CO2 Values Research Articles

A new approach for upgrading Biogas produced at a local wastewater treatment plant

<p>Biogas is globally recognized as a crucial source of renewable energy. After undergoing proper treatment, the purified form of biogas, known as "biomethane", has the potential to be injected into existing natural gas infrastructure or compressed for use as a vehicle fuel. The principal pollutants which cause a reduction in the energy density of biogas and impede its utilization, specifically in engines, are carbon dioxide, hydrogen sulfide, and siloxanes. Furthermore, the presence of carbon dioxide in biogas has a significant impact on global warming. In this study, the water scrubbing method, which is the most used method in biogas upgrading processes, was utilized due to its low operating cost. With the decreasing availability of clean water resources around the world and the challenges of utilizing them, the reuse of treated wastewater has become increasingly important. Therefore, in this study, treated wastewater was used as scrubbing water for biogas instead of clean water. In addition, the biogas used in the study is the gas produced in the wastewater treatment plant of a local municipality, thus contributing to the uniqueness of the study. Prior to upgrading, the biogas content produced in the plant had CH4 and CO2 values of 62% and 37%, respectively. However, after the implementation of upgraded technology, these values increased to 96% (CH4) and 3% (CO2). These results clearly demonstrate the success of the new method.</p>

Analysis of Chainsaw Emissions during Chestnut Wood Operations and Their Health Implications

In Italy, the use of chainsaws for field operations such as Felling (FE), Delimbing (DE), and Bucking (BU) is widespread due to the topography, the medium–small size of farms, and the predominant presence of broad-leaved forests managed through coppicing. However, this has led to an increase in injuries and illnesses due to exposure to physical factors (e.g., noise, dust, and vibrations) and chemical agents (e.g., various volatile compounds). Occupational health and safety legislation in Italy has undergone several phases, including the approval of U.T. 81/2008. The present study aims to evaluate the noise generated by chainsaws and the concentration of pollutants (CO, VOC, and C6H6) present in chainsaw exhaust gases during interventions in a chestnut coppice in relation to the limits set by current legislation. The analysis of the noise generated by chainsaws during chestnut cutting operations showed that it exceeded the legal noise limits during all chainsaw activities, with peak levels of about 110 dB. The detected noise could cause important critical issues in relation to the health and safety of specialized operators. Furthermore, the correlation between the specific work (FE, DE, and BU) and the ratio between maximum and average values of CO and VOC emissions was evaluated. Notably, comparable levels of maximum VOC emissions were observed during the FE and BU phases. However, the average emission values during these phases exhibited significant differences, suggesting higher VOC production when the engine was running but not actively engaged in cutting. The highest emissions were recorded during the FE phase (CO = 135 ppm, VOC = 17.28 ppm, and C6H6 = 2.13 ppm).

Statement of Retraction: Nursing application values of a new Co(II) complex on postpartum hemorrhage disease

Statement of Retraction: Nursing application values of a new Co(II) complex on postpartum hemorrhage disease

Kinetic Analysis of Catalytic Dry Reforming of Methane Using Ni-ZrO2/MCM-41 Catalyst

This work investigates the kinetics of catalytic dry reforming of methane (CDRM) to produce hydrogen gas using nickel-based catalysts. A new catalyst was prepared, Ni-ZrO2@MCM-41 (MCMZ) and used in the CDRM reaction. The textural, physical, and morphological scans are used to characterize the prepared catalyst. The performance of the newly prepared catalyst in terms of temperature effects and long-term stability is assessed. The reaction activation energy is studied as well. The outcomes of this study revealed that the MCMZ provided the highest conversion values for CH4 and CO2, with 89 and 91%, respectively. The optimum reaction temperature to achieve the highest syngas conversion was 800 °C. In addition, two new models that present CH4 and CO2 conversions for MCMZ as a function of reaction time to predict the rate of catalyst activity were built with very high accuracy. It was found that the activation energy was within the expected limits. Finally, the constants and reaction rate were determined. To conclude, this research creates a new catalyst with high performance to enhance hydrogen gas production from methane with carbon dioxide that contributes significantly to the field of yielding alternative energy sources.

Human biomonitoring of trace metals from different altitudinal settings of Pakistan.

Human biomonitoring of toxic trace elements is of critical importance for public health protection. The current study aims to assess the levels of selected trace metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) into paired human nail and hair samples (n = 180 each) from different altitudinal setting along the Indus River, and which were measured by using inductively coupled plasma mass spectrometry (ICP-MS). The human samples (hair and nail) were collected from four different ecological zones of Pakistan which include frozen mountain zone (FMZ), wet mountain zone (WMZ), riverine delta zone (RDZ), and low-lying southern areas (LLZ). Our results showed the following occurrence trends into studied hair samples: higher values (ppm) of Zn (281), Co (0.136), and Mn (5.65) at FMZ; Cr (1.37), Mn (7.83), and Ni (1.22) at WMZ; Co (0.15), Mn (11.89), and Ni (0.99) at RDZ; and Mn (8.99) and Ni (0.90) at LLZ. While in the case of nails, the levels (ppm) of Mn (9.91) at FMZ and Mn (9.38, 24.1, and 12.5), Cr (1.84, 3.87, and 2.33), and Ni (10.69, 8.89, and 12.6) at WMZ, RDZ and LLZ, respectively, showed higher concentration. In general, among the studied trace elements, Mn and Ni in hair/nail samples were consistently higher and exceeded the WHO threshold/published reference values in most of the studied samples (> 50-60%) throughout the Indus basin. Similarly, hair/nail Pb values were also higher in few cases (2-10%) at all studied zones and exceeded the WHO threshold/published reference values. Our area-wise comparisons of studied metals exhibited altitudinal trends for Cd, Cr, Zn, and Mn (p < 0.05), and surprisingly, the values were increasing from south to north (at higher altitudes) and indicative of geogenic sources of the studied toxic elements, except Mn, which was higher at lower floodplain areas. Estimated daily intake (EDI) values showed that food and drinking water had the highest contribution towards Zn, Cu, Mn, and Ni and accumulation at all studied zones. Whereas, dust also acts as the main exposure route for Mn, Co, Cr, and Cd followed by the food, and water.

Investigation of treatment volume versus circulating blood volume during Rheocarna treatment.

Rheocarna's therapeutic effect is associated with fibrinogen (Fib) and low-density lipoprotein cholesterol (LDL-C) adsorptive removal. This study aimed to retrospectively investigate the association between treatment volume (TV) and circulating blood volume (CBV) and the Fib removal rate (Fib-RR) and LDL-C-RR. CBV and TV/CBV, cut-off value (CO value), and area under the receiver operating characteristic (ROC) curve (AUC) were calculated. The Fib-RR and LDL-C-RR at the midterm and end of treatment were compared. The groups were further categorized into three groups with TV/CBV lower than or higher than the CO value at the midterm and end (midterm/end; Group L: lower than/lower than CO; Group L/H: lower than/higher than CO; Group H: higher than/higher than CO), and the Fib-RR and LDL-RR of each group at the midterm and end were compared. ROC analysis revealed a TV of 1.480 times the BV as CO value, which showed a maximum Youden index predicting a Fib-RR of 20% (AUC: 0.828). Among the three groups, Group L and Group L/H demonstrated significantly higher Fib-RR and LDL-C-RR at the end of the study than in the midterm, while Group H exhibited no difference. The results reveal that a treatment volume of 1.5 times the circulating blood volume is a sufficient solute removal capacity in the Rheocarna-enabled cases.

Stability study of flame structure using photodiodes in surface flame burners

Radiation spectroscopy can be effective in identifying pollutants and species. By examining a photodiode, the frequency peaks obtained from the analysis, and the range in which the cell flame is converted to a surface flame, we obtained the value ratio of the cell flame to the surface flame in the range of 0.7–0.74 in different powers. The frequency peak in this range decreases from the maximum value of 9.9823 Hz to its minimum value of 9.058 Hz in different powers. By analyzing the temperature compared to the frequency peak, we found that in the range of equivalence ratio 0.7–0.75, the frequency peak decreases from 9.5 to 9.9 Hz to 8.7–9 Hz. The temperature has an increasing behavior, and in the equivalence ratio, the temperature is in the range of 1400–1500 °C, i.e., at its maximum value. We observed the cell formation process and its conversion to surface flame by flame detection. The flame height in the cellular and superficial regions is in the range of 0.65–0.85, which is the minimum flame height of 3–10 mm, and NO and CO were examined in the ratio of different equations and compared with temperature. In the ratio equivalence ratio of 0.77–0.81 in the temperature range of 1500 °C (maximum), the value of NO is about 16 ppm (maximum), and the value of CO is about 2 ppm (minimum). That is, when the temperature is at its maximum, it becomes CO minimum and NO maximum. This can be used for different applications such as similar and industrial burners.

Diagnosis of multiple gases using a multi-pass ring cavity to enhance Raman scattering

Spontaneous Raman scattering is widely used to enable simultaneous concentration measurements of all relevant species with overcomes whose signal is weak and susceptible to fluorescence interference. A multi-pass ring-cavity scheme is proposed to enhance Raman scattering signal. The Raman spectra of CO2, N2, O2 and H2O in the air are acquired under condition of low excitation power which is 200 mW laser of 532 nm. Compared with the results obtained by single collection without ring cavity, the Raman signal level is enhanced 40 times and the signal-to-noise ratio is improved by 43 times at maximum. Power of pump is taken into consideration to analyze its impact on signal. A limit of detection (3σ criterion standard) of 83 ppm for CO2 is calculated for the multi-pass ring-cavity. The limit of detection of 14 ppm for CH4 is also estimated by the theoretical ratio of cross section values of CO2 and CH4. When power of excitation is low, high level of signal of multi-species gases is acquired with fine detection sensitivity through ring cavity.

Mediterranean Wildfires’ Effect on Soil Quality and Properties: A Case from Northern Euboea, Greece

Mediterranean Wildfires’ Effect on Soil Quality and Properties: A Case from Northern Euboea, Greece

Numerical investigation of combustion in a panela furnace using openfoam

To develop biomass combustion as a viable renewable energy source it is necessary to improve the furnace efficiency and investigate the potential of agricultural wastes as fuels. Computational Fluid Dynamics (CFD) modeling is a valuable tool to accomplish these objectives, OpenFOAM is a powerful open-source CFD software that has been little used in this type of application. This paper reports the study of combustion in a device of great importance for Colombia, the panela furnace, using a model developed in OpenFOAM. The combustion chamber of a Ward-Cimpa furnace, measuring 2.68 m in width and 3.32 m in height was modeled. This model was validated, by comparing the simulated values of CO and temperature at the furnace exit with data taken from literature, resulting in differences of 13.72 % and 12.23 % respectively. These discrepancies are slightly lower than those reported in other studies about the subject. The model was employed to analyze the effect of the air-flow rate on the combustion performance. The findings indicate that the increase in air-flow causes an increase in combustion activity manifested in higher temperature and CO2 emissions, which could indicate that in common operational conditions, the furnace operates under deficient air conditions and its performance could be improve by using higher air flow rates.

Estimation of the main air pollutants from different biomasses under combustion atmospheres by artificial neural networks

The production of biofuels to be used as bioenergy under combustion processes generates some gaseous emissions (CO, CO2, NOx, SOx, and other pollutants), affecting living organisms and requiring careful assessments. However, obtaining such information experimentally for data evaluation is costly and time-consuming and its in situ obtaining for regional biomasses (e.g., those from Northeast Brazil (NEB) is still a major challenge. This paper reports on the application of artificial neural networks (ANNs) for the prediction of the main air pollutants (CO, CO2, NO, and SO2) produced during the direct biomass combustion (N2/O2:80/20%) with the use of ultimate analysis (carbon, hydrogen, nitrogen, sulfur, and oxygen). 116 worldwide biomasses were used as input data, which is a relevant alternative to overcome the lack of experimental resources in NEB and obtain such information. Cross-validation was conducted with k-fold to optimize the ANNs and performance was analyzed with the use of statistical errors for accuracy assessments. The results showed an acceptable statistical performance for all architectures of ANNs, with 0.001–12.41% MAPE, 0.001–5.82 mg Nm−3 MAE, and 0.03–52.30 mg Nm−3 RMSE, highlighting the high precision of the emissions studied. On average, the differences between predicted and real values for CO, CO2, NO, and SO2 emissions from NEB biomasses were approximately 0.01%, 10−6%, 0.14%, and 0.05%, respectively. Pearson coefficient provided consistent results of concentration of the ultimate analysis in relation to the emissions studied and effectiveness of the test set in the developed models.

Two-component intra-cavity photoacoustic spectroscopy sensor using Y-shaped photoacoustic cell with two resonant cavities

In this paper, an intra-cavity photoacoustic spectroscopy (PAS) gas sensing system based on a 3D printed Y-shaped PAS cell with two longitudinal resonant cavities is designed for two-component detection. The sensor embeds the Y-shaped photoacoustic cell in the resonator of fiber ring laser for the intra-cavity gas detection, improving the laser power in the gas detection. The two resonant cavities of the Y-type PAS cell are formed into C-band and the L-band lasers, guaranteeing the laser stable output of C-band and the L-band. Comparing with the conventional dual-wavelength laser, the dual-wavelength laser scheme proposed in the paper eliminates the model competition and possesses much higher laser stability. A dedicated wavelength modulator is used to control the fiber bragger grating (FBG) to generate the stress change, and then scan the absorption peaks of the corresponding gases. The second harmonic (2f) PAS signal is used to calculate the gas concentration. The acetylene (C2H2) and carbon dioxide (CO2) were detected based on the frequency division multiplexing (FDM) technique using two resonant cavities. A microphone is used to simultaneously detect the photoacoustic signals of two resonance cavities. A demodulation frequency with a frequency intervals of 100 Hz ensures there is no cross-interference in demodulation of signals from each resonant cavity. The trace detection of C2H2 and CO2 was realized at normal temperature and pressure. The PAS signal intensity was further improved by optimizing the modulation amplitude and incident laser power. The minimum detection limits (MDLs) and the linear fit R-squared values (R2) of C2H2 and CO2 were 529 ppbv, 0.99971, 282 ppmv and 0.99991, respectively. It indicates that the two-component gas sensing system in this paper has good linearity and high sensitivity. It provides a valuable trace gas detection device for multi-component gas detection.

Diagnosing the Quasi-Equilibrium Response of ENSO Variability under a Range of CO2 Levels

Abstract Several recent studies have highlighted differences in simulated properties of El Niño–Southern Oscillation (ENSO) under transient and equilibrium responses to increasing CO2. However, the reasons behind these disparate responses and the extent to which they are robust to different scales of CO2 forcing remain unclear. In this study, we adopt a climate system model with reduced SST bias in the eastern tropical Pacific and incrementally apply abrupt increases in CO2, analyzing outputs after each simulation reaches quasi-equilibrium with the imposed forcing. The results suggest that ENSO activity under quasi-equilibrium first increases and then decreases with increasing CO2, peaking in simulations with CO2 concentrations similar to the present day. Bjerknes–Jin stability analysis indicates that changes in the ENSO growth rate result primarily from changes in the thermocline feedback and thermodynamic damping terms. While thermodynamic damping increases monotonically with increasing CO2, the positive thermocline feedback varies within the range of internal variability up to twice the preindustrial value of CO2 and then weakens sharply with further increases. The mechanisms behind these changes include weaker mean ocean upwelling and weaker dynamical coupling between the atmosphere and subsurface ocean associated with substantial near-surface freshening at higher levels of CO2. These changes steepen the thermodynamic barrier to mixing between the surface and subsurface, weakening the east–west temperature gradient in the mean state and suppressing variability in the cold tongue. Analysis of similar model simulations from the Coupled Model Intercomparison Project (CMIP6) archive indicates that changes in the Bjerknes–Jin stability index are robust but do not establish a consensus as to the mechanisms behind them. Significance Statement This study investigates how El Niño–Southern Oscillation changes with increasing CO2 forcing by using a global model with improved tropical Pacific climate. The simulations roughly correspond to scenarios in which emissions are reduced to maintain CO2 concentrations at near-constant values over a long period, with levels ranging from about 2/3 to more than 5 times the present-day concentration. Analysis of these simulations suggests that ENSO activity is strongest when CO2 concentrations are similar to the present-day and becomes substantially weaker when CO2 is more than double its present-day value. Reduced ENSO activity with further increases in CO2 is caused by weaker interactions between the atmosphere and the subsurface ocean. Both the amplitude of warm (El Niño) events and the occurrence frequency of warm and cold (La Niña) events decrease as ENSO events become first more difficult to grow and then more difficult to trigger with increasing CO2.

A review of the Indian Ocean carbon dynamics, acidity, and productivity in a changing environment

The Indian Ocean dynamics is governed by the seasonal reversal of monsoon winds and the associated ocean currents. The relatively deep thermocline along the equator due to a lack of steady easterlies, low-latitude connection to the neighbouring Pacific, and a lack of northward heat export due to the position of the Asian continent are important factors in regulating the ocean state. These features make it a unique ecosystem among the world's tropical oceans and determine key features of potential air-sea interaction at different time scales. The pCO2 shows a large seasonal variation linked with monsoon circulation. The Indian Ocean’s northwestern part acts as an atmospheric CO2 source, whereas the northeastern part acts as a net atmospheric CO2 sink. The region between the latitudes of 15°S-50°S in the Indian Ocean is a major subduction zone because of positive wind stress curl. The subducted water masses are transported to the northern Indian Ocean by the cross-equatorial cell (a shallow meridional overturning circulation). Based on the regional studies carried out on the carbonate system in the Indian Ocean, the area north of 15°S is a source of atmospheric CO2, while the area between 15°S and 50°S is a sink. A recent synthesis of models (observational climatology) over different spatial scales provides an estimate of the mean value of CO2 in the north of 37.5°S of the Indian Ocean as − 0.19 ± 0.1 PgC/yr (−0.07 ± 0.14 PgC/yr) during 1985–2018. The estimated decrease in pH (acidification) using model outputs in the Indian Ocean basin is 0.0675 units during 1961–2010, in which the contribution of dissolved inorganic carbon and surface temperature is 69.3 % and 13.8 %, respectively. The range of the Indian Ocean’s annual primary production based on satellite estimates over the last two decades (1998–2018) is 7.72–8.70 Gt C/yr, whereas the climatological mean is 8.24 ± 0.30 Gt C/yr. This paper consolidates the current state of understanding of the Indian Ocean carbon fluxes, acidification, and productivity using available field and satellite-based measurements, model simulations, and re-constructed datasets. It provides an overview of the functioning of the Indian Ocean’s air-to-sea CO2 exchange and highlights its influence on global climate. Finally, it aims to highlight the grey areas of the Indian Ocean carbon cycle that need to be understood.

Venous-to-arterial carbon-dioxide tension difference as a useful predictor of patient prognosis after major surgery

PurposeChange in venous-to-arterial carbon dioxide partial pressure difference[P(v-a)CO2] could be a useful marker to assess tissue perfusion status. Herein, we assessed the predictive values of postoperative P(v-a)CO2 measurements for mortality in critically ill patients after major surgery. The correlation between P(v-a)CO2 values and other conventional parameters of patient prognosis was also evaluated. MethodsPatients admitted to the intensive care unit(ICU) after abdominal surgery were enrolled. Arterial and venous blood gas analyses were performed within 1 h(T0) and after 24 h(T1) of admission to the ICU, respectively. The relationship between P(v-a)CO2 levels at T1 and other conventional parameters were assessed using a Bland-Altman plot. Logistic regression analysis was performed to examine the predisposing factors of mortality after surgery. ResultsA total of 231 patients were finally analyzed. We divided the participants into the high PvaCO2 group[P(v-a)CO2 ≥ 8.6] and the low PvaCO2 group[P(v-a)CO2 < 8.6]. Seven-day-, 28-day, and in-hospital mortality were significantly higher in the high PvaCO2 group than in the low PvaCO2 group. There was significant agreement between P(v-a)CO2 values at T1 and APACHE II scores, lactate levels at T1 and total SOFA scores at T1. In multivariate logistic analysis, an increased P(v-a)CO2 value at T1 was the only significant risk factor of 7-day mortality after surgery. [odds ratio:1.341, 95%confidence interval: 1.050–1.714, p=0.019]. ConclusionP(v-a)CO2 measurements could be not only a significant predictor of postoperative prognosis, but also a useful surveillance parameter to maintain tissue perfusion after abdominal surgery in patients with a potential risk of fatal complication-related tissue hypoperfusion.

Towards a Miniaturized Photoacoustic Sensor for Transcutaneous CO2 Monitoring.

A photoacoustic sensor system (PAS) intended for carbon dioxide (CO2) blood gas detection is presented. The development focuses on a photoacoustic (PA) sensor based on the so-called two-chamber principle, i.e., comprising a measuring cell and a detection chamber. The aim is the reliable continuous monitoring of transcutaneous CO2 values, which is very important, for example, in intensive care unit patient monitoring. An infrared light-emitting diode (LED) with an emission peak wavelength at 4.3 µm was used as a light source. A micro-electro-mechanical system (MEMS) microphone and the target gas CO2 are inside a hermetically sealed detection chamber for selective target gas detection. Based on conducted simulations and measurement results in a laboratory setup, a miniaturized PA CO2 sensor with an absorption path length of 2.0 mm and a diameter of 3.0 mm was developed for the investigation of cross-sensitivities, detection limit, and signal stability and was compared to a commercial infrared CO2 sensor with a similar measurement range. The achieved detection limit of the presented PA CO2 sensor during laboratory tests is 1 vol. % CO2. Compared to the commercial sensor, our PA sensor showed less influences of humidity and oxygen on the detected signal and a faster response and recovery time. Finally, the developed sensor system was fixed to the skin of a test person, and an arterialization time of 181 min could be determined.

Environmental data monitoring and infection risks in UK care-homes in the context of COVID-19

The COVID-19 pandemic drew attention to the critical role of building ventilation as a measure for controlling infection transmission. With the substantial number of COVID-19 outbreaks in care homes worldwide, the effectiveness of ventilation is an important consideration for infection control and wider exposure to indoor air pollutants. In this study, we used IoT-based sensors in two residential care homes to evaluate ventilation in various areas, including bedrooms, corridors, and communal spaces. Our monitoring focused on carbon dioxide (CO2) levels as a proxy for ventilation, as well as temperature and humidity, during the spring of 2022. We also developed a ventilation model using the software CONTAM and coupled it with an infection risk model to assess airborne transmission risks under different weather and occupancy conditions. Our results suggest that ventilation is generally adequate based on UK COVID-19 guidelines at the time, with CO2 below 800 ppm for the majority of the time, and opening windows in communal spaces in elderly care environments can help preserve indoor ventilation during periods of high occupancy. However, modelling data suggests that low CO2 values may be indicative of low occupancy in many spaces and therefore ventilation rates may not be sufficient to mitigate infection transmission. Encouraging positive ventilation behaviours in staff and residents, potentially supported by visible CO2 monitors, and taking additional precautions such as using air cleaners, enabling additional window openings or staff wearing masks during outbreaks and periods of high disease prevalence is likely to be beneficial for resident and staff health.

Techno-economic assessment of the CO2 value chain with CCUS applied to a waste-to-energy Italian plant

Recently, post-combustion CO2 removal has been considered also for the CO2 separation from the flue gases of Waste-to-Energy (WtE) plants, that manage high amounts of Municipal Solid Waste (MSW) by combusting it and generating power and heat. Moreover, because of the presence in MSW of an organic waste fraction, net negative CO2 emissions are feasible when integrating CCUS systems into WtE plants. Currently, to the best of the authors’ knowledge, there are only few incineration plants around the world that are successfully coupled with a carbon capture system, resulting in near-zero (or even negative) CO2 emission power generation.This work focuses on the evaluation of the whole value chain of the non-biogenic CO2 that is emitted in a power plant located in Northern Italy and on its possible utilization, from the CO2 source in the flue gas to the market-ready product.The design of the process for the CO2 removal from the flue gas has been carried out specifically for the considered flue gas to be treated with an aqueous solution of MonoEthanolAmine 30% wt., the benchmark solvent used in other types of power plants (fuelled by coal and natural gas). The main process parameters (e.g., lean loading, absorber packing height, regenerator packing height, regenerator pressure, gas inlet temperature, solvent inlet temperature) have been selected in order to optimize the reboiler duty and the water requirement, the latter being usually not considered in literature works dealing with this type of analysis. Then, the CO2 utilization has been evaluated, considering the options of both sequestration in the Adriatic Sea and utilization of CO2 for production of sodium bicarbonate, on the basis of the information available in the literature.In compliance with Directive 2003/87/EC and with the Italian legislation, Waste-to-Energy plants that treat municipal solid waste are currently exempt from the application of the CO2 Emissions Trading System (ETS). This article speculates about the application of the ETS to an urban WtE plant, located in Northern Italy, and evaluates its economic implications by comparing the purchase of emission quotas with the construction of a CCS or CCU plant.A business plan, detailing the obtained revenues from the utilization and from the avoided cost of purchasing emission allowances and the expenses related to the operation of the carbon capture plant, taking into account the taxes and the inflation, has been created and used for comparing the two considered CO2 value chains. For the option of CO2 sequestration, sensitivity analyses on the variation of investment costs (+10 %), operating costs (+10 %) and revenues (−10 %) have been performed and the breakeven value of the ETS certificate that can make the Net Present Value (NPV) non-negative has been determined. For the option of CO2 utilization, the revenue from sodium bicarbonate that can make its production profitable has been evaluated.

Assessing the Settling Velocity of Biofilm-Encrusted Microplastics: Accounting for Biofilms as an Equivalent to Surface Roughness.

While it is well established that a biofilm contributes to the sinking of plastics, the underlying mechanisms of how it influences the vertical transport of plastics have not been well explained. In this context, our study dives into the intricate effects of biofouling on the settling velocity (Ws) of microplastics (MPs) within the fluid. We adopt the perspective that the biofilm is a form of surface roughness impacting the drag coefficient (Cd) and vertical settling of MPs. By advancing the biofouling process model, we simulate the temporal variations of density and biofilm thickness of biofouled floating MPs, accounting for realistic parameters and assuming a layer-by-layer growth of biofilm on plastisphere surfaces. MPs of polyethylene (PE) exhibit a quicker initiation of descent compared to their polypropylene (PP) counterparts. Furthermore, leveraging computational fluid dynamics (CFD) simulation, the method to predict the Cd of spherical MPs with surface roughness is established. By treating the thickness of the biofilm as roughness height, an explicit method to predict the Ws of biofouled MPs is derived. The settling experiments for biofouled MPs conducted not only support the combination of the biofouling model and the explicit method to predict the Ws of biofouled MPs but also enhance the prediction accuracy by introducing a ratio parameter Co to better relate the equivalent surface roughness height (k) to the biofilm thickness (σ), i.e., k = Co·σ, where the recommended value of Co for spherical PP and PE MPs is between 0.5 to 0.8. This study, thus, provides new insights into the dynamics of biofouled MPs in hydraulic ecosystems.

Effects of compression ratio on the performance and emission levels of a CI engine fueled with safflower oil methyl ester through an engine simulation approach

In recent years, the research community has shown significant interest in the potential of biodiesel as a renewable alternative to conventional fossil-based fuels. Nevertheless, the experimental investigation of the effects of diverse biodiesel formulations on internal combustion engines demands a significant investment of time and financial resources. Consequently, the numerical alternative methodologies are advocated as a viable substitute for practical experiments. Numerical simulations offer the opportunity for a meticulous examination of the characteristics of internal combustion engines under diverse operational conditions and various biodiesel blends, thereby optimizing efficiency and cost-effectiveness. This study focused on the simulation of performance and emission characteristics of a diesel engine running on safflower (Carthamus tinctorius L.) oil methyl ester (SOME) and traditional diesel fuel using AVL simulation software. Furthermore, the simulation results were compared with a laboratory study carried out under identical conditions. The simulated engine underwent testing across various compression ratios (CRs) (ranging from 12:1 to 18:1) and engine loads (from 25% to full load) while sustaining a consistent speed of 1500 rpm. The simulation findings revealed that the engine exhibited its highest BSFC as 0.495 kg/kWh with SOME fuel, at a CR of 12:1, modestly lower than the corresponding experimental observation of 0.520 kg/kWh. Concurrently, the lowest value of BSFC, recorded as 0.267 kg/kWh with diesel fuel and a CR of 18:1, demonstrated a marginal deviation from the experimental result of 0.281 kg/kWh. Additionally, SOME fuel usage was correlated with diminished CO and HC emissions. The experimental findings indicated the lowest value of CO and HC emissions, as 0.14% and 21.7 ppm, respectively, with SOME fuel at a CR of 18:1, marginally below the simulation-derived values of 0.13% and 20.8 ppm. Conversely, diesel fuel at a CR of 12:1 exhibited maximal CO and HC emissions, registering 0.38% and 199.5 ppm, respectively, in the experimental study. In comparison, the simulation values were slightly lower at 0.36% and 194.1 ppm. Moreover, the experimental investigation identified SOME fuel as yielding the highest CO2 emission, reaching a peak of 11.9% under a CR of 18:1, while the simulation showed a slightly lower value of 11.2%. In contrast, diesel fuel at a CR of 12:1 resulted in the lowest CO2 emission at 3.85% in the experiment, with the simulation reporting a slightly reduced value of 3.77%. Regarding NOx emissions, the experiment recorded the peak at 1687 ppm with SOME fuel and a CR of 18:1, slightly surpassing the simulation’s value of 1643 ppm. Conversely, the experimental data indicated the lowest NOx emission as 103 ppm with diesel fuel and a CR of 12:1, with the simulation suggesting a slightly lower value of 98.2 ppm under identical conditions. The simulation results demonstrated favorable concordance with experimental findings, notably strengthening with an increase in CR.