Real-road NOx and CO2 emissions of city and highway China-6 heavy-duty diesel vehicles

The emission of heavy-duty vehicles has raised great concerns worldwide. The complex working and loading conditions, which may differ a lot from PEMS tests, raised new challenges to the supervision and control of emissions, especially during real-world applications. On-board diagnostics (OBD) technology with data exchange enabled and strengthened the monitoring of emissions from a large number of heavy-duty diesel vehicles. This paper presents an analysis of the OBD data collected from more than 800 city and highway heavy-duty vehicles in China using remote OBD data terminals. Real-world NOx and CO2 emissions of China-6 heavy-duty vehicles have been examined. The results showed that city heavy-duty vehicles had higher NOx emission levels, which was mostly due to longer time of low SCR temperatures below 180°C. The application of novel methods based on 3B-MAW also found that heavy-duty diesel vehicles tended to have high NOx emissions at idle. Also, little difference had been found in work-based CO2 emissions, and this may be due to no major difference were found in occupancies of hot running.

Spatiotemporal dynamics and influencing factors of CO2 emissions under regional collaboration: Evidence from the Beijing-Tianjin-Hebei region in China

Against the backdrop of global climate change and the "dual carbon" target, cities have a significant responsibility to achieve carbon reduction targets. As a crucial urban agglomeration in northern China, effectively balancing economic growth with CO2 emission reduction to achieve high-quality economic development remains a significant challenge that the Beijing-Tianjin-Hebei region should address both presently and in the future. The objective of this study is to utilize nighttime lighting data and energy consumption information to quantify the CO2 emissions of diverse cities within the Beijing-Tianjin-Hebei region spanning from 2006 to 2020. The research aims to analyze the spatial progression patterns of CO2 emissions across these urban centers, identify key determinants and their interrelations, and delve into the underlying mechanisms pivotal for advancing carbon mitigation strategies within urban agglomerations. The results indicate that: with an exception in Beijing where CO2 emissions slightly decreased compared to 2006, CO2 emissions increased across cities in the Beijing-Tianjin-Hebei region by 2020. High-value CO2 emission areas are primarily concentrated in central of the study area, exhibiting negative spatial correlation characteristics. Based on its urban development positioning, it is imperative for the Beijing-Tianjin-Hebei urban agglomeration to formulate and implement carbon reduction strategies on innovative development, industrial upgrading, and ecological protection among other aspects towards coordinated low-carbon development.

Investigating the effects of climate change and anthropogenic activities on SOC storage and cumulative CO2 emissions in forest soils across altitudinal gradients using the century model

This study investigated the impact of climate change, grazing, manure application, and liming on soil organic carbon (SOC) stock and cumulative carbon dioxide (CO2) emissions in forest soils across different altitudes. Despite similar soil texture, acidity, and salinity across elevations, SOC stock significantly increased with altitude due to cooler temperatures and higher precipitation. The highest SOC stock (97.46 t ha-1) was observed at 2000-2500 m, compared to the lowest (44.23 t ha-1) at 500-1000 m. The Century C Model accurately predicted SOC stock, with correlation and determination coefficients exceeding 0.98. A climate change scenario projecting decreased precipitation (2.15 mm per decade) and increased temperature (0.4 °C) revealed potential SOC stock losses ranging from 28.36 to 36.35 %, particularly at higher altitudes. Grazing further decreased SOC stock, with a more pronounced effect at higher elevations. However, manure application (40 t ha-1 every four years) and liming (7-10 t ha-1 every three years) had positive effects on SOC stock, again amplified at higher altitudes and with an increase in lime application rate. In scenarios combining climate change with manure application and climate change with liming, manure application and liming mitigated some negative impacts of climate change, but could not fully offset them, resulting in 1.49-5.42 % and 0.39-4.07 % decreases respectively. Simulations of cumulative CO2 emissions mirrored the distribution of SOC stock, with higher emissions observed at higher altitudes and with management practices that increased SOC stock. This study emphasizes the critical role of conserving high-altitude forest soils and implementing optimal forest management strategies to combat climate change by minimizing SOC losses.

Recent CO2 emission and projections in Chinese provinces: New drivers and ensemble forecasting

Although extensive studies focused on the driver of changing CO2 emission, the roles of labor and capital were largely ignored in shaping spatiotemporal change in CO2 emission and forecasting differences on CO2 emission was few considered, hindering relevant policymaking towards sustainable development in both climate change mitigation and economic growth for developing countries in particular. To fill the gap above, the study explored the roles of capital and labor in contributing to recent CO2 emission in a case of China over 2010-2019 and projecting provincial CO2 emissions to 2030, by proposing two new spatiotemporal logarithmic mean Divisia index models with Cobb-Douglas production function and developing an ensemble forecasting model including machine learning. We found, first, the effects of capital and labor inputs and carbon factor were the positive drivers affecting aggregate CO2 emissions, while the effects of the total-factor productivity and energy intensity were negative drivers. Second, the effects of capital and labor inputs were the negative drivers for narrowing the emission gap. Third, the ensemble forecasting model can improve the generalization ability of CO2 emission predictions. Therefore, we recommend that policymakers focus on optimizing the carbon reduction effects of capital and labor inputs while promoting the development of a circular economy to achieve sustainable economic growth.

Thermal and structural changes of a starch flexible film and cellulosic semi-rigid tray during the biodegradation process under controlled composting conditions

Biopolymers used to mitigate the environmental impact needed establish biodegradation percentage. The thermal and structural changes of two plastic materials, a flexible film based on cassava starch - Poly(lactic acid) (PLA) and a semi-rigid cassava flour-stay cellulose fique fiber, were evaluated biodegradation under ISO 4855-1 standard. The tests were carried out for four weeks at constant temperature and flow of 58 °C ± 2 °C and 250 mL/h, using a mature compost as inoculum. The percentages of CO2, thermal, morphological, and structural changes, variation of degradation temperatures, glass transition temperatures (Tg), Melting temperatures (Tm) and enthalpies of fusion (Hm), were properly evaluated as indicators of the materials biodegradation of two materials. Scanning electron microscopy (SEM), showed the microorganisms colonization on the materials surface, evidencing the appearance of cracks and microbial population. The flexible film showed a biodegradation percentage of 98.24 %, the semi-rigid tray 89.06 %, and the microcrystalline cellulose, 81.37 %.

Undervalued dry riverbeds: A key factor in equating intermittent river CO2 emissions to perennial rivers

Intermittent rivers in semiarid and arid regions, constituting over half of the world's rivers, alternate the carbon cycle interactions among the biosphere, hydrosphere, and atmosphere. Inadequate quantification of flow duration and river water surface area, along with overlooked CO2 emissions from dry riverbeds, result in notable inaccuracies in global carbon cycle assessments. High-resolution remote sensing images combined with intensive field measurements and hydrological modelling were used to estimate and extract the flow duration, river water surface area and dry riverbed area of Huangfuchuan, an intermittent river watershed that acts as a major tributary of the Yellow River in semiarid Northwest China. CO2 emission rates and partial pressures in water and air across the watershed were in-situ measured. In 2018, the flow duration of Huangfuchuan increased from less than 5 days in the first-order tributary to 150 days in the sixth-order mainstream. River water surface area estimated by remote sensing extraction plus the hydrodynamic model simulation varied from 3.9 to 88.6 km2 under 5 %-95 % discharge frequencies. CO2 emissions from the water-air interface and dry riverbed in 2018 were estimated at 582.3 × 103 and 355.2 × 103 ton, respectively. The estimated total annual emission (937.5 × 103 ton) aligns closely with the range of emissions (67.3 × 103-1377.2 × 103 ton) calculated for the water-air interface alone, derived using DEM river length and hydraulic geometry method. This similarity can be attributed to the overestimation of flow duration and flow velocity, as well as the over- or under-estimation of river water surface area and slope. The new method proposed in this study has large potential to be applied in estimating CO2 emissions from data-scarce intermittent rivers located in mountainous regions and provides a standardized solution in the estimation of CO2 emission. Results of this research reveal the spatiotemporal distribution of CO2 emissions along an intermittent river system and highlight the substantial role of dry riverbed in carbon cycle.

Aerobic and anaerobic decomposition rates in drained peatlands: Impact of botanical composition

Drained peatlands in temperate climates are under threat from climate change and human activities. The resulting decomposition of organic matter plays a major role in regulating the associated land subsidence rates, yet the determinants of aerobic and anaerobic peat decomposition rates are not fully understood. In this study, we sought to gain insight into the drivers of decomposition rates in botanically diverse peatlands (sedge, reed, wood, and moss dominant) under oxic and anoxic conditions. Peat samples were collected from the anoxic zone and incubated for 24 h (short) and 15 weeks (long) under either oxic or anoxic conditions. CO2 emissions, hydrolytic and oxidative exoenzyme potential activities, phenolic compound concentrations, and several edaphic factors were measured at the end of each incubation period. We found that 15 weeks of oxygen exposure of anoxic peat samples accelerated the average CO2 emissions by 3.9-fold. Reed and sedge peat respired more than wood and moss peat under anoxic conditions. Interestingly, CO2 emissions from anoxic peat layers under permanently anoxic conditions were substantial and given the thickness of peat deposits in the field, such activities may play an important role in long-term land subsidence rates and total CO2 emissions from drained peatlands. The results from the long-term incubations showed that decomposition rates appear to be also controlled by factors other than oxygen intrusion such as substrate availability. In summary, the botanical composition of the peat matrix, incubation conditions and time of incubation are all important factors that need to be considered when predicting peat decomposition and subsequent land subsidence rates.

Influence of ambient temperature on the CO2 emitted of light-duty vehicle

Because of global warming, people have paid more attention to greenhouse gas emitted by vehicles. To quantify the impact of temperature on vehicle CO2 emissions, this study was conducted using the world light vehicle test cycle on two light-duty E10 gasoline vehicles at ambient temperatures of -10, 0, 23, and 40℃, and found that CO2 emission factors of Vehicle 1 in the low-speed phase were 22.07% and 20.22% higher than those of Vehicle 2 at cold start and hot start under -10℃. The reason was vehicle 1 had a larger displacement and more friction pairs than vehicle 2. There was the highest CO2 emission at the low-speed phase due to low average speed, frequent acceleration, and deceleration. The CO2 temperature factor and the ambient temperature had a strong linear correlation (R2 = 0.99). According to CO2 temperature factors and their relationships, CO2 emission factors of other ambient temperatures could be calculated when the CO2 emission factor of 23℃ was obtained, and the method also could be used to obtain the CO2 temperature factors of different vehicles. To separate the effect of load setting and temperature variation on CO2 emission quantitatively, a method was proposed. And results showed that the load setting was dominant for the CO2 emission variation. Compared with 23℃, the CO2 emission for vehicle 1 caused by load setting variation were 62.83 and 47.42 g/km, respectively at -10 and 0℃, while those for vehicle 2 were 45.01 and 35.63 g/km, respectively.

Comprehensive life cycle assessment of NH2-functionalized magnetic graphene oxide for mercury removal: Carbon emissions and economic evaluation

Heavy metals contamination critically affects human health and ecosystems, necessitating pioneering approaches to diminish their adverse impacts. Hence, this study synthesized aminated magnetic graphene oxide (mGO-NH2) for the removal of mercury (Hg) from aqueous solutions. Although functionalized GO is an emerging technology at the early stages of development, its synthesis and application require special attention to the eco-environmental assessment. Therefore, the life cycle assessment and life cycle cost of mGO-NH2 were investigated from the cradle-to-gate approach for the removal of 1 kg Hg. The adsorption process was optimized based on pH, Hg concentration, adsorbent dose, and contact time at 6.48, 40 mg/l, 150 mg/l, and 35 min, respectively, resulting in an adsorption capacity of 184.17 mg/g. Human carcinogenic toxicity with a 40.42% contribution was the main environmental impact, relating to electricity (35.76%) and ethylenediamine (31.07%) usage. The endpoint method also revealed the pivotal effect of the mGO-NH2 synthesis on human health (90.52%). The most energy demand was supplied by natural gas and crude oil accounting for 70.8% and 22.1%, respectively. A 99.02% CO2 emission originated from fossil fuels consumption based on the greenhouse gas protocol (GGP). The cost of mGO-NH2 was about $143.7/kg with a net present value of $21064.8 per kg Hg removal for a 20-year lifetime. Considering the significant role of material cost (>70%), the utilization of industrial-grade raw materials is recommended to achieve a low-cost adsorbent. This study demonstrated that besides the appropriate performance of mGO-NH2 for Hg removal, it is essential that further studies evaluate eco-friendly approaches to decrease the adverse impacts of this emerging product.

Simultaneous achievement of removing bensulfuron-methyl and reducing CO2 emission in paddy soil by Acinetobacter YH0317 immobilized boron-doping biochar

Herbicide residue and greenhouse gas (GHG) emission are two main problems in the paddy rice field, which have barely been considered simultaneously. Herein, a bensulfuron-methyl (BSM)-degrading bacterium named Acinetobacter YH0317 was successfully immobilized on two kinds of biochars and subsequently applied in the paddy soil. The BSM removal rate of Acinetobacter YH0317 immobilized boron-doping biochar (BBC) was 80.42% after 30 d, which was significantly higher than that of BBC (39.05%) and Acinetobacter YH0317 (49.10%) applied alone. BBC acting as an immobilized carrier could enable Acinetobacter YH0317 to work in harsh and complex environment and thus improve the BSM removal efficiency. The addition of Acinetobacter YH0317 immobilized BBC (TP5) significantly improved the soil physicochemical properties (pH, SOC, and NH4+-N) and increased the diversity of soil microbial community compared to control group (CG). Meanwhile, Acinetobacter YH0317 immobilized BBC reduced the CO2-equivalent emission by 41.0%. Metagenomic sequencing results revealed that the decreasing CO2 emission in TP5 was correlated with carbon fixation gene (fhs), indicating that fhs gene may play an important role in reducing CO2 emission. The work presents a practical and supportive technique for the simultaneous achievement on the soil purification and GHG emission reduction in paddy soil.

Are electric vehicles really the optimal option for the transportation sector in China to approach pollution reduction and carbon neutrality goals?

Profound worldwide fleet electrification is thought to be the primary route for achieving the target of carbon neutrality. However, when and how electrification can help mitigate environmental impacts and carbon emissions in the transport sector remains unclear. Herein, the overall life-cycle environmental impacts and carbon saving range of two typical A-class vehicles in China, including electric vehicle (EV) and internal combustion engine vehicle (ICEV), were quantified by the life cycle assessment model for endpoint damage with localization parameters. The results showed that the EV outperformed the ICEV for the total environment impact after a travel distance of 39,153 km and for carbon emissions after 32,292 km. The ICEV was more carbon-friendly only when the driving distance was less than 3229 km/a. Considering a full lifespan travel distance of 150,000 km, the whole life-cycle average environmental impacts of EV and ICEV were calculated as 8.6 and 17.5 mPt/km, respectively, but the EV had 2.3 times higher impacts than the ICEV in the production phase. In addition, the EV unit carbon emission was 140 g/km, 46.8% lower than that of the ICEV. Finally, three potential reduction scenarios were considered: cleaner power mix, energy efficiency improvement and composite scenario. These scenarios contributed 19.1%, 13.0% and 32.1% reductions, respectively. However, achieving carbon peak and neutrality goals in China remains a great challenge unless fossil fuels are replaced by renewable energy. The research can provide scientific reference for the method and practice of emission reduction link identification, eco-driving choice and emission reduction path formulation.

Scalable phosphorylated cellulose production with improved environmental sustainability, crosslinkability and processability using 3D bioprinting for dye remediation

In the present work, phosphorylated cellulose (PC) gel has been produced following an environmentally benign approach using agro-based chemicals with improved yield. The PC gels produced were transparent, negatively charged with high consistency, charge content (1133.33 mmol/kg), degree of substitution (DS) of 0.183 and increased yield (>87 %). The XPS and EDS analysis confirms the covalently bonded phosphate groups at weight percent of 9.42 % and 11.01 %, respectively. The life cycle assessment (LCA) shows that PC gel production via the phosphorylation route is an ecologically favourable strategy compared with traditional TEMPO oxidation, resulting in 1.67 times lower CO2 emission. The rheological studies of PC gels show shear-thinning behaviour with improved 3D printability followed by heat-induced crosslinking of phosphate groups. The mechanistic insights for the condensation of phosphate to form a phosphoric ester group during cross-linking were evaluated through 31P solid-state NMR and XPS studies. Interestingly, the 3D-printed structures showed high structural stability under both compression and tensile load in both dry and wet conditions, with high water absorption (5408.33 %) and swelling capacity of 700 %. The structures show improved methylene blue (MB) remediation capabilities with a maximum removal efficiency of 99 % for 10-200 mg/L and more than seven times reusability. This work provides a green, facile and energy-efficient strategy for fabricating PCs with easy processability through additive manufacturing techniques for producing value-added products, opening up new avenues for high-performance applications.

Mycorrhizosphere bacteria inhibit greenhouse gas emissions from microplastics contaminated soil by regulating soil enzyme activities and microbial community structure

Microplastics (MPs) accumulation in terrestrial ecosystems can affect greenhouse gases (GHGs) production by altering microbial and soil structure. Presently, research on the MPs effect on plants is not consistent, and underlying molecular mechanisms associated with GHGs are yet unknown. For the first time, we conducted a microcosm study to explore the impact of MPs addition (Raw vs. aged) and Trichoderma longibrachiatum and Bacillus subtilis inoculation (Sole vs. combination) on GHGs emission, soil community structure, physiochemical properties, and enzyme activities. Our results indicated that the addition of aged MPs considerably enhanced the GHGs emissions (N2O (+16%) and CO2 (+21%), respectively), C and N cycling gene expression, microbial biomass carbon, and soil physiochemical properties than raw MPs. However, the soil microbial community structure and enzyme activities were enhanced in raw MPs added treatments, irrespective of the MPs type added to soil. However, microbial inoculation significantly reduced GHGs emission by altering the expression of C and N cycling genes in both types of MPs added treatments. The soil microbial community structure, enzymes activities, physiochemical properties and microbial biomass carbon were enhanced in the presence of microbial inoculation in both type of MPs. Among sole and combined inoculation of Trichoderma and Bacillus subtilis, the co-applied Trichoderma and Bacillus subtilis considerably reduced the GHGs emission (N2O (-64%) and CO2 (-61%), respectively) by altering the expression of C and N cycling genes regardless of MPs type used. The combined inoculation also enhanced soil enzyme activities, microbial community structure, physiochemical properties and microbial biomass carbon in both types of MPs treatment. Our findings provide evidence that polyethylene MPs likely pose a high risk of GHGs emission while combined application of Trichoderma and Bacillus subtilis significantly reduced GHGs emission by altering C and N cycling gene expression, soil microbial community structure, and enzyme activities under MPs pollution in a terrestrial ecosystem.

Renewable energy technology innovation and urban green economy efficiency

Green economy efficiency is the core-factor of urban economic and environmental development. As a sustainable instruments, renewable energy technology innovation (RETI) not only reflects the low energy-consumption, but also promotes the reasonable and balanced relationship between resources utilization and urban economy. In this regard, this paper selects China's cities to investigate the effect of RETI on urban green economy efficiency from 2004 to 2020 based on theoretical analyses and previous studies. The paper finds that RETI can promote urban green economy efficiency significantly, passing a series of robustness test, and its effect has connected differently with the factor of regional factor, cleaner production level and environment pollution. Meanwhile, RETI promotes urban green economy efficiency by reducing CO2 emission and polluting manufacturing agglomeration. To date, this study has discovered the green economy efficiency improvement effects of RETI, providing theoretical basis and practical recommendations for government, technological agency and urban industries.

Coal fly ash and bottom ash low-cost feedstocks for CO2 reduction using the adsorption and catalysis processes

Combustion of fossil fuels, industry and agriculture sectors are considered as the largest emitters of carbon dioxide. In fact, the emission of CO2 greenhouse gas has been considerably intensified during the last two decades, resulting in global warming and inducing variety of adverse health effects on human and environment. Calling for effective and green feedstocks to remove CO2, low-cost materials such as coal ashes "wastes-to-materials", have been considered among the interesting candidates of CO2 capture technologies. On the other hand, several techniques employing coal ashes as inorganic supports (e.g., catalytic reduction, photocatalysis, gas conversion, ceramic filter, gas scrubbing, adsorption, etc.) have been widely applied to reduce CO2. These processes are among the most efficient solutions utilized by industrialists and scientists to produce clean energy from CO2 and limit its continuous emission into the atmosphere. Herein, we review the recent trends and advancements in the applications of coal ashes including coal fly ash and bottom ash as low-cost wastes to reduce CO2 concentration through adsorption and catalysis processes. The chemical routes of structural modification and characterization of coal ash-based feedstocks are discussed in details. The adsorption and catalytic performance of the coal ashes derivatives towards CO2 selective reduction to CH4 are also described. The main objective of this review is to highlight the excellent capacity of coal fly ash and bottom ash to capture and selective conversion of CO2 to methane, with the aim of minimizing coal ashes disposal and their storage costs. From a practical view of point, the needs of developing new advanced technologies and recycling strategies might be urgent in the near future to efficient make use of coal ashes as new cleaner materials for CO2 remediation purposes, which favourably affects the rate of global warming.

The carbon budget of China: 1980-2021

As one of the world's largest emitters of greenhouse gases, China has set itself the ambitious goal of achieving carbon peaking and carbon neutrality. Therefore, it is crucial to quantify the magnitude and trend of sources and sinks of atmospheric carbon dioxide (CO2), and to monitor China's progress toward these goals. Using state-of-the-art datasets and models, this study comprehensively estimated the anthropogenic CO2 emissions from energy, industrial processes and product use, and waste along with natural sources and sinks of CO2 for all of China during 1980-2021. To recognize the differences among various methods of estimating greenhouse emissions, the estimates are compared with China's National Greenhouse Gas Inventories (NGHGIs) for 1994, 2005, 2010, 2012, and 2014. Anthropogenic CO2 emissions in China have increased by 7.39 times from 1980 to 12.77 Gt CO2 a-1 in 2021. While benefiting from ecological projects (e.g., Three Norths Shelter Forest System Project), the land carbon sink in China has reached 1.65 Gt CO2 a-1 averaged through 2010-2021, which is almost 15.81 times that of the carbon sink in the 1980s. On average, China's terrestrial ecosystems offset 14.69% ± 2.49% of anthropogenic CO2 emissions through 2010-2021. Two provincial-level administrative regions of China, Xizang and Qinghai, have achieved carbon neutrality according to our estimates, but nearly half of the administrative regions of China have terrestrial carbon sink offsets of less than 10% of anthropogenic CO2 emissions. This study indicated a high level of consistency between NGHGIs and various datasets used for estimating fossil CO2 emissions, but found notable differences for land carbon sinks. Future estimates of the terrestrial carbon sinks of NGHGIs urgently need to be verified with process-based models which integrate the comprehensive carbon cycle processes.

The native SOC increase in woodland and lawn soil amended with biochar surpassed greenhouse - A seven-year field trial

The effects of applying biochar with the same characteristics and at the same dose on the storage, composition, and underlying mechanisms of native organic carbon (n-SOC) dynamics in different ecosystems are still unclear. This study aimed to explore the effects of biochar amendment (7 years) on carbon sequestration and the n-SOC pools of woodland, lawn, and greenhouse soils. The 'water floating method' and improved 'combustion loss method' were used in this study to quantify residual biochar in soil. The results showed that after 7 years, the amount of biochar left in woodland, lawn, and greenhouse soils was 67.12 %, 87.50 %, and 88.13 % of the initial applied amount, respectively. And the n-SOC content increased approximately 2.07, 3.07, and 0.22 times, respectively, mainly due to increases in the native soil humin (n-HM) content of the soil. Biochar also increased the proportion of large aggregates in woodland and lawn soil and increased the t-SOC content of aggregates in each particle size fraction. Additionally, biochar increased the t-SOC of greenhouse soil aggregates but had no significant effect on the distribution of aggregates. The presence of biochar increased native soil easily oxidizable carbon (n-EOC) and microbial biomass carbon (n-MBC) in all three ecosystems. And increases in n-MBC in woodland and lawn soils occurred, which promoted the depletion of native soil hot water dissolvable organic carbon (n-HWOC) and increased CO2 emissions. Furthermore, the microbial respiration quotient (qCO2) of woodland and greenhouse soils was reduced by biochar, and that of lawn soil was unchanged. The carbon use efficiency (CUE) of lawn soils were reduced, possibly because biochar reduced the abundance of soil fungi/bacteria (F/B). In summary, the 7-year application of biochar significantly enhanced the n-SOC content in woodland and lawn soils, mainly due to an increase in humin, while a weaker enhancement was observed in greenhouse soil.

Enhanced-efficiency nitrogen fertilizer provides a reliable option for mitigating global warming potential in agroecosystems worldwide

Enhanced-efficiency nitrogen fertilizer (EENF), developed to improve synchronization between crop nitrogen demand and nitrogen supply, can guarantee global food security and mitigate nitrogen fertilizer-induced environmental consequences. However, comprehensive assessments of how EENF affects CH4 and CO2 emissions from paddies and drylands and the associated benefits are lacking. Here, we present the results of a global meta-analysis conducted to assess the above issues. Our results showed that, on average, applying nitrification inhibitors and coated controlled-release urea to paddy fields significantly decreased CH4 emissions by 24.0 % and 25.3 %, respectively, likely due to the weakened inhibition of NH4+ on CH4 oxidation. A similar effect on CO2 emission was observed when farmers used nitrification inhibitors and coated controlled-release urea in the drylands. The meta-analysis results revealed that all EENF products could help mitigate the global warming potential of paddies and drylands. After incorporating the benefit of global warming potential mitigation into the cost-benefit analysis, coated controlled-release urea application in paddies and drylands produced the largest environmental gains of $ 76.34 ha-1 and $ 79.35 ha-1, respectively. However, the relatively lower purchasing cost and larger yield increase of urease inhibitors resulted in the largest net profits for farmers. Moreover, a greater economic return was generally achieved by applying EENF to paddy fields than by applying EENF to drylands. These findings highlight the role of EENF in mitigating the global warming potential of global paddy and dryland fields, which has facilitated the comprehensive recognition of EENF-induced impacts.

Crop production and water quality under 1.5 °C and 2 °C warming: Plant responses and management options in the mid-Atlantic region

The 2015 "Paris Agreement" aims to limit the global average temperature rise to significantly less than 2 °C, preferably within 1.5 °C above pre-industrial levels. A multitude of studies have focused on evaluating how different sectors respond to such levels of warming. Nonetheless, most of these studies fail to provide a clear roadmap to mitigate these impacts. A case in point is the anticipated decline in corn and soybean yields and increased phosphorus (P) and nitrogen (N) discharge into water bodies, a trend linked to past agricultural practices and climate change. In this research, we employ a novel assessment of how existing management practices under 1.5 °C and 2 °C global warming (GW) scenarios can affect nutrient availability in time and space as well as crop yield in a typical agricultural watershed in the Mid-Atlantic Region, specifically the Upper Maurice River Watershed (UMRW) in New Jersey. Using the Soil and Water Assessment Tool (SWAT) with multiple Global Climate Model (GCM) projections, we found that compared to 1.5 °C, a 2 °C GW scenario would exacerbate runoff, leading to amplified nutrient leaching. These losses decrease nutrient availability during the crop growing season. Moreover, a mismatch between the timing of fertilizer application and crop nutrient absorption caused nutrient-related stress. This nutrient and anticipated temperature stress resulted in a more significant decrease in crop yields under the 2 °C GW scenario than the 1.5 °C scenario. We have designed a management scenario to reduce future nutrient losses while increasing crop yields. The strategy involves altering the timing of planting/harvesting and the fertilizer application rate in response to a warming climate. This approach is projected to increase corn and soybean yields by +39 % (+21 %) and +2 % (+17 %), respectively, under the 1.5 °C (2.0 °C) GW scenario for the RCP-4.5 pathway. Simultaneously, it is expected to decrease the N and P loads at 1.5 °C (2.0 °C) GW. Comparable projections are also observed under the RCP-8.5 pathway.

Towards a low-carbon future for China's power supply chain: Critical sectors identification and scenario analysis

The power sector is a significant contributor to global carbon emissions and has received widespread attention from scholars; however, the path to achieving supply chain-wide carbon reductions in China from a provincial perspective remains unclear. This study combined multi-regional input-output and betweenness-based methods to identify the critical upstream sectors that indirectly drive large amounts of carbon emissions through power supply chains. The point source data of coal-fired units were collected to ensure the accuracy of the disaggregated input-output table. In addition, a scenario analysis was conducted to examine the effects of different electricity policy combinations on supply chain-wide emissions during the 14th Five-Year Plan (FYP). Our findings indicate that the embodied carbon intensity of the coal-fired power sector in Northwest China is among the highest in the country, ranging from 36.39 to 82.10 tons/10000 CNY. Therefore, the shift of the power sector to Western China during the 14th FYP will partially offset the positive emission reduction effect of the structural transformation of the power system. To achieve a low-carbon power supply chain, it is necessary to improve the production efficiency of critical transmission sectors and the low-carbon technology levels of major emitting sectors. Our results provide valuable insights for provincial governments to plan low-carbon transformation paths for the power sector.

Muti-objective optimization on energy consumption, CO2 emission and production cost for iron and steel industry

Due to high material density, high energy consumption density and CO2 emission density, it is not only difficult but significant to clarify the relationship between energy consumption, the CO2 emission and the production cost in different conditions. However, the previous researches rarely refer how to balance the energy consumption, the CO2 emission and the production cost after the fluctuation of material, energy and carbon price as well as what will happen to them if production structure changes. Therefore, based on the conservation law of mass and energy, to study iron and steel manufacturing process (ISMP), this paper, taking carbon price into consideration, establishes a muti-optimization model of energy consumption, CO2 emission and cost. After optimization with different objectives, the production cost per tonne of crude steel is reduced by 192.03 CNY (7.71%), the CO2 emission per tonne of crude steel is reduced by 224.22 kg (13.37%), and the energy consumption per tonne of steel is reduced by 51.20 kgce (9.10%). Moreover, based on the optimization results under different objectives, it is ironmaking process (coal ratio and ore ratio) and steelmaking process (amount of scrap steel) that has more impact on three above as well as ore blending and coal blending have a great influence on production cost but little effect on energy consumption and CO2 emission.

Technical design of an innovative biomass/gasification-driven power plant with heat recovery hybrid system: CO2 emission comparison between the designed plant and fossil fuel-powered plants

This study aims to introduce, conceptualize, and design a novel biomass/gasification-driven hybrid energy configuration. The proposed hybrid configuration has four subsystems: reformer solid oxide fuel cell (RSOFC), biomass/gasification, homogeneous charge compression ignition engine (HCCIE) plus waste heat recovery system (WHRS). RSOFC and HCCIE systems are embedded to generate electric energy. The syngas required for these two subsystems is captured from the biomass/gasification subsystem. In addition to generating electrical energy, fuel cell is responsible for providing combustible fuel to the HCCIE subsystem. The embedded engine in the system can improve the proposed configuration efficiency by increasing the rate of electrical energy production. In addition, the dissipated heat of fuel cell and engine subsystems is recovered by WHRS. The proposed energy configuration is evaluated and discussed from energetically, exergetically and exergoeconomic and environmental aspects to obtain a comprehensive feasibility study of the plant. The offered hybrid design has new component's structure and relationships that have not been reported in the publications. The analysis indicated that the proposed hybrid configuration is capable of generating approximately 1100 kW and 366.3 W of electric and thermal power, respectively, with the overall energetic and exergetic efficiencies of 69.4% and 52.1%. Exergoeconomic analysis results revealed that the specific fuel cost of the total proposed configuration was approximately 1.96 USD per GJ. In addition, compared to a coal and petroleum oil-based power generation plants, the proposed hybrid configuration can have approximately 2.75-fold and 97.7% lower CO2 emissions, sequentially. Besides, the proposed system can rival other similar biomass-driven designs.

Management actions mitigate the risk of carbon dioxide emissions from urban lakes

Lakes are recognized as important sources of carbon dioxide (CO2) emissions, which vary greatly across land use type. However, CO2 emissions from lakes in urban landscapes are generally overlooked despite their daily connections to human activity. Furthermore, the role of management actions in CO2 emissions remained unclear mostly because of the lack of long-term observations. Here, the CO2 partial pressure (pCO2) from two urban lakes (Lake Wuli and Lake Donghu) in eastern China were investigated based on 16-year (2002-2017) field measurements. This long-term measurements showed the annual mean pCO2 were 1150 ± 612 μatm for Lake Wuli and 1143 ± 887 μatm for Lake Donghu, with corresponding estimated flux of 21.12 ± 19.60 mmol m-2 d-1 and 16.42 ± 20.39 mmol m-2 d-1, respectively. This indicates significant CO2 evasion into the atmosphere. Strong links between CO2 and human-derived nutrients (e.g., ammonium) and dissolved organic carbon, dissolved oxygen, and trophic state index were found. Although pCO2 was relatively uniform across sites and seasons in each lake, substantial inter-annual variability with significant decreasing trends were found. The decrease in annual CO2 can be partly explained by the reduction of pollutant loadings with management actions, which held the hypotheses that management actions mitigated the CO2 emission risks. Overall, management actions (e.g., ecological restoration and municipal engineering) should be considered for better understanding the roles of anthropogenic aquatic ecosystems in carbon cycle.

Nitrogen addition stimulated soil respiration more so than carbon addition in alpine meadows

The soil carbon (C) and nitrogen (N) availability are important in the regulation of soil C cycling under climate change. Fertilizers alter soil C and N availability, which can affect C balance. However, the impact of fertilizers on C balance in grassland restoration has been equivocal and warrants more research. We determined the direct and indirect effects of the addition of three levels of C (sucrose) (0, 60, and 120 kg C ha-1 yr-1), three levels of N (urea) (0, 50, and 100 kg N ha-1 yr-1), and a combination of C plus N at each of the levels on soil respiration (Rs) dynamics and C balance in an alpine meadow in northern Tibet (4700 m above sea level). This study was undertaken during the middle of the growing season in 2011-2012. The addition of C and/or N stimulated CO2 emission, which was 2-fold greater in 2011 (102-144 g C m-2) than in 2012 (43-54 g C m-2). The rate of Rs increased with the addition of N, but was not affected with the addition of C plus N. Microbial biomass C, dissolved organic C and inorganic N were the main drivers of Rs. We concluded that N addition stimulated Rs to a greater extent than C addition in the short term. The application of fertilizer in the restoration of degraded grassland should be re-considered.

Metabolism and carbonate buffering drive seasonal dynamics of CO2 emissions from two German reservoirs

Biological metabolism drives much of the variation in CO2 in terrestrial ecosystems but does not explain CO2 oversaturation and emission in net autotrophic lakes and reservoirs. The unexplained CO2 could be attributed to the equilibria between CO2 and the carbonate buffering system, which is seldom integrated into CO2 budgets, let alone its interplay with metabolism on CO2 emissions. Here, we perform a process-based mass balance modeling analysis based on an 8-year dataset from two adjacent reservoirs with similar catchment sizes but contrasting trophic states and alkalinity. We find that in addition to the well-acknowledged driver of net metabolic CO2 production, carbonate buffering also determines the total amount and seasonal dynamics of CO2 emissions from the reservoirs. Carbonate buffering can contribute up to nearly 50% of whole-reservoir CO2 emissions, by converting the ionic forms of carbonate to CO2. This results in similar seasonal CO2 emissions from reservoirs with differing trophic state, even in low alkalinity system. We therefore suggest that catchment alkalinity, instead of trophic state, may be more relevant in predicting CO2 emissions from reservoirs. Our model approach highlights the important role of carbonate buffering and metabolism that generate and remove CO2 throughout the reservoirs on a seasonal scale. The inclusion of carbonate buffering could diminish a major uncertainty in the estimation of reservoir CO2 emissions and increase the robustness of aquatic CO2 emission estimates.