A study of regulated and green house gas emissions from a prototype heavy-duty compressed natural gas engine under transient and real life conditions

The dependence of oil production in the Gulf Cooperation Council (GCC) region may have environmental consequences. This research explores the nonlinear effects of oil rents and the economic growth of six GCC countries on their per capita CO2, CH4, N2O, and Greenhouse Gas (GHG) emissions, considering spatial linkages through 1980–2014. We apply fixed effects (FE) and corroborate the spatial dependency in all estimated pollution models. Spatial Durbin model (SDM) is utilized to estimate the direct and spillover effects. We find the inverted U-shaped relationship of economic growth with CO2, CH4, N2O and GHG emissions, and of oil rents with CH4 and GHG emissions. Monotonic positive effects of oil rents on CO2 emissions and U-shaped relationship between oil rents and N2O emissions are also found. Urbanization has positive effect on the CO2, CH4 and GHG emissions and has negative effect on N2O emissions. Financial market development (FMD) has negative effects on all types of investigated emissions. Foreign direct investment (FDI) has negative effects on CO2 and N2O emissions. Energy use has positive effects on CO2 and N2O emissions. Further, the neighboring spillover effects of economic growth, oil rents, urbanization, FDI, energy use and FMD are found statistically significant for some investigated emissions. Hence, oil rents, energy use, urbanization and economic growth are responsible for environmental degradation of home and neighboring countries in the GCC region, and we recommend implementing tighter laws to protect the environment.

Climatic temperature controls the geographical patterns of coastal marshes greenhouse gases emissions over China

Biomethane CNG hybrid: A reduction by more than 80% of the greenhouse gases emissions compared to gasoline

China's CH4 and CO2 emissions: Bottom-up estimation and comparative analysis

This study investigates the effect of energy consumption on greenhouse gas (GHG) emissions in 33 African countries from 1995–2017. It contributes to the literature by investigating the effect of disaggregated measures of energy consumption (coal, oil and other liquids, renewable energy, and electricity) on GHG emissions (CO2, N2O, CH4, and total GHG emissions) in Africa and identifies the transmission channels through which energy consumption affects GHG emissions. The system GMM is used in the study as it accounts for possible endogeneity and the potential correlation between the error term and the country fixed effects. The results show that coal consumption significantly increases CO2, CH4, and total GHG emissions and reduces N2O emissions. Oil consumption increases CO2 and total GHG emissions but reduces N2O and CH4 emissions. Renewable energy consumption reduces CO2 and CH4 emissions but increases N2O emissions. Finally, electricity consumption promotes CO2, N2O, CH4 and total GHG emissions in Africa. Further analyses show that foreign trade and economic growth are the channels through which oil consumption increases GHG emissions. The adverse effect of electricity is through urbanization. Renewable consumption could decrease GHG emissions through sustainable urbanization and trade policies. The findings suggest that countries should gradually reduce coal consumption and encourage renewable energy consumption, which has the lowest impact on the environment.

Abstract. Greenhouse gas (GHG) emissions represent a pivotal driver of global climate change, with vehicular emissions, particularly from light-duty vehicles, emerging as a prominent source of GHGs. Despite extensive research on gaseous pollutants, studies on GHG emissions within the framework of carbon neutrality remain scarce. This study delves into the emission characteristics of three primary GHGs (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) from various light-duty vehicles, encompassing conventional gasoline and hybrid vehicles and bi-fuel taxis. As anticipated, with advancements in emission standards and powertrains, vehicular GHG emissions have significantly decreased. However, our findings also revealed surprising trends. While engine technology upgrades reduced CO2, they unexpectedly increased CH4 and N2O emissions. Additionally, hot starts, beneficial for reducing CO2 and CH4 emissions, caused heightened N2O emissions, which is noteworthy under operating conditions with frequent start–stop events. Intriguingly, compressed natural gas (CNG), generally perceived as cleaner, increased CH4 emissions. Regarding the impact of three-way-catalyst (TWC) converters on GHG emissions, under “TWC deteriorated” conditions, N2O emissions from CNG-powered vehicles were approximately 3 times higher than those under “TWC worked” conditions, which can be attributed to the significant increase in nitrogen oxides (NOx). Considering the global warming potential (GWP), the “TWC deteriorated” scenario paradoxically decreased GWP values, highlighting the complex interaction between emission control technologies and their environmental impacts. This study provides crucial insights into vehicular GHG emissions, which are essential for developing effective strategies aimed at mitigating emissions and enhancing the efficiency of emission control systems.

Prescribed fires or wildfires are common in natural ecosystems. Biochar input during fires can impact soil greenhouse gas (GHG) emissions, including methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O). Meadows are functionally important ecosystems due to their large carbon (C) and nitrogen (N) stocks and potential to mitigate GHG emissions. The effects of biochar on meadow GHG emissions may be sensitive to whether it is derived from more than one type of vegetation, especially with N addition and warming. To further our understanding of how input of fire-derived biochar affects meadow soil GHG emissions, especially under the context of N deposition and warming, we conducted this study to examine potential non-additive effects of these factors. We collected soils from meadows dominated by Miscanthus sinensis and Arundinella hirta at Wugong Mountain (Jiangxi, China). Biochar was produced by pyrolyzing the aboveground vegetation of each of the two species at 450 °C for 1 h. Mixed biochar was produced by 1:1 ratio. Soil GHG emissions and N transformations were measured by incubating soils with biochar (control, M. sinensis biochar, A. hirta biochar, mixed biochar) and N addition (control vs. 6 g m−2) treatments at different temperatures (10, 15, 20, or 25 °C). Biochar input consistently increased both CH4 and N2O flux, but only A. hirta and mixed biochar decreased CO2 emission rates. Mixed biochar imposed non-additive effects on cumulative CH4 and CO2 emissions. Biochar decreased soil nitrification rates and increased the temperature sensitivity of soil N2O emission rates. The results indicated that biochar input during fires in meadows impacts soil GHG emissions and N transformations. Input of biochar into meadow soil following fire impacted GHG emissions, and mixing biochar derived from different species imposed non-additive effects on CH4 and CO2 emissions. The variable and non-additive biochar effects on soil GHG emissions showed that fire-induced alterations in meadow soil GHG emissions will depend on the species composition of the local plant community. The effects of biochar on meadow soil GHG emissions after fires should be considered in future budgets of meadow soil GHG emissions and prediction of prescribed fire impacts on meadow ecosystems under the context of N deposition and warming.

The cropping system conversion, from rice to vegetable, showed various influences on the greenhouse gases (GHG) emission with conversion time and fertilizer/irrigation management. In this study, we evaluated the DeNitrification-DeComposition (DNDC) model for predicting carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) emissions and crop yields as rice converted to vegetable cropping system under conventional or no fertilization from 2012 to 2014. Then, we quantified the long-term (40 years) impacts of rice-vegetable cropping system conversions and fertilization levels (0, 50, 100 and 150% conventional fertilization rate) on GHGs emissions and global warming potentials (GWP) using the calibrated model. The DNDC model-simulated daily GHG emission dynamics were generally consistent with the measured data and showed good predictions of the seasonal CH4 emissions (coefficient of determination (R2) = 0.96), CO2 emissions (R2 = 0.75), N2O emissions (R2 = 0.75) and crop yields (R2 = 0.89) in response to the different cropping systems and fertilization levels across the two years. The overall model performance was better for rice than for vegetable cropping systems. Both simulated and measured two-year data showed higher CH4 and CO2 emissions and lower N2O emissions for rice than for vegetable cropping systems and showed positive responses of the CO2 and N2O emissions to fertilizations. The lowest GWP for vegetable without fertilization and highest the GWP for rice with fertilization were obtained. These results were consistent with the long-term simulation results. In contrast to the two-year experimental data, the simulated long-term CH4 emissions increased with fertilization for the rice-dominant cropping systems. The reasonable cropping systems and fertilization levels were recommended for the region.

Spring thawing can affect the soil carbon and nitrogen cycling processes and lead to changes in the emissions of greenhouse gases. The temporal variations and impact factors of soil GHGs fluxes were measured in Phragmites australis and Carex appendiculata with the static chamber from the end of March to the end of May in 2018 in riparian wetlands of Xilin River, which is typical inland river meandering through steppe region in Inner Mongolia, China. The results showed that soil CH4 and N2O emissions of the P. australis were significantly higher than those of the Carex appendiculata, whereas CO2 emissions were no significant difference. The responses of soil GHG fluxes to soil environmental factors in P. australis and Carex appendiculata differed. In the P. australis community, soil CO2 and CH4 emissions were influenced jointly by mainly the soil temperature and microbial biomass nitrogen, whereas soil N2O emission was mainly affected by the soil temperature. The dominant controlling factor for CO2 and N2O was soil temperature in the Carex appendiculata, whereas CH4 was mainly regulated by soil water content. The global warming potential of P. australis was significantly higher than that of Carex appendiculata. Those findings highlight the difference in soil greenhouse gas fluxes in different plant communities and the importance of CH4 and N2O emissions during the spring thaw, which contributes to predicting the riparian wetland soil greenhouse gases and their global warming potential under global climate changes.

Understanding microbial associations with greenhouse gas (GHG) emissions is essential for promoting climate-friendly prawn production, yet it remains largely unexplored. To examine microbial-GHG relationships, this study analysed CO2, CH4, and N2O emissions, characterised microbial communities, and measured the abundances of key functional genes (mcrA, pmoA, amoA, and nosZ) in water and sediment from Bangladeshi prawn farms. Results showed that microbial richness was positively correlated with CO2 and N2O emissions but negatively with CH4 emissions. Methanogenic archaea, most abundant in high-salinity farms, were positively associated with CH4 flux; however, their negative relationship with CO2 emission appeared insignificant. Conversely, the negative correlation between the relative abundance of anaerobic methanotrophs (ANME) and CH4 emission suggests that CH4 oxidation facilitated by ANME could be a promising strategy for reducing CH4 emissions. N2O emission was negatively linked to most bacterial and archaeal classes; however, N2O-consuming Chloroflexi exhibited a positive correlation with N2O emission. Additionally, a strong link between the mcrA gene in water and CH4 production may relate to previous findings of methane production in oxygenated water. This multidisciplinary study enhances our understanding and opens avenues for further research into reducing emissions by modulating microbial communities within prawn farming systems.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-22768-8.

Energy supply utilities release significant amounts of greenhouse gases (GHGs) into the atmosphere. It is essential to accurately estimate GHG emissions with their uncertainties, for reducing GHG emissions and mitigating climate change. GHG emissions can be calculated by an activity-based method (i.e., fuel consumption) and continuous emission measurement (CEM). In this study, GHG emissions such as CO2, CH4, and N2O are estimated for a heat generation utility, which uses bituminous coal as fuel, by applying both the activity-based method and CEM. CO2 emissions by the activity-based method are 12–19% less than that by the CEM, while N2O and CH4 emissions by the activity-based method are two orders of magnitude and 60% less than those by the CEM, respectively. Comparing GHG emissions (as CO2 equivalent) from both methods, total GHG emissions by the activity-based methods are 12–27% lower than that by the CEM, as CO2 and N2O emissions are lower than those by the CEM. Results from uncertainty estimation show that uncertainties in the GHG emissions by the activity-based methods range from 3.4% to about 20%, from 67% to 900%, and from about 70% to about 200% for CO2, N2O, and CH4, respectively, while uncertainties in the GHG emissions by the CEM range from 4% to 4.5%. For the activity-based methods, an uncertainty in the Intergovernmental Panel on Climate Change (IPCC) default net calorific value (NCV) is the major uncertainty contributor to CO2 emissions, while an uncertainty in the IPCC default emission factor is the major uncertainty contributor to CH4 and N2O emissions. For the CEM, an uncertainty in volumetric flow measurement, especially for the distribution of the volumetric flow rate in a stack, is the major uncertainty contributor to all GHG emissions, while uncertainties in concentration measurements contribute a little to uncertainties in the GHG emissions.Implications:Energy supply utilities contribute a significant portion of the global greenhouse gas (GHG) emissions. It is important to accurately estimate GHG emissions with their uncertainties for reducing GHG emissions and mitigating climate change. GHG emissions can be estimated by an activity-based method and by continuous emission measurement (CEM), yet little study has been done to calculate GHG emissions with uncertainty analysis. This study estimates GHG emissions and their uncertainties, and also identifies major uncertainty contributors for each method.

Salt-affected soils contain high levels of soluble salts (saline soil) and exchangeable sodium (alkali soil). Globally, about 932 million ha (Mha), including 831 Mha of agricultural land, is salt-affected. Salinity and sodicity adversely affect soil microbial diversity and enzymatic activities, and thereby carbon and nitrogen dynamics and greenhouse gas (GHG) emissions from soils. In this review article, we synthesize published information to understand the impact of salinity and sodicity on GHG production and emissions from salt-affected soils, and how various reclamation amendments (gypsum, phosphogypsum, organic manure, biochar, etc.) affect GHG emissions from reclaimed soils. Nitrous oxide (N2O) and methane (CH4) emissions are of greater concern due to their 298 and 28 times higher global warming potential, respectively, compared to carbon dioxide (CO2), on a 100-year time scale. Therefore, CO2 emissions are given negligible/smaller significance compared to the other two. Generally, nitrous oxide (N2O) emissions are higher at lower salinity and reduced at higher salinity mainly due to: (a) higher ammonification and lower nitrification resulting in a reduced substrate for denitrification; (b) reduced diversity of denitrifying bacteria lowered down microbial-mediated denitrification process; and (c) dissimilatory nitrate reduction to ammonium (DNRA), and denitrification processes compete with each other for common substrate/nitrate. Overall, methane (CH4) emissions from normal soils are higher than those of salt-affected soils. High salinity suppresses the activity of both methanogens (CH4 production) and methanotrophs (CH4 consumption). However, it imposes more inhibitory effects on methanogens than methanotrophs, resulting in lower CH4 production and subsequent emissions from these soils. Therefore, reclamation of these soils may enhance N2O and CH4 emissions. However, gypsum is the best reclamation agent, which significantly mitigates CH4 emissions from paddy cultivation in both sodic and non-sodic soils, and mitigation is higher at the higher rate of its application. Gypsum amendment increases sulfate ion concentrations and reduces CH4 emissions mainly due to the inhibition of the methanogenesis by the sulfate reductase bacteria and the enhancement of soil redox potential. Biochar is also good among the organic amendments mitigating both CH4 and N2O emission from salt-affected soils. The application of fresh organic matter and FYM enhance GHG emissions for these soils. This review suggests the need for systematic investigations for studying the impacts of various amendments and reclamation technologies on GHG emissions in order to develop low carbon emission technologies for salt-affected soil reclamation that can enhance the carbon sequestration potential of these soils.

Micro/nanoplastic pollution heterogeneously increased greenhouse gas emissions from wetlands: A multilevel meta-analysis

Reducing greenhouse gas (GHG) emissions from agricultural fields is crucial for mitigating climate change and promoting sustainable agriculture. This study conducted a meta-analysis of 82 domestic experimental studies to assess the effects of fertilization, tillage, and straw return on CH4, CO2, and N2O emissions across different regions in China. The key findings include: fertilization measures: split fertilization increased CH4 and N2O emissions, whereas a single application had the strongest impact on CO2 emissions. The application of carbon alone or in combination with NPK reduced GHG emissions, while the combination of nitrogen and farmyard manure significantly increased CH4 and CO2 emissions. Tillage measures: tillage generally reduced CH4 and CO2 emissions but increased N2O emissions. No-tillage effectively suppressed CH4 emissions, while rotary tillage significantly reduced CO2 emissions. Straw return: straw returning through rotary tillage led to the highest increase in CH4 and CO2 emissions, whereas direct straw return most notably enhanced N2O emissions. This study provides insights into optimizing agricultural practices to mitigate GHG emissions and offers guidance for sustainable and low-carbon agricultural development.

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