CO2 Removal Rate Research Articles

Reforestation Opportunities in Indonesia: Mitigating Climate Change and Achieving Sustainable Development Goals

Reforestation in the tropics is highlighted as an important intervention to mitigate climate change globally because of its potential for high CO2 removal rates, ranging from 4.5 to 40.7 t CO2e ha−1 yr−1 during the first 20 years of tree growth. Reforestation is critical to meeting emissions’ targets of the Paris Climate Agreement, as well as achieving Indonesia’s Nationally Determined Contribution (NDC) targets. Increasing carbon stocks through forest and land rehabilitation activities (RHL) is one of the Ministry of Environment and Forestry (MoEF) five main strategies for reducing greenhouse gas (GHG) emissions from the land sector. This study focuses on reforestation opportunities to support Indonesia’s NDC in reducing GHG emissions by 2030. We identified unproductive areas of land (shrub, open land) with highly degraded conditions as potential areas for reforestation. Based on Indonesian data of land cover change, we found that reforestation activities during 2019–2030 (11 years) under a realistic, ambitious and very ambitious scenario may remove carbon up to −0.25 GtCO2e (equal to −23 MtCO2e yr−1), −1.3 GtCO2e (equal to −124 MtCO2e yr−1) and −2.7 GtCO2e (equal to −247 MtCO2e yr−1), respectively. Based on international data of land cover change (Hansen et al. 2013), reforestation activities during 2019–2030, under a realistic, ambitious, and very ambitious scenario, have the opportunities to remove −17 MtCO2e yr−1, −118 MtCO2e yr−1, and −241 MtCO2e yr−1, respectively. This study demonstrates that ambitious and very ambitious scenarios of reforestation activities can significantly contribute to Indonesia’s forestry-related NDC in 2030 by reducing the Indonesia Business As Usual (BAU) emissions up to 17% and 35%.

Biomethane upgrading to transportation fuel quality using spent coffee for carbon dioxide capture in pressure swing adsorption

Biomethane upgrading from raw biogas is a potential fuel for transportation to minimize the greenhouse gases emissions from the transport sector. Biomethane upgrading a binary biogas comprising 32% CO2 and 68% CH4 by pressure swing adsorption of two beds-four steps process, mediated by spent coffee was experimentally studied. Breakthrough curves experiment was conducted to investigate the methane/carbon dioxide adsorption over spent coffee adsorbent at pressure of 2 bar. From the experimental results, a model was developed using Aspen Adsorption platform to estimate the temperature profile of the spent coffee’s bed at four positions of 1 cm, 5 cm, 7.5 cm, and 10 cm. In addition, the upgrading process performance in the presence of three different moisture contents of 3%, 5%, and 10% was also investigated. The experimental data showed that the developed model could represent the process performance with high degree of accuracy. Results from this study reveal that spent coffee with PSA system operated under specific operating conditions yielded biomethane with purity of 97% and recovery of 95.43%. Introduction of moisture with concentration up to 10% improved the CO2 removal rate and accordingly the biomethane purity. This study presents raw coffee as an effective adsorbent, competing other classes of carbon-based materials in separating CO2 to produce high biomethane purity that matches the transportation fuel quality.

Direct measurement of CO2 drawdown in mine wastes and rock powders: Implications for enhanced rock weathering

Enhanced rock weathering (ERW) sequesters CO2 via solubility and mineral trapping and can be implemented by the mining industry to reduce their net greenhouse gas emissions. Kimberlite residues from Venetia Diamond Mine in South Africa, as well as powdered forsterite, serpentinite, wollastonite skarn, and 10 wt.% brucite mixed with quartz sand, were tested as potential feedstocks for ERW. A CO2 flux system directly measured CO2 removal rates and sensors tracked laboratory conditions and pore water saturation during a series of 2-week experiments. With respect to kimberlites, unweathered residues achieved the greatest drawdown rate of -870 g CO2/m2/yr at 48% saturation. In contrast, fine and coarse residues previously exposed to mine process water achieved fluxes of -150 and -160 g CO2/m2/yr at 60% saturation. Brucite reached -2940 g CO2/m2/yr at 14% saturation compared to forsterite, serpentinite, and wollastonite that achieved fluxes of -500, -260, and -190 g CO2/m2/yr, respectively, at higher saturations of 53–60%. Mineralogical composition had the greatest effect on CO2 fluxes, followed by water content which drives carbonation reactions and affects permeability. Solid inorganic carbon increased in the brucite, wollastonite, and unweathered kimberlite, indicating that CO2 was stored via mineral trapping as opposed to solubility trapping in the other experiments. Increasing the exposure of unweathered residues, expanding dispersal area, and optimizing water saturation would lead to greater CO2 removal at mine sites.

Creative absorber design and optimization for CO2 capture with aqueous piperazine

The Texas Carbon Management Program is preparing a Front-End Engineering Design (FEED) of the PZASTM (Piperazine with the Advanced StripperTM) for CO2 capture at a natural gas combined cycle power plant in West Texas. This paper develops the absorber design for the capture system and studies the operational strategies of the absorber in response to ambient temperature swing. The design uses 2 absorber trains, and each train integrates absorption and a water-wash section in one column. Each column has a cross-section area of 174 m2 and consists of 3 sections of MellapakPlus® 252Y structured packing. Packing heights for each section are 3, 4.9, and 2.7 m from top to bottom. A pump-around intercooler applied at the bottom bed circulates solvent and eliminates the direct contact cooler. The baseline CO2 removal rate is 90% and will vary between 78% and 90% with ambient temperature. The system uses air cooling to eliminate cooling water usage. The water balance in the system will be managed by operating the water wash at a high circulation rate (1300 kg/h) to condense water during the night and make up for water loss during the day. The proposed design reduces the capital cost of the absorber column by minimizing the packing height and eliminating the direct contact cooler (DCC), and improves the energy cost by lowering the pump-around intercooling temperature and increasing the pump-around rate.

Targeting arterial partial pressure of carbon dioxide in acute respiratory distress syndrome patients using extracorporeal carbon dioxide removal.

A retrospective analysis of SUPERNOVA trial data showed that reductions in tidal volume to ultraprotective levels without significant increases in arterial partial pressure of carbon dioxide (PaCO2 ) for critically ill, mechanically ventilated patients with acute respiratory distress syndrome (ARDS) depends on the rate of extracorporeal carbon dioxide removal (ECCO2 R). We used a whole-body mathematical model of acid-base balance to quantify the effect of altering carbon dioxide (CO2 ) removal rates using different ECCO2 R devices to achieve target PaCO2 levels in ARDS patients. Specifically, we predicted the effect of using a new, larger surface area PrismaLung+ device instead of the original PrismaLung device on the results from two multicenter clinical studies in critically ill, mechanically ventilated ARDS patients. After calibrating model parameters to the clinical study data using the PrismaLung device, model predictions determined optimal extracorporeal blood flow rates for the PrismaLung+ and mechanical ventilation frequencies to obtain target PaCO2 levels of 45 and 50 mm Hg in mild and moderate ARDS patients treated at a tidal volume of 3.98 ml/kg predicted body weight (PW). Comparable model predictions showed that reductions in tidal volumes below 6 ml/kg PBW may be difficult for acidotic highly severe ARDS patients with acute kidney injury and high CO2 production rates using a PrismaLung+ device in-series with a continuous venovenous hemofiltration device. The described model provides guidance on achieving target PaCO2 levels in mechanically ventilated ARDS patients using protective and ultraprotective tidal volumes when increasing CO2 removal rates from ECCO2 R devices.

Simulation of H2S and CO2 removal from IGCC syngas by cryogenic distillation

The H2S and CO2 through absorption methods absorbed at low temperature and high pressure, while desorption was operated at high temperature and low pressure, presenting repeated lifting temperatures, that is, the cold fever. The captured CO2 required the further drying and compression to meet the requirements for transport and storage, existing repeated work. The cryogenic distillation used the difference of boiling point of IGCC syngas components to achieve H2S and CO2 removal through a range of multicompression, condensation and separation steps. The cryogenic distillation process was simulated by Aspen Plus, which removed water by flash, then H2S by desulfurization tower, and CO2 by decarburization tower. The tower parameters, such as reflux ratio, stage number and feed stage, were optimized to study their effect on H2S and CO2 removal rate. Under the optimal conditions, the simulated results of cryogenic distillation were compared with absorption methods (Rectisol, Selexol, Purisol and MDEA), it removed 85% of CO2 from the syngas, 98.2% of H2S and 100% of NH3 and could achieve the integration of carbon capture and storage without repeated work. The CO2 purity by cryogenic distillation process was as high as 99.94% to completely meet the requirements for transport and storage. It required no absorbent, hence avoiding solvent regeneration and loss. Its process was simple with two towers to achieve gas separation and reduce the operation cost. It is a potential to achieve H2S and CO2 removal from IGCC syngas with simple operation process and without repeated work and solvent consumption to reduce energy and cost.

Unravelling CO2 capture performance of microalgae cultivation and other technologies via comparative carbon balance analysis

Microalgae cultivation, absorption, adsorption, and membrane separation are widely applauded as promising technologies to sequester CO2 from flue gas. Herein, comparative carbon balance was used to elucidate their CO2 capture performance in the aspects of CO2 emission rates (direct, indirect, total, and net), CO2 removal efficiencies (apparent and actual), and CO2 removal rate per power input ratio. Screening criteria for effective CO2 capture system rule out energy-intensive sorption processes, put forward low energy membrane separation, and disclose alterable competency of microalgae cultivation. For CO2 capture from flue gas, microalgae (Chlorella vulgaris) cultivation in open raceway ponds was only inferior to membrane separation. To improve microalgal CO2 capture, the sensitivity analysis was performed by replacing original microalgae species (C. vulgaris) or cultivation system (open raceway pond). The microalgal CO2 capture in open raceway ponds became worse following the substitution of C. vulgaris with alternatives (Botryococcus braunii, Chlorella kessleri, Chlorella pyrenoidosa, Scenedesmus obliquus, Spirulina sp., or Tetraselmis suecica). For microalgal (C. vulgaris) CO2 capture, the competent cultivation systems included open raceway pond and airlift photobioreactor, while the bubble column, flat panel, or tubular photobioreactors were classified as non-competent systems. In short, microalgal (C. vulgaris) CO2 capture was technically feasible in open raceway pond or airlift photobioreactor; further, the use of airlift photobioreactor was preferred for better CO2 capture and microalgae biomass production. Due to the necessity of a huge working volume, the low scalability of microalgae cultivation could hamper the industrial application of microalgal CO2 capture from flue gas.

Offsetting the Impact of CO2 Emissions Resulting from the Transport of Maiêutica’s Academic Campus Community

The authors aim to investigate the number of trees necessary to capture the CO2 emissions from house–campus travelling, to and from the Maiêutica Academic Campus in the north of Portugal. A sample of the academic community was given an online survey in order to assess mobility practices. Based on the data collected, CO2 emissions, as well as the number of trees necessary to mitigate these emissions, were calculated. The authors estimate that the total emissions resulting from house–campus commutes amount to 2937 tCO2 year−1. To mitigate this amount of carbon dioxide, 138 ha would be necessary to plant 96,539 trees, according to the species’ respective CO2 removal rates. The estimated tree area necessary to neutralize the community’s mobility related CO2 emissions is so high that other alternatives must be considered: a preferred use of public transportation, carpool system, online theoretical classes, rescheduling timetables, green roofs installation, and photovoltaic panels.

Immobilized Microalgae-Based Photobioreactor for CO2 Capture (IMC-CO2PBR): Efficiency Estimation, Technological Parameters, and Prototype Concept

Microalgae-mediated CO2 sequestration has been a subject of numerous research works and has become one of the most promising strategies to mitigate carbon dioxide emissions. However, feeding flue and exhaust gas into algae-based systems has been shown to destroy chloroplasts, as well as disrupt photosynthesis and other metabolic processes in microalgae, which directly limits CO2 uptake. CO2 biosequestration in existing photobioreactors (PBRs) is also limited by the low biomass concentration in the growth medium. Therefore, there is a real need to seek alternative solutions that would be competitive in terms of performance and cost-effectiveness. The present paper reports the results of experiments aimed to develop an innovative trickle bed reactor that uses immobilized algae to capture CO2 from flue and exhaust gas (IMC-CO2PBR). In the experiment, ambient air enriched with technical-grade CO2 to a CO2 concentration of 25% v/v was used. The microalgae immobilization technology employed in the experiment produced biomass yields approximating 100 g DM/dm3. A relationship was found between CO2 removal rates and gas volume flux: almost 40% of CO2 was removed at a feed of 25 dm3 of gas per hour, whereas in the 200 dm3/h group, the removal efficiency amounted to 5.9%. The work includes a determination of basic process parameters, presentation of a developed functional model and optimized lighting system, proposals for components to be used in the system, and recommendations for an automation and control system for a full-scale implementation.

Basic Study of Anode Off-Gas Recycling Solid Oxide Fuel Cell Module with Fuel Regenerator

In recent years, with the rise of global environmental protection activities, it is becoming necessary to reduce CO2 emissions in social activities. In the field of power generation, it is very important to capture CO2 emissions and increase the conversion efficiency from chemical energy to electrical energy. Because the increased electrical efficiency can lead to the increased power, it is likely to reduce the consumption of fossil fuels for power generation, resulting in reduced CO2 emissions. In our previous report, the effect of a fuel regenerator in a two-stage solid oxide fuel cell (SOFC) module on the electrical efficiency was studied. The results showed that the electrical efficiency was considerably improved by removing H2O and CO2 from the anode off-gas by the fuel regenerator. The highest electrical efficiency was obtained when 100% of H2O and CO2 were removed from the anode off-gas, and it was estimated to be a net alternating current (AC) of 71.8% (lower heating value (LHV)). Although it is necessary to maintain the module at a high temperature in order to realize the system, a 4.8 kW two-stage SOFC module with a fuel regenerator was developed and confirmed to have the electrical efficiency equivalent to a net AC of 66.0% (LHV) with the thermal self-sustainability. In 2020, a demonstration test using a highly efficient two-stage SOFC system has started. In this study, we focused on an anode off-gas recycling SOFC module with a fuel regenerator. The reason why we studied the module is that it can generate highly efficient power and capture a large amount of CO2 at the fuel regenerator. Therefore, the effect of the fuel regeneration on both the electrical efficiency and capture of CO2 was examined. The authors are presently not aware of any reports of examining the effect of the fuel regenerator, which removes CO2 and/or H2O extensively from the anode off-gas, on the electrical efficiency and CO2 capture in an anode off-gas recycling SOFC module. The calculation was carried out under the following conditions. CH4 was used as a fuel, and the ratio of steam to carbon of the inlet fuel was 2.5 or more in order to avoid the carbon deposition. The temperature of both the reformer and SOFC stack was set at 700°C. The area specific resistance and current density of the SOFC stack were assumed to be 0.383 ohm cm2 and 0.25 A cm–2, respectively. The lowest available fuel concentration, which is assumed to be the ratio of the partial pressure of hydrogen to water vapor (= p(H2) / p(H2O)), was set by calculating the outlet fuel concentration when operating a single-pass SOFC stack with a maximum fuel utilization rate of 80%. For estimating the system performance, the inverter efficiency and auxiliary device loss rate were assumed to be 95% and 6%, respectively. The Nernst voltage was determined from the inlet and outlet gas composition of the stack which is calculated by a process simulation software. The electrical efficiency was estimated from the cell voltage and fuel utilization rate. The highest electrical efficiency was obtained when both the fuel utilization rate and recycle rate were 100%, and the removal rates of CO2 and H2O at the fuel regenerator were 100% and 44.4%, respectively. The reason to remove only 44.4% of H2O from the anode off-gas is to keep the ratio of steam to carbon of the inlet fuel at 2.5. The electrical efficiency was a net AC of approximately 75.5% (LHV) with 100% of CO2 capture at the fuel regenerator. In addition, the CO2 removal rate was studied to reduce to 63.9% because there is a margin in the fuel concentration of the SOFC stack. Even if the removal rates of CO2 and H2O at the fuel regenerator were 63.9% and 44.4%, respectively, the electrical efficiency was estimated to be a net AC of approximately 74.9% (LHV), and the CO2 capture at the fuel regenerator was 100%. These results show that the anode off-gas recycling SOFC module can generate highly efficient power as well as the two-stage SOFC module when using the fuel regenerator. Furthermore, the anode off-gas recycling SOFC module has advantage of capturing CO2 at the fuel regenerator. Although it is not easy to generate highly efficient power with the thermal self-sustainability, it is expected that the anode off-gas recycling SOFC module with the fuel regenerator is developed and put into practical use in the future.

Enhancement of the photosynthetic and removal performance for microalgae-based technologies by co-culture strategy and strigolactone induction

In this study, digestate and biogas were treated simultaneously based on fungi-microalgae symbionts and fungi-microalgae-bacteria symbionts, respectively. The effects of strigolactone (GR24) on the biomass of symbionts and photosynthesis of algae, and purification of digestate and biogas were explored. With the induction of GR24, the metabolism of microorganism-microalgae systems and photosynthesis of microalgae were enhanced causing the rapid growth of the symbionts, further strengthening the purification performance of the systems. Moreover, the GR24 enhanced the CO2 removal performance of the co-culture systems via increasing the carbonic anhydrase activity of microalgae cells. The fungi-microalgae-bacteria co-culture strategy with GR24 induction was found to obtain great photosynthetic and removal performance, possessing the 73.54 ± 6.83% CO2 removal rate and 88.61 ± 8.24% COD removal rate.

Analysis of lighting conditions of indoor living walls: Effects on CO2 removal

Vertical greening systems, or living walls, are becoming increasingly used indoors for improving the sustainability of buildings, including for the mitigation of excess CO2 levels, derived from human respiration. However, light provision within indoor environments is often insufficient for the efficient functioning of many plant species, leading to low photosynthetic CO2 removal rates, and the need for supplementary light sources. In this study, we investigated the performance of supplementary lighting employed for indoor living wall systems, and whether optimised lighting conditions could lead to improved CO2 removal. In situ trials with several medium-large indoor living walls were performed to sample the lighting scenarios currently employed. We concluded that the majority of plants in existing systems were exposed to suboptimal lighting and will have a net-zero CO2 removal efficiency. Sealed chamber experiments using two common living wall plant species were conducted to explore the effect of varying lighting conditions on CO2 removal efficiency. Comparisons on optimal and “best case” in situ conditions were carried out, showing that CO2 removal efficiency was significantly correlated with both leaf and stem angles, which suggest phototropism may influence in situ CO2 removal. After a ten-day experimental period, the highest CO2 removal efficiency for both test plant species was observed at 200 μmol m−2 s−1 light flux density (~10500 lux) at 15° from the vertical growing surface. Our results indicate that most current lighting systems are inadequate for healthy plant photosynthesis and CO2 removal, and that modified lighting systems could improve this performance. The estimation of the CO2 removal ability of a 5 m2 passive living wall decreases from an ACH of 0.21 h−1, achieved in an optimal light exposure condition, to only 0.03 h−1 when plants are exposed to sub-optimal conditions. To reduce maintenance costs, technical guidelines for indoor living wall lighting should be established, and lighting suppliers should recognise the developing niche market for specialised indoor living wall lighting.

Comparison of Circular and Parallel-Plated Membrane Lungs for Extracorporeal Carbon Dioxide Elimination.

Extracorporeal carbon dioxide removal (ECCO2R) is an important technique to treat critical lung diseases such as exacerbated chronic obstructive pulmonary disease (COPD) and mild or moderate acute respiratory distress syndrome (ARDS). This study applies our previously presented ECCO2R mock circuit to compare the CO2 removal capacity of circular versus parallel-plated membrane lungs at different sweep gas flow rates (0.5, 2, 4, 6 L/min) and blood flow rates (0.3 L/min, 0.9 L/min). For both designs, two low-flow polypropylene membrane lungs (Medos Hilte 1000, Quadrox-i Neonatal) and two mid-flow polymethylpentene membrane lungs (Novalung Minilung, Quadrox-iD Pediatric) were compared. While the parallel-plated Quadrox-iD Pediatric achieved the overall highest CO2 removal rates under medium and high sweep gas flow rates, the two circular membrane lungs performed relatively better at the lowest gas flow rate of 0.5 L/min. The low-flow Hilite 1000, although overall better than the Quadrox i-Neonatal, had the most significant advantage at a gas flow of 0.5 L/min. Moreover, the circular Minilung, despite being significantly less efficient than the Quadrox-iD Pediatric at medium and high sweep gas flow rates, did not show a significantly worse CO2 removal rate at a gas flow of 0.5 L/min but rather a slight advantage. We suggest that circular membrane lungs have an advantage at low sweep gas flow rates due to reduced shunting as a result of their fiber orientation. Efficiency for such low gas flow scenarios might be relevant for possible future portable ECCO2R devices.

Water as a Blood Model for Determination of CO2 Removal Performance of Membrane Oxygenators.

CO2 removal via membrane oxygenators has become an important and reliable clinical technique. Nevertheless, oxygenators must be further optimized to increase CO2 removal performance and to reduce severe side effects. Here, in vitro tests with water can significantly reduce costs and effort during development. However, they must be able to reasonably represent the CO2 removal performance observed with blood. In this study, the deviation between the CO2 removal rate determined in vivo with porcine blood from that determined in vitro with water is quantified. The magnitude of this deviation (approx. 10%) is consistent with results reported in the literature. To better understand the remaining difference in CO2 removal rate and in order to assess the application limits of in vitro water tests, CFD simulations were conducted. They allow to quantify and investigate the influences of the differing fluid properties of blood and water on the CO2 removal rate. The CFD results indicate that the main CO2 transport resistance, the diffusional boundary layer, behaves generally differently in blood and water. Hence, studies of the CO2 boundary layer should be preferably conducted with blood. In contrast, water tests can be considered suitable for reliable determination of the total CO2 removal performance of oxygenators.

Novel microbial-electrochemical filter with a computer-feedback pH control strategy for upgrading biogas into biomethane

A novel microbial-electrochemical filter was designed and operated based on a combined microbial electrolysis cell and bio-trickling filter principles with the aim to maximize gas–liquid mass-transfer efficiency and minimize costs associated with bubbling biogas through liquid-filled reactor. CO2/biogas feed to the MEF was done via a computer-feedback pH control strategy, linking CO2 feed directly to the OH− production. As a result current efficiency was constant at around 100% throughout the period of experiments.CO2 from biogas was almost completely removed at cathodic pH setpoint of 8.5. Maximum CO2 removal rate was 14.6 L/L/day (equivalent to 29.2 L biogas/L/day). Net energy consumption was around 1.28 kWh/Nm3CO2 or 0.64 kWh/m3 biogas (maximum 49% energy efficiency). An ability to maintain a constant pH means elevated pH from increasing applied potential (current) is no longer an issue. The process can potentially be up-scaled and operated at a much higher current and therefore CO2 removal rate.

Experimental Results of Post-combustion CO2 Capture in a CFB-type Reaction System Using 85 kg PEI-based Dry Sorbents

In this study, the high-concentrated CO2 has been recovered in the CFB-type dry sorbent CO2 capture process using 85 kg PEI-based sorbents, which were developed by KAIST. The CO2 uptake was measured by TGA was 0.067 kg-CO2/kg-solid. The process consists of a fast fluidized bed type sorption reactor, a bubbling fluidized bed type regenerator and sorbent cooler. The 85 kg of sorbent was charged to the process and the solid circulation rate, which was quantitatively controlled by manipulating the rpm of the rotary valve, was 145 kg/h so that it took about 35 minutes for the sorbents to cycle through the process. The CO2 removal efficiency at absorber and CO2 purity at regenerator were measured or calculated with an on-line IR gas analyser. The dynamic sorption capacity was calculated using the amount of CO2 absorbed in the absorber and the solid circulation rate. The performances were as follows: about 60% of the CO2 removal efficiency, 100 kg/day of the CO2 removal rate, 91% of the CO2 purity, and 2.9 wt.% of the dynamic sorption capacity. As a result, the dynamic sorption capacity was rather low, about 43% of the sorbent performance measured by TGA, because the solid residence time in the sorption reactor was insufficient. If the height of the sorption reactor would be increased to ensure the solid residence time enough to increase the dynamic sorption capacity to 0.04 kg-CO2/kg-solid, then 85% CO2 removal efficiency and 138 kg/day CO2 removal rate would be possible.

Suitable CO2 Solubility Models for Determination of the CO2 Removal Performance of Oxygenators.

CO2 removal via membrane oxygenators during lung protective ventilation has become a reliable clinical technique. For further optimization of oxygenators, accurate prediction of the CO2 removal rate is necessary. It can either be determined by measuring the CO2 content in the exhaust gas of the oxygenator (sweep flow-based) or using blood gas analyzer data and a CO2 solubility model (blood-based). In this study, we determined the CO2 removal rate of a prototype oxygenator utilizing both methods in in vitro trials with bovine and in vivo trials with porcine blood. While the sweep flow-based method is reliably accurate, the blood-based method depends on the accuracy of the solubility model. In this work, we quantified performances of four different solubility models by calculating the deviation of the CO2 removal rates determined by both methods. Obtained data suggest that the simplest model (Loeppky) performs better than the more complex ones (May, Siggaard-Anderson, and Zierenberg). The models of May, Siggaard-Anderson, and Zierenberg show a significantly better performance for in vitro bovine blood data than for in vivo porcine blood data. Furthermore, the suitability of the Loeppky model parameters for bovine blood (in vitro) and porcine blood (in vivo) is evaluated.

CFD simulation of CO2 absorption by water-based TiO2 nanoparticles in a high pressure stirred vessel

This work presents the modeling and simulation of CO2 capture by a water-based Titanium dioxide (TiO2) solid nanoparticle in a stirred high-pressure vessel at a constant temperature. Photocatalytic material such as TiO2 has excellent properties, namely it is nontoxic, inexpensive, and non-polluting. CFD model equations are developed and solved using COMSOL software package. The effect of the concentration of a solid nanoparticle in a water-based TiO2 solution, the size of TiO2 nanoparticles and the rate of mixing on the CO2 absorption rate is investigated. A 2D mathematical model considers both shuttle and micro-convention mechanisms. Results reveal that the best TiO2 concentration range is between 0.5 and 1 kg/m3 and that a particle size of 10 nm is more efficient than higher particle sizes. A moderate mixing rate maximizes the CO2 removal rate. The theoretical predictions are validated using lab experimental data and those in the available literature. Results confirm that the model calculations match with the experimental results. Accordingly, the model successfully predicts the experimental data and can be used for further studies.

Advanced Ultra-Supercritical Coal-Fired Power Plant with Post-Combustion Carbon Capture: Analysis of Electricity Penalty and CO2 Emission Reduction

This article presents the performance analysis of a 700 MW future planned advanced ultra-supercritical (A-USC) coal-fired power plant fitted with post-combustion carbon capture and storage (CCS) technology. The reference A-USC unit without CCS achieves a net efficiency of 47.6% with CO2 emissions of 700 kgCO2/MWh. Relatively to subcritical units, the net efficiency of the A-USC is 8%-pts higher while CO2 emissions are 16.5% lower. For a CO2 removal rate of 90%, the net efficiency of the CCS integrated A-USC unit is 36.8%. The resulting net efficiency loss is 10.8%-pts and the electricity output penalty is 362.3 kWhel/tCO2 for present state CCS technology. The study continues with the assessment of interface quantities between the capture unit and the steam cycle affecting the performance of the A-USC. Improved CO2 absorbents could alleviate the net efficiency loss by 2–3%-pts, and enhanced CO2 compression strategies and advanced heat integration could further reduce the efficiency loss by 0.5–1.2%-pts and 0.4–0.6%-pts, respectively. The total efficiency gain from CCS technology upgrades is estimated at 3.6%-pts, thus bringing down the net efficiency loss to 7.2%-pts and the electricity output penalty to 241.7 kWhel/tCO2.

Performance of different microalgae-based technologies in nutrient removal and biogas upgrading in response to various GR24 concentrations

Microalgae-based technology is an emerging strategy for the simultaneous purification of nutrients in biogas slurry and CO2 in biogas. To evaluate effects of synthetic analogue of strigolactone (GR24) concentration on removal efficiency, mono-cultivation of microalgae and co-cultivation of algae with fungus or activated sludge were performed in a photobioreactor. The GR24 concentration of 10−9 M was contributed to the optimum growth characteristics, photosynthetic performance and purification effects in the co-cultivation system of Chlorella vulgaris with activated sludge. The optimal growth rate and mean daily productivity for Chlorella vulgaris were 0.419 ± 0.04 d−1 and 0.342 ± 0.029 g L−1 d−1, respectively. The photosynthetic performance parameters Fv/Fm, PIABS, ΨO, and ΦEO were 0.89 ± 0.08, 6.89 ± 0.62, 0.97 ± 0.09, and 0.69 ± 0.06, respectively, indicating that GR24 with a concentration of 10−9 M was more helpful for photosynthesis of microalgae. Moreover, the maximum removal rate of chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and CO2 were obtained by the induction of 10−9 M of GR24, which were 77.33 ± 7.25%, 78.86 ± 7.51%, 78.12 ± 7.57% and 69.33 ± 6.86%, respectively. This research therefore provides an effective strategy for wastewater bioremediation and high-quality biogas energy acquisition.