10 Search Results

Abstract The Intergovernmental Panel on Climate Change concludes that CO ₂ capture and storage (CCS) is critical for climate‐stabilizing energy transitions. In CCS, captured CO ₂ is sequestered in saline aquifers within sedimentary basins. The CO ₂ storage capacity and the rate of injection are functions of the geology of the saline aquifer, which is uncertain. To minimize impacts of this uncertainty, CCS projects could include backup plans, such as co‐locating geologic CO ₂ storage (GCS) sites with or near existing CO ₂ ‐enhanced oil recovery (CO ₂ ‐EOR) operations. These “stacked storage” projects could hedge against uncertainty in themore » saline formation performance because captured CO ₂ could be injected into either location in the event of unexpected events (e.g., the injectivity decreases). Here, we investigate the possibility and ramifications of developing CCS networks in Oklahoma that are amendable to stacked storage. We find that stacked storage is possible in Oklahoma but the counties with the lowest‐cost saline storage resources do not have existing CO ₂ ‐EOR operations. At the systems level, we find it is slightly more expensive (e.g., $1/tCO ₂ to $5/tCO ₂ ) to site GCS in counties with CO ₂ ‐EOR projects. This increased expense is largely due to increased CO ₂ transportation costs because hundreds of km of additional pipeline is required to capture CO ₂ from the lowest‐cost sources. Overall, our results suggest that it is optimal to build more pipelines and avoid injecting CO ₂ in some of the lowest‐cost saline storage resources, to enable capturing CO ₂ from the least‐cost sources. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.« less

Water scarcity and climate change are dual challenges that could potentially threaten energy security. Yet, integrated water–carbon management frameworks coupling diverse water- and carbon-mitigation technologies at high spatial heterogeneity are largely underdeveloped. Here we build a global unit-level framework to investigate the CO₂ emission and energy penalty due to the deployment of dry cooling—a critical water mitigation strategy—together with alternative water sourcing and carbon capture and storage under climate scenarios. We find that CO₂ emission and energy penalty for dry cooling units are location and climate specific (for example, 1–15% of power output), often demonstrating notably faster efficiency losses thanmore » rising temperature, especially under the high climate change scenario. Despite energy and CO₂ penalties associated with alternative water treatment and carbon capture and storage utilization, increasing wastewater and brine water accessibility provide potential alternatives to dry cooling for water scarcity alleviation, whereas CO₂ storage can help to mitigate dry cooling-associated CO₂ emission tradeoffs when alternative water supply is insufficient. By demonstrating an integrative planning framework, our study highlights the importance of integrated power sector planning under interconnected dual water–carbon challenges.« less

Coal mine drainage (CMD) impairs tens of thousands of kilometers of U.S. waterways each year, in part with the leaching of low concentrations of rare earth elements (REEs). REEs are essential for modern technologies, yet economically viable natural deposits are geospatially limited, thus engendering geopolitical concerns, and their mining is energy intense and environmentally destructive. This work summarizes laboratory-scale experimentalresults of a trap-extract-precipitate (TEP) process and uses the mass and energy balances to estimate the economic costs and environmental impacts of the TEP. The TEP process uses the alkalinity and filtering capacity of stabilized flue gas desulfurization (sFGD) material ormore » water treatment plant (WTP) sludge to remediate CMD waters and extract REEs. Passive treatment systems that use WTP sludge are cheaper than those that use sFGD material ($$\$$$$89,300/year or $$\$$$$86/gT-REE vs. $$\$$$$89,800/year or $$\$$$$278/gT-REE) and have improved environmental performance across all indicators from two different impact assessment methods. These differences are largely attributable to the larger neutralizing capacity of WTP sludge in the treatment application.« less

Rare earth elements (REEs) (including scandium, yttrium and a group of 15 lanthanides) are often considered to be critical components in the productions of renewable energy hardware, electric vehicles, health care and military equipment, and consumer electronic products. The demand of REEs has been projected to be growing at an annual rate of 5-9% in the next 25 years. In 2011, the global demand of total rare earth oxides (REOs) was estimated to be approximately 105,000 tons, which is expected to grow to 210,000 tons by 2025. China overwhelmingly dominates the current worldwide rare earth productions but has strategically restrictedmore » its exports, causing significant instability for the global market. In response to the increasing demand for REEs and the supply dominance of China, identifying alternative sources of REEs has become a critical issue for the United States and other countries. Coal, coal ash, and coal mine drainage (CMD) are considered to be the alternative sources of REEs. In the U.S., high REE concentrations have been reported to be closely associated with coal deposits, including the Appalachian Basins. When surface and/or groundwater come in contact with geologic strata containing sulfide minerals exposed by coal mining, the accelerated oxidation of sulfide minerals in the presence of ferric iron and/or oxygen can produce sulfuric acid. The process promotes the weathering of REE-bearing rocks and minerals in the host geologic strata. Compared to average river water and seawater, the concentrations of REEs can be orders of magnitude higher in CMD. In this study, we demonstrated a trap-extract-precipitate (TEP) process that can effectively recover REEs from CMD. The three-stage TEP process uses alkaline industrial by-products to capture REEs from CMD and then applies an extraction/precipitation procedure to produce a feedstock that can be economically processed to produce marketable rare earth oxides. The alkaline industrial by-products tested in this study include the residual from a water softening process (DRWP sludge) and two types of stabilized flue gas desulfurization materials (sFGDs). sFGD material is a mixture of lime (CaO) and two coal combustion by-products, calcium sulfite FGD by-product and fly ash. The objectives of this study are to (1) validate the effectiveness and feasibility; (2) determine mechanisms controlling the rare earth recovery, (3) quantify the associated economic and environmental benefits, and (4) evaluate the full-scale application. To achieve these objectives, tasks to be carried out in this proposed project are organized into three phases. In the first phase, the research team collaborated with Ohio Department of Natural Resources, American Electric Power, The Wilds (a nonprofit wildlife conservation organization), and a private landowner to carry out field investigations aimed to screen and evaluate the seasonal changes of rare earths in the CMD discharges that have high recovery potentials. Next, the recovery of REEs from CMD was tested using a series of lab-scale column and batch tests under, respectively, percolation and completely mixed conditions. Results obtained from these lab-scale studies show that all three tested solids are very effective in retaining REEs. Over 98% of the CMD REEs that contacted the solids were captured before the solids exhausted their neutralization capacities. We also determined an extraction process using a non-acid, organic ligand extraction solution that can effectively remobilize the retained REEs from the spent solids (over 90%). The REE concentrate (>7.5 wt. % of total REEs) is then formed in an aeration process. The TEP process uses environmentally benign industrial by-products and a naturally-occurring organic ligand to mitigate CMD and recover REEs. Techno-economic analysis (TEA) and life-cycle assessment (LCA) was carried out in the third phase. The engineering-economic costs and net energy, net CO2 emissions, and water and other requirements were investigated to understand the economic and environmental implications of this process. This work uses mass and energy balances from laboratory-scale experiments to estimate the economic costs and environmental impacts. The results suggest that passive treatment systems that use DRWP sludge are preferred over those that use sFGD material, because of lower economic costs ($89,300/yr with a unit cost of $86/gT-REE vs. $89,800/yr, or $278/gT-REE) and improved environmental performance across all indicators from two different impact assessment methods. These differences are largely attributable to the larger capacity of DRWP sludge in the passive treatment application. We envision this TEP process can be integrated with abandoned mine land (AML) reclamation to create an approach that can add economic incentives for AML reclamation, remediate CMD discharge, and eliminate public safety hazards and threats to local environment and ecological systems posed by AMLs. It can restore lands and communities that are adversely impacted by legacy mining.« less

CO₂ capture and storage (CCS) technology is likely to be widely deployed in the coming decades in response to major climate and economics drivers: CCS is part of every clean energy pathway that limits global warming to 2 °C or less and receives significant CO₂ tax credits in the United States. These drivers are likely to stimulate the capture, transport, and storage of hundreds of millions or billions of tonnes of CO₂ annually. A key part of the CCS puzzle will be identifying and characterizing suitable storage sites for vast amounts of CO₂. We introduce a new software tool calledmore » SCO₂T (Sequestration of CO₂ Tool, pronounced “Scott”), a dynamic CO₂ injection and storage model, to rapidly characterize saline storage reservoirs. The tool is designed to rapidly screen hundreds of thousands of reservoirs, perform sensitivity and uncertainty analyses, and link sequestration engineering (injection rates, reservoir capacities, plume dimensions) to sequestration economics (costs constructed from around 70 separate economic inputs). We describe the novel science developments supporting SCO₂T including a new approach to estimating CO₂ injection rates and CO₂ plume dimensions as well as key advances linking sequestration engineering with economics. We perform a sensitivity and uncertainty analysis of geology parameter combinations—including formation depth, thickness, permeability, porosity, and temperature—to understand the impact on carbon sequestration. Through the sensitivity analysis, we show that increasing depth and permeability both can lead to increased CO₂ injection rates, increased storage potential, and reduced costs, while increasing porosity reduces costs without impacting the injection rate (CO₂ is injected at a constant pressure in all cases) by increasing the reservoir capacity. Through uncertainty analysis—where formation thickness, permeability, and porosity are randomly sampled—we show that final sequestration costs are normally distributed with upper bound costs around 50% higher than the lower bound costs. While site selection decisions will ultimately require detailed site characterization and permitting, SCO₂T provides an inexpensive dynamic screening tool that can help prioritize projects based on the complex interplay of reservoir, infrastructure (e.g., proximity to pipelines), and other (e.g., land use, legal) constraints on the suitability of certain regions for CCS.« less

Geologic carbon sequestration is the process of injecting and storing CO₂ in subsurface reservoirs and is an essential technology for global environmental security (e.g., climate change mitigation) and economic security (e.g., CO₂ tax credits). To meet energy, economic, and environmental goals, society will have to identify vast volumes of high-capacity, low-cost, and viable storage reservoirs for sequestering CO₂. In turn, this requires understanding how major geologic characteristics (such as reservoir depth, thickness, permeability, porosity, and temperature) and design and operational decisions (such as injection well spacing) impact CO₂ injection rates, storage capacity, and economics. Although many numerical simulation tools exist,more » they cannot repeat the required thousands or millions of simulations to identify ideal reservoir properties and the sensitivity and interaction between geologic parameters and operational decisions. Here, we use SCO₂T—a fast-running, reduced-order modeling framework—to explore the sensitivity of major geologic parameters and operational decisions to engineering (CO₂ injection rates, plume dimensions, and storage capacities and effectiveness) and costs. Our results show, for the first time, benefits and impacts such as allowing CO₂ plumes to overlap, how different well spacing patterns affect CO₂ sequestration, the effects on costs of including brine treatment and disposal, and the effect of restricting injection rates to 1 MtCO₂ per y based on well limitations. We reveal multiple novel and unintuitive findings including: (i) deeper reservoirs have reduced carbon sequestration costs until injection rates reach 1 MtCO₂ per y, at which point deeper reservoirs become more expensive, (ii) thicker formations allow for increased injection rates and storage capacity, but thickness barely impacts plume areas, (iii) higher geothermal gradients result in reduced sequestration costs, unless brine treatment/disposal costs are included, at which point reservoirs having lower geothermal gradients are more economical because they produce less brine for each unit of injected CO₂, and (iv) allowing plumes to overlap has a significantly positive impact of increasing storage capacities but has only a small influence on reducing sequestration costs. Altogether, our results illustrate new scientific conclusions to help identify suitable sites to inject and store CO₂, to help understand the complex interaction between geology and resulting costs, and to help support the pursuit of meeting global sequestration targets.« less

Coal power generation dominates electricity supply in Developing Asia, and more than 400 gigawatts (GW) of new coal-fired capacity is planned for operation by 2030. Past studies on thermal electricity-water nexus have not accounted for this new capacity, and use coarse spatial and temporal resolutions in the assessment of long-term power system reliability. Here, high-resolution hydro-climatic simulations and asset-level power plant water use models are integrated to quantify water constraints on coal-fired power plants in Developing Asia, for different scenarios of future climate change, cooling system choice, and capacity expansion. Future climate change and capacity expansion decrease the annual usablemore » capacity factor (UF) of coal power generation in Mongolia, Southeast Asia, and parts of India and China. The negative impacts are lessened by widening the geographic areas of aggregation. Under near-term mitigation scenarios with high penetrations of CO₂ capture technology, the regional average water withdrawal intensity of coal power generation is 50–80% higher than current conditions. With careful siting, the increased water withdrawal intensity does not necessarily constrain future electricity production on annual or monthly time scales, but decreases system reliability by increasing the probability of low UF at daily time scale. Our findings highlight the unaccounted-for-risk in Developing Asia's long-term power plan featuring coal power generation. Regional capacity expansion should consider the reliability of future thermal power assets under long-term hydroclimate change using high-resolution models and multiple scenarios.« less

Hydrocarbon depleted fractured shale (HDFS) formations could be attractive for geologic carbon dioxide (CO₂) storage. Shale formations may be able to leverage existing infrastructure, have larger capacities, and be more secure than saline aquifers. We compared regional storage capacities and integrated CO₂ capture, transport, and storage systems that use HDFS with those that use saline aquifers in a region of the United States with extensive shale development that overlies prospective saline aquifers. We estimated HDFS storage capacities with a production-based method and costs by adapting methods developed for saline aquifers and found that HDFS formations in this region might bemore » able to store with less cost an estimated ~14× more CO₂ on average than saline aquifers at the same location. The potential for smaller Areas of Review and less investment in infrastructure accounted for up to 84% of the difference in estimated storage costs. We implemented an engineering-economic geospatial optimization model to determine and compare the viability of storage capacity for these two storage resources. Across the state-specific and regional scenarios we investigated, our results for this region suggest that integrated CCS systems using HDFS could be more centralized, require less pipelines, prioritize different routes for trunklines, and be 6.4–6.8% ($5-10/tCO₂) cheaper than systems using saline aquifers. In conclusion, overall, CO₂ storage in HDFS could be technically and economically attractive and may lower barriers to large scale CO₂ storage if they can be permitted.« less

Global climate change is a pressing problem caused by the accumulation of anthropogenic greenhouse gas emissions in the atmosphere. Carbon dioxide (CO₂) capture and storage is a promising component of a portfolio of options to stabilize atmospheric CO₂ concentrations. Meaningful capture and storage requires the permanent isolation of enormous amounts of CO₂ away from the atmosphere. In this paper, we investigate the effectiveness of heterogeneity-induced trapping mechanism, in potential synergy with a self-sealing gravitational trapping mechanism, for secure CO₂ storage in marine sediments. We conduct the first comprehensive study on heterogeneous marine sediments with various thicknesses at various ocean depths.more » Prior studies of gravitational trapping have assumed homogeneous (deep-sea) sediments, but numerous studies suggest reservoir heterogeneity may enhance CO₂ trapping. Heterogeneity can deter the upward migration of CO₂ and prevent leakage through the seafloor into the seawater. Using geostatistically-based Monte Carlo simulations of CO₂ transport in heterogeneous sediment, we show that strong spatial variability in permeability is a dominant physical mechanism for secure CO₂ storage in marine sediments below 1.2 km water depth (less than half of the depth needed for the gravitational trapping). We identify thresholds for sediment thickness, mean permeability and porosity, and their relationships to meaningful injection rates. Our results for the U.S. Gulf of Mexico suggest that heterogeneity-assisted trapping has a greater areal extent with more than three times the CO₂ storage capacity for secure offshore CO₂ storage than with gravitational trapping. Finally, these characteristics offer CO₂ storage opportunities that are closer to coasts, more accessible, and likely to be less costly.« less