Low Concentrations Of Carbon Dioxide Research Articles

Alkaline hydrogenotrophic methanogenesis in Methanococcus vannielii at low carbon dioxide concentrations

Capture of carbon dioxide from the atmosphere is challenging and thermodynamically expensive because of its dilute concentration (421 ppm, December 2023). Utilizing the concentrating effect of dissolving atmospheric CO2 in alkaline solution to form dissolved inorganic carbon (DIC), we explored the potential of an alkalotolerant hydrogenotrophic methanogen, Methanococcus vannielii, to capture and convert CO2 at low partial pressures to methane. Kinetic constants for CO2 reduction to CH4 were determined from experiments in serum bottles at low pCO2 at 30˚C. At pH 7, 8, and 9, the apparent KM is 0.4, 1.2, and 1.2 mM DIC and the apparent vmax is 5.6, 7.8, and 2.9 mmol CH4 L−1 OD−1 hr−1, respectively. Using atmosphere-equilibrated DIC concentrations at pH 7, 8, and 9, methane formation rates were 1.1, 2.3, and 2.1 mmol CH4 L−1 OD−1 hr−1, respectively. Our data show that alkaline hydrogenotrophic methanogenesis is an alternative to photosynthetic CO2 fixation for biological capture and conversion of CO2 at atmospheric concentrations at reasonable rates.

Enhancing carbon dioxide separation from natural gas in dynamic adsorption by a new type of bimetallic MOF; MIL-101(Cr-Al)

This study explores the use of a high surface area nano-adsorbent for selective adsorption and separation of very low concentrations of carbon dioxide from methane. The adsorbent, MIL-101(Cr-Al) with unsaturated metal sites, was prepared by one pot facile hydrothermal method and it was compared with MIL-101(Cr). Characterizations of the synthesized samples were conducted using XRD, FESEM, EDAX, elemental mapping, and BET analyses. Static adsorption experiments were carried out at pressures ranging from close to 1 bar up to 50 bar and at temperatures of 25 and 35 °C. The ideal selectivity of carbon dioxide relative to methane and the isosteric heat of adsorption were also calculated. Results indicated that with the bimetallic modification method, the CO2/CH4 selectivity increased from 5.2 to 5.7 at the pressure of 1 bar and from 8.2 to 8.3 at the pressure of 50 bar and temperature of 35 °C. Dynamic adsorption experiments were conducted for the mixture of CH4, CO2 and He (85 %-5% −10 % mol%). The dynamic selectivity of CO2/CH4 at the pressure of 15 bar with the space time of 1.12 min was increased from 1.82 to 4.2 using bimetallic MIL-101(Cr-Al).

Advancing power plant decarbonization with a flexible hybrid carbon capture system

Carbon dioxide capturing from natural gas-fired power plants is challenging due to high flow rate and the low carbon dioxide concentration of flue gas. This is an emerging field where many concepts and scientific principles are still in development. In this paper, a novel design is proposed for decarbonizing a natural gas-fired combined cycle power plant using a solar-assisted hybrid membrane-amine carbon capture and storage system. The design incorporates a solar field with thermal energy storage integrated with the capture plant reboiler along with multi-stage carbon dioxide selective membrane modules for selective exhaust gas recirculation (SEGR) combined with exhaust gas recirculation (EGR) to increase the concentration of Carbon dioxide in the flue gas. It is hypothesized that the proposed design could enhance the performance of the power plant integrated with carbon capture in terms of flexibility and sustainability. In this regard, a comprehensive process modeling and simulation framework is developed to accurately investigate the interactions between different components of the integrated process. The results show that the carbon dioxide concentration in the flue gas increases from 3.9 mol% in the conventional power plant to 10.87 mol% in the EGR + SEGR case (26 % of flue gas to EGR and 50 % to SEGR) and increases to 18.08 mol% by the SEGR case (76 % of flue gas to SEGR). Solar thermal energy is an efficient solution for reducing or eliminating the need for steam extraction for the stripper reboiler, resulting in a significant increase in net power output compared to the non-solar cases. The proposed designs lead to a 19.4 % increase in system power output in the SEGR case and a 13.8 % increase in the EGR + SEGR case compared to the baseline case. Also, the specific reboiler duty and required packing material volume in the absorber and stripper are significantly improved in the proposed designs. Moreover, the power plant carbon intensity in the proposed designs can be reduced by up to 10.3 %. The EGR + SEGR case offers an optimal solution as it requires a significantly smaller membrane area, approximately 71 % smaller membrane area compared to SEGR. The proposed designs and analysis have the potential to contribute significantly to the decarbonization of fossil-fueled power plants and enhance the sustainability and flexibility of the power sector.

Improved Apparatus for Dynamic Column Breakthrough Measurements Relevant to Direct Air Capture of CO2.

Dynamic column breakthrough (DCB) measurements are valuable for characterizing the adsorption of gaseous species by solid sorbents and are typically used for high concentrations of adsorptives, often at elevated temperatures and pressures. However, adsorbents for the direct capture of carbon dioxide from natural air demand measurement capability at low partial pressures of CO2 at atmospherically relevant temperatures and pressures. We have developed a new apparatus focused on the measurement of DCB curves under typical tropospheric conditions. The new apparatus is described in detail and validated with breakthrough curve measurements. Adsorption capacities are reported at (233.1 to 323.1) K and (351 to 1078) hPa for low carbon dioxide concentrations on 13X zeolite samples on the order of a few hundred milligrams. Measurement uncertainties related to timing, flow, temperature, and concentrations are analyzed and the present results at 273 K, 298 K, and 323 K are compared with static measurements obtained with a manometric adsorption analyzer. In addition, experiments at a typical atmospheric CO2 concentration of 400 μL · L-1 have been performed.

Mass screening of rice mutant populations at low CO2 for identification of lowered photorespiration and respiration rates.

Identifying rice (Oryza sativa) germplasm with improved efficiency of primary metabolism is of utmost importance in order to increase yields. One such approach can be attained through screening genetically diverse populations under altered environmental conditions. Growth or treatment under low carbon dioxide (CO2) concentrations can be used as a means of revealing altered leaf photorespiration, respiration and other metabolic variants. We developed a pipeline for very high throughput treatment of gamma- and ethyl methanesulfonate- (EMS) induced mutant populations of IR64 rice seedlings at very low CO2 for 7 days. 1050 seedlings per batch at 5th leaf stage were exposed to 60 ppm CO2 for the first day and 30 ppm for the remaining three days. Following this, putative candidates were identified by measuring chlorophyll depletion using SPAD. Screening results showed a distinct difference between the mutants and the WTs. The mean chlorophyll loss in WTs ranged from 65% to 11% respectively, whereas in the mutant lines chlorophyll loss ranged from 0 to 100%, suggesting considerable phenotypic variation. Rice mutants with a reduced chlorophyll reduction (<10%) were identified as 'Chlorophyll retention mutants' (CRMs) under low CO2 stress. In total, 1909 mutant lines (14,000 seedlings) were screened for chlorophyll content under 30 ppm CO2, with 26 lines selected for detailed screening. These 26 putative candidates were self-seeded to produce an M5 generation, used to determine the genetic control of the altered response to low CO2. Gas exchange of light and CO2 response revealed that there were significant variations among photosynthetic properties in two selected rice mutants. The CO2 compensation points in the absence of photorespiration and leaf respiration rates were lower than the WTs and anatomical analyses showed that CRM 29 had improved mesophyll cell area. We propose that this approach is useful for generating new material for breeding rice with improved primary metabolism.

Overcoming the Entropy Penalty of Direct Air Capture for Efficient Gigatonne Removal of Carbon Dioxide

Atmospheric carbon poses an existential threat to civilization via global climate change. Hundreds of gigatonnes of carbon dioxide must be removed from earth’s atmosphere in the next three decades, necessitating a low-cost, energy-efficient process to extract low concentrations of carbon dioxide for conversion to a stable material permanently stored for thousands of years. In this work, the challenge of removing gigatonnes of CO2 is described via the scale of effort and the thermodynamics of collecting and reducing this diffuse chemical, the accumulation of which imparts a substantial entropy penalty on any atmospheric carbon capture process. The methods of CO2 reduction combined with upstream direct air capture (DAC) including absorption, membrane separation, and adsorption are compared with biomass torrefaction and permanent burial (BTB). A Monte Carlo model assesses the mass, energy, and economics of the full process of biomass torrefaction from biomass collection and transport to stable carbon burial to determine that 95% of scenarios could remove carbon for less than $200 per CO2-tonne-equivalent. Torrefied carbon is further discussed for its long-term stability and availability at the scale required to substantially mitigate the threat of climate change.

CO2 bee anaesthetic can cause complications

Most people don't really pay attention to the air they breathe. However, if you go up a mountain, where the oxygen levels are lower, you'll notice as you huff and puff while taking a normal walk around town. Changes in the amounts of the different gases that make up the air we breathe can have noticeable effects in other animals as well, especially insects. ‘Low concentrations of carbon dioxide (CO2) are often used as an attractant or repellent’, says Anna Cressman of Pennsylvania State University, USA; however, high concentrations can cause behavioural and physiological changes, and can even result in unconsciousness. Frequently, researchers use 100% CO2 to anaesthetize insects (called CO2 narcosis), but the side-effects of exposure to high levels of CO2 are often not considered. Working with Etya Amsalem, also of Pennsylvania State University, Cressman asked what is causing these side-effects in bumblebees (Bombus impatiens) – the lack of oxygen, or the high level of CO2 itself.Carbon dioxide is usually found at levels of around 0.04% in normal air, so the duo pumped either 100% CO2, 50% CO2, normal air with low oxygen, or 100% nitrogen gas (which means that there is no oxygen) into a chamber containing bees for 1 min, recording how many of the bees passed out, and then filmed the insects to monitor how they behaved once they awoke, as well as checking how the different gases affected bees with different roles, queens and workers, in the colony.Sure enough, when the team compared the effects of pure CO2 and 100% nitrogen, the bees’ responses were quite different. Even though both gases knocked the bees out, after recovering from the sedation, the bees that had inhaled 100% CO2 had different side-effects from the bees anaesthetised with pure nitrogen. The CO2-anaesthetised bees pumped their abdomens more and the queens took longer to regain consciousness. In addition, when Cressman compared the effects of the different gases on worker and queen bees, the workers produced smaller eggs after several doses of 100% CO2, whereas the queens produced larger eggs after a single dose of the pure gas. Cressman also compared the impact of the two gases on the expression of six specific genes – involved in egg production and protection from low oxygen levels – and she discovered that the genes reacted differently.The responses of the queen bees and workers to pure CO2 also differed: the queens seemed to be more vulnerable to the gas than the workers, only requiring one dose, to begin showing side-effects during their recovery, in contrast to the workers, which required multiple doses of the gas before the side-effects became apparent. ‘The fact that the physiological changes are different suggests that CO2 is not simply depriving the bees of oxygen but does something else and is likely to have a more direct impact on cells’, Amsalem concludes.So, inhaling CO2 can affect bees with different roles in the colony in different ways, and researchers should be aware of the potential complications that this may cause when using the gas to anaesthetize insects in their experiments.

Eco-Physiological Adaptations of the Xylotrophic Basidiomycetes Fungi to CO2 and O2 Mode in the Woody Habitat.

The aim of this research is to study of eco-physiological adaptations of xylotrophic fungi (Basidiomycota, Agaricomycetes) to hypoxia, anoxia and hypercapnia as the main environmental factors that determine the activity of fungi in woody habitat. The study was carried out on seven species of polypore fungi widespread in the preforest-steppe pine-birch forests of the Central Urals, including both white (D. tricolor, D. septentrionalis, F. fomentarius, H. rutilans, T. biforme) and brown (F. betulina, F. pinicola) rot. Their CO2 and O2 gas exchange were analyzed in natural samples of woody substrates (Betula pendula, Pinus sylvestris) and basidiocarps by the chamber method using a CO2/O2 gas analyzer. It was shown that the intensity of O2 gas exchange is positively related to the oxygen concentration but is not very sensitive to a decrease in its content in the woody habitat. Xylotrophic fungi are able to completely exhaust the O2 in the habitat, and this process is linear, indicating that they do not have threshold values for oxygen content. Oxygen consumption is accompanied by an adequate linear increase in CO2 concentration up to 18-19%. At a concentration of 5-10%, carbon dioxide does not affect the gas exchange of xylotrophic fungi and can even enhance it, but at 20% it significantly reduces its intensity. Xylotrophic fungi are resistant to high CO2 concentrations and remain viable at 100% CO2 concentration and are capable of growth under these conditions. In an oxygen-free habitat, anaerobic CO2 emissions are recorded; when O2 appears, its consumption is restored to the level preceding anoxia. Xylotrophic fungi are the specialized group of saprotrophic microaerophilic and capnophilic facultative anaerobes adapted to develop at low oxygen and high carbon dioxide concentration, anoxia.

Possibilities of Biogas Upgrading on a Bio-Waste Sorbent Derived from Anaerobic Sewage Sludge

The development of biogas upgrading technologies is now an essential issue in recovering fuel-grade methane. Nowadays, trends in biogas upgrading include investigations of low-cost and renewable materials as sorbents for biogas enrichment to produce biomethane. Therefore, in this work, wastewater anaerobic sludge stabilized with calcium oxide was used as the bio-waste sorbent to capture carbon dioxide from biogas, employing a fixed bed column. The biogas flow rate was the parameter considered for examining the breakthrough responses. It was observed that breakthrough time decreases with increasing biogas inflow rate from 570 ± 10 min at 5 mL/min to 120 ± 12 min at 35 mL/min. The maximum sorption capacity of 127.22 ± 1.5 mg CO2/g TS of sorbent was estimated at 15 mL/min. Biomethane concentration in biogas increased from 56.5 ± 1.7 v% in the raw biogas to 98.9 ± 0.2 v% with simultaneous low carbon dioxide content of 0.44 ± 0.2 v%. A strong positive correlation (R2 = 0.9919) between the sorption capacity and the biogas flow rate was found in the range of biogas inflow rates between 5 mL/min and 15 mL/min. Moreover, the correlation analysis showed a strong negative relationship (R2 = 0.9868) between breakthrough time and the mass of carbon dioxide removal, and the biogas flow rates ranged from 10 mL/min to 20 mL/min.

The Impact of Atmospheric Plasma/UV Laser Treatment on the Chemical and Physical Properties of Cotton and Polyester Fabrics

Atmospheric plasma treatment can modify fabric surfaces without affecting their bulk properties. One recently developed, novel variant combines both plasma and UV laser energy sources as a means of energising fibre surfaces. Using this system, the two most commonly used fibres, cotton and polyester, have been studied to assess how respective fabric surfaces were influenced by plasma power dosage, atmosphere composition and the effects of the presence or absence of UV laser (308 nm XeCl) energy. Plasma/UV exposures caused physical and chemical changes on both fabric surfaces, which were characterised using a number of techniques including scanning electron microscopy (SEM), radical scavenging (using 2,2-diphenyl-1-picrylhydrazyl (DPPH)), thermal analysis (TGA/DTG, DSC and DMA), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). Other properties studied included wettability and dye uptake. Intermediate radical formation, influenced by plasma power and presence or absence of UV, was key in determining surface changes, especially in the presence of low concentrations of oxygen or carbon dioxide (20%) mixed with either nitrogen or argon. Increased dyeability with methylene blue indicated the formation of carboxyl groups in both exposed cotton and polyester fabrics. In the case of polyester, thermal analysis suggested increased cross-linking had occurred under all conditions.

Carbon Dioxide and Health

Background: Acute exposure to carbon dioxide could be caused diseases but in chronic exposure might be caused some mild to moderate symptoms and signs. Objective of this study was to determine the health effects of carbon dioxide in low to moderate concentration. Methods: The people who were employed in different industries were participated in this study. Groups were followed for brain and heart injury symptoms and signs. These groups were exposed to low concentrations of carbon dioxide; according to working sections, 4 groups were participated: working section A, working section B, working section C and working section D. Symptoms and signs were determined. Data were analyzed with SPSS 16.ANOVA, Chi-2, Exact test and relative risks with considering P&lt;0.05 as significant level. Results: Working section D, had the most carbon dioxide concentration; 825.10±0.01 PPM. brain and heart injury symptoms and sign were determined. Loss of concentration, chest pain and headaches were the most in group D and relative risks were shown significant risks of carbon dioxide. Relative risks for loss of concentration was 2.25(1.34-3.77). Also relative risks for chest pain were 1.35(1.02-2.10). Conclusions: Carbon dioxide had health effects in low to moderate concentration and might be caused loss of concentration and chest pain.

Control of Electric Nozzles for Feeding Plants with Carbon Dioxide in Protected Ground

The task of supplying plants in vegetable farms of the Russian Federation is relevant today. There is an urgent question about the implementation of carbon dioxide fertilization of plants in protected soil structures. The low concentration of carbon dioxide in the cultivation of plants serves as a factor limiting the yield. (Research purpose) The research purpose is to develop an algorithm for the microprocessor for supplying carbon dioxide to protected ground structures using electric nozzles. (Materials and methods) Since the content of carbon dioxide in the atmospheric air is only 0.03 percent, it is necessary to create an installation capable of dosing carbon dioxide. With insufficient air exchange, the CO2 content in greenhouses as a result of its intensive absorption by plants can fall below 0.01 percent and photosynthesis practically stops. The article presents the calculation to reduce the cost of protected crops using a carbon dioxide generation plant. The domestic and foreign literature have been analyzed. The article compares the characteristics of the injectors. There were described the method of calculating the number of injectors and the method of supplying carbon dioxide to the plants of the protected ground. (Results and discussion) The article presents the electrical equipment used in the installation. The electrical principle scheme of the installation includes the Mitsubishi FX2N microcontroller. The microcontroller is controlled by an algorithm for the supply of carbon dioxide. (Conclusions) It is possible to solve the problem of lack of carbon dioxide when growing plants by supplying gas with electric nozzles to the construction of a protected ground with direct control by a microcontroller. The use of electromagnetic nozzles makes it possible to dose the supplying of plants with CO2.

Effects of Different Carbon Dioxide-Modified Atmosphere Packaging and Low-Temperature Storage at 13 °C on the Quality and Metabolism in Mango (Mangifera indica L.)

Mangoes (Mangifera indica L.) were stored under four different carbon dioxide-modified atmosphere packaging (MAP) combinations at 13 ± 1 °C to investigate their effects on moisture distribution and content, physiological metabolism, as well as fruit quality. The mangoes stored under C7 combination (7% CO2 + 3% O2 + 90% N2) maintained respiration rate, inhibited the increase in 1-aminocyclocarboxylic acid-1-carboxylic acid synthase (ACS) content, and slowed down the senescence process of the fruit. The mangoes subjected to C7 combination also maintained higher firmness, protopectin, and free moisture content. The C7 combination suppressed the increase in soluble pectin and malondialdehyde (MDA) content, with the lowest weight loss. The yellowing rate of the mango pulp preserved under the C7 combination condition was significantly reduced, and the loss of vitamin C was reduced from the 0th to the 6th day of storage. The treatment with lower carbon dioxide content was not as effective as C7 combination. In conclusion, 7% CO2 + 3% O2 + 90% N2 MAP conditions delayed pulp yellowing and biochemical characteristics and maintained firmness and free moisture content along with better quality of mango for 30 days at low temperature.

Flue gas carbonation curing of cement paste and concrete at ambient pressure

High pressure carbonation with pure gas is commonly adopted in early-age concrete carbonation curing for performance enhancement and emission reduction. However, the processes of CO2 purification and compression are energy-intensive. This paper is to investigate the feasibility of directly utilizing flue gas at ambient pressure for carbonation curing. To accommodate the low carbon dioxide concentration in flue gas, cement paste was first studied to identify desirable curing conditions and regimes. Five curing regimes including “Closed (C)”, “Cyclic closed (CC)”, “Continuous supply (CS)”, “Continuous supply plus circulation (CSC)”, and “Cyclic closed circulation (CCC)” were examined to improve the reaction efficiencies and material properties under ambient pressure flue gas carbonation. Pure gas carbonation at ambient and high pressures were studied as references. It was found that gas supply, gas circulation, curing pressure, and CO2 concentration could affect CO2 uptake. The cyclic closed circulation (CCC) process yielded the highest CO2 uptake in flue gas carbonation, reaching about 50% reaction efficiency by pure gas at the same duration. It also presented comparable strength with pure gas carbonation at 28 d. Furthermore, the microstructure of cement paste under ambient pressure flue gas carbonation appeared to be comparable to that under pure gas carbonation although its CO2 uptake was only half. X-ray diffraction (XRD) results indicated that portlandite was the first reactant during carbonation curing regardless of gas pressure or CO2 concentration. A higher quantity of well-crystalline carbonates was observed after ambient pressure flue gas carbonation under CCC regime than pure gas carbonation by thermogravimetric analysis (TGA). Additionally, the Fourier transform infrared spectroscopy (FTIR) results also suggested that ambient pressure flue gas carbonation of CCC had seemingly enhanced the intermingling effect between carbonate and C–S–H compared to pure gas carbonation at either high or ambient pressure. The net CO2 emission analysis revealed that the CO2 sequestration efficiency in cement pastes was 75% in high pressure pure gas carbonation and reached 98% in ambient pressure flue gas carbonation. Furthermore, the cost estimate showed the cost of carbonation for 1-tonne cement or sequestration of 1-tonne CO2 was lowest in ambient pressure flue gas carbonation, which resulted from the elimination of CO2 capture, purification and compression.

Estimation of the real-time infiltration rate using a low carbon dioxide concentration

The real-time infiltration rate in a building is an important factor in controlling ventilation for energy saving and achieving acceptable indoor air quality. Recently, the occupant-generated CO2 tracer gas method has received considerable attention in that there is no need to inject a tracking gas and it can be easily calculated real-time infiltration rate through indoor and outdoor CO2 monitoring. However, data noise at low CO2 concentrations and a small drop in indoor concentrations during unoccupied periods can increase uncertainty in predicting infiltration rates. Besides, using an arbitrary reference value as the background CO2 concentration can lead to over or underestimation of the predicted values. The purpose of this study is to present an alternative form of the mass-balance equation for determining real-time infiltration rates and to review the issues that need to be considered in actual calculations. Field measurements were performed in a test room where four people work intermittently. In this study, an appropriate time interval setting method that exceeds the measurement uncertainty limit of the device is proposed, and a moving average technique is used to suppress noise signals in a low CO2 concentration. In addition, it is recommended to use the hourly average value of outdoor concentration and data with an indoor CO2 concentration higher than 1000 ppm. The originality of this work is to quantitatively analyze the uncertainty effect of outdoor carbon dioxide concentration information and to provide clear guidelines for determining the valid data interval carbon dioxide concentrations in predicting infiltration rates.

FC 052ACID-BASE BALANCE DURING IN-SERIES EXTRACORPOREAL CARBON DIOXIDE REMOVAL AND CONTINUOUS VENOVENOUS HEMOFILTRATION: PREDICTIONS FROM A MATHEMATICAL MODEL

Abstract Background and Aims Critically ill acute kidney injury (AKI) patients may require treatment by extracorporeal carbon dioxide removal (ECCO2R) devices to allow protective or ultraprotective mechanical ventilation and avoid hypercapnic acidosis. Continuous venovenous hemofiltration (CVVH) and ECCO2R devices can be arranged in series to form a single extracorporeal circuit; such a circuit has been proposed to be optimal, based carbon dioxide removal efficacy, if the ECCO2R device is placed proximal to the CVVH device (Allardet-Servent et al, Crit Care Med 43:2570-2581, 2015). Method We developed a mathematical model of whole-body, acid-base balance during extracorporeal therapy using in-series ECCO2R and CVVH devices for treatment of mechanically ventilated AKI patients. Equilibrium acid-base chemistry in blood was assumed as reported previously (Rees and Andreassen, Crit Rev Biomed Eng 33:209-264, 2005). Published clinical data from Allardet-Servent et al of mechanically ventilated (6 mL/kg predicted body weight or PBW) AKI patients treated by CVVH without ECCO2R were used to adjust model parameters to fit plasma levels of arterial partial pressure of carbon dioxide (PaCO2) and arterial plasma bicarbonate concentration ([HCO3]). The effects of applying ECCO2R at an unchanged tidal volume and a reduced tidal volume (4 mL/kg PBW) on PaCO2 and [HCO3] were then simulated assuming carbon dioxide removal rates from the ECCO2R device measured in the clinical study (91 mL of CO2/min when ECCO2R was proximal and 72 mL of CO2/min when CVVH was proximal). Results Agreement of model predictions with the clinical data was good, and model predictions were relatively independent of the in-series position of the devices (see Table). Total carbon dioxide removal from the CVVH device via ultrafiltration predicted by the model was lower after applying ECCO2R at both the unchanged tidal volume (25 mL of CO2/min when ECCO2R was proximal and 39 mL of CO2/min when CVVH was proximal) and the reduced tidal volume (30 mL of CO2/min when ECCO2R was proximal and 44 mL of CO2/min when CVVH was proximal). The reduced removal of total carbon dioxide via ultrafiltration when ECCO2R was proximal resulted from the lower total carbon dioxide concentration in blood entering the CVVH device. Thus, independent of the in-series position of the devices, the magnitude of this difference in total carbon dioxide removal by the CVVH device (14 mL of CO2/min) approximately cancels out the relative greater efficacy of the ECCO2R device (19 mL of CO2/min). Conclusion The described mathematical model has quantitative accuracy. It suggests that overall acid-base balance when using ECCO2R and CVVH devices in a single, combined extracorporeal circuit will be similar, independent of their in-series position.

The Well-Being of Children in Nurseries Does Not Have to Be Expensive: The Real Costs of Maintaining Low Carbon Dioxide Concentrations in Nurseries

There are different standards and regulations outlining the requirements regarding building air quality as well as in nurseries. These requirements specify air stream supplies and carbon dioxide concentration levels, both of which ensure proper indoor air quality. Mechanical ventilation should be used to maintain acceptable carbon dioxide levels. This article analyses the use of ventilation equipped with decentralized units, which helps secure the well-being of children. This paper proposes and evaluates economically affordable ventilation units. An algorithm for selecting the size of the devices is described by the supplied air stream depending on the number of children present at the nursery. A method of transferring the investment costs related to the assembly of the given units to the parents is proposed. Air quality in terms of CO2 concentrations was based on the following levels: 750 ppm, 1000 ppm, 1500 ppm. This assessment also includes the investment costs resulting from device usage and the costs of electricity consumed by the fans. These results showed the additional costs that assure the air quality improvement do not have to be high (45 PLN/month, ~10 EUR/month) per child attending the nursery. A 3% tuition increase returns the investment costs on mechanical ventilation within four years.

Recovery of methane and adding value to the digestate of biomass produced by high rate algal ponds or waste activated sludge, used to treat brewery effluent

There is an opportunity to anaerobically digest the sludge or algal biomass generated from the activated sludge (AS) and high rate algal pond (HRAP) brewery effluent treatment processes to produce methane, allowing the recovery of the carbon into a valuable product, prior to its disposal. This study evaluated the use of HRAP and AS waste biomasses for methane production during anaerobic digestion (AD), documented its efficiency, and described the digestate (waste) that was produced from the AD process. Brewery effluent grown algal and waste activated sludge (WAS) biomasses are suitable feed stocks for anaerobic digesters and this trial suggests that this process can be exploited commercially. It is recommended to operate WAS and algae fed anaerobic digesters at a total solids feeding rate of 1−2 g/lreactor/d and a hydraulic retention time of 17 days. The biogas yield of algal and WAS substrates was similar (Student t-test p > 0.05) with an average gas production of 241 mL/g volatile solids fed. Biogas from algae fed digesters had a significantly higher methane content (64.73 ± 0.81 %) and lower carbon dioxide content (22.94 ± 0.24 %) when compared to WAS fed digesters (60.08 ± 0.18 % and 27.37 ± 0.43 % respectively) due to it being a less oxidised substrate. The water quality parameters of the digestate from both WAS and algae fed digesters were similar (Student t-test p > 0.05) and has the potential to be used as a fertiliser in agriculture. The quality of this digestate as a fertiliser and its impact on the receiving soil needs to be researched.

Study on competitive adsorption characteristics of CO/CO2/CH4 multi-component low concentration gases in coal

ABSTRACT Coal spontaneous combustion indicator gases are one of the important indicators to judge coal spontaneous combustion, but coal spontaneous combustion is not the only source of these gases, the coal will also absorb these gases. Therefore, the study of gas adsorption characteristics in coal is of great significance for the prevention of coal fire. In this work, the adsorption characteristics of the low concentrations of carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4) in coal were studied and the competitive adsorption relationships among these three gases were identified by sorption isotherms. Experiments were performed on two coal samples from the Linnancang Coal Mine (LNC coal sample, named after the first word of the mine name) and Xixizhuang Coal Mine (XXZ coal sample, same as above), which were submitted to different gas atmosphere. A mathematical approach for calculating the adsorptive volume of each gas component under four experimental conditions was proposed, and the relationship between the adsorption capacities of CO, CO2 and CH4 and pressure was obtained during the adsorption and desorption. The results show that for the XXZ coal sample, the adsorption volume of CO under the maximum pressure conditions during the standard gas adsorption and desorption process is 7.7×10−2 mL/g, while the comparable values in gas-He, gas-CH4 and gas-CO2 are 3.5×10−2 mL/g, 1.9×10−2 mL/g, and 1.2×10−2 mL/g, respectively. The adsorption volumes of CO, CO2 and CH4 decrease with increasing pressure, but the decreasing trend is lower than that of standard gas adsorption under low-concentration conditions. The adsorption capacity of the desorption process under the same pressure conditions is greater than that of the adsorption process. In the adsorption state composed of CO, CO2, and CH4 gases, there are mutual constraints and influences between the gases, showing competitive adsorption behavior. Both CO2 and CH4 have obvious inhibitory effects on CO, while He does not inhibit CO adsorption.

Effect of packaging design with two functional films on the quality of figs stored at ambient temperature

This work aims to study the effect of a new packaging design with two functional films on the postharvest preservation of figs under ambient temperature (T = 25 ± 1°C, RH = 60 ± 5%). Water vapor permeable film, oxygen-permeable film, and polyethylene terephthalate tray were used to make the packaging. During the experiment, the gas composition in the packaging, water loss rate, hardness, appearance, and nutrient contents of figs were tested and recorded. The atmosphere with low oxygen composition and high carbon dioxide concentration was formed in the packaging. New packaging could reduce the water loss of figs and slow down the decrease of hardness and the loss of nutrients. The shelf life of figs was prolonged to 4 days under ambient temperature by functional films, while the control group was only 2 days. Practical applications Two kinds of functional films (Water vapor permeable film and oxygen-permeable film) were used to make a new packaging design for figs. The packaging could effectively prolong the storage time of fresh figs to 4 days under ambient temperature. It was of great significance to the storage, transportation, and sale of figs after harvest. Two kinds of functional films can also be used to preserve other fresh fruits and vegetables that are difficult to store.