CO2 Levels Research Articles

Analyzing the environmental impact of fuel switching: Evidence from ARDL analysis for policy considerations

The rise in global temperatures, driven by increased CO2 levels, is a pressing concern. Developing nations like Malaysia face challenges in transitioning to cleaner energy due to resource constraints, making natural gas a crucial transitional solution. This study introduces the Fuel Switch Variable to analyze the impact of shifting fuel consumption patterns on CO2. Using data from 1980 to 2020 and the ARDL model, findings show that policies promoting natural gas over oil and coal reduce CO2 emissions, while economic and population growth increase emissions. Policymakers should incentivize fuel switching, enforce energy efficiency standards, and invest in new technologies.

Remittance and carbon dioxide emissions in the Southern African Customs Union region: Is there a modified environmental Kuznets curve?

The remittance-carbon dioxide (CO2) emissions nexus remains a hotly debated topic in the literature, with the majority of studies offering mixed conclusions. This study attempts to reconcile these disparities by investigating the nonlinear effect of remittances on the CO2 emissions in top-remittance receiving countries in Southern African Customs Union (SACU) region, using the modified Environmental Kuznets Curve framework which focuses on the effect that remittances might have on CO2emissions. The Cross-Sectional Autoregressive Distributed Lag (CS-ADRL) approach is applied to these top-remittance receiving countries from 1990 to 2020, representing a pioneering investigation for these countries. The finding of this study reveal that both the estimated coefficient of remittances and its quadratic term are statistically significant, with remittances displaying a positive coefficient and the quadratic term exhibiting a negative coefficient. This pattern confirms the presence of a modified EKC hypothesis, meaning as remittances increases, CO2 levels displays an unambiguous inverted U-shaped trajectory.

Impact of Soybean Biodiesel Blends with Mixed Graphene Nanoparticles on Compression Ignition Engine Performance and Emission: An Experimental and ANN Analysis

The extensive use of fuels in power generation plants, industries, and transportation has led to a scarcity of fossil fuels and has contributed to global warming. This has prompted researchers to focus on improving internal combustion engine performance, as the transportation system accounts for 50% of global fuel consumption. Soybean biodiesel plays a vital role in reducing emissions and fuel consumption in engines. In the current work, a blend of soybean oil is used as a biodiesel (B20, B40, and B60), with and without the addition of graphene nanoplatelets (GNPs) examined on a constant-speed compression ignition (CI) engine with respect to pure diesel. The blends are denoted as B20GNP10, B20GNP20, B20GNP40, B20GNP60, B20GNP80, and B20GNP100, according to their proposition of biodiesel and graphene nanoplatelets. Similar blends were prepared for B40 and B60 combinations with similar GNPs concentrations. The prepared blend properties were measured, and good thermophysical properties were found. The trial includes testing the engine emissions and performance at altering loads ranging from 0 to 12 kg for all blends. The artificial neural network (ANN) tool is used to forecast the accuracy of experimental results. Compared to pure diesel, the B60GNP100 blend at 12 kg load condition showed the lowest brake specific fuel consumption at 12.58 % and the highest brake thermal efficiency at 27.13%. Emissions were estimated using a gas analyzer, and the outcomes indicated that the biodiesel blends have controlled levels of CO, CO2, NOx, and HC compared to pure diesel. The ANN model with 99.99% accuracy was developed using experimental data, confirming the accuracy of the experimental results with lower simulation time and cost. Additionally, the B60GNP100 blend yielded better results compared to previous studies.

Influence of Organic Compounds on Ni, Co, Cu, Cr, and Pb Accumulation by Nodules in Agro-Dark-Humus Podbels (Planosols) in the South of Primorskii Region

The involving of organic compounds in accumulation of Ni, Co, Cu, Cr, and Pb by Fe–Mn nodules in agro-dark-humus podbels (Planosols (Aric)) under different types of long-term agrotechnical impact has been studied in the south of Primorskii region. The profile patterns of the level of SOC content in soils and in nodules indicate the active deposition of organic compounds in nodules in the lower parts of soil profiles in the of fallow and phytomeliorative variants of the experiment. Fulvic acids were noted to predominate in the composition of humus in the nodules in these variants. The long-term application of organic fertilizers contributed to the decrease of SOC incorporation into nodules and to the increase of the part of humic acids in nodules. Nodules were characterized by a high accumulation levels of Co and Pb in all variants of the experiment. Accumulation of Ni, Cr, and Cu was recorded in nodules from particular horizons of studied soils. The intensity of elements accumulation in nodules of different variants of the experiment varied. Accumulation of Ni was controlled by the content of Mn-containing compounds. The most active sorption phases of nodules from soils with a longer period of organic matter transformation (fallow variant and long-term addition of manure variant) were Fe-containing and organic compounds.

Extreme drought events and land surface temperature variations on the northeastern Tibetan Plateau over the last 350 ka

The northeastern Tibetan Plateau (NETP) is located in the ecologically vulnerable northwestern China, with semi-humid and semi-arid conditions. Long-term paleo-hydrological and paleo-temperature variations and their mechanisms over the NETP remain ambiguous, primarily due to the limited availability of well-dated, long-term depositional archives and suitable proxies. In this paper, we investigate climate variations and their underlying mechanisms in the region using Glycerol Dialkyl Glycerol Tetraethers (GDGTs) spanning the last 350 ka. Our results suggest that the NETP underwent substantial drying during glacial periods, with the driest period occurring during the last glacial period. The intensity of drought during glacial periods is comparable to that in the Westerlies-dominated region but differs from that in the East Asian monsoon region. This suggests that the influence of the Westerlies surpassed that of the East Asian summer monsoon (EASM), becoming the major driver of warm-season drought events on the NETP during glacial periods. Additionally, the peaks of aridity events coincide with summer insolation maxima during glacial periods, which may be related to the direct influence of local insolation on regulating evaporation. The reconstructed land surface temperatures were about 6.7 °C during interglacial periods and 2.6 °C during glacial periods, which may be linked to a combination of variations in insolation, CO2 levels, and other internal feedback mechanisms. However, an unusual warming occurred during the last glaciation, with an average temperature of about 4.8 °C. This warming may be related to variations in soil moisture and vegetation resulting from extreme drought. Our study highlights the sensitivity of hydrological variations over the NETP to insolation and Westerlies, as well as the critical roles of soil moisture and vegetation in land surface temperature variations.

Impact of Diluents on Flame Stability With Blends of Natural Gas and Hydrogen

Abstract Two potential decarbonization pathways for natural gas (NG)-fueled gas turbine engines include blending hydrogen (H2) into NG and postcombustion carbon capture. H2 blending changes several combustion properties, including flame speed and stretch sensitivity. The use of post-combustion carbon capture systems is typically facilitated by the implementation of exhaust gas recirculation (EGR), where exhaust gases are injected into the inlet of the engine, increasing carbon dioxide (CO2) concentration at the outlet and, hence, increasing the efficiency of carbon capture technologies. In this work, we explore the impact of H2 blending and EGR on the stability of a swirl-stabilized, central-piloted flame. Mixtures of NG and H2 are tested at a range of different diluent compositions, with oxygen varied from 21% to 15% by volume in the oxidizer. In all cases, a constant adiabatic flame temperature is maintained to mimic the operation of a gas turbine at a given turbine inlet temperature. A variable-length combustor is used for testing, where combustor length is varied to understand the dynamic stability characteristics of the system. Results show that EGR and H2 work in opposition to each other, where higher levels of EGR result in poor flame holding and higher levels of H2 result in better flame holding. Increasing H2 generally increases the amplitude of thermoacoustic instability at each condition, a result of the change in flame position in this particular combustor. Importantly, H2 can be added to NG to improve flame holding without significantly decreasing CO2 levels in the products, showing that H2 blending can be a method for counteracting combustor operability issues that arise from high levels of EGR necessary to improve the efficiency of typical carbon capture systems.

Effect of Separating Air into Primary and Secondary in an Integrated Burner Housing on Biomass Combustion

Pellet burners, although they are commonly used devices, require high-quality fuels and yet are characterized by relatively high levels of CO and NO emissions and their variability. This article presents a combustion study of an original biomass burner that separates air into primary for biomass gasification and secondary for oxidizing the gasification products, with ducts placed in the housing of the burner. This study introduces a new burner design that separates air into primary and secondary streams within an integrated burner housing, aiming to optimize biomass combustion efficiency and reduce harmful emissions. Two burner designs were proposed, with a high secondary air nozzle (HCrown) and a low secondary air nozzle (LCrown). These two burners were compared with a typical retort burner (Ret). The LCrown burner reduced particulate matter emissions by 36% and CO emissions by 74% with respect to a typical retort burner. This study showed that the distance of the secondary air nozzles from the gasifying part has a significant impact on the operation of the burner and the possibility of reducing emissions of CO and NO. These results highlight the potential of the innovation to significantly improve combustion quality while simultaneously reducing environmental impact.

An integrated experimental-modeling approach to identify key processes for carbon mineralization in fractured mafic and ultramafic rocks.

Controlling atmospheric warming requires immediate reduction of carbon dioxide (CO2) emissions, as well as the active removal and sequestration of CO2 from current point sources. One promising proposed strategy to reduce atmospheric CO2 levels is geologic carbon sequestration (GCS), where CO2 is injected into the subsurface and reacts with the formation to precipitate carbonate minerals. Rapid mineralization has recently been reported for field tests in mafic and ultramafic rocks. However, unlike saline aquifers and depleted oil and gas reservoirs historically considered for GCS, these formations can have extremely low porosities and permeabilities, limiting storage volumes and reactive mineral surfaces to the preexisting fracture network. As a result, coupling between geochemical interactions and the fracture network evolution is a critical component of long-term, sustainable carbon storage. In this paper, we summarize recent advances in integrating experimental and modeling approaches to determine the first-order processes for carbon mineralization in a fractured mafic/ultramafic rock system. We observe the critical role of fracture aperture, flow, and surface characteristics in controlling the quantity, identity, and morphology of secondary precipitates and present where the influence of these factors can be reflected in newly developed thermo-hydro-mechanical-chemical models. Our findings provide a roadmap for future work on carbon mineralization, as we present the most important system components and key challenges that we are overcoming to enable GCS in mafic and ultramafic rocks.

Monitoring the Net Primary Productivity of Togo’s Ecosystems in Relation to Changes in Precipitation and Temperature

Climate variability significantly impacts plant growth, making it crucial to monitor ecosystem performance for optimal carbon sequestration, especially in the context of rising atmospheric CO2 levels. Net Primary Productivity (NPP), which measures the net carbon flux between the atmosphere and plants, serves as a key indicator. This study uses the CASA (Carnegie–Ames–Stanford Approach) model, a radiation use efficiency method, to assess the spatio-temporal dynamics of NPP in Togo from 1987 to 2022 and its climatic drivers. The average annual NPP over 36 years is 4565.31 Kg C ha−1, with notable extremes in 2017 (6312.26 Kg C ha−1) and 1996 (3394.29 Kg C ha−1). Productivity in natural formations increased between 2000 and 2022. While climate change and land use negatively affect Total Production (PT) from 2000 to 2022, they individually enhance NPP variation (58.28% and 188.63%, respectively). NPP shows a strong positive correlation with light use efficiency (r2 = 0.75) and a moderate one with actual evapotranspiration (r2 = 0.43). Precipitation and potential evapotranspiration have weaker correlations (r2 = 0.20; 0.10), and temperature shows almost none (r2 = 0.05). These findings contribute to understanding ecosystem performance, supporting Togo’s climate commitments.

Adaptive strategies and thermal perceptions in intermittently used congregational Spaces: A case study

In spaces with considerable volumes that are sporadically used and typically not operating at full capacity, existing thermal comfort models face limitations. This research aims to reveal disparities between these models and survey-based comfort assessments. Comfort calculations were conducted using conventional thermal comfort models based on measured parameters and compared with survey data. Notable differences prompted the formulation of a more robust correlation, accounting for 83.4 % of the variations in Predicted Mean Votes (PMV). A regression model derived from survey data shows a high coefficient of determination (R2 = 0.84), supporting its applicability for large intermittently used spaces like mosques. Addressing limitations of existing models, this research introduces a practical and simplified approach to predicting thermal comfort, enhancing assessments in these distinctive spaces. The study also examines mosque indoor air quality dynamics. Despite sporadic ventilation, CO2 levels rose from 1500 ppm to 2500 ppm during Friday prayers, posing potential health risks. Before prayers, indoor CO2 and humidity met ASHRAE Standard 62, ISO 7730, and EN15231 values. To mitigate health concerns from elevated CO2 levels, improved ventilation systems are necessary. Comfort temperatures were only achieved during prayer periods.

Experimental study on coal oxidation and temperature rise under different air leakage modes due to atmospheric pressure changes

ABSTRACT The spontaneous combustion of residual coal in enclosed goafs may induce coupled thermodynamic disasters with severe consequences. To study the dynamic characteristics of coal oxidation and temperature increase in an enclosed goaf under varying atmospheric pressure conditions, the air leakage model was analyzed through theoretical derivation. The resistance, temperature, and CO concentration during coal oxidation under different air leakage modes were further studied using a self-built experimental system. The results indicated three air leakage modes of coal oxidation in an enclosed goaf: constant, intermittent, and reciprocating. The resistance of the three modes increased from 5 Pa to 7 Pa with time. Compared to constant air leakage, the time of resistance change was advanced by 1428 s and 1897 s under intermittent and reciprocating air leakage, respectively. Additionally, both intermittent and reciprocating air leakage promote coal oxidation and produce higher CO levels compared to constant air leakage. However, intermittent air leakage is more likely to produce higher temperature points, while reciprocating air leakage is more likely to cause large areas of coal oxidation. The order of the promoting effect of the intermittent and reciprocating half cycle on coal oxidation is 60 s, 300 s, 600 s, and 1200 s. These results are significant for understanding coal spontaneous combustion and efficiently managing enclosed goafs.

Microbial and Quality Attributes of Beef Steaks under High-CO2 Packaging: Emitter Pads versus Gas Flushing.

Over 21 days of cold storage, the quality and microbial composition of beef steaks in response to different high-CO2 packaging conditions achieved by flushing gas mixtures or embedding gas emitters into the packages were studied. The results revealed that the high levels of CO2, achieved by either the gas flushing or the CO2 emitter pads, effectively controlled the number of aerobic counts. The headspace CO2 increased quickly in response to using the CO2 emitter pads, and the meat samples presented different pH levels and surface color (a* and b*) values compared to the samples packaged with the gas flushing technique. Excessive accumulation of gas in the packages that contained CO2 emitters resulted in package swelling and higher levels of drip loss. The longest overall quality and attractive red color of the meat samples were observed when the packages were initially flushed with the headspace gas mixture containing high levels of oxygen. Overall, using CO2 emitters for meat packaging can be suggested when a topfilm with proper permeability to O2 and CO2 gases is used to regulate the internal CO2/O2 and gas/product ratios.

Large-scale data-driven uniformity analysis and sensory prediction of commercial banana ripening process

Artificial intelligence (AI) and machine learning (ML) have found prominent yet mostly academic applications in the food supply chain specifically to preserve and optimize the quality of fresh produce and achieve uniformity across the various stages of the cold chain. Nevertheless, the practical use of AI/ML for predictive analytics within real and large-scale commercial food processes, such as banana ripening, is sparse. This study proposes a novel data-driven approach tested and validated on two new large-scale datasets to automate and optimize the banana ripening process in refrigerated marine containers by successfully employing ML in uniformity analysis of the peel color and the pulp temperature of bananas based on atmospheric conditions. The results demonstrate high correlations between the gas concentrations and the uniformity of the process, suggesting that the uniformity of the peel color and the pulp temperature of fruit can be achieved by controlling the concentrations of the CO2 and O2 gas levels. Furthermore, this study, for the first time, achieves accurate algorithmic predictions of oxygen levels from other atmospheric variables to provide an alternative approach for continuous, improved and more cost-effective monitoring of the atmospheric conditions during ripening. A wide-range of predictive models are tested and validated where the Long Short Term Memory regression provides the lowest root-mean-square-errors (0.033 and 0.202) with robust R-squared values (0.999 and 0.959) for two datasets.

Appraising machine learning algorithms in predicting noise level and emissions from gasoline-powered household backup generators

AbstractMachine learning is presently receiving great attention. However, machine learning applications to gasoline engine research are limited. This paper investigated the implementation of various machine learning models in predicting the emissions (CO2, CO, and PM2.5) and noise levels of gasoline-powered household generators for the first time. Data of operating and installed capacity, efficiency (input) and emissions, and noise level (output) obtained from 166 generators were used in extreme gradient boosting, artificial neural network (ANN), decision tree (DT), random forest (RF), and polynomial regression (PNR) algorithms to develop predictive models. Results revealed high prediction performance (R2 = 0.9377–1.0000) of these algorithms marked with very low errors. The implementation of PNR followed by the RF exhibited the best models for predicting CO2, CO, PM2.5, and the noise level of generators. R2 of 1.000 and 0.9979–0.9994, mean squared error of < 10−6 and 2 × 10−5–8.6 × 10−5, mean absolute percentage error of 9.15 × 10−16–1.3 × 10−15 and 7.1 × 10−3–8.1 × 10−2, and root mean squared error of 3.3 × 10−16–5.4 × 10−16 and 4.4 × 10−3–9.3 × 10−2 were recorded for all the output parameters using PNR and RF respectively. DT models had the least prediction capacity for CO, CO2, and noise levels (R2 = 0.9493–0.9592) while ANN produced the least performance for PM2.5 (R2 = 0.9377). This study further strengthens machine learning applications in engine research for the prediction of various output parameters.

Experimental Study on Coal Oxidation and Temperature Rise Under Reciprocating Air Leakage

ABSTRACT Reciprocating air leakage often occurs in the goaf of coal mines because of changes in internal or external pressure. However, its impact on the spontaneous combustion of coal in the goaf is uncertain. Therefore, a comparative study of constant air leakage and reciprocating air leakage was carried out using a self-built system. The results indicate that reciprocating air leakage promotes coal oxidation and produces higher CO levels compared to constant air leakage. Further investigation was carried out to examine the effect of air leakage rate and reciprocating half-cycle (referred to as half-cycle hereafter) on coal oxidation and temperature rise. The results show that there is a linear relationship between resistance and air leakage rate in the coal oxidation heating space; however, the half-cycle length has little effect on resistance. The influence of a fixed air leakage rate on temperature and CO concentration does not always increase, with the maximum value achieved at 1.2 m3/h. Shorter half-cycles result in higher temperatures and CO concentrations. Gradually increasing air leakage rates and shortening half-cycles can promote coal oxidation and temperature rise and lead to higher CO production compared to previous scenarios. Additionally, the effect of using four different air leakage rates or half-cycle lengths is greater than that of using two. These research findings offer a theoretical foundation for preventing and controlling coal spontaneous combustion in goafs under complex air leakage conditions.

Effect of copper and temperature on the photosynthetic physiological characteristics of Ulva linza under elevated CO2 concentrations

Copper (Cu) is vital for macroalgae's functions, but high concentrations can be toxic. Rising CO2 levels affect algal growth and Cu bioavailability. In this study, the results reveal that at 5 °C, low Cu increased Ulva linza growth, while high Cu and elevated CO2 decreased growth. At 10 °C, low Cu and elevated CO2 enhanced growth, but high Cu did not have a significant impact. At 15 °C, high Cu reduced growth, but elevated CO2 offset this effect. Furthermore, under elevated CO2 conditions, the chloroplast structure of the algae appeared to be denser, accompanied by a large amount of starch granules, compared to low CO2 conditions. These results emphasize that lower temperatures, in conjunction with elevated CO2 concentration, could intensify the toxic effects of high Cu concentrations on thalli. However, at higher temperatures, elevated CO2 concentration appeared to be capable of mitigating the detrimental effects of heavy metals on algae.

Comparing the outcome of using high-flow nasal cannula oxygen therapy versus noninvasive ventilation for chronic obstructive pulmonary disease patients with acute hypercapnic respiratory failure

BackgroundNoninvasive ventilation (NIV) is frequently employed as a treatment option for acute hypercapnic respiratory failure (AHRF) resulting from chronic obstructive pulmonary disease (COPD). Limited research has substantiated the claims made in recent studies regarding the feasibility of employing high flow nasal cannula (HFNC).AimOur study assessed the outcome of using HFNC versus NIV for COPD patients with AHRF.Patients and methodsEighty COPD patients with AHRF were confined to the respiratory intensive care unit (RICU) at Ain-Shams University Hospitals from December 2021 to 2023 and subdivided into two groups (40/group), where the first group was placed on NIV while the second group was placed on HFNC. Data during their hospital stay as demographic data, vital data, arterial blood gases, device duration, treatment failure, and mortality were recorded.ResultsThe majority were males with mean age 63.75 ± 9.05 years along with treatment failure and complications 25%, 12.5.% in NIV versus 45%, and zero% in HFNC, respectively, with longer hospital stay in NIV 10–15 days to 7–10 days in HFNC, and with no difference in mortality rate in both groups.ConclusionBoth modalities NIV and HFNC were effective for treating COPD with AHRF. However, NIV group was significantly superior than HFNC along with apparently faster improvement in ventilatory and respiratory status especially in high CO2 level while less complications and duration of hospital stay in HFNC with no difference in mortality in both groups.

Maintaining Indoor Air Quality in Government Offices with Frontline Services

This study sought to assess the Indoor Air Quality (IAQ) of the Local Government Unit of Matungao, Lanao del Norte Frontline Offices, by measuring the Carbon Dioxide (CO2) level. The study also sought to assess if minor interventions (putting indoor plants and opening of windows and doors on the first hour in the morning) can significantly affect the CO2 level in the offices. The offices involved in the study are those that offer frontline services for the community. Paired T-test was utilized in the study. In the first and second week of the data gathering, the offices were assessed based on their regular operations, and on the third week, the interventions were made for all the offices. The first and second week of the assessment shows that, the Rural Health Unit (RHU) and Human Resource and Management Office (HRMO) are the offices which have average CO2 levels that are close to 1000ppm, which implies that these offices do not have efficient air ventilation. On the third week of assessment, the result still shows the same, with RHU and HRMO, and other offices are still on the normal range. The results shows that even with the interventions made on all of the eight offices, CO2 level didn’t show a significant change.

Elevated atmospheric CO2 alters the multi-element stoichiometry of pollen-bearing oak flowers, with possible negative effects on bees

Increasing atmospheric CO2 levels change the elemental composition in plants, altering their nutritional quality and affecting consumers and ecosystems. Ecological stoichiometry provides a framework for investigating how CO2-driven nutrient dilution in pollen affects bees by linking changes in pollen chemical element proportions to the nutritional needs of bees. We investigated the consequences of five years of Free Air CO2 Enrichment (FACE) in a mature oak-dominated temperate forest on the elemental composition of English oak (Quercus robur) pollen. We measured the concentrations and proportions of 12 elements (C, N, P, S, K, Na, Ca, Mg, Cu, Zn, Fe, and Mn) in Q. robur pollen-bearing flowers collected from the Birmingham Institute for Forest Research (BIFoR) FACE facility. An elevated CO2 (eCO2) level of 150 ppm above ambient significantly reduced the S, K, and Fe levels and altered the multi-element ratio, with different elements behaving differently. This shift in pollen multi-element composition may have subsequent cascading effects on higher trophic levels. To assess the impact on bees, we calculated the stoichiometric mismatch (a measure of the discrepancy between consumer needs and food quality) for two bee species, Osmia bicornis (red mason bee) and Apis mellifera (honey bee), that consume oak pollen in nature. We observed stoichiometric mismatches for P and S, in pollen under eCO2, which could negatively affect bees. We highlight the need for a comprehensive understanding of the changes in pollen multi-element stoichiometry under eCO2, which leads to nutrient limitations under climate change with consequences for bees.

Algal Biofuels: A Comprehensive Review and Analysis

The depletion of fossil fuels and increased atmospheric CO2 levels have precipitated a global energy and environmental crisis. The cultivation of microalgae offers a viable remedy by utilizing solar energy and assimilating CO2 for biofuel production via photosynthesis. Microalgae demonstrate rapid growth in diverse environments, rendering them a dependable biomass source for large-scale biofuel generation. Furthermore, their biofuel production can be tailored through the manipulation of growth conditions or genetic engineering. This review aims to highlight the variety of biofuels produced from microalgae and the methodologies to optimize their yield. This review also explores the economic implications of algal biofuel production in both open ponds and closed photobioreactors. Various strategies for the photo-production of biohydrogen utilizing the hydrogenase enzyme from green algae are investigated. Additionally, certain microalgae species are recognized for their potential as biodiesel sources due to their high lipid content. The lipid profiles of leading oil-producing algal strains under optimal conditions are assessed. This review further examines the potential of microalgae in synthesizing petroleum-based chemicals and in generating bioethanol and biogas from algal biomass.