problems and relatively high transportation costs. However, there are numerous shallow (<300 m deep) active and decommissioned coal mines that have large reservoir capacities. The coal remaining in place after the mining will provide some sequestration capacity. Yet the key question is whether other materials that could be placed in the mined void space underground or on the surface would enhance the CO 2 sorption.Herein we will suggest a novel process that includes capturing GHG in abundant materials, which can be facilitated by controlled sequential heating and cooling of these solids. By taking advantage of the properties of waste materials generated during coal production and the exhaust heat generated by the power plants, such an approach permits the integration of the entire CO 2 cycle, from generation to deposition. Coupling coal extraction/preparation with power generation facilities would improve the economics of "zero-emission" power plants due to the proximity of all the involved facilities (Figure 1). Challenges and opportunitiesTo assess the feasibility of this concept, engineers need to consid...

Air invasion in a granular layer immersed in a fluid: morphology and dynamics

“…In many situations, however, the propagation of air in a porous medium, biaised by gravity, is not limited by a solid bottom wall and the gas can explore freely all directions. In particular, we mention the example of liquid injection in the ground for enhanced oil recovery [26], or the recent topic of CO 2 storage which aims at reducing greenhouse effect and global warming by injecting carbon dioxide several hundred meters below in the subsurface [27,28]. In this latter case, it is important to estimate the morphology of the region invaded by the gas below the injection point [29].…”

Mineralization of Carbon Dioxide: A Literature Review

“…Carbonate growth is systematically oriented normal to the flow, which facilitates the development of chemical gradients with cationic supersaturation conditions for carbonate precipitation near the walls. [49,50] and even irreversible [51]. Mineral precipitation and dissolution reactions under low-water CO 2 conditions have received much less attention than those of the aqueous-phase-dominated (CO 2 dissolved in water) systems [31], although the water-bearing CO 2 (water dissolved in liquid or supercritical CO 2 ) phase can mediate important geochemical reactions as well [52].…”

“…The main CO 2 uptake was most likely related to adsorption on clay minerals. The processes and mechanisms of such adsorption are not quite understood yet [51,58]. For example, water molecules usually compete with CO 2 for surface sorption sites.…”

Addressing the CO 2 emissions of the world's largest coal producer and consumer: Lessons from the Haishiwan Coalfield, China

“…Coupling coal extraction/preparation with power generation facilities would improve the economics of "zero-emission" power plants due to the proximity of all the value-chain facilities. [55] [FIGURE 17 PLACEHOLDER]…”