Biogas is often considered as a source of renewable energy, for heat and power production. However, biogas has greater promise as a source of concentrated CO2 in addition to methane, making it a rich supply of carbon and hydrogen for the generation of fuel and chemicals. In this work, we use the concept of attainable region in the enthalpy-Gibbs free energy space to identify opportunities for effective biogas valorization that maximizes the conversion of CO2. The AR concept allows us to study a chemical process without knowing the exact reaction mechanism that the species in the process use. Deriving Material Balance equations that relate a reactive process's output species to its input species is sufficient to identify process limits and explore opportunities to optimize its performance in terms of material, energy, and work. The conversion of biogas to valuable products is currently done in two steps; the high temperature and endothermic reformer step, followed by the low temperatur... [more]

As a low-carbon fuel, feedstock, and energy source, hydrogen is expected to play a vital role in the decarbonization of high-temperature process heat during the pyroprocessing steps of clinker production in cement manufacturing. However, to accurately assess its potential for reducing CO2 emissions and the associated costs in clinker production applications, a techno-economic analysis and a study of facility-level CO2 emissions are necessary. Assuming that up to 20% hydrogen can be blended in clinker fuel mix without significant changes in equipment configuration, this study evaluates the potential reduction in CO2 emissions (scopes 1 and 2) and cost implications when replacing current carbon-intensive fuels with hydrogen. Using the direct energy substitution method, we developed an Excel-based model of clinker production, considering different hydrogen–blend scenarios. Hydrogen from steam methane reformer (gray) and renewable-based electrolysis (green) are considered as sources of hyd... [more]

In designing low-carbon processes, the unintended emission of CO2 remains a significant concern due to its global environmental impact. This paper explores carbon management within chemical processes, specifically examining the correlation between the process material balance (PMB) and CO2 emissions to understand and identify the potential for reducing these emissions. We interrogate the foundational issue of carbon discharge by analyzing the interplay among mass, energy, and entropy balances, which collectively influence the PMB. We introduce the concept of the Target Material Balance (TMB), which represents the material balance of a process corresponding to minimum CO2 emissions within the given constraints. We could ask what decisions in the design and operation of processes result in higher CO2 emissions than the TMB. We will focus on the interaction between reactions and recycles and how the arrangement of recycles in processes can inadvertently change the PMB, thereby increasing... [more]

This work investigates the water impact of carbon capture technologies employed in coal and natural gas power generation, viz. integrated gasification combined cycle, oxy-fuel combustion, solid oxide fuel cells and post-combustion solvent-based. The Water Impact per CO2 Avoided (WICa) metric was developed to understand the tradeoff between water usage and global warming potential, and additionally as a decision-making tool. It relates the impact on available water resources to greenhouse gas reduction over the cradle-to-plant-exit lifecycle by leveraging existing metrics, including the Water Impact Index (WII), water withdrawal, water consumption, water quality, and Water Scarcity Index (WSI). The results show that some carbon capture technologies increase the overall water usage of power generation plants, thereby increasing the water impact per CO2 avoided. Solid oxide fuel cells and oxy-fuel technology, though not mature in comparison to post-combustion capture, have the least water... [more]

For the enzymatic carboxylation of resorcinol to 2,6-dihydroxybenzoic acid (2,6-DHBA) using gaseous CO2 in an aqueous triethanolamine phase, an adsorption-based in situ product removal was demonstrated. The aim is to improve the reaction yield, which is limited by an unfavourable thermodynamic equilibrium. First, a screening for a high-affinity adsorber was carried out. Then, the application of a suitable adsorber was successfully demonstrated. This enabled achieving reaction yields above 80% using the adsorber for in situ product removal. The applied biotransformation was scaled up to 1.5 L at lab-scale. Furthermore, a downstream process based on the elution and purification of the product bound to the adsorber was developed to obtain 2,6-DHBA in high purity. Recycling is one of the key factors in this system, making it possible to recycle the reaction medium, the adsorber and the solvents in additional batches.

The increased concentration of CO2 in the atmosphere has a strong impact on global warming. Therefore, efficient technologies must be used to reduce CO2 emissions. One of the methods is the biofixation of CO2 by microalgae and cyanobacteria. This is now a widely described technology that can improve the economics of biomass production and reduce CO2 emissions. There are no reports on the possibility of using it to clean exhaust gases from biogas combustion. The aim of the research was to determine the possibility of using Arthrospira platensis cultures to remove CO2 from biogas combustion. The efficiency of biomass production and the effectiveness of biological CO2 fixation were evaluated. The use of exhaust gases led to a more efficient increase in cyanobacterial biomass. The growth rate in the exponential phase was 209 ± 17 mgVS/L·day, allowing a biomass concentration of 2040 ± 49 mgVS/L. However, the use of exhaust gases led to a decrease in the pH of the culture medium and a rapid... [more]

Given the environmental problems caused by burning fossil fuels, it is believed that converting carbon dioxide (CO2) into chemical inputs is a great ally to generating clean energy. In this way, investigative studies related to electrochemical CO2 reduction (CO2RE) concerning the behavior of metal catalysts have received attention about the processes involved. CO2RE can be an important tool to mitigate the presence of this gas in the Earth’s atmosphere. Given these considerations, in this review, we report the main catalysts used to act as CO2RE. Among them, we emphasize catalysts based on Ni, Zn, and Cu, which encompass the main properties related to the electrochemical conversion of CO2. Regarding the Cu-based catalyst, it presents high conversion efficiency but low selectivity. Furthermore, we also describe the main mechanisms related to the electrochemical conversion of CO2.

In the realm of Natural Gas Combined Cycle (NGCC) power plants, it is crucial to prioritize the mitigation of CO2 emissions to ensure environmental sustainability. The integration of post-combustion carbon capture technologies plays a pivotal role in mitigating greenhouse gas emissions enhancing the NGCC’s environmental profile by minimizing its carbon footprint. This research paper presents a comprehensive investigation into the integration of solar thermal energy into the Besmaya Natural Gas Combined Cycle (NGCC) power plant, located in Baghdad, Iraq. Leveraging advanced process simulation and modeling techniques employing Aspen Plus software, the study aims to evaluate the performance and feasibility of augmenting the existing NGCC facility with solar assistance for post-carbon capture. The primary objective of this research is to conduct a thorough simulation of the Besmaya NGCC power plant under its current operational conditions, thereby establishing a baseline for subsequent ana... [more]

In this work, four hundred and forty experimental solubility data points of 14 systems composed of methane and ionic liquids are considered to train a multilayer perceptron model. The main objective is to propose a simple procedure for the prediction of methane solubility in ionic liquids. Eight machine learning algorithms are tested to determine the appropriate model, and architectures composed of one input layer, two hidden layers, and one output layer are analyzed. The input variables of an artificial neural network are the experimental temperature (T) and pressure (P), the critical properties of temperature (Tc) and pressure (Pc), and the acentric (ω) and compressibility (Zc) factors. The findings show that a (4,4,4,1) architecture with the combination of T-P-Tc-Pc variables results in a simple 45-parameter model with an absolute prediction deviation of less than 12%.

Chemical sequestration is one important manner of CCUS. The injection of CO2 into an oil reservoir can not only sequestrate CO2 but also raise the oil recovery factor. The performance of chemical sequestration of CO2 depends on the interaction between CO2 solution and reservoir rock. In this paper, we have conducted three different scales of experiments, e.g., microscopic scale, core scale, and time scale, to fully investigate the interaction and resultant variation to mineral content, microscopic structure, porosity, and permeability under reservoir conditions (i.e., reservoir temperature of 90 °C) in Jimusar shale oil formation. The microscopic-scale experiment applied SEM and hyperspectral scanning to obtain microscopic pore throat structure and element distribution before and after soaking the rock in CO2 solution. The core-scale experiment employed XRD to evaluate mineral content variation caused by CO2 solution. Core flooding experiments were conducted to evaluate porosity and pe... [more]

Global population growth requires the use of various natural resources to satisfy the basic needs of humanity. Fossil fuels are mainly used to produce electricity, transportation and the artificial air conditioning of habitats. Nevertheless, countries around the world are looking for alternative energy sources due to the decrease in the availability of these fuels and their high environmental impact. The mixture of hydrogen and carbon monoxide (H2 + CO), commonly called syngas, is a high-value feedstock for various industrial applications. By varying the composition of syngas, especially the H2/CO molar ratio, it can be used to produce methanol, fuels or synthetic natural gas. However, when this ratio is very low, the separation of this gas usually represents a great problem when making the energy balance, which is why it is proposed to adapt a combustion process in chemical cycles, taking advantage of the energy of this gas, reducing the energy impact of the process. During the presen... [more]

Large-scale deployment of CO2 capture, transport, and storage (CCTS) requires the rolling-out of extensive value chains. In this study, we present the development, design, techno-economic, environmental, and regulatory analysis of four pioneering chains that capture and condition CO2 from existing European industrial plants and their multi-modal transport to selected ports in Northern Europe. The pioneering chains can avoid between 65% and 87% of the industrial emissions, including scope 3, with a cost of CO2 avoided ranging between 100 and 300 euro/tCO2. The economic and environmental performance of the CCTS chains are substantially affected by the geographic location of the industrial emitters and the CO2 volumes to be transported. The analysis relies on the assumption that the four industrial plants would be early movers. While, in the future, technology maturation and infrastructure development are expected to reduce costs and emissions associated with the CCTS chain, this study q... [more]

The repeatable and cost-efficient generation of nanobubbles is still a challenge. In most cases, the hydrodynamic generation of nanobubbles is used at larger scales. Therefore, every cost reduction possible in nanobubble generation is needed. In this work, we decided to check how the generation of nanobubbles changes when the surrounding liquid properties change. The generation of nanobubbles was carried out in a novel setup, designed by us. We investigated the minimum liquid velocity needed for nanobubble generation and propose correlations describing this based on the physicochemical properties of the liquid and gas phases. As carbon dioxide nanobubbles are commonly used for the treatment of ischemia and chronic wounds, the investigation of their stability enhancement is crucial for the wider public. We investigated the minimum rotation rate of the impeller needed for CO2 nanobubble generation and the influence of a biomedical surfactant (Pluronic P-123) addition and concentration ch... [more]

Carbon dioxide (CO2) is widely used in the prevention and control of spontaneous coal combustion. In this manuscript, three low-rank coals with different metamorphic degrees were selected as the research objects. The temperature-programmed experiments, in situ infrared cooling experiments, simulation of the competitive adsorption of CO2 and oxygen (O2) in coal pores, and simulation study of the CO2 inhibition of the coal oxygen composite reaction were used to obtain the role and effect of CO2 in preventing oxygen adsorption in coal at the low-temperature oxidation stage. It was concluded that CO2 can displace the O2 near the pore wall to physically prevent the adsorption of O2. Through the changing law of heating rate and a kinetics analysis, it was found that CO2 can increase its activation energy by 5.3−108.3% during the slow heating stage of coal and reduce its heat rate. At around 120 °C, coal loses the protective effect of CO2. From the changes in functional groups, it can be seen... [more]

Injecting CO2 into tight oil reservoirs is a potential approach for enhanced oil recovery (EOR) and CO2 sequestration. However, the effects of different pore-scales on EOR are poorly understood, and this has a significant impact on recovery. In this paper, a pore size correction model based on X-ray computerized tomography (CT) and nuclear magnetic resonance (NMR) was developed in order to establish the relationship between the pore radius and the transverse relaxation time. Different pore-scales are divided according to the cumulative distribution characteristics of the transverse relaxation time (T2). CO2 flooding and huff-n-puff experiments were conducted to investigate the dynamic displacement behaviors in different pore-scales. The results indicate that there are three pore-scales: micropores (T2 < 0.3 ms), intermediate pores (0.3 ms < T2 < 100 ms), and macropores (100 ms < T2). However, there are also pseudo-sweep pores (PPs), equilibrium pores (EPs), and sweep pores... [more]

International shipping is crucial for global freight transport, but is mainly based on fossil fuels, leading to significant greenhouse gas (GHG) emissions. Global GHG emissions must peak by 2025 and drop by at least 43% by 2030 to limit global warming within 1.5◦C. This calls for urgent action in all sectors as well as shipping. Scaling up alternative fuels may take too long, considering technical modifications onboard the vessels, as well as fuel production and infrastructure for distribution. Many alternative fuels are also inherently dependent on access to clean electricity, which is already in a shortage. Carbon capture from ships is another route to emission reduction that can be implemented faster and without increasing the demand for renewable electricity.
Tankers, dry bulk carriers, and container vessels contribute a majority of global shipping emissions and are therefore prime candidates for carbon capture and storage. Solvent-based post-combustion capture is mature and suita... [more]

Airfoil fin printed circuit heat exchangers (PCHEs) have broad application prospects in the naval, aerospace, electric power, and petrochemical industries. The channel structure is a critical factor affecting their thermal-hydraulic characteristics. In this study, a novel PCHE channel structure with staggered NACA 0025 airfoil-shaped fins was proposed; accordingly, the thermal-hydraulic characteristics of the novel channel structure using carbon dioxide as the working fluid at different fin heights under different operating conditions (trans-, near-, and far-critical) were investigated. The results indicated that the thermal-hydraulic performance of the PCHE under the trans-critical operating condition was better than that under the near-critical and far-critical operating conditions. Compared with conventional airfoil fin channels, the novel airfoil fin channel attained comparable comprehensive performance while reducing the fin volume by 50%, thus achieving a more lightweight PCHE de... [more]

Carbon capture and storage (CCS) technology can reduce CO2 emissions by 85 to 95% for power plants and kilns with high CO2 emissions. Among CCS technologies, carbon dioxide capture using steel slag is a method of carbonating minerals by combining oxidized metals in the slag, such as CaO, MgO, and SiO2, with CO2. This study assessed the amount of CO2 captured and the sequestration efficiency in operating a mineral carbonation plant with a CO2 capture capacity of 5 tons/day by treating the exhaust gas from a municipal waste incinerator and identified the characteristics of the mineral carbonation products. As a result, the average concentration of CO2 in the inflow and outflow gas during the reaction time was 10.0% and 1.1%, respectively, and the average CO2 sequestration efficiency was 89.7%. This resulted in a conversion rate of CaO of > 90%. This study manifested that mineral carbonation products are more stable than steel slag as a construction material and are effective at sequester... [more]

It is quite essential to obtain an excellent CO2 adsorption capacity, CO2 adsorption selectivity and water vapor stability at the same time for practical CO2 capture after combustion. Through the combination of ultramicropore and the high density of CO2-philic sites without OMSs, an ultra-microporous Cu-based metal−organic framework has been designed and synthesized, featuring a high CO2 capacity (99 cm3 g−1 and 56.6 cm3 g−1 at 273 K and 298 K, respectively), high selectivity over N2 (118 at a scale of CO2/N2 15/85, 298 K) and excellent water vapor stability, simultaneously. Theoretical calculations indicate that neighboring ketonic O atoms with suitable distance play vital roles in boosting CO2 selective capture.

This review investigates the effects of the Brazilian agriculture production and forestry sector on carbon dioxide (CO2) emissions. Residual biomasses produced mainly in the agro-industrial and forestry sector as well as fast-growing plants were studied. Possibilities to minimize source-related emissions by sequestering part of carbon in soil and by producing biomass as a substitute for fossil fuel were extensively investigated. The lack of consistency among literature reports on residual biomass makes it difficult to compare CO2 emission reductions between studies and sectors. Data on chemical composition, heating value, proximate and ultimate analysis of the biomasses were collected. Then, the carbon sequestration potential of the biomasses as well as their usability in renewable energy practices were studied. Over 779.6 million tons of agricultural residues were generated in Brazil between 2021 and 2022. This implies a 12.1 million PJ energy potential, while 4.95 million tons of for... [more]

Natural gas-fired combined cycle plants are nowadays one of the most efficient and environmentally friendly energy complexes. High energy efficiency and low specific emissions are achieved primarily due to the high average integral temperature of heat supply in the Brayton−Rankine cycle. In this case, the main sources of energy losses are heat losses in the condenser of the steam turbine plant and heat losses with the exhaust gases of the waste heat boiler. This work is related to the analysis of the thermodynamic and economic effects in the transition from binary to trinary cycles, in which, in addition to the gas and steam−water cycles, there is an additional cycle with a low-boiling coolant. A method for the feasibility study of a waste heat recovery unit for trinary plants is proposed. The schematic and design solutions described will ensure the increased energy and economic performance of combined cycle power plants. Based on the results of the thermodynamic optimization of the st... [more]

CO2 adsorption is one of the promising CCS technologies, and activated coke is a solid adsorbent with excellent adsorption properties. In this study, activated coke was prepared by using bituminous coal and coconut shells activated with KOH or CaCl2 in a physically activated atmosphere and modified with ammonia. The effect of the active agent impregnation ratio on the physicochemical properties of activated coke was investigated by N2 adsorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The CO2 adsorption performance of activated coke was tested, and the effect of nitrogen-containing functional groups on CO2 adsorption was investigated by experiments and simulations. The results showed that the specific surface area of activated coke reached 629.81 m2/g at a KOH impregnation ratio of 0.5 and 610.66 m2/g at a CaCl2 impregnation ratio of 1. The maximum CO2 adsorption capacity of activated coke reached 71.70 mg/g and 90.99 mg/g for c... [more]

This paper presents the results of a simulation study on the selection of an energy-optimal refrigeration system based on natural refrigerants as a function of outdoor climate parameters as a decision variable in a supermarket application. Simulations were conducted for twelve locations. Three new original refrigeration systems were presented: Cascade R744/R717 which is an advanced booster extended with an ammonia condensing system (CASC_1); Cascade R744/R717 with CO2 pump-fed MT and pressure-fed LT evaporators (CASC_2); and the R717 booster with CO2 pump-fed MT and LT evaporators (CB_NH3). As a reference system, a CO2 booster system with multi-ejectors and flooded evaporators (CB_EJ) was adopted. The CB_EJ system has been confirmed to be energy optimal for cold and temperate climates (Cfb, Dfa and cooler). In warm temperate climates (Csa, BSk, Cfa and similar), the energy consumption of CB_NH3 was the lowest. CASC_2 and CB_NH3 are energy optimal for hot climates (BWh, Af, Aw). The CB_... [more]

The role of interzonal airflows is especially pronounced in naturally ventilated buildings. In such buildings, reversed airflows in the ventilation stacks might occur as well. This affects the air exchange rate and contaminant distribution in buildings. A significant increase in carbon dioxide concentration is a characteristic phenomenon for poorly ventilated rooms. This paper demonstrates the application of metabolic carbon dioxide concentration measurements for interzonal airflow estimation in naturally ventilated buildings. The presented method is based on the continuous measurements of CO2 concentration at one point in each zone. These measurements are used to estimate airflow pattern in a multizone building by applying an inverse analysis. The developed methodology employs an iterative Levenberg-Marquardt procedure to maximise the nonlinear likelihood function. The validity of the method was verified against measurements carried out in a single naturally ventilated room. Further,... [more]

When gas hydrates dissociate into gas and liquid water, many gas bubbles form in the water. The large bubbles disappear after several minutes due to their buoyancy, while a large number of small bubbles (particularly sub-micron-order bubbles known as ultra-fine bubbles (UFBs)) remain in the water for a long time. In our previous studies, we demonstrated that the existence of UFBs is a major factor promoting gas hydrate formation. We then extended our research on this issue to carbon dioxide (CO2) as it forms structure-I hydrates, similar to methane and ethane hydrates explored in previous studies; however, CO2 saturated solutions present severe conditions for the survival of UFBs. The distribution measurements of CO2 UFBs revealed that their average size was larger and number density was smaller than those of other hydrocarbon UFBs. Despite these conditions, the CO2 hydrate formation tests confirmed that CO2 UFBs played important roles in the expression of the promoting effect. The ana... [more]