Global Air Pollution Research Articles

A sustainable model using RSM and MCDM techniques to evaluate performance and emission characteristics of a diesel engine fueled with diphenylamine antioxidant and CeO2 nanoparticle additive biodiesel blends

Overconsuming fossil fuels has worsened global warming and air pollution, requiring us to investigate alternate fuels for compression ignition engines. Biodiesel is a renewable fuel and environmentally favorable. Biodiesel's most significant disadvantage is increased nitrogen oxide (NOx) emissions. The intent of the present study was to examine the impact of antioxidant diphenylamine (DPA) and nanoparticle ceria (CeO2) additive inclusion in a B30 blend on engine performance and exhaust emission characteristics. For this study, diesel, Jatropha biodiesel (B30), 100 ppm of antioxidant diphenylamine (50 ppm) with ceria nanoparticle (50 ppm) is added to the B30 blend named as B30+DPA100 and antioxidant diphenylamine (50 ppm) with ceria nanoparticle (50 ppm) is added to the B30 blend named as B30+DPA50+CeO250 fuel blends has been used. A hybrid response surface methodology and multi-criteria decision-making techniques (entropy method, TOPSIS, and VIKOR) have been used to develop a sustainable model and find the optimal setting of input parameters in terms of ranking. From experimental findings, the inclusion of antioxidants (DPA) and nanoparticle (CeO2) at 50 ppm to B30 significantly reduced NOx emission. The brake-specific fuel consumption and NOx have been found reduced by 5.67% and 18.87%, respectively, for B30+DPA50+CeO250 as compared to B30. At the same time, brake thermal efficiency increased by 1.01%. The brake mean effective pressure and maximum cylinder pressure) have been found increased by 0.68% and reduced by 4.52%, respectively, for B30+DPA50+CeO250 as compared to B30. The alternative ranking of the input parameters has been found fuel injection pressure (300), compression ratio (17), and load (12) as Rank 1 for TOPSIS and VIKOR. Therefore, the B30+DPA50+CeO250 blend is appropriate for improving diesel engine performance and diminishing exhaust emissions.

Complementing carbon tax with renewable energy investment to decarbonize the energy system in China

Building a low-carbon energy system is particularly essential to address global climate change and regional air pollution. Focusing on China, this study integrated a power system decision model into a computable general equilibrium (CGE) model to comprehensively explore the low-carbon transition, environmental benefits, and economic costs of a combined carbon tax (CTax) and renewable energy investment (REI) policy. This study finds that a dynamic CTax (with a carbon price of 290 and 590 RMB/ton CO2 in 2035 and 2050, respectively) can reduce the share of coal-fired power from 65 % in 2017 to 22 % in 2050. This will reduce coal consumption by 0.8 billion tons of standard coal equivalent (tce), thus resulting in a coal share decline in the energy system from 60 % in 2017 to 29 % in 2050. Regarding environmental benefits, CTax can mitigate CO2 and air pollutant emissions by 3.9 and 0.9 Gt, respectively, in 2050. Complementing CTax with REI can further reduce coal consumption by 0.2 billion tce and lower the coal-fired power share to 12 %. Regionally, emission reductions in East China can be enhanced owing to REI, which can mitigate the inequity in emission reductions resulting from the CTax. However, this study finds that employing CTax alone may negatively affect the economy. In particular, across the Jin-Meng and Shan-Gan-Ning regions, the gross domestic product (GDP) will decrease by 3.35 % and 2.73 %, respectively. However, complementing CTax with REI can dampen these negative impacts, reducing the national GDP loss from −0.94 % to −0.68 %.

Global Anthropogenic Emissions of Full-Volatility Organic Compounds.

Traditional global emission inventories classify primary organic emissions into nonvolatile organic carbon and volatile organic compounds (VOCs), excluding intermediate-volatility and semivolatile organic compounds (IVOCs and SVOCs, respectively), which are important precursors of secondary organic aerosols. This study establishes the first global anthropogenic full-volatility organic emission inventory with chemically speciated or volatility-binned emission factors. The emissions of extremely low/low-volatility organic compounds (xLVOCs), SVOCs, IVOCs, and VOCs in 2015 were 13.2, 10.1, 23.3, and 120.5 Mt, respectively. The full-volatility framework fills a gap of 18.5 Mt I/S/xLVOCs compared with the traditional framework. Volatile chemical products (VCPs), domestic combustion, and on-road transportation sources were dominant contributors to full-volatility emissions, accounting for 30, 30, and 12%, respectively. The VCP and on-road transportation sectors were the main contributors to IVOCs and VOCs. The key emitting regions included Africa, India, Southeast Asia, China, Europe, and the United States, among which China, Europe, and the United States emitted higher proportions of IVOCs and VOCs owing to the use of cleaner fuel in domestic combustion and more intense emissions from VCPs and on-road transportation activities. The findings contribute to a better understanding of the impact of organic emissions on global air pollution and climate change.

The Many Pollutant Identities of Carbon Dioxide: Global Climate Monitoring and Air Pollution Research in New Zealand, 1968–1975

In the late 1960s, New Zealand and the United States collaborated to establish a southern hemispheric carbon dioxide (CO 2 ) monitoring station on New Zealand’s coastal cliffs. The New Zealand CO 2 Project, as it came to be known, is an underappreciated landmark in the history of environmental monitoring. The archival record of its early years reveals the extent to which efforts to measure atmospheric carbon dioxide concentrations interacted closely with one of the most hotly debated political issues of the mid-twentieth century: urban air pollution. The designation of CO 2 as air pollution on a planetary scale had profound legal implications in an era in which clean air legislation increasingly brought air pollution within the scope of governmental regulation, and administrative agencies began to jostle for control of the monitoring enterprise. The precise nature of CO 2 as an air pollutant, however, was difficult to pin down. In these initial years of concerted carbon dioxide monitoring, when the lines between climate science and air pollution research were still blurred, CO 2 developed its many pollutant identities. The nature of these identities – and the ways in which scientists and science administrators negotiated their boundaries – retain their relevance today, as nations continue to link air pollution and climate legislation in the twenty-first century.

Disentangling the impact of COVID-19 lockdown and meteorological factors on air quality in Colombo, Sri Lanka: A data clustering approach

Introduction: Human activities disrupted by COVID-19 have reduced global air pollution. Meteorological day-to-day and year-to-year variability affects pollution levels and complicates estimating reductions. This paper uses data clustering to remove the complexity of non-linear relationships by separating meteorology from complex emission patterns before modelling. The case study is based on PM2.5 concentration time series data and meteorological data for 2018 to 2021 in Colombo, Sri Lanka.
 Materials and methods: The southwest monsoon brings sea breezes from the Indian Ocean to land from May to October. To separate the effect of the monsoon winds on PM2.5 concentrations, analysis of time series data, polar plots, clusters, and Theil-Sen trends were used based on hourly-average air pollution and meteorological data for the whole dataset.
 Results: Two clear clusters were identified from scatterplots, representing the monsoon and non-monsoon periods. The study suggests that due to the combined effect of the monsoon winds and a reduction in the levels of traffic as a result of perturbations in human activity, the PM2.5 concentrations decreased at an average rate of 10.61 µg/m3/year (95% CI: 12.86 - 8.11) over the four years. During the non-monsoon season, due to traffic reductions alone, PM2.5 concentrations reduced at an average rate of 7.95 µg/m /year (95% CI: 10.07 – 5.51).
 Conclusion: These results are relevant to policymakers in the post pandemic planning of traffic and industry, with the methodology readily adapted for use in other locations where a separation of effects may be beneficial.

A Review of the Impacts of COVID-19 on Air Pollution in the World

Introduction: The COVID-19 epidemic has polluted millions of people and has caused millions of deaths worldwide. Therefore, this study aims to review the effects of COVID-19 on global air pollution.
 Materials and Methods: In this narrative review, articles related to the objectives of the study were selected in reliable scientific databases such as Web of Science, Ovid, Google Scholar, PubMed, and Scopus. A total of 294 browsing sources and ultimately 90 sources were selected.
 Results: In the COVID-19 pandemic, NO2 dropped from 53 to 11% in most countries, and PM2.5 and PM10 from 91 to 6% in some countries. CO dropped from 92 to 5% and SO2 had a decreasing trend from 77 to 7% in most countries, except for the largest cities in Britain, Poland, Taiwan, and Iran. Unlike other pollutants, O3 in most countries increased from 0.3 to 63%, but O3 decreased in some countries.
 Conclusion: In the lockdown period, the reduction of most air pollutants except O3 was observed in many countries. But after restarting, polluting activities have incresed again. Therefore, the rules implemented during lockdown time can be introduced as an appropriate option in emergencies to reduce air pollution.

Global Warming, Air Pollution and Health

A new field of biomedical ethics is opening up, concerning what should be done to reduce the direct and indirect impacts of greenhouse gas emissions on human health. Some of these impacts could be described as ‘direct’, in the form of fatalities and illnesses due to the increasingly frequent heatwaves in many countries of recent years, ascribable to anthropogenic climate change. Other impacts are mediated through the air pollution that results from emissions from vehicles in the form of a cocktail of carbon oxides including carbon monoxide, nitrogen dioxide and particulates. Most of the world’s cities have streets with unsafe pollution levels, and one child’s death in Britain has been officially ascribed to air pollution (BBC 2020). This presentation aims to validate the above claims about the impacts of emissions on health, and to suggest remedies. The early phasing out of vehicles powered by internal combustion engines is the ultimate remedy for the latter set of impacts, while the urgent replacement of energy generated from fossil-fuel sources with renewable energy is the best way to remediate the former set. More immediate remedies for air pollution include restricting the use of roads and streets in urbanised areas by vehicles to bicycles and light vehicles with small engines. Medical and nursing education should include the diagnosis and treatment of pulmonary conditions resulting from increased levels of carbon oxides, nitrogen oxides and particulates. Medical and nursing practice should focus on the early identification of vulnerable adults and children at risk from air pollution, and warnings against walking, running or cycling along the most polluted thoroughfares.

Experimental assessment of lamella heat exchanger as cold intake air system for spark ignition engine by utilizing vehicle air conditioning system

Global warming and air pollution have become major concerns for humanity, especially in the last few decades. The transport sector contributes significantly to a large proportion of urban air pollution due to the dramatic increase in vehicle production and transportation growth, resulting in harmful emissions. Cooling the intake air temperature is one of the alternative strategies to reduce exhaust emissions and improve combustion conditions. The present study adopted the Lamella heat exchanger (LHE) as an intake air cooling device for a 1.5 L naturally aspirated engine. The design size of LHE is based on the maximum space available in the test vehicle for its installation. A refrigerant derived from the vehicle air conditioning (VAC) system acts as a coolant medium for LHE. For experimental testing, two types of vehicle statuses are considered, i.e., moving and static, to evaluate the performance of the cooling device in both positions. Engine power, torque, exhaust emissions, and fuel consumption are designated as evaluating parameters. The results depict that lowering the temperature of the intake air by 30–40°C through LHE reduces the increased quantity of exhaust emissions due to the VAC system by 43.6%, 39.5%, 47.3%, and 64.5% for CO, CO2, HC, and NOx respectively. Further, the amount of lost engine power and torque due to the VAC system is partially recovered by 17% and 24%, respectively, by introducing cold air into the engine. Convincingly, LHE has a significant potential to improve engine performance.

Estimation of green mining GDP for 40 countries

AbstractMining is an important economic activity and a source of fiscal resources in many countries. However, its contribution to GDP does not reflect the depletion of non‐renewable natural resources and the environmental damage caused. For this reason, methodologies have emerged that allow correcting the traditional GDP through the so‐called green GDP. The main objective of this study is to use the same method, data from the same source, and economic valuation of the same components to compare the green GDP among countries and its evolution over time. Specifically, the green mining GDP (in millions of dollars for the year 2014) is estimated for 40 countries, valuing the depreciation of natural capital and the environmental damage associated with global and local air pollutants emissions. The results show that the green mining GDP represents only 24.4% of the mining GDP in all the countries studied from 2000 to 2014. However, the indicator is quite heterogeneous among countries and years analyzed. For example, 25 countries have had a positive green mining GDP in all years, and 10 countries have achieved it in recent years. Thus, it is concluded that there is ample space to develop more sustainable mining in many countries.

Optimization of water removal from oil by eggplant stems using response surface methodology

Eggplant stems are among the most produced organic wastes. Unfortunately, the burning and irregular storage of eggplant stems outdoors causes both global air pollution and environmental pollution. Environmental impacts can be minimized by recycling eggplant stems, turning them into valuable products and using them as valuable additives. In this study, the water-binding capacity (WBC) and water-binding capacity in oil (WBCO) potential of eggplant stems was investigated. In the first step, optimization of the alkaline treatment of eggplant stems was carried out. Alkaline treatment optimization parameters such as sodium hydroxide (NaOH) concentration (0.050, 0.125 and 0.200 M), temperature (20, 40 and 60°C) and reaction time (30, 90 and 150 min) were investigated using response surface methodology. In the second stage, WBC and WBCO tests of eggplant stems were carried out. According to the experimental results, capacity efficiencies of 30.64 and 98.20% were obtained for WBC and WBCO, respectively, at 0.125 M sodium hydroxide concentration, 60°C temperature and 150 min reaction time. In addition, eggplant stems demonstrated the ability to retain water effectively for up to five cycles. The high WBC of eggplant stems in oil after alkali treatment showed that they could be a suitable and inexpensive candidate for use in biodiesel purification and methane production.

Reversal of trends in global fine particulate matter air pollution

Ambient fine particulate matter (PM2.5) is the world’s leading environmental health risk factor. Quantification is needed of regional contributions to changes in global PM2.5 exposure. Here we interpret satellite-derived PM2.5 estimates over 1998-2019 and find a reversal of previous growth in global PM2.5 air pollution, which is quantitatively attributed to contributions from 13 regions. Global population-weighted (PW) PM2.5 exposure, related to both pollution levels and population size, increased from 1998 (28.3 μg/m3) to a peak in 2011 (38.9 μg/m3) and decreased steadily afterwards (34.7 μg/m3 in 2019). Post-2011 change was related to exposure reduction in China and slowed exposure growth in other regions (especially South Asia, the Middle East and Africa). The post-2011 exposure reduction contributes to stagnation of growth in global PM2.5-attributable mortality and increasing health benefits per µg/m3 marginal reduction in exposure, implying increasing urgency and benefits of PM2.5 mitigation with aging population and cleaner air.

Geophysical Uncertainties in Air Pollution Exposure and Benefits of Emissions Reductions for Global Health

AbstractExposure to fine particulate matter (PM2.5) air pollution is associated with large‐scale health consequences, but the ranges in estimates of global air pollution exposure and PM2.5‐related global premature mortality remain understudied. Using four model/observation‐based PM2.5 data sets and six Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models, we compare ranges in current PM2.5‐related mortality estimates based on model/observation combinations to the range of projected emissions reductions and the resulting impacts on global health from CMIP6 models. Although estimates of current mortality are sensitive to the PM2.5 data set (6.54–9.23 million/year using the central estimate from the Global Exposure Mortality Model), the projected near‐term benefits of emissions reductions for reduced mortality are much more certain. Specifically, until the middle of the century, uncertainty ranges in projected avoided deaths are less than the magnitude of ranges in present‐day mortality estimates, even when projected future changing socio‐demographic factors are considered. Under a low‐emissions scenario, avoided cumulative early deaths could reach 275 million (range: 243–351 million) by 2100, assuming no future socio‐demographic changes. Avoided cumulative deaths could reach 124 million (range: 74–246 million) if changing future socio‐demographic factors are considered. As the global population ages and becomes more sensitive to breathing polluted air, there will be an increasing need for policies that both reduce air pollution and improve public health.

Is there an EKC between economic growth and air pollutant emissions in SAARC countries? Evidence from disaggregated analysis.

The manufacturing and construction (M&C) sector not only plays a vital role in promoting economic growth, but is also a significant contributor to global air pollution. Growing concerns regarding air pollutant emissions necessitate a more disaggregated (i.e., sectoral) investigation in order to identify the major contributors. This study employs aggregated and disaggregated data to determine the fundamental effects of economic growth (i.e., overall growth and sectoral growth) on air pollutant emissions (APE) (specifically, PM2.5 and PM10 released by the M&C sector) in SAARC economies between 1995 and 2018. It assesses the environmental Kuznets curve (i.e., inverted U-shaped and N-shaped) using the feasible generalized least squares (FGLS), panel-corrected standard errors (PCSE), and generalized method of moments (GMM) techniques. The sectoral analysis reveals the presence of an N-shaped EKC while the overall analysis indicates an inverted U-shaped EKC. Population, financial development (FD), and merchandise exports (MX) have no influence on the estimates. Population and FD increase APE in all models, whereas the effects of MX vary between models. As SAARC economies are capital-deficient, these economies can adopt unbalanced environmental protection policies. First, focus on major contributing sectors (e.g., M&C sector) to curb APE, then focus on less emitting sectors in turn. By implementing pollution reduction strategies on M&C sector activities, governments may reach their threshold (peak) points earlier than expected. A reduction in APE is impossible without rigorous monitoring and application. Being capital-deficient nations and given the collective nature of the problem, a Transboundary Haze/Pollution agreement is required to solve this issue.

Economic and environmental effects of financing subsidies for non-conventional renewable energies with a carbon tax – A comparison of intersectoral models

Non-conventional renewable energy (NCRE) subsidies have been introduced in various countries to help reduce greenhouse gas (GHG) emissions. However, other social priorities limit the allocation of fiscal resources to this climate policy in Chile. This study analyzes the option of financing NCRE subsidies through carbon taxes in the thermoelectric sector. Specifically, two intersectoral models (the Leontief price model and the SAM price model) are used to simulate the impact of this mix of climate policies on prices, production, employment, and emissions of global and local air pollutants. The results of both models show that CO2 emissions would be reduced slightly in the short term, which is explained by the low current tax rate, the inelasticity of energy demand, and the indirect stimulus of subsidies on production in other sectors of the economy. In addition, it is concluded that the Leontief price model overestimates the impacts since it omits the falls in labor income and household consumption that the SAM price model captures. So, it is recommended to use models based on a social accounting matrix to evaluate energy policies when more sophisticated intersectoral models with endogenous prices and quantities (computable general equilibrium models) are unavailable.

Urban–rural disparity in global estimation of PM2·5 household air pollution and its attributable health burden

Polluting fuels and inefficient stove technologies are still a leading cause of premature deaths worldwide, particularly in low-income and middle-income countries. Previous studies of global household air pollution (HAP) have neither considered the estimation of PM2·5 at national level nor the corresponding attributable mortality burden. Additionally, the effects of climate and ambient air pollution on the global estimation of HAP-PM2·5 exposure for different urban and rural settings remain largely unknown. In this study, we include climatic effects to estimate the HAP-PM2·5 exposure from different fuel types and stove technologies in rural and urban settings separately and the related attributable global mortality burden. Bayesian hierarchical models were developed to estimate an annual average HAP-PM2·5 personal exposure and HAP-PM2·5 indoor concentration (including both outdoor and indoor sources). Model variables were selected from sample data in 282 peer-reviewed studies drawn and updated from the WHO Global HAP dataset. The PM2·5 exposure coefficients from the developed model were applied to the external datasets to predict the HAP-PM2·5 exposure globally (personal exposure in 62 countries and indoor concentration in 69 countries). Attributable mortality rate was estimated using a comparative risk assessment approach. Using weighted averages, the national level 24 h average HAP-PM2·5 exposure due to polluting and clean fuels and related death rate per 100 000 population were estimated. In 2020, household use of polluting solid fuels for cooking and heating led to a national-level average personal exposure of 151 μg/m3 (95% CI 133-169), with rural households having an average of 171 μg/m3 (153-189) and urban households an average of 92 μg/m3 (77-106). Use of clean fuels gave rise to a national-level average personal exposure of 69 μg/m3 (62-76), with a rural average of 76 μg/m3 (69-83) and an urban average of 49 μg/m3 (46-53). Personal exposure-attributable premature mortality (per 100 000 population) from the use of polluting solid fuels at national level was on average 78 (95% CI 69-87), with a rural average of 82 (73-90) and an urban average of 66 (57-75). The average attributable premature mortality (per 100 000 population) from the use of clean fuels at the national level is 62 (54-70), with a rural average of 66 (58-74) and an urban average of 52 (47-57). The estimated HAP-PM2·5 indoor concentration shows that the use of polluting solid fuels resulted in a national-level average of 412 μg/m3 (95% CI 353-471), with a rural average of 514 μg/m3 (446-582) and an urban average of 149 μg/m3 (126-173). The use of clean fuels (gas and electricity) led to an average PM2·5 indoor concentration of 135 μg/m3 (117-153), with a rural average of 174 μg/m3 (154-195) and an urban average of 71 μg/m3 (63-80). Using time-weighted HAP-PM2·5 indoor concentrations, the attributable premature death rate (per 100 000 population) from the use of polluting solid fuels at the national level is on average 78 (95% CI 72-84), the rural average being 84 (78-91) and the urban average 60 (54-66). From the use of clean fuels, the average attributable premature death rate (per 100 000 population) at the national level is 59 (53-64), the rural average being 68 (62-74) and the urban average 45 (41-50). A shift from polluting to clean fuels can reduce the average PM2·5 personal exposure by 53% and thereby lower the death rate. For all fuel types, the estimated average HAP-PM2·5 personal exposure and indoor concentrations exceed the WHO's Interim Target-1 average annual threshold. Policy interventions are urgently needed to greatly increase the use of clean fuels and stove technologies by 2030 to achieve the goal of affordable clean energy access, as set by the UN in 2015, and address health inequities in urban-rural settings. Wellcome Trust, The Lancet Countdown, the Engineering and Physical Sciences Research Council, and the Natural Environment Research Council.

Global air pollution exposure and poverty

Air pollution is one of the leading causes of health complications and mortality worldwide, especially affecting lower-income groups, who tend to be more exposed and vulnerable. This study documents the relationship between ambient air pollution exposure and poverty in 211 countries and territories. Using the World Health Organization’s (WHO) 2021 revised fine particulate matter (PM2.5) thresholds, we show that globally, 7.3 billion people are directly exposed to unsafe average annual PM2.5 concentrations, 80 percent of whom live in low- and middle-income countries. Moreover, 716 million of the world’s lowest income people (living on less than $1.90 per day) live in areas with unsafe levels of air pollution, especially in Sub-Saharan Africa. Air pollution levels are particularly high in lower-middle-income countries, where economies tend to rely more heavily on polluting industries and technologies. These findings are based on high-resolution air pollution and population maps with global coverage, as well as subnational poverty estimates based on harmonized household surveys.

Optical and Physical Characteristics of Aerosol Layers in Australia Based on CALIPSO

Atmospheric aerosols have important impacts on global radiative forcing, air pollution, and human health. This study investigated the optical and physical properties of aerosol layers over Australia from 2007 to 2019 using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Level 2 aerosol products. Australia was divided into three sub-regions (western highlands, central plains, and eastern ranges). Interannual and seasonal optical property variations in aerosol layers in the three sub-regions were analyzed and compared. Results showed that annual mean values of AODL (lowest aerosol layer AOD) and AODT (total AOD of all aerosol layers) were always higher in the eastern ranges region than the other two regions from 2007 to 2019. The reason could be that Australian population was predominantly located in the eastern ranges region, where more human activities could bring significant aerosol loadings. BL (base height of the lowest aerosol layer), HL (top height of the lowest aerosol layer), and HH (top height of the highest aerosol layer) all showed trends of “western highlands > eastern mountains > central plains”, indicating that the higher the elevation, the higher the BL, HL, and HH. TL (thickness of the lowest aerosol layer) was higher during the day than at night, which might account for increased diurnal atmospheric convection and nocturnal aerosol deposition. DRL (depolarization ratio of the lowest aerosol layer) was higher in the western highlands and central plains than the eastern mountains, probably because these two regions have large deserts with more irregularly shaped dust aerosols. CRL (color ratio of the lowest aerosol layer) had slightly higher values in the eastern ranges than the other two regions, probably due to the wet climate of the eastern ranges, where aerosols were more hygroscopic and had larger particle sizes. This study can provide technical support for the control and management of regional air pollutants.

Highly efficient degradation of sulfur-containing volatile organic compounds by amorphous MnO2 at room temperature: Implications for controlling odor pollutants

Sulfur-Containing Volatile Organic Compounds (S-VOCs) are notorious for global air pollution due to their odorous characteristics and exhibiting adverse health effects. Nevertheless, the catalytic degradation of S-VOCs at low temperatures is still a tremendous challenge for air purification. In this study, methyl mercaptan (CH3SH), a typical S-VOCs contaminant, could be completely removed by amorphous MnO2 with high efficiency (100 %) for 40 h at room temperature, and demonstrating significantly enhanced stability (over 100 h) in the presence of 20 %RH (Relative humidity), which is far superior to the performance of previous reported catalysts. The amorphous MnO2 with surface-rich oxygen vacancies can trigger the formation of more reactive oxygen species (ROS) and stronger O2 adsorption capability comparing with the crystalline MnO2, the corresponding results are characterized by XPS and EPR. Moreover, In Situ-DRIFTS coupled with DFT calculations revealed that the CH3SH could be transformed into CO32-/SO42- by ROS. Unexpectedly, the amorphous MnO2 also displayed excellent activity and stability towards to other typical S-VOCs, which is beneficial for the actual industrial application. The findings can provide novel insights into the design of highly efficient and stable catalysts to eliminate odor gaseous pollutants over a broad operating concentration window at room temperature.

Global declines of offshore gas flaring inadequate to meet the 2030 goal

Monitoring of gas flaring (GF)—the burning of natural gas associated with oil extraction—over most oil- and gas-producing areas is challenging due to high costs or difficult field investigations. As GF contributes to both global warming and air pollution, an up-to-date picture (locations, emissions and trends) of global offshore GF can help countries’ energy decarbonization efforts substantially. Although high-resolution satellite sensors regularly capture high-temperature signals from GF, retrieving spatially explicit information and estimating GF volumes from petabyte images remain challenging. Here we developed a monitoring framework and compiled a 20 m resolution inventory of offshore GF sites by analysing ~8.53 million Sentinel-2 images. A robust model (R2 > 0.99) was established to estimate offshore GF volumes from Sentinel-2 metrics. Our findings reveal that Sentinel-2 can pinpoint global offshore GFs to support scientifically sound decision-making; a vital few (~20%) sites are responsible for >80% of offshore GF volumes, calling for more targeted regulations; and the offshore GF volumes have declined by 26.4% from 2016 to 2021. We conclude that the Zero Routine Flaring Initiative by the Global Gas Flaring Reduction Partnership committing governments and oil companies to end routine flaring by no later than 2030 could be 5 years behind schedule. Monitoring of gas flaring (GF) can be expensive and practically difficult, but better information about global offshore GF is needed to inform decarbonization policies. This study presents a monitoring framework, a detailed inventory of offshore GF sites and estimates of GF volumes globally.

Prospect of Direct Dimethyl Ether Production from CO2: Reactor Design Development

The increasing emissions of carbon dioxide (CO2) and volatile hydrocarbons via burning of fossil fuels result in a significant amount of global warming and air pollution. With the concern over the impact of fossil fuel to the environment, the interest in alternative fuel production from the CO2 generated through utilization of new technologies has risen rapidly. Several clean alternative fuels, including dimethyl ether (DME) have been investigated for a more sustainable and greener environment. DME has a high cetane number but produces much lower NOx emission upon combustion. DME is typically synthesized using syngas based on conventional indirect DME route, where the process begins with conversion of syngas into methanol and subsequently dehydrated to DME in separate units. Recently, a direct single-step route to produce DME through dehydrogenation of CO2 and dehydration of methanol by utilising a novel bifunctional catalyst has been investigated. In direct DME, the dehydrogenation and dehydration occur simultaneously in a single reactor, which eliminate the need for a methanol production plant. However, the use of conventional fixed-bed reactor (FBR) for the direct DME synthesis causes many challenges including catalyst deactivation, where water appears in the reaction area, limiting the conversion of CO2 reactants into DME and consequently, the DME yield. It is also essential to manage the exothermic heat generated from the catalyst for better DME yield. In order to overcome these hurdles, several types of reactors have been proposed such as fluidized bed reactor, slurry reactor, microreactor and catalytic membrane reactor. In this paper, different types of reactors are first discussed and its applications related to the direct DME production from CO2 are highlighted. Finally, the challenges and difficulties of reactor development are addressed and future direction is outlined.