Hydrogen and carbon dioxide pipelines – why a different engineering approach is required

Alternative, but expensive, energy transition scenario featuring carbon capture and utilization can preserve existing energy demand technologies

The challenge facing society in the 21st century is to improve the quality of life for all citizens in an egalitarian way, providing sufficient food, shelter, energy, and other resources for a healthy meaningful life, while at the same time decarbonizing anthropogenic activity to provide a safe global climate, limiting temperature rise to well-below 2°C with the aim of limiting the temperature increase to no more than 1.5°C. To do this, the world must achieve net zero greenhouse gas (GHG) emissions by 2050. Currently spreading wealth and health across the globe is dependent on growing the GDP of all countries, driven by the use of energy, which until recently has mostly been derived from fossil fuel. Recently, some countries have decoupled their GDP growth and greenhouse gas emissions through a rapid increase in low carbon energy generation. Considering the current level of energy consumption and projected implementation rates of low carbon energy production, a considerable quantity of fossil fuels is projected to be used to fill the gap, and to avoid emissions of GHG and close the gap between the 1.5°C carbon budget and projected emissions, carbon capture and storage (CCS) on an industrial scale will be required. In addition, the IPCC estimate that large-scale GHG removal from the atmosphere is required to limit warming to below 2°C using technologies such as Bioenergy CCS and direct carbon capture with CCS to achieve climate safety. In this paper, we estimate the amount of carbon dioxide that will have to be captured and stored, the storage volume, technology, and infrastructure required to achieve the energy consumption projections with net zero GHG emissions by 2050. We conclude that the oil and gas production industry alone has the geological and engineering expertise and global reach to find the geological storage structures and build the facilities, pipelines, and wells required. Here, we consider why and how oil and gas companies will need to morph from hydrocarbon production enterprises into net zero emission energy and carbon dioxide storage enterprises, decommission facilities only after CCS, and thus be economically sustainable businesses in the long term, by diversifying in and developing this new industry.

Direct air capture (DAC) technology is still facing some challenges that need to be addressed before the technology can be widely deployed. One major challenge is the high overall system energy requirement, and it is the main bottleneck in DAC commercialization. This study aims to unlock the potential of integrating DAC with Heat Ventilation and Air Conditioning (HVAC) systems. A thermodynamic model is used to test the effect of varying the adsorption and desorption conditions on DAC unit performance, and to assess the characteristics of DAC unit positioned in six different locations within air the handling unit (AHU). The results show that by only locating the DAC unit in Position 6 (i.e., positioning the DAC unit after the exhaust fan in AHU) in comparison to a stand-alone unit, the efficiency of the DAC system is improved at varying times through the summer season in Qatar. Specifically locating DAC unit at Position 6 increases DAC efficiency from 5.3% to 27.19% for 8th of June 2022 at 11:00 am in Qatar. Additionally, using the DAC unit with other filters in AHU allows for full air recirculation for 10 h. Based on this scenario and the weather data for 20th of July at 12:00 pm, the hottest day in Qatar in 2022, a reduction of 44% in cooling load is achieved. Locating the DAC unit at a point before the air is supplied from AHU is the best, however, in case of full recirculation of air, positioning the DAC unit after the exhaust fan will achieve better performance.

The “Direct Air Capture Recovery of Energy for CCUS Partnership (DAC RECO2UP)” project employs a team approach and supports the U.S. Department of Energy Office of Fossil Energy and Carbon Management’s (DOE-FECM) goal to decrease the cost of capture through the testing of existing direct air capture (DAC) materials in integrated field units that produce a concentrated carbon dioxide (CO2) stream of at least 95% purity. Solid-amine CO2 adsorption-desorption contactor technology, proven in the laboratory, is undergoing high-fidelity design/validation. Recoverable energy is readily available from a large number of commercial locations where DAC can be deployed; therefore, advancing the fidelity of energy recovery to directly reduce the cost of DAC is a key project objective. In addition, many commercial facilities have low-concentration CO2 vents that are uneconomical to treat alone but could provide more efficient mass and thermal transport to DAC systems with integrated energy recovery and flexible CO2 treatment capabilities. Technology scale-up leverages past research and occurs in a commercially relevant environment at the National Carbon Capture Center. Prescreening techno-economic analysis, risk assessments, and life cycle analysis are being performed by experienced team members. Results of the project will address critical technical barriers that, when solved, will improve the capital and operating costs of DAC while validating commercial relevance of cost and product quality/need.

Direct air capture (DAC) is an emerging negative CO2 emission technology that aims to introduce a feasible method for CO2 capture from the atmosphere. Unlike carbon capture from point sources, which deals with flue gas at high CO2 concentrations, carbon capture directly from the atmosphere has proved difficult due to the low CO2 concentration in ambient air. Current DAC technologies mainly consider sorbent-based systems; however, membrane technology can be considered a promising DAC approach since it provides several advantages, e.g., lower energy and operational costs, less environmental footprint, and more potential for small-scale ubiquitous installations. Several recent advancements in validating the feasibility of highly permeable gas separation membrane fabrication and system design show that membrane-based direct air capture (m-DAC) could be a complementary approach to sorbent-based DAC, e.g., as part of a hybrid system design that incorporates other DAC technologies (e.g., solvent or sorbent-based DAC). In this article, the ongoing research and DAC application attempts via membrane separation have been reviewed. The reported membrane materials that could potentially be used for m-DAC are summarized. In addition, the future direction of m-DAC development is discussed, which could provide perspective and encourage new researchers' further work in the field of m-DAC.

IntroductionTo achieve net-zero targets, it is essential to evaluate and model the costs and scalability of emerging carbon dioxide removal technologies like direct air capture with CO2 storage (DACCS) and bioenergy with carbon capture and storage (BECCS). Yet such efforts are often impeded by varying assessments of the climate impact and potential contributions of these technologies. This study explores the future costs and scalability of DACCS and BECCS to advance net-zero goals.MethodsWe analyze expert opinions on these technologies’ potential costs and deployment scales for 2030, 2040, and 2050. Data was collected from 34 experts, comprising 21 DACCS and 13 BECCS specialists. They provided 90% confidence interval estimates and ‘best estimates’ for future costs and deployment under two International Energy Agency (IEA) policy scenarios—Stated Policies (STEPS) and Net Zero Emissions by 2050 (NZE).ResultsWe find that BECCS costs start at a lower level but decrease more slowly, whereas DACCS costs decline more steeply from a higher initial cost. However, DACCS estimates varied significantly among experts, showing no convergence over time. Regarding potential scalability, both technologies are associated with substantially higher deployment under the NZE scenario. Yet the combined estimated capacity of DACCS and BECCS by 2050 is only about a quarter of the CO2 removals projected by the IEA for its NZE scenario (1.9 GtCO2).DiscussionThis study provides valuable insights into the future of DACCS and BECCS technologies in Europe, especially since our experts expect that DACCS and BECCS costs will be even higher (and deployment scales lower) than those predicted by recent IEA tracking, opening future research directions.

Batteries or silos: Optimizing storage capacity in direct air capture plants to maximize renewable energy use

The extraction of CO2 directly from the atmosphere (Direct Air Capture) is commonly employed using supported amine sorbents. This adsorption technology is under rapid development with novel sorbents materials emerging and with processes being demonstrated on increasingly larger scale. Optimization of such processes require accurate knowledge on sorbent characteristics and knowledge on how operational variables change process performance. This study is primarily focused on the latter, where we aim to quantify the influence of operational parameters on the energy duty and CO2 productivity. In addition, we examined the influence of weather conditions on the adsorption rate. For this, we developed a dynamic model of the complete temperature-pressure swing adsorption cycle (TPSA). The model is validated by experimental results on a kg-scale direct air capture system. The impact of selected operational variables is assessed by two-dimensional sensitivity analyses. We show that desorption temperature is preferably high, limited by the chemical stability of the sorbent material in this particular case. In addition, the sorbent working capacity should be large when opting for an optimization towards energy duty, whereas it reaches a clear optimum in terms of CO2 productivity. Finally, we conclude that weather conditions and diurnal variations can significantly affect the performance of a direct air capture process and should certainly be considered during design and operation. With these insights and the developed model, this study provides a sound basis for further process development and optimization of direct air capture using fixed bed technology combined with solid amine sorbents.

Proposed is an electrochemical nickel hydroxide based hydroxide exchange membrane carbon capture (HEMCC) device for Direct Air Capture (DAC) of CO2. DAC has been identified as one of the key net negative carbon technologies to achieve net zero carbon emissions. Net negative carbon technologies are required to offset continued emissions from dilute CO2 sources such as agriculture and construction. The majority of current DAC technologies at scale (>1 KT∙yr-1) are adsorbent based technologies with significant energy cost. The traditional DAC energy cost is primarily driven by the temperature swing required to regenerate the sorbent and has been shown to be 1.8 MWh·ton-1 at the system level.Electrochemical pH swing devices are a growing research area for carbon capture devices with the goal of lowering the energy cost required for DAC. A pH gradient is built by generating OH- at the cathode and consuming OH- at the anode. An acid-base equilibrium with CO2 allows for the capture of CO2 at the cathode and release at the anode. This extends from other electrochemical CO2 capture devices based on pKa shifts of an electrochemically active organic species allowing for the capture and release of CO2. Electrochemical CO2 capture is considered promising based on potentially low energy costs to capture CO2 in comparison with current temperature swing adsorption technologies.This work explores Ni(OH)2 electrodes to produce the pH gradient for CO2 capture and release. At the cathode NiOOH is reduced to Ni(OH)2 while at the anode Ni(OH)2 is oxidized to NiOOH. The symmetrical electrodes allow for a low voltage requirement; the thermodynamic potential difference of standard electrochemical reactions is zero. Most of the voltage observed is to produce the pH gradient with the remainder driving the polarization of the electrodes. There is a resistance component as well, but this is small in comparison due to the low current densities used in the device, nominally 2 mA·cm-1.Two similar devices are presented, a traditional MEA (membrane electrode assembly) and a flow-through MEA. The traditional MEA separates the two Ni(OH)2 electrodes with an 80μm Piperion® membrane. While the flow-through membrane separates the electrodes with a three piece membrane consisting of two 80μm Piperion® membranes with a porous membrane between them. In the traditional MEA system air is passed over the cathode for capture, while the flow-through MEA the air is passed through the porous membrane isolated from the electrodes.The traditional MEA has been used to establish a baseline performance of the device and has been shown to capture CO2 at an energy cost of 1 MWh·ton-1 at the device level. An understanding has been built around the components of that energy cost including the relationship of flux to current density, effect of a regeneration process, transient battery behavior, and gas losses coinciding with changing the polarization of the batteries.The flow-through MEA looks to address of transient battery behavior and gas losses. It allows for denser, higher capacity electrodes, which can lean on traditional Ni-MH battery technology used in alkaline batteries used today. The higher capacities, limit the transient battery effect on flux in the device. Gas losses are addressed by having a continuous inlet air stream to the device and continuous outlet product.

Design of steam-assisted temperature vacuum-swing adsorption processes for efficient CO2 capture from ambient air

The world is increasingly facing the direct effects of climate change triggering warnings of a crisis for the healthy existence of humankind. The dominant driver of the climate emergency is the historical and continued accumulation of atmospheric CO2 altering net radiative forcing on the planet. To address this global issue, understanding the core chemistry of CO2 manipulation in the atmosphere and proximally in the oceans is crucial, to offer a direct partial solution for emissions handling through negative emissions technologies. Many technologies have been proposed to develop a strategic and economic solution for carbon capture, storage, and utilization. In this paper, we review recent advances in technologies proposed for carbon capture and release via electrochemical process for point source/flue gas, direct air capture (DAC), and ocean/seawater capture. Electrochemical approaches to carbon capture are favorable in terms of reaction conditions, their ability to be incorporated into transformation processes, modularity, low relative carbon footprint, and compatibility with the availability of renewable electricity sources. We offer a critical comparative analysis of land- and ocean-based capture technologies to help guide future research and innovation.

Direct air capture (DAC) is increasingly recognized as a necessary puzzle piece to achieve the Paris climate targets. However, the current high cost and energy intensity of DAC act as a barrier. Short-term strategies for initial deployment, technology improvement, and cost reduction are needed to enable large-scale deployment. We assess and compare two near-term pathways leading to the same installed DAC capacity and thus yielding the same cost reductions: its combination with CO2 storage as direct air carbon capture and storage, or its deployment for CO2 utilization as direct air carbon capture and utilization e.g. for synthetic fuels, chemicals, and materials; we characterize these as Direct and Spillover pathways. Drawing on the Multi-level Perspective on Technological Transition as a heuristic, we examine both technical and immaterial factors needed to scale up DAC under the two pathways, in order to assess the pathways’ relative advantages and to identify possible short-term bottlenecks. We find neither pathway to be clearly better: the Direct pathway offers technical advantages but faces regulatory barriers that need to be resolved before deployment, while the Spillover pathway offers market and governance advantages but faces challenges related to hydrogen production and increasing resource needs as it scales up. There may be reasons for policymakers to therefore pursue both approaches in a dynamic manner. This could involve prioritizing the Spillover pathway in the short term due to possibly fewer short-term regulatory barriers and its ability to produce net-zero emission products for existing and accessible markets. Once short-term governance obstacles have been addressed, however, the Direct pathway may allow for more efficient scaling of DAC capacity and cost reductions, especially if by then the needed infrastructure and institutions are in place.

A rapid build-out of direct air capture (DAC), deployed in order to mitigate climate change, will require significant amounts of both low-carbon thermal and electrical energy. Firm low-carbon power resources, including nuclear, geothermal, or natural gas with carbon capture, which also will become more highly valued as variable renewable energy penetration increases, would be able to provide both heat and electricity for DAC. In this study, we examined the techno-economic synergy between a hypothetical DAC plant in the year 2030 and a nuclear small modular reactor, and determined two avenues for which this relationship could benefit the nuclear plant. First, we demonstrated that, under certain assumptions, selling a portion of its energy to a DAC facility allows the nuclear plant to take in 21% less revenue from selling electricity to wholesale markets than its projected levelized cost, and still break even. Second, after estimating a potential revenue stream, we showed that an integration with DAC allows for the nuclear plant's capital costs to be up to 35% higher than what would be required if only selling electricity to wholesale markets. This could enable the nuclear plant to operate economically even in the face of variable and decreasing wholesale electricity prices, and also could offer developers more financial certainty when planning a new project. Ultimately, this study shows that the need for low-carbon energy for DAC plants might incentivize the development of advanced nuclear plants and firm low-carbon resources more broadly.

Electrochemical systems of alkali solution electrolysis and electrodialysis are prospective candidates for large-scale direct air capture (DAC) applications. In this study, electrolysis and electrodialysis DAC systems based on the pH-swing method are modeled and compared. The attainable membrane K+ selectivity and CO2 absorption ratio are modeled to accurately predict system performance. Considering the electrolysis system has dual functions for hydrogen production and DAC, its minimum energy demand for DAC is 1255 kJ mol–1 under a current density of 0.14 A cm–2, while the electrodialysis system has a minimum energy consumption of 1451 kJ mol–1 under a current density of 0.012 A cm–2. The effects of cycle solution flow rate and concentration are analyzed, and it is found that the solution pH difference between compartments needs to be greater than 5.25 to achieve optimum performance for both systems. Finally, the systems are simulated with 100% K+ selectivity and CO2 absorption ratio, and the results show that the lower limits on DAC energy demand for electrolysis and electrodialysis systems under such ideal conditions are reduced by around 90%, to 162 and 154 kJ mol–1, respectively. The improvement of K+ selectivity in electrochemical cells, and optimization of the air contactor to obtain higher CO2 absorption ratios are promising areas deserving further research.

The global shift toward low-carbon and sustainable energy marks a critical step in advancing decarbonization and resilient energy systems. This study presents a process-to-system modeling of a geothermal energy integrated with direct air capture (DAC) and district heating systems. The designed geothermal-DAC-district heating configuration demonstrates a technically robust and thermodynamically synergistic pathway toward carbon-negative energy systems. By effectively integrating geothermal power generation with an all-electric DAC and heat recovery system, this designed configuration advances deep decarbonization goals and aligns directly with the United Nations Sustainable Development Goals (SGDs) on affordable clean energy, sustainable cities, and climate action. The analysis indicates that the turbine output and DAC performance are highly sensitive to geothermal operating parameters, suggesting that maximizing CO2 capture efficiency requires operation at low flashing pressures and elevated reservoir pressures to ensure stable turbine performance and uninterrupted DAC operation. Employing the operational results obtained from the sensitivity analyses and parametric studies, the designed configuration captures 666.6 tCO2 per year employing 8 DAC units and provides district heating to 124 households. The findings reveal that geothermal-DAC integration enables continuous, zero-emission CO2 removal using renewable baseload energy while supporting community-scale heating demands, positioning the system as a viable technological pathway toward carbon neutrality and a sustainable energy infrastructure.