Reduction Of Carbon Monoxide Research Articles

Experimental investigation of ternary biodiesel blends combustion in a diesel engine to reduce emissions

The study presents an experimental investigation of two new ternary biodiesel blends, namely, ManCr_Pa (a mixture of Mandarin, Crambe biodiesel and paraffin as an additive) and AvBn_Pa (mix of Avocado, Bush nut biodiesel and paraffin) by modifying the critical fuel properties closer to the diesel fuel. Those ternary blends' performance, emission and combustion characteristics were compared with diesel and typical B5 blends at the same engine conditions. The result reveals that at high engine rpm, the new ternary biodiesel blends exhibited nearly similar engine performance to that of diesel fuel with a significant reduction of carbon monoxide (33.3%), hydrocarbons (33.3 to 73.3%) and particulate matter (17.8 to 28.8%). For instance, brake power (BP), brake mean effective pressure (BMEP), and brake thermal efficiency (BTE) slightly decreased by 0.25 to 0.38, 0.27 to 0.42 and 0.04%, respectively, whereas brake specific fuel consumption (BSFC) slightly increased by 0.52%. The ternary blends also demonstrated closer combustion behaviour, i.e. heat release rate (HRR) with diesel at full load conditions. Compared with the typical B5 blend, the modified ternary biodiesel blends showed better engine performance with a substantial reduction of emissions. Interestingly, the ternary blends exhibited lower NOx emissions than the B5 blend. The study concluded that the newly developed ternary biodiesel blends are superior to ordinary B5 blends and closely performing fuel to standard diesel. The results of this study have important implications for using these new blends as substitutes for diesel while realising similar benefits.

Synthesis of 1-Hexanol/Hexyl hexanoate Mixtures from Grape Pomace: Insights on Diesel Engine Performances at High Bio-Blendstock Loadings

The production of oxygenated bio-additives for traditional fuels represents a key challenge due to their depletion in the near-future and their positive contribution to the reduction in environmental pollution. The present study considers the synthesis of 1-hexanol/hexyl hexanoate mixtures, two oxygenated Diesel bio-additives produced through the hydrogenation of hexanoic acid, obtainable from the fermentation of a wide variety of waste biomasses. In our case, crude hexanoic acid was produced through the fermentation of grape pomace, an abundant Italian agrifood waste. Commercial 5 wt% Re/γ-Al2O3 was adopted for the catalytic hydrogenation of crude hexanoic acid, and the support acidity allowed the tuning of the reaction selectivity toward the formation of hexyl hexanoate, instead of 1-hexanol, reaching yields of 40 and 25 mol%, respectively. The effects of each bio-additive on Diesel engine performance and exhaust emissions (soot, nitrogen oxides, carbon monoxide, unburned hydrocarbons) were evaluated, highlighting noteworthy positive effects especially on the reduction in carbon monoxide and soot emissions, if compared with those of Diesel fuel alone. Similar promising performances were achieved by employing Diesel blend mixtures of 1-hexanol/hexyl hexanoate, mimicking typical compositions of the rhenium-catalyzed post-hydrogenation mixtures. Even in such cases, 1-hexanol/hexyl hexanoate mixtures can be blended with commercial Diesel fuel, up to high loadings currently not yet investigated (20 vol%), without altering the engine performances and, again, significantly lowering soot and carbon monoxide emissions by more than 40%. This work highlights the possibility of obtaining such oxygenated bio-additives starting from waste through to a fully sustainable process and proves their beneficial effects on the reduction in exhaust emissions with no changes in engine performance.

Adoption of smokeless Chulha (Stove) in rural of Meghalaya and its feasibility: A case study

The smokeless chulha is a kind of stove that can directly impact the health of women in rural areas who are burning firewood as cooking fuel. The present study aimed to evaluate the impact of the smokeless chulha and to compare the social and economic benefits associated with it. The smokeless Chulhas (stoves) were distributed among the villagers in Tuber Kmai village of Meghalaya, India and its impact was compared with the traditional chulha used by the villagers. The efficacy of the smokeless chulhas was measured and compared with traditional chulhas in term of cooking time, fire wood consumption, gases, volatile compounds and particulate matter emitted. To measure the amount of gases, volatile compounds and particulate matter released, multifunctional air gas and particulate matter Detector (Labart, India) was used. Compared to traditional chulha, smokeless chulha showed 68.7 % reduction in firewood consumption and 45% reduction in cooking time. In addition, smokeless chulha showed 68.9% and 98% reduction in carbon dioxide and carbon monoxide compared to traditional chulha. Further, a significant reduction (p < 0.05) was observed for particulate matter (75%-87%), formaldehyde (75%) and total volatile organic compounds (88.5%). The results indicate that smokeless chulha could save a huge number of natural resources by reducing the cutting of forest. Moreover, smokeless chulha has a positive economic impact on family income.

Promoting Effect of Microwave Field on Gas Phase Diffusion Limited Magnetite Reduction in Carbon Monoxide

To investigate the effect of microwave irradiation on the rate of magnetite reduction while increasing the gas phase diffusion rate limit, the microstructure and kinetics of CO reduction of magnetite powder were studied. The investigation was conducted through microwave irradiation and conventional heating at 900~1100 °C. Under the two heating methods, the iron crystal is selectively reduced and gradually expanded along the direction normal to the length of the ore powder, forming a strip of iron crystal that penetrates the powder and expands outward across the width. The microwave field can effectively improve the sintering of minerals. The changes in Avrami exponents m and k in the reduction process were determined by combining the Johnson–Mehl–Avrami (JMA) model with the lnln method. The microwave field did not change the limiting step. Microwave irradiation proves to be the most effective means to enhance both the initial reduction rate and the rate during the primary iron crystal precipitation phase. The morphology of the iron crystal takes on a dense punctate shape, influenced by the rate of diffusion control.

Enhancing waste cooking oil biodiesel yield and characteristics through machine learning, response surface methodology, and genetic algorithms for optimal utilization in CI engines

ABSTRACT The current study seeks to predict and optimize the biodiesel production yield and physicochemical properties of waste cooking oil. Using Box-Behnken design (BBD), L46 orthogonal arrays were developed for experimentation at five factors and three levels. Furthermore, three different boosting algorithms (AdaBoost, ExtraTrees, and Gradient-Boosting regression) were used to develop an ML-based prognostic model using experimental data. Based on the coefficient of determination (R2) (0.997 for biodiesel yield, 0.999 for kinematic viscosity, 0.996 for calorific value, and 0.999 for flash point), the Gradient-Boosting model has the most accurate predictions, followed by ExtraTrees and AdaBoost. Through the implementation of GA, the most optimal conditions for biodiesel production were obtained, including a molar ratio of 7.24:1, catalyst concentrations of 1.49 wt.%, reaction temperatures of 65°C, reaction times of 59.95 minutes, and stirring speeds of 733.32 rpm. Experimental validation of these optimized conditions is closely aligned with the predicted values. Furthermore, the study evaluates engine performance and emission parameters to assess the impact of different biodiesel/diesel blends (B10, B20, and B30) compared to pure diesel. The utilization of these biodiesel blends demonstrates satisfactory performance, effectively reducing carbon monoxide (CO) and hydrocarbon (HC) emissions. However, nitrogen oxide (NOx) emissions increase compared to pure diesel.

Experimental evaluation and neural network modelling of reactivity-controlled compression ignition engine using cashew nut shell oil biodiesel-alumina nanoparticle blend and gasoline injection

The current desire is for enhanced combustion techniques that improve engine efficiency while successfully reducing emissions. Reactivity controlled compression ignition (RCCI) combustion encompasses the ability to increase fuel efficiency and decrease oxides of nitrogen emissions compared to conventional compression ignition (CI) combustion. This study presents a novel investigation that focuses on the capabilities of the RCCI engine, utilizing a unique combination of gasoline and diesel blended with cashew nut shell oil biodiesel (CNSOB) and the addition of aluminum oxide (Al2O3) nanoparticles. CNSOB extracted from waste shell has an oil content of 30–35 wt% yield. The cost of the oil range between is ₹. 40–50 in India. The engine operates on a blend of gasoline, known for its low reactivity, and diesel blended with CNSOB, a renewable and environmentally friendly alternative to diesel. The effects of varying proportions of the blend (B0, B50, and B100) and the addition of Al2O3 nano additive (25 and 50 ppm) on the efficiency and emissions of RCCI combustion are comprehensively analyzed experimentally. The results reveal that RCCI combustion significantly improves engine performance compared to compression ignition engines. A 2% increase in maximum in-cylinder pressure indicates improved combustion efficiency. Furthermore, fuel economy is improved by up to 2% due to increased engine brake thermal efficiency (BTE). Further, nitrogen oxide (NOx) emissions are reduced by up to 54% during RCCI combustion, demonstrating its potential for reducing pollution. Utilizing CNSOB biodiesel results in a 50% reduction in hydrocarbon (HC) emissions as well as a 17% reduction in carbon monoxide (CO) emissions. This indicates improved air quality and reduces environmental pollution. The incorporation of Al2O3 nano additives into the RCCI engine results in a 5% reduction in brake specific energy consumption (BSEC), showing better engine energy efficiency. Based on the results of the investigation, a neural network framework was developed. The neural network framework was developed to replicate both the efficiency and pollution parameters of the RCCI engine using the experimentally determined relationship between input factors and output parameters. The neural network model was trained using 70% of the available data, and its performance was evaluated by comparison of predictions with the corresponding observations from experiments. The forecast outcomes matched those of the trial, demonstrating the artificial neural network (ANN) models effectiveness and precision in predicting the engine performance and emissions.

Physical properties, engine performance, and exhaust emissions of waste fish oil biodiesel/bioethanol/diesel fuel blends

In the current study, the physicochemical, engine performance, and exhaust emission of different ternary fuel blends containing waste fish oil (WFO) biodiesel, bioethanol, and petro-diesel have been investigated. WFO Biodiesel was prepared from waste fish oil via transesterification method. Different physiochemical properties including the kinematic viscosity, density, flash point, pour point, cloud point, and heat value have been measured for different fuel blends and compared with the neat petro-diesel. The performance and exhaust emission of engine have been also studied using different fuel blends using a single-cylinder diesel engine in full load condition at 1800 rpm. It was found that the engine torque, engine power, and thermal efficiency of the ternary fuel blends was reduced by 2.45%, 9.25%, 2.35% averagely in comparison with the neat petro-diesel, respectively. The average break specific fuel consumption was also increased by 10.44% compared to the neat petro-diesel. The emission of carbon monoxide (CO), carbon dioxide (CO2), unburned hydrocarbons (UHC), and nitrogen oxides (NOx) was also measured. It was also found that the utilization of ternary fuel blends results in a considerable reduction in CO and UHC emission by 50.55% and 43.87% on average compared to the neat petro-diesel, respectively. The emission of NOx was also increased by 28.25% on average compared to the neat petro-diesel. It was also found that the NOx emission can be adjusted by tuning the WFO biodiesel and bioethanol contents of the ternary fuel blends.

Thermodynamic Analysis of Carbon Deposition on the Fuel Electrode of a Reversible Solid Oxide Cell

Fouling via carbon deposition occurs in reversable solid oxide cells (RSOCs) when it operates with carbon-based fuels or performs CO2 electrolysis. Carbon deposition is known to degrade performance and, in some cases, lead to delamination and irreversible cell damage. In this study, research was conducted using thermodynamic analysis to investigate the potential of solid carbon formation during electrolysis mode by analyzing the chemical potential of electro-neutral oxygen (O2) at the interface between the electrolyte and the fuel electrode. The chemical potential of electro-neutral oxygen is calculated based on a local chemical equilibrium assumption and addresses the isothermal transport of ions and electrons across the electrolyte. The O2 chemical potential at the fuel electrode/electrolyte interface is used to evaluate the affinity of carbon deposition reactions by the corresponding Gibbs free energy changes. Our analysis shows that regardless of the chemical makeup and physical properties of a cell an oxygen chemical potential threshold is ultimately reached as applied cell voltage during electrolysis is increased which beyond this threshold carbon deposition is inevitable. Our study is expanded to include the role of fuel electrode ionic resistance on the chemical potential of O2 at the fuel electrode/electrolyte interface and shows that an increase in ionic resistance results in more favored carbon deposition. Additional findings indicate that at 800 deg. C the electrochemical reduction of carbon monoxide is thermodynamically favored at lower local CO partial pressures over the Boudouard reaction during electrolysis mode.

Ag-Based Gas Diffusion Electrodes for the Electrochemical CO2 Reduction by Pulsed Hydrogen Bubble Templation

Energy-conversion technologies like the electrocatalytic nitrogen reduction reaction (N2RR), carbon monoxide reduction reaction (CORR) and in particular the electrochemical carbon dioxide reduction reaction (CO2RR) can contribute decisively to overcome the challenge of reducing greenhouse gas emissions. By reducing CO2 electrochemically, the carbon-cycle can be closed and industrially desired chemicals like syngas (CO + H2), formic and acetic acid, or hydrocarbons, such as methanol and ethylene, can be produced fossil-fuel free, depending on the catalyst material applied. Ag-based catalysts are very promising in the field of CO2RR, since they show high selectivities towards the reduction of CO2 to CO and current efficiencies of up to 100 %. In aqueous-fed systems, a significant drawback is the limited CO2 solubility, resulting in long diffusion pathways of CO2 within the bulk electrolyte 1, 2. Consequently, industrial conditions cannot be reached for CO2 electrolysis in aqueous solution in H-cell configurations due to the CO2 depletion within the porous electrodes that limit lab scale testing of CO2RR to current densities of approx. 35 mAcm-². One way to achieve commercially relevant current densities (> 200 mAcm-²) is the utilization of gas diffusion electrodes (GDEs) in flow cell configuration. These enable a decrease in CO2 diffusion lengths to approx. 50 nm, enhancing the mass transport to the catalyst 3.In our contribution, we will demonstrate a facile and fast production process of Ag-based GDEs by combining pulsed electrochemical deposition of the Ag catalyst with ionomer infiltration of the electrode. Using the dynamic hydrogen bubble templation method (DHBT), we utilized the parasitic hydrogen evolution reaction (HER) to aid in a solvent free structuring of the 3D catalyst network. In this work, we focused on the deposition parameters by varying different pulse-to-pause ratios in order to increase the amount of deposited catalyst and thus, successfully reduced the overpotential during CO2RR operation (Fig. 1, left). To inhibit electrode flooding and decrease CO2 mass transport limitations during CO2RR, we infiltrated the electrode with a perfluorinated ionomer. SEM and EDS analyses showed a uniform Ag/F distribution along the cross section of the electrodes (Fig. 1, right), which resulted in the conversion of CO2 to CO at industrially viable current densities.References S. Hernandez-Aldave and E. Andreoli, Catalysts, 10(6), 713 (2020).Z. Sun, T. Ma, H. Tao, Q. Fan and B. Han, Chem, 3(4), 560–587 (2017).T. Burdyny and W. A. Smith, Energy Environ. Sci., 12(5), 1442–1453 (2019). Figure 1

Assessing the Impact of COVID-19 Lockdown on Air Pollutants and Wildfires in China

This research paper focuses on the impact of COVID-19 lockdown on air pollutants and wildfires in various provinces of China. The study uses machine learning techniques to analyze the association between lockdown restrictions and the subsequent decline in air pollution emissions, which in turn led to a reduction in fire count (FC). The frequency and severity of wildfires have been rising in China, with major negative effects on the country's air quality. Globally unprecedented responses to the COVID-19 epidemic have included lockdowns and limitations on human activity. The purpose of this study is to evaluate how the COVID-19 lockdown has affected air pollutants and wildfires in China. Specially, the focus is on the reduction in ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO) levels in the air. Satellite images were used before and during the lockdown to gauge the impact. The observed reduction in NO2, O3 and CO concentrations during the COVID-19 lockdown demonstrate the potential advantages of taking action to reduce air pollution. The study tries to find connections between the incidence of wildfires and the subsequent emission of air pollutants using machine learning methods. The study creates maps showing the influence of lockdown restrictions on the levels of air pollutants and the number of fires by analyzing historical data on air pollution measurements. These findings highlight the significance of sustainable practices, environmental regulations and offer insightful information regarding the interaction between human activities, air pollutants and wildfires in China.

Investigation of the drop-in capabilities of a renewable 1-Octanol based E-fuel for heavy-duty engine applications

This article presents the results of an investigation of neat 1-Octanol and its blends with Diesel, which can be potential drop-in fuels for heavy-duty compression ignition engines. Fuel blends consisting of 10 %, 20 %, and 30 % 1-Octanol by volume in Diesel, including neat 1-Octanol, were investigated for ignition and combustion performances. The ignition behavior was assessed using a constant-volume combustion-chamber-based ignition tester. The experimental investigation was conducted on a heavy-duty single-cylinder engine by varying the combustion center. In addition, injection-rate shaping was performed to understand the effects of various injection-rate shapes, namely square, ramp, and boot rate shapes, on the performance of neat 1-Octanol.The ignition tester results indicated an increased ignition sensitivity of neat 1-Octanol towards the chamber pressure and temperature compared to that of Diesel. At an elevated chamber temperature (650 °C) and pressure (20 bar), the ignition delay of neat 1-Octanol approaches closer to that of Diesel. Engine experiments revealed an improved thermal efficiency with neat 1-Octanol and its blends by up to 1.2 %, owing to their improved mixture homogenization capabilities. Furthermore, neat 1-Octanol and its blend led to a drastic reduction in smoke and carbon monoxide. In addition, it results in the highest peak during the premixed heat release, and with a square injection-rate shape, an additional minor improvement in thermal efficiency was observed. The relative changes in carbon monoxide and hydrocarbon emissions between the injection-rate shapes were negligible. At higher load, the boot-rate shape results in lower NOx formation than the square-rate shape at an almost identical thermal efficiency. Overall, the 10 % 1-Octanol, 20 % 1-Octanol and 30 % 1-Octanol blends, which fulfill the Cetane number requirements for the given fuel norms, can be used as drop-in fuels, as they exhibit a comparable or even better performance than Diesel.

Pb-rich Cu grain boundary sites for selective CO-to-n-propanol electroconversion

Electrochemical carbon monoxide (CO) reduction to high-energy-density fuels provides a potential way for chemical production and intermittent energy storage. As a valuable C3 species, n-propanol still suffers from a relatively low Faradaic efficiency (FE), sluggish conversion rate and poor stability. Herein, we introduce an “atomic size misfit” strategy to modulate active sites, and report a facile synthesis of a Pb-doped Cu catalyst with numerous atomic Pb-concentrated grain boundaries. Operando spectroscopy studies demonstrate that these Pb-rich Cu-grain boundary sites exhibit stable low coordination and can achieve a stronger CO adsorption for a higher surface CO coverage. Using this Pb-Cu catalyst, we achieve a CO-to-n-propanol FE (FEpropanol) of 47 ± 3% and a half-cell energy conversion efficiency (EE) of 25% in a flow cell. When applied in a membrane electrode assembly (MEA) device, a stable FEpropanol above 30% and the corresponding full-cell EE of over 16% are maintained for over 100 h with the n-propanol partial current above 300 mA (5 cm2 electrode). Furthermore, operando X-ray absorption spectroscopy and theoretical studies reveal that the structurally-flexible Pb-Cu surface can adaptively stabilize the key intermediates, which strengthens the *CO binding while maintaining the C–C coupling ability, thus promoting the CO-to-n-propanol conversion.

Spatial heterogeneity in global atmospheric CO during the COVID–19 lockdown: Implications for global and regional air quality policies

The COVID–19 lockdown (LD) provided a unique opportunity to examine the changes in regional and global air quality. Changes in the atmospheric carbon monoxide (CO) during LD warrant a thorough analysis as CO is a major air pollutant that affects human health, ecosystem and climate. Our analysis reveals a decrease of 5–10% in the CO column during LD (April–May 2020) compared to the pre-lockdown (PreLD, March 2020) periods in regions with high anthropogenic activity, such as East China (EC), Indo-Gangetic Plain (IGP), North America, parts of Europe and Russia. However, this reduction did not occur in the regions of frequent and intense wildfires and agricultural waste burning (AWB). We find high heterogeneity in the CO column distributions, from regional to city scales during the LD period. To determine the sources of CO emissions during LD, we examined the ratios of nitrogen dioxide (NO2), sulfur dioxide (SO2) to CO for major cities in the world. This facilitated the identification of contributions from different sources; including vehicles, industries and biomass burning during LD. The comparison between CO levels during the LD and PreLD periods indicates a notable reduction in the global tropospheric CO, but no significant change in the stratosphere. It is found that CO emissions decreased during LD in the hotspot regions, but rebounded after the LD restrictions were lifted. This study, therefore, highlights the importance of policy decisions and their implementations in the global and regional scales to improve the air quality, and thus to protect public health and environment.

Synthesis of spirulina microalgae biodiesel, and experimental research of its effects on compression ignition engine responses with iron II-III oxide (Fe3O4) nanoparticle supplementation

The raw material from which biodiesel is produced, the pioneer of alternative fuels in compression ignition engines, has increased importance in recent years. Third-generation biodiesels, which do not harm the food chain and environment, have become popular in recent years. In this study, fuel mixtures were obtained by mixing biodiesel produced from spirulina microalgae, the third-generation biodiesel type, with diesel and iron II-III oxide (Fe3O4) at different concentrations. Microalgae biodiesel (MAB) was mixed with diesel at two different percentages (10% and 20%), and three diverse quantities of Fe3O4 (25, 50, and 75 ppm) were added to 20MAB80D. Since the effects of the fuel mixture containing 20% MAB on the engine response are more optimistic, nanoparticles were added to the fuel containing 20% MAB. These fuel blends were evaluated under various engine loads (from 25% to 100%) at a constant engine speed (1500 rpm), and a compression ratio (15.5:1). Brake thermal efficiency (BTHE) and brake mean effective pressure (BMEP) improved with the addition of both MAB and Fe3O4. Compared to diesel (D100), the highest increases were achieved with 20MAB80D75IO fuel, with an average of 28.64% and 13.18%, respectively. With the 20MAB80D, these increases averaged 12.85% and 3.85%, respectively. On the other hand, brake-specific fuel consumption (BSFC) response increased with MAB and decreased with Fe3O4. With 20MAB80D75IO fuel, it showed an average decrease of 19.02% compared to BSFC diesel. With the 20MAB80D, there was an average increase of 11.31%. MAB and Fe3O4 contributed to reducing carbon monoxide (CO) and hydrocarbon (HC) emissions, which are products of incomplete combustion. With 20MAB80D75IO fuel, an average of 24.21% and 57.36% reductions were achieved, respectively, compared to D100. With the 20MAB80D, there was an average of 20.14% and 22.62% reductions, respectively. Conversely, NOx produced by 20MAB80D75IO was 11.63% higher than D100, while NOx produced by 20MAB80D was 3.83% higher. In conclusion, the experimental data obtained using Fe3O4 nanoparticles added to improve engine responses by improving the properties of MAB produced as third-generation biofuels revealed that MAB would be an excellent alternative fuel and Fe3O4 was a suitable additive.

Metal-Organic Framework Derived Cu-Ag Interface for Selective Carbon Monoxide Electroreduction to Acetate.

Electrochemical carbon monoxide reduction reaction (CORR) is a potential way to obtain high-value multi-carbon (C2+ ) products. However, achieving high selectivity to acetate is still a challenge. Herein, we develop a two-dimensional Ag-modified Cu metal-organic framework (Ag0.10 @CuMOF-74) that demonstrates Faradaic efficiency (FE) for C2+ products up to 90.4 % at 200 mA cm-2 and an acetate FE of 61.1 % with a partial current density of 122.2 mA cm-2 . Detailed investigations show that the introduction of Ag on CuMOF-74 favors the generation of abundant Cu-Ag interface sites. In situ attenuated total reflection surface enhanced infrared absorption spectroscopy confirms that these Cu-Ag interface sites improve the coverage of *CO and *CHO and the coupling between each other and stabilize key intermediates *OCCHO and *OCCH2 , thus significantly promoting to the acetate selectivity on Ag0.10 @CuMOF-74. This work provides a high-efficiency pathway for CORR to C2+ products.

Systematic review and meta-analysis investigating nicotine, cotinine and carbon monoxide exposures in people who both smoke and use nicotine replacement therapy.

To determine effects of concurrent smoking and nicotine replacement therapy (NRT) use on reported heaviness of smoking, nicotine (cotinine) body fluid and exhaled air carbon monoxide (CO) concentrations. Systematic review and meta-analysis of RCTs, which test interventions permitting concurrent NRT use and smoking and comparing, within participants, outcomes when smoking with those when smoking and using NRT concurrently. Measurements included reported number of cigarettes smoked per day (CPD), body fluid cotinine and expired air CO concentrations. Twenty-nine studies were included in the review. Meta-analysis of nine showed that, compared with when solely smoking, fewer cigarettes were smoked daily when NRT was used (mean difference during concurrent smoking and NRT use, -2.06 CPD [95% CI = -3.06 to -1.07, P < 0.0001]). Meta-analysis of seven studies revealed a non-significant reduction in exhaled CO during concurrent smoking and NRT use (mean difference, -0.58 ppm [95% CI = -2.18 to 1.03, P = 0.48]), but in the three studies that tested NRT used in the lead-up to quitting (i.e. as preloading), a similar reduction in exhaled CO was statistically significant (mean difference, -2.54 ppm CO [95% CI = -4.14 to -0.95, P = 0.002]). Eleven studies reported cotinine concentrations, but meta-analysis was not possible because of data reporting heterogeneity; of these, seven reported lower cotinine concentrations with concurrent NRT use and smoking, four reported no differences, and none reported higher concentrations. People who smoke and also use nicotine replacement therapy report smoking less heavily than people who solely smoke. When nicotine replacement therapy is used in the lead-up to quitting (preloading), this reported smoking reduction has been biochemically confirmed. There is no evidence that concurrent smoking and nicotine replacement therapy use result in greater nicotine exposure than solely smoking.

Systematic review and meta-analysis investigating nicotine, cotinine, and carbon monoxide exposures in people who both smoke and use nicotine replacement therapy.

Smoking is a major international public health problem. To determine effects of concurrent smoking and nicotine replacement therapy (NRT) use on reported heaviness of smoking, nicotine (cotinine) body fluid, and exhaled air carbon monoxide (CO) concentrations. Systematic review and meta-analysis of randomised controlled trials (RCTs) that test interventions permitting concurrent NRT use and smoking, and comparing, within participants, outcomes when smoking with those when smoking and using NRT concurrently. In total, 29 studies were included in the review. Meta-analysis of nine showed that, compared to when solely smoking, fewer cigarettes were smoked daily when NRT was used (mean difference during concurrent smoking and NRT use, -2.06 CPD [95% confidence interval {CI} = -3.06 to -1.07, P<0.0001]). Meta-analysis of seven studies revealed a non-significant reduction in exhaled CO during concurrent smoking and NRT use (mean difference, -0.58 ppm [95% CI = -2.18 to 1.03, P = 0.48]), but in the three studies that tested NRT 'preloading', a similar reduction in exhaled CO was statistically significant (mean difference, -2.54 ppm CO [95% CI = -4.14 to -0.95, P = 0.002]). Overall, 11 studies reported cotinine concentrations, but meta-analysis was not possible due to data reporting heterogeneity; of these, seven reported lower cotinine concentrations with concurrent NRT and smoking, four reported no differences, and none reported higher concentrations. People who smoke but who also use NRT reported smoking less heavily than when solely smoking, and when NRT was used as 'preloading' this reported smoking reduction was biochemically confirmed. There was no evidence concurrent smoking and NRT use resulted in greater nicotine exposure than smoking.

Energy and exergy analysis of VCR engine fueled with rubber-seed oil methyl ester using response surface methodology

This study presents a comprehensive analysis of the thermodynamic performance of a variable compression ratio engine fueled with rubber-seed oil methyl ester blended with diesel. The objective is to evaluate the energy and exergy characteristics according to the first and second laws of thermodynamics for various compression ratios and supercharging pressures. A 3.5 kW engine with compression ratios values ranging from 18:1 to 22:1 and SC pressures of 0, 0.25, and 0.5 bar (g) at 80% load was considered. The inlet manifold pressure was controlled using a centrifugal-type blower (1.5 m3/min, 350 W, 240 V AC) with an adjustable valve. Key fuel energy parameters including shaft energy, cylinder pressure, brake specific energy consumption, thermal efficiency, heat release rate, absorbed energy by cooling water, exhaust gas temperature, exergy efficiency, exergy destruction, exhaust energy, and emissions were analyzed. Results showed significant improvements in shaft energy (35.51%), thermal efficiency (35.37%), and heat release rate (25.17 J/°CA) for compression ratios 20 and supercharging pressure of 0.25 bar, with a reduction in brake specific energy consumption of 2.912 kJ/s kW. The second law efficiency and irreversibility were observed to be 60.31% and 0.0118 kW/K, respectively. Experimental findings demonstrated a reduction in carbon monoxide (25.12%) and hydrocarbon (40%) under the aforementioned conditions. Response surface methodology was employed to predict optimal operating conditions, and the equations were validated using analysis of variance and p-test. The D-optimality test facilitated the determination of optimal operating parameters for different responses through multi-objective optimization techniques. Individual desirability values were combined to obtain a composite desirability of 0.9054. The study identified compression ratios 18 with a supercharging pressure of 1.78 bar as the optimum operating condition for 20% fuel blends in a low-speed agricultural diesel engine, resulting in a remarkable improvement of 41.24% in energy efficiency and 68.45% in exergy efficiency, with minimal emissions.

Investigations on reactivity controlled compression ignition combustion with different injection strategies using alternative fuels produced from waste resources

Reactivity-controlled compression ignition (RCCI) is a promising low-temperature combustion (LTC) strategy that results in low oxides of nitrogen (NOx) and soot emissions while maintaining high thermal efficiency. At the same time, RCCI leads to increased unburned hydrocarbon (HC) and carbon monoxide (CO) emissions in the exhaust, particularly under low loads. The current work experimented novel port-injected RCCI (PI-RCCI) strategy to overcome the high unburned emission limitations at low load conditions in RCCI. PI-RCCI is a port injection strategy in which low-reactivity fuel (LRF) is injected using a low-pressure injector, and the high-reactivity fuel (HRF) is injected through a high-pressure common rail direct injection (CRDI) injector. The low volatile HRF is injected into a heated fuel vaporizer maintained at 180°C in the intake manifold during the suction stroke. Modifying a single-cylinder, light-duty diesel engine with the necessary intake and fuel injection systems allows engine operation in both RCCI and PI-RCCI modes. Alternative fuels from waste resources such as waste cooking oil biodiesel (WCO) and plastic waste oil (WPO) are used as the HRF and LRF fuel in RCCI and PI-RCCI. To achieve maximum thermal efficiency in RCCI, the premixed energy ratio and the start of injection of the direct-injected fuel are optimized at all load conditions. The engine performance and exhaust emissions characteristics in PI-RCCI are compared with RCCI as a baseline reference. The results show a 70% and 48% reduction in CO and HC emissions, respectively, in PI-RCCI than in RCCI. Further, the brake thermal efficiency (BTE) was enhanced by around 20%, and the brake-specific fuel consumption (BSFC) was reduced by 13% in PI-RCCI. The NOx emissions decreased without any considerable changes in soot emission in PI-RCCI. The current study shows that fuels derived from waste resources can be used in RCCI and PI-RCCI modes with better engine performance and lower emissions.

Adoption of cleaner technologies and reduction in fire events in the hotspots lead to global decline in carbon monoxide

Carbon Monoxide (CO) is not a greenhouse gas (GHG), but has the capacity to change atmospheric chemistry of other GHGs such as methane and ozone, and therefore indirectly affects Earth's radiative forcing of the GHGs and surface temperature. Here, we use the CO mixing ratio at 850 hPa from the Tropospheric Emission Spectrometer (TES) reanalysis and the Measurement of Pollution in the Troposphere (MOPITT) satellite measurements for the period 2005–2019 to examine the spatio-temporal changes in CO across the latitudes. We find a substantial decrease in global CO, about −0.21 ± 0.09 ppb/yr (−0.23 ± 0.12%/yr) with the TES data and about −0.36 ± 0.07 ppb/yr (−0.45 ± 0.08%/yr) with the MOPITT satellite measurements during the study period. The highest CO decreasing trend is observed in Eastern China (−2.7 ± 0.37 ppb/yr) followed by Myanmar (−2.142 ± 0.59 ppb/yr) and South America (−1.08 ± 0.82 ppb/yr). This negative trend in CO is primarily due to the decrease in biomass burning and stringent environmental regulations in the respective regions and countries. The sources including road transport, which account for about 33.6% of CO emissions, followed by industries (18.3%) and agricultural waste burning (8.8%), might also be responsible for the reduction in CO due to the adaptation of improved emission control technology and regulations in the past decades from 2005 to 2019. Therefore, the study provides new insights on the current trends of global CO distribution and reasons for recent reduction in global CO emissions, which would be useful for future decision-making process to control air pollution.