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Recent concerns surrounding climate change and the contribution of fossil fuels to greenhouse gas (GHG) emissions have sparked interest and advancements in renewable energy sources including wind, solar, and hydroelectricity. These energy sources, often referred to as "clean energy", generate no operational onsite GHG emissions. They also offer the potential for clean hydrogen production through water electrolysis, presenting a viable solution to create an environmentally friendly alternative energy carrier with the potential to decarbonize industrial processes reliant on hydrogen. To conduct a full life cycle analysis, it is crucial to account for the embodied emissions associated with renewable and nuclear power generation plants as they can significantly impact the GHG emissions linked to hydrogen production and its derived products. In this work, we conducted a comprehensive analysis of the embodied emissions associated with solar photovoltaic (PV), wind, hydro, and nuclear electricity. We investigated the implications of including plant-embodied emissions in the overall emission estimates of electrolysis hydrogen production and subsequently on the production of synthetic ammonia, methanol, and Fischer-Tropsch (FT) fuels. Results show that average embodied GHG emissions of solar PV, wind, hydro, and nuclear electricity generation in the United States (U.S.) were estimated to be 37, 9.8, 7.2, and 0.3 g CO 2 e/kWh, respectively. Life cycle GHG emissions of electrolytic hydrogen produced from solar PV, wind, and hydroelectricity were estimated as 2.1, 0.6, and 0.4 kg of CO 2 e/kg of H 2 , respectively, in contrast to the zero-emissions often used when the embodied emissions in their construction were excluded. Average life cycle emission estimates (CO 2 e/kg) of synthetic ammonia, methanol, and FT-fuel from solar PV electricity are increased by 5.5, 16, and 49 times, respectively, compared to the case when embodied emissions are excluded. This change also depends on the local irradiance for solar power, which can result in a further increase of GHG emissions by 35-41% in areas of low irradiance or reduce GHG emissions by 21-25% in areas with higher irradiance.

Although Africa contributes less than 5% to global greenhouse gas (GHG) emissions, its role in global climate action is pivotal. To date, 53 African countries have submitted their Nationally Determined Contributions (NDCs), and four have committed to a net-zero target. However, many of Africa's NDCs are vaguely expressed and without specific focus on explicit sectoral decarbonization targets. Furthermore, Africa's huge land-based carbon dioxide removal (CDR) potential remains unclear in the context of enabling net-zero (NZ) emissions within the continent. This study achieves two objectives: Under a NZ GHG emission trajectory in Africa, we uncover the implications of a targeted zero-emission electricity sector by 2030, on the energy landscape and other sustainability factors. This study also features the role of land-based biological removal methods─bioenergy carbon capture and storage (BECCS) and afforestation/reforestation (A/R)─in net zero actualization in Africa. Our results reveal a unified but disparate actualisation of the mid-century net zero emission goal across the continent, as all regions except North Africa achieve carbon neutrality. The industrial sector faces significant difficulties in transitioning and contributes substantially to positive emissions on the continent, with its share of total residual emissions reaching 49-64% by 2050. This difficulty persists even with targeted sectoral decarbonization of the electricity sector, although it is significantly reduced by the availability of BECCS as a CDR option. Under the zero-emission electricity pathway, emissions in buildings and transport sectors are reduced due to rapid electrification. A trade-off emerges in the net zero pathway concerning land allocation for negative emissions versus other land use activities. A key result shows that achieving a net zero target in Africa leads to a cumulative loss of $102 billion in fossil fuel infrastructure within the electricity sector by mid-century, which doubles when the zero-emission electricity goal is achieved.

Waste-to-energy systems can provide a functional demonstration of the economic and environmental benefits of circularity, innovation, and reimagining existing systems. This study offers a robust quantification of the greenhouse gas (GHG) emission reduction potential of the adoption of anaerobic digestion (AD) technology on applicable large-scale dairy farms in the contiguous United States. GHG reduction estimates were developed through a robust life cycle modeling framework paired with sensitivity and uncertainty analyses. Twenty dairy configurations were modeled to capture important differences in housing and manure management practices, applicable AD technologies, regional climates, storage cleanout schedules, and methods of land application. Monte Carlo results for the 90% confidence interval illustrate the potential for AD adoption to reduce GHG emissions from the large-scale dairy industry by 2.45-3.52 MMT of CO 2 -eq per year considering biogas use only in renewable natural gas programs and as much as 4.53-6.46 MMT of CO 2 -eq per year with combined heat and power as an additional biogas use case. At the farm level, AD technology may reduce GHG emissions from manure management systems by 58.1-79.8% depending on the region. Discussion focuses on regional differences in GHG emissions from manure management strategies and the challenges and opportunities surrounding AD adoption.

Cellulosic biomass-based sustainable aviation fuels (SAFs) can be produced from various feedstocks. The breakeven price and carbon intensity of these feedstock-to-SAF pathways are likely to differ across feedstocks and across spatial locations due to differences in feedstock attributes, productivity, opportunity costs of land for feedstock production, soil carbon effects, and feedstock composition. We integrate feedstock to fuel supply chain economics and life-cycle carbon accounting using the same system boundary to quantify and compare the spatially varying greenhouse gas (GHG) intensities and costs of GHG abatement with SAFs derived from four feedstocks (switchgrass, miscanthus, energy sorghum, and corn stover) at 4 km resolution across the U.S. rainfed region. We show that the optimal feedstock for each location differs depending on whether the incentive is to lower breakeven price, carbon intensity, or cost of carbon abatement with biomass or to have high biomass production per unit land. The cost of abating GHG emissions with SAF ranges from $181 Mg -1 CO 2 e to more than $444 Mg -1 CO 2 e and is lowest with miscanthus in the Midwest, switchgrass in the south, and energy sorghum in a relatively small region in the Great Plains. While corn stover-based SAF has the lowest breakeven price per gallon, it has the highest cost of abatement due to its relatively high GHG intensity. Our findings imply that different types of policies, such as volumetric targets, tax credits, and low carbon fuel standards, will differ in the mix of feedstocks they incentivize and locations where they are produced in the U.S. rainfed region.

China's dairy farming is undergoing a critical transition from extensive to industrial systems. To achieve sustainable milk production within China's dual-carbon goals, understanding the multidimensional impacts of industrialization on greenhouse gas (GHG) emissions is imperative. This study comprehensively analyzed the implications of China's dairy industrialization on GHG emissions and explored future mitigation potential. Results indicated that industrial systems exhibited lower methane but higher carbon dioxide intensities, with net GHG intensity lower than other systems. During 2002-2020, China's milk production increased by 165%, while GHG emissions increased by 105% to 50.27 Tg CO 2 eq, accompanying an industrialization rate increased from 16% to 75%. The industrialization progress played a mitigating effect on GHG primarily through intensification within individual production systems before 2008 and transformation between systems post-2008. However, the industrialization's effect was relatively modest compared to other socio-economic factors. By 2030, 11.8 Tg CO 2 eq will be triggered by predicted milk production growth, but only 0.6 Tg can be offset by system transformation. Integrating measures to improve feed, herd, and manure management on industrial farms could decouple GHG emissions from milk production and achieve a carbon peak before 2030. We suggest transforming to improved industrial systems as a necessary step toward sustainable livestock production.

The dietary preferences of the elderly population exhibit distinct variations from the overall averages in most countries, gaining increasing significance due to aging demographics worldwide. These dietary preferences play a crucial role in shaping global food systems, which will result in changed environmental impacts in the future such as greenhouse gas (GHG) emissions. We present a quantitative evaluation of the influence of population aging on the changes in GHG emissions from global food systems. To achieve this, we developed regional dietary coefficients (DCs) of the elderly based on the Global Dietary Database (GDD). We then reconciled the GDD with the dataset from the Food and Agriculture Organization of the United Nations (FAO) to calculate the food GHG emissions of the average population in each of the countries. By applying the DCs, we estimated the national food GHG emissions and obtained the variations between the emissions from aged and average populations. We employed a modified version of the regional integrated model of climate and the economy model (RICE) to forecast the emission trends in different countries based on FAO and GDD data. This integrated approach allowed us to evaluate the dynamic relationships among aging demographics, food consumption patterns, and economic developments within regions. Our results indicate that the annual aging-embodied global food GHG emissions will reach 288 million tonnes of CO 2 equivalent (Mt CO 2 e) by 2100. This estimation is crucial for policymakers, entrepreneurs, and researchers as it provides insights into a potential future environmental challenge and emphasizes the importance of sustainable food production and consumption strategies to GHG emission mitigations associated with aging dietary patterns.

Clean hydrogen has the potential to serve as an energy carrier and feedstock in decarbonizing energy systems, especially in "hard-to-abate" sectors. Although many countries have implemented policies to promote electrolytic hydrogen development, the impact of these measures on costs of production and greenhouse gas emissions remains unclear. Our study conducts an integrated analysis of provincial levelized costs and life cycle greenhouse gas emissions for all hydrogen production types in China. We find that subsidies are critical to accelerate low carbon electrolytic hydrogen development. Subsidies on renewable-based hydrogen provide cost-effective carbon dioxide equivalent (CO 2e ) emission reductions. However, subsidies on grid-based hydrogen increase CO 2e emissions even compared with coal-based hydrogen because grid electricity in China still relies heavily on coal power and likely will beyond 2030. In fact, CO 2e emissions from grid-based hydrogen may increase further if China continues to approve new coal power plants. The levelized costs of renewable energy-based electrolytic hydrogen vary among provinces. Transporting renewable-based hydrogen through pipelines from low- to high-cost production regions reduces the national average levelized cost of renewables-based hydrogen but may increase the risk of hydrogen leakage and the resulting indirect warming effects. Our findings emphasize that policy and economic support for nonfossil electrolytic hydrogen is critical to avoid an increase in CO 2e emissions as hydrogen use rises during a clean energy transition.

The expansion of renewable energy and the large-scale deployment of carbon dioxide (CO 2 ) capture and storage (CCS) can decarbonize the power sector. The use of CO 2 to extract geothermal heat from naturally porous and permeable sedimentary basins to generate electricity (CO 2 -plume geothermal (CPG) system) presents an opportunity to simultaneously generate renewable energy and geologically store CO 2 . In this study, we estimate the life cycle greenhouse gas (GHG) impacts of CPG systems through 12 scenarios in which CPG systems are combined with one of six CO 2 sources (e.g., bioenergy with carbon capture and storage (BECCS) and iron and steel facilities) and operate in two geological settings. We find the life cycle GHG emissions of CPG systems ranging from -0.25 to -6.18 kg CO 2 eq/kWh. CPG systems can achieve the highest emissions reductions when utilizing the CO 2 captured from BECCS. We evaluate uncertainty through a Monte Carlo simulation, demonstrating consistent net reductions in life cycle emissions and a local, one-parameter-at-a-time sensitivity analysis that identifies the CO 2 capture capacity as the high-impact parameter of the results. Through the production of electricity, CPG systems can provide additional environmental benefits to the deployment of large-scale CCS.

The transformation of the global power structure caused by the carbon neutrality goal will promote copper consumption. It is crucial to explore the decarbonization pathways of the copper industry to help fulfill greenhouse gas (GHG) emission reduction targets. This study utilized material flow analysis and life cycle assessment methods to investigate 12 different subscenarios based on international trade, circular economy, technology evolution, and environmental market factors. Policy combination scenario is employed to reveal the mechanism of decarbonization. The results show that refined copper consumption in China is expected to increase by 62.3% in 2060 compared to 2020. The GHG emissions of China's copper industry will reach 9.1 million tonnes (Mt) CO 2 e in 2060, technology evolution and environmental market are crucial for realizing carbon neutrality goal of this industry, accounting for 26.4 and 47.2% of emissions reductions, respectively, between 2020 and 2060. International trade and circular economy play important roles in the high-quality carbon peaking stage; however, imported copper and domestic secondary copper will constitute the basic supply of copper resources in China in the long run, and the comparative advantages of them will gradually weaken. Policy combination scenario can achieve the incentive synergy effect, with GHG reduced to 0.5 Mt CO 2 e in 2060. The enhanced application of policies such as material substitution and carbon emission trading will further promote industry to achieve net-zero GHG emission. We suggest regulating the industry's structure based on the international systemic circulation pattern and accelerating the construction of a green circular chain in the short term to achieve sustainable copper supply and high-quality carbon peaking. Promoting a high-quality technology development strategy and enhancing the environmental markets are recommended in the long term to achieve carbon neutrality.

Decoupling global economic growth from carbon emissions is essential for mitigating global climate change while maintaining continuous economic growth. Traditional production-side decoupling analysis alone is insufficient to capture the decoupling status between carbon emissions and the value added throughout global supply chains. This study investigates the decoupling status between value added and greenhouse gas (GHG) emissions during 1995-2019 from consumption and income perspectives. We find that the decoupling statuses of 17 regions (especially Russia, Australia, and Malta) show significant differences across multiple perspectives. For example, Malta's direct GHG emissions decreased with its GDP growth from a production perspective (i.e., achieved strong decoupling). However, its consumption-based GHG emissions increased with the growth of consumption-based value added (i.e., expansive negative decoupling). Moreover, most international pairs have not yet achieved strong decoupling from consumption and income perspectives. International multilateral cooperation is crucial for decoupling global GHG emissions from economic growth across global supply chains. This study provides insights into the decoupling between embodied GHG emissions and value added from consumption and income perspectives. The findings of this study can complement existing policies on global GHG emission mitigation and sustainable development.

Fully fluorinated greenhouse gases (FFGHGs), including sulfur hexafluoride (SF 6 ), nitrogen trifluoride (NF 3 ), and perfluorocarbons (PFCs), have drawn attention because they have long atmospheric lifetimes (up to thousands of years) and high global warming potential. Targeting SF 6 , NF 3 , and four PFCs (CF 4 , C 2 F 6 , C 3 F 8 , and c -C 4 F 8 ), this study projects future FFGHG emission patterns in China, explores their mitigation potential, and evaluates the effects of FFGHG emission reduction on the achievement of the country's carbon neutrality goal and climate change. FFGHG emissions are expected to increase consistently, ranging from 506 to 1356 Mt CO 2 -eq yr -1 in 2060 under the business-as-usual (BAU) scenario. If mitigation strategies are sufficiently employed, FFGHG emissions under three mitigation scenarios: Technologically Feasible 2030, Technologically Feasible 2050, and Technologically Feasible 2060, will eventually decrease to approximately 49-78, 70-110, and 98-164 Mt CO 2 -eq yr -1 in 2060, respectively, compared to the BAU scenario. Extensive implementation of FFGHG emission mitigation technologies will curb temperature rise by 0.008-0.013 °C under the slowest mitigation scenario, compared to 0.013-0.026 °C under the BAU scenario. Well-coordinated policies and reforms on FFGHG emission mitigation are recommended to prevent potential adverse effects on the climate to a certain extent.

Electricity consumption and sludge yield (SY) are important indirect greenhouse gas (GHG) emission sources in wastewater treatment plants (WWTPs). Predicting these byproducts is crucial for tailoring technology-related policy decisions. However, it challenges balancing mass balance models and mechanistic models that respectively have limited intervariable nexus representation and excessive requirements on operational parameters. Herein, we propose integrating two machine learning models, namely, gradient boosting tree (GBT) and deep learning (DL), to precisely pointwise model electricity consumption intensity (ECI) and SY for WWTPs in China. Results indicate that GBT and DL are capable of mining massive data to compensate for the lack of available parameters, providing a comprehensive modeling focusing on operation conditions and designed parameters, respectively. The proposed model reveals that lower ECI and SY were associated with higher treated wastewater volumes, more lenient effluent standards, and newer equipment. Moreover, ECI and SY showed different patterns when influent biochemical oxygen demand is above or below 100 mg/L in the anaerobic-anoxic-oxic process. Therefore, managing ECI and SY requires quantifying the coupling relationships between biochemical reactions instead of isolating each variable. Furthermore, the proposed models demonstrate potential economic-related inequalities resulting from synergizing water pollution and GHG emissions management.

Renewable liquid fuels production from landfill waste provides a promising alternative to conventional carbon-intensive waste management methods and has the potential to contribute to the transition toward low-carbon fuel pathways. In this work, we investigated the life cycle greenhouse gas (GHG) emissions of producing Fischer-Tropsch diesel from landfill gas (LFG) using the TriFTS catalytic conversion process and compared it to fossil-based petroleum diesel. A life cycle-based comparison was made between TriFTS diesel and other LFG waste management pathways, LFG-to-Electricity and LFG-to-Compressed renewable natural gas (RNG), on a per kilogram of feedstock basis as well as on a per MJ of energy basis, which also included the LFG-to-Direct Combustion pathway. The study considered flaring of LFG as the common underlying counterfactual scenario for all of the waste-to-energy product pathways. We estimated the life cycle GHG emissions for TriFTS diesel to be -36.4 carbon dioxide equivalent (grams CO 2 e)/MJ which is significantly lower than its fossil fuel counterpart which was estimated to be 90.5 g CO 2 e/MJ on a cradle-to-grave basis. The life cycle emission results from both perspectives (per kg feedstock and per MJ energy output) show that TriFTS diesel is a viable alternative energy pathway from LFG when compared to other pathways, primarily due to the main product being a renewable fuel that can serve as a drop-in fuel for diesel-based uses, within both the waste industry as well as the larger market. Further sensitivity analysis was performed based on the production of TriFTS diesel with the counterfactual waste management scenario of LFG-to-Flaring as well as the alternative LFG-to-Electricity waste management pathway. The sensitivity of the carbon intensity for TriFTS diesel to flaring efficiency and the carbon intensity of the electricity grid were also investigated. The study highlights the potential for the TriFTS conversion process technology to contribute to the waste industry's closed loop and decarbonization initiatives and to provide low carbon fuel for transportation.

Three concepts necessary for understanding the greenhouse effect are infrared radiation, absorption of infrared radiation by greenhouse gases, and steady-state energy flow. Herein, we describe adaptations to three classic demonstrations for teaching these concepts. William Hershel's discovery of infrared radiation has been adapted into a fast and reliable demonstration using a pyranometer. We provide guidelines for building a ball-and-spring model of carbon dioxide that demonstrates the absorption of IR and the three fundamental vibrational modes of carbon dioxide and their relative frequencies. Finally, we describe an adaptation of Blanck's plastic water-flow device to demonstrate how adding greenhouse gases can alter the steady-state flow of energy through the atmosphere. [ABSTRACT FROM AUTHOR]

Road infrastructure is an integral part of built environment stocks, as it delivers essential social and economic services. While previous work has assessed material stocks, flows, and embodied emissions, spatially refined mapping of materials accumulated in road infrastructure can highlight hitherto underappreciated synergies between improved spatial planning, material stock efficiency, and urban mining. In this study, we mapped the materials stocked in road infrastructure across Belgium, explored the patterns of material stock efficiency and the recyclability of end-of-life road materials, and examined the greenhouse gas (GHG) emissions reductions of improving stock efficiency and recycling. We assembled data scattered across various governmental sources and crowdsourced platforms and developed a comprehensive database to warehouse locational information on road typology, layer geometry and thickness, material characteristics, traffic volume, climatic conditions, and soil conditions. Our results reveal a strong but nonlinear correlation between material stock efficiency and population density, indicating that spatial planning can reduce the required road stocks and associated GHG emissions. Urban mining potentials in road infrastructure hinge on multiple factors, such as the proximity to recycling facilities and the degradation of pavements during use. Our counterfactual analysis shows that urban road planning and reusing recycled asphalt can cut GHG emissions by up to 53 and 70%, respectively. Therefore, material-efficient road planning and improved material recycling can help realize circular economy potentials and mitigate GHG emissions moving forward.

Brazil is the second-largest ethanol producer in the world, primarily using sugar cane as feedstock. To foster biofuel production, the Brazilian government implemented a national biofuel policy, known as RenovaBio, in which greenhouse gas (GHG) emission reduction credits are provided to biofuel producers based on the carbon intensities (CI) of the fuels they produce. In this study, we configured the GREET model to evaluate life cycle GHG emissions of Brazilian sugar cane ethanol, using data from 67 individual sugar cane mills submitted to RenovaBio in 2019/2020. The average CI per megajoule of sugar cane ethanol produced in Brazil for use in the U.S. was estimated to be 35.2 g of CO 2 equivalent, a 62% reduction from U.S. petroleum gasoline blendstock without considering the impacts of land use change. The three major GHG sources were on-field N 2 O emissions (24.3%), sugar cane farming energy use (24.2%), and sugar cane ethanol transport (19.3%). With the probability density functions for key input parameters derived from individual mill data, we performed stochastic simulations with the GREET model to estimate the variations in sugar cane ethanol CI and confirmed that despite the larger variations in sugar cane ethanol CI, the fuel provided a robust GHG reduction benefit compared to gasoline blendstock.

Increased use of vehicle electrification to reduce greenhouse gas (GHG) emissions has led to the need for an accurate and comprehensive assessment of the carbon footprint of traction batteries. Unfortunately, there are few lifecycle assessments (LCAs) of commercial lithium-ion batteries available in the literature, and those that are available focus on the cradle-to-gate stage, often with little or no consideration of the use phase. To address this shortfall, we report both cradle-to-gate and use-phase GHG emissions for the 2020 Model Year Ford Explorer plug-in hybrid electric vehicle (PHEV) NMC622 battery. Using primary industry data for battery design and manufacturing, cradle-to-gate emissions are estimated to be 1.38 t CO 2 e (101 kg CO 2 e/kWh), with 78% from materials and parts production and 22% from cell, module, and pack manufacturing. Using mass-induced energy consumptions of 0.6 and 1.6 kWh/(100 km 100 kg) for charge-depleting and -sustaining modes, respectively, the mass-induced use-phase emission of the battery is estimated to be 1.04 t CO 2 e. We show that battery emissions during the cradle-to-gate and use phases are comparable and that both phases need to be considered. A holistic and harmonized LCA approach that includes battery use is required to reduce carbon footprint uncertainties and guide future battery designs.

The promotion of sustainable mobility choices is a crucial element of transport decarbonization. It requires a fundamental understanding of the choices available to urban dwellers and of the equity and justice implications of green mobility solutions. In this study, we quantified personal mobility-related greenhouse gas (GHG) emissions in the Greater Toronto and Hamilton Area (GTHA) and their associations with various land use, built environment, and socioeconomic factors. Our study captured personal, household, and neighborhood-level characteristics that are related to high emissions and disparities in emissions across the study region. We observed that the top 30% of emitters generated 70% of all transportation GHG emissions. Household income, family size, and vehicle ownership were associated with increased mobility emissions, while increased population density was associated with lower emissions. The percentage of visible minorities in a neighborhood was associated with lower emissions, but this effect was small. We further contrasted the spatial distribution of traffic-related air pollution with mobility GHG emissions. The results suggest that individuals who emit less GHG live in areas with higher air pollution. A computer vision-based model was used to predict GHG emissions from aerial images of neighborhoods, demonstrating that areas with high land use mixture were linked to a lower generation of mobility-based GHG emissions.

Decarbonization of transportation fuels represents one of the most vexing challenges for climate change mitigation. Biofuels derived from corn starch have offered modest life cycle greenhouse gas (GHG) emissions reductions over fossil fuels. Here we show that capture and storage of CO 2 emissions from corn ethanol fermentation achieves ∼58% reduction in the GHG intensity (CI) of ethanol at a levelized cost of 52 $/tCO 2 e abated. The integration of an oxyfuel boiler enables further CO 2 capture at modest cost. This system yields a 75% reduction in CI to 15 gCO 2 e/MJ at a minimum ethanol selling price (MESP) of $2.24/gallon ($0.59/L), a $0.31/gallon ($0.08/L) increase relative to the baseline no intervention case. The levelized cost of carbon abatement is 84 $/tCO 2 e. Sensitivity analysis reveals that carbon-neutral or even carbon-negative ethanol can be achieved when oxyfuel carbon capture is stacked with low-CI alternatives to grid power and fossil natural gas. Conservatively, fermentation and oxyfuel CCS can reduce the CI of conventional ethanol by a net 44-50 gCO 2 /MJ. Full implementation of interventions explored in the sensitivity analysis would reduce CI by net 79-85 gCO 2 /MJ. Integrated oxyfuel and fermentation CCS is shown to be cost-effective under existing U.S. policy, offering near-term abatement opportunities.

Greenhouse gas (GHG) emissions from integrated urban drainage systems (IUDSs), including sewer, wastewater treatment plants (WWTPs), and receiving water systems, have not yet been integrated due to the lack of modeling tools. Here, we updated the computable general equilibrium-based System Dynamics and Water Environmental Model (CGE-SyDWEM), a recently developed model simulating the water-energy-carbon nexus at the watershed level, to calculate the direct and indirect (electricity use and external) GHG emissions from IUDSs considering carbon mitigation strategies and water engineering practices. The updated CGE-SyDWEM was applied to an estuary watershed in Shenzhen, the fourth largest city in China. With increasing socio-economic development and water infrastructure systems upgrading, GHG emissions are projected to increase from 129.2 (95% CI: 95.9-162.5) kt in 2007 to 190.7 (144.8-236.6) kt in 2025, with 89% from WWTPs (direct: 17%; electricity use: 65%; and external: 7%), 10% from the sewer (direct: 1% and electricity use: 9%) and 1% from receiving waters (direct). Carbon mitigation can reduce GHG emissions by 7% and emission intensity by 6% by 2025, with 63% contributed by external emission reduction from chemical uses. The integrated model can aid water, energy, and carbon decision-makers in finding cost-effective solutions for water and energy security in the future.

The European Union (EU) has set a 37.5% GHG reduction target in 2030 for the mobility sector, relative to 1990 levels. This requires increasing the share of zero-emission passenger vehicles, mainly in the form of electric vehicles (EVs). This study calculates future GHG emissions related to passenger vehicle manufacturing and use based on stated policy goals of EU Member States for EV promotion. Under these policies, by 2040 the stock of EVs would be about 73 times larger than those of 2020, contributing to a cumulative in-use emission reduction of 2.0 gigatons CO 2 -eq. Nevertheless, this stated EV adoption will not be sufficiently fast to reach the EU's GHG reduction targets, and some of the GHG environmental burdens may be shifted to the EV battery manufacturing countries. To achieve the 2030 reduction targets, the EU as a whole needs to accelerate the phase-out of internal combustion engine vehicles and transit to e-mobility at the pace of the most ambitious Member States, such that EVs can comprise at least 55% of the EU passenger vehicle fleet in 2030. An accelerated decarbonization of the electricity system will become the most critical prerequisite for minimizing GHG emissions from both EV manufacturing and in-use stages.

Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero gradient test indicate a flux measurement precision of 4.8 W m-2 for water vapor, 0.010 mg m-2 s-1 for CO2, and 0.029 μg m-2 s-1 for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O , CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m-2 year-1) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m-2 year-1). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes. [ABSTRACT FROM AUTHOR]

This paper presents the inclusion of new, relevant impact categories for agriculture life cycle assessments. We performed a specific case study with a focus on the applicability of spatially explicit characterization factors. The main goals were to provide a detailed evaluation of these new impact category methods, compare the results with commonly used methods (ReCiPe and USEtox) and demonstrate how these new methods can help improve environmental assessment in agriculture. As an overall conclusion, the newly developed impact categories helped fill the most important gaps related to land use, water consumption, pesticide toxicity, and nontoxic emissions linked to fertilizer use. We also found that including biodiversity damage due to land use and the effect of water consumption on wetlands represented a scientific advance toward more realistic environmental assessment of agricultural practices. Likewise, the dynamic crop model for assessing human toxicity from pesticide residue in food can lead to better practice in pesticide application. In further life cycle assessment (LCA) method developments, common end point units and normalization units should be agreed upon to make it possible to compare different impacts and methods. In addition, the application of site-specific characterization factors allowed us to be more accurate regarding inventory data and to identify precisely where background flows acquire high relevance. [ABSTRACT FROM AUTHOR]

Increasing the use of biofuels influences atmospheric greenhouse gas concentrations. Although widely recognized, uncertainties related to the particular impacts are typically ignored or only partly considered. In this paper, various sources of uncertainty related to the GHG emission savings of biofuels are considered comprehensively and transparently through scenario analysis and stochastic simulation. Technology and feedstock production chain-specific factors, market-mediated factors and climate policy time frame issues are reflected using as a case study Fischer-Tropsch diesel derived from boreal forest biomass in Finland. This case study shows that the GHG emission savings may be positive or negative in many of the cases studied, and are subject to significant uncertainties, which are mainly determined by market-mediated factors related to fossil diesel substitution. Regardless of the considerable uncertainties, some robust conclusions could be drawn; it was likely of achieving some sort of but unlikely of achieving significant savings in the GHG emissions within the 100 year time frame in many cases. Logging residues (branches) performed better than stumps and living stem wood in terms of the GHG emission savings, which could be increased mainly by blocking carbon leakage. Forest carbon stock changes also significantly contributed to the GHG emission savings. [ABSTRACT FROM AUTHOR]

Recent emission measurement campaigns have improved our understanding of the total greenhouse gas (GHG) emissions across the natural gas supply chain, the individual components that contribute to these emissions, and how these emissions vary geographically. However, our current understanding of natural gas supply chain emissions does not account for the linkages between specific production basins and consumers. This work provides a detailed life cycle perspective on how GHG emissions vary according to where natural gas is produced and where it is delivered. This is accomplished by disaggregating transmission and distribution infrastructure into six regions, balancing natural gas supply and demand locations to infer the likely pathways between production and delivery, and incorporating new data on distribution meters. The average transmission distance for U.S. natural gas is 815 km but ranges from 45 to 3000 km across estimated production-to-delivery pairings. In terms of 100-year global warming potentials, the delivery of one megajoule (MJ) of natural gas to the Pacific region has the highest mean life cycle GHG emissions (13.0 g CO 2 e/MJ) and the delivery of natural gas to the Northeast U.S. has the lowest mean life cycle GHG emissions (8.1 g CO 2 e/MJ). The cradle-to-delivery scenarios developed in this work show that a national average does not adequately represent the upstream GHG emission intensity for natural gas from a specific basin or delivered to a specific consumer.

The United States Postal Service (USPS) plans to purchase 165,000 next-generation delivery vehicles (NGDVs) between 2023 and 2032. The USPS submitted an environmental impact statement (EIS) for two NGDV procurement scenarios: (1) 90% internal combustion engine vehicles (ICEVs) and 10% battery electric vehicles (BEVs) ("ICEV scenario") and (2) 100% BEVs ("BEV scenario"). To correct several significant deficiencies in the EIS, we conduct a cradle-to-grave life cycle greenhouse gas (GHG) assessment of these two scenarios. Our analysis improves upon the USPS's EIS by including vehicle production and end-of-life emissions, future grid decarbonization, and more accurate vehicle operating emissions. In our base case, we find that the ICEV and BEV scenarios would result in 15% greater and 8% fewer GHG emissions, respectively, than the USPS estimate. Favorable vehicle and grid development would result in 63% lower BEV scenario emissions than the USPS estimate. Consequently, we calculate a cumulative lifetime emission reduction of 57-82% (14.7-21.4 Mt CO 2 e) from procuring 100% BEVs instead of 10% BEVs, compared to the USPS's estimate of 10.3 Mt. Given the long NGDV lifetimes, committing to the ICEV scenario squanders an ideal use case for BEVs, jeopardizes meeting our climate goals, and forgoes potential climate and environmental justice co-benefits.

Future ships need to operate with low or possibly zero greenhouse gas (GHG) emissions while ensuring low influence on other environmental impacts and that the operation is economically feasible. This study conducts a life-cycle evaluation of potential decarbonization solutions involving selected energy carriers (electrolytic hydrogen, electro-ammonia, electro-methanol, and electricity) in different propulsion system setups (engines, fuel cells, and carbon capture technologies) in terms of environmental impact and costs. The results of the study show that the assessed decarbonization options are promising measures to reduce maritime GHG emissions with low-carbon-intensive electricity. The same order of GHG reduction is shown to be possible independent of the propulsion system and energy carrier used onboard. However, the carbon abatement cost ranges from 300 to 550 €/tCO 2 eq, and there is a trade-off with environmental impacts such as human toxicity (cancer and non-cancer effects) and freshwater ecotoxicity mainly linked with the wind infrastructure used for electricity production. Electro-ammonia in fuel cells is indicated to be effective in terms of the carbon abatement cost followed by the so-called HyMethShip concept. The higher abatement cost of all options compared to current options indicates that major incentives and policy measures are required to promote the introduction of alternative fuel and propulsion systems.

Peatlands are an important source of the atmospheric greenhouse gas methane (CH4). Although CH4 cycling and fluxes have been quantified for many northern peatlands, imprecision in process-based approaches to predicting CH4 emissions suggests that our understanding of underlying processes is incomplete. Microbial anaerobic oxidation of CH4 (AOM) is an important CH4 sink in marine sediments, but AOM has only recently been identified in a few nonmarine systems. We used 13C isotope tracers and followed the fate of 13C into CO2 and peat in order to study the geographic extent, relative importance, and biogeochemistry of AOM in 15 North American peatlands spanning a 1500 km latitudinal transect that varied in hydrology, vegetation, and soil chemistry. For the first time, we demonstrate that AOM is a widespread and quantitatively important process across many peatland types and that anabolic microbial assimilation of CH4-C occurs. However, AOM rate is not predicted by CH4 production rates and the primary mechanism of C assimilation remains uncertain. AOM rates are higher in fen than bog sites, suggesting electron acceptor constraints on AOM. Nevertheless, AOM rates were not correlated with porewater ion concentrations or stimulated following additions of nitrate, sulfate, or ferric iron, suggesting that an unidentified electron acceptor(s) must drive AOM in peatlands. Globally, we estimate that AOM could consume a large proportion of CH4 produced annually (1.6-49 Tg) and thereby constrain emissions and greenhouse gas forcing. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has accelerated the growth of e-commerce and automated warehouses, vehicles, and robots and has created new options for grocery supply chains. We report and compare the greenhouse gas (GHG) emissions for a 36-item grocery basket transported along 72 unique paths from a centralized warehouse to the customer, including impacts of micro-fulfillment centers, refrigeration, vehicle automation, and last-mile transportation. Our base case is in-store shopping with last-mile transportation using an internal combustion engine (ICE) SUV (6.0 kg CO 2 e). The results indicate that emissions reductions could be achieved by e-commerce with micro-fulfillment centers (16-54%), customer vehicle electrification (18-42%), or grocery delivery (22-65%) compared to the base case. In-store shopping with an ICE pick-up truck has the highest emissions of all paths investigated (6.9 kg CO 2 e) while delivery using a sidewalk automated robot has the least (1.0 kg CO 2 e). Shopping frequency is an important factor for households to consider, e.g. halving shopping frequency can reduce GHG emissions by 44%. Trip chaining also offers an opportunity to reduce emissions with approximately 50% savings compared to the base case. Opportunities for grocers and households to reduce grocery supply chain carbon footprints are identified and discussed.

China is facing the dual challenge of achieving food security and agricultural carbon neutrality. Developing spatially explicit crop emission profiles can help inform policy to mitigate agricultural greenhouse gases (GHGs), but previous life-cycle studies were conducted mostly at national and provincial levels. Here, we estimate county-level carbon footprint of China's wheat and maize production based on a nationwide survey and determine the contribution of different strategies to closing regional emission gaps. Results show that crop carbon footprint varies widely between regions, from 0.07 to 3.00 kg CO 2 e kg -1 for wheat and from 0.09 to 2.30 kg CO 2 e kg -1 for maize, with inter-county variation generally much higher than interprovince variation. Hotspots are mainly concentrated in Xinjiang and Gansu provinces, owing to intensive irrigation and high plastic mulch and fertilizer inputs. Closing the regional emission gaps would benefit mostly from increasing crop yields and nitrogen use efficiency, but increasing manure use (e.g., in Northeast, East, and Central China) and energy use efficiency (e.g., in North and Northwest China) can also make important contributions. Our county-level carbon footprint estimates improve upon previous broad-scale results and will be valuable for detailed spatial analysis and the design of localized GHG mitigation strategies in China.

We perform a state-specific life-cycle assessment of greenhouse gases (GHG) (CO 2eq ) and sulfur dioxide (SO 2 ) emissions in India for representative passenger vehicles (two-wheelers, three-wheelers, four-wheelers, and buses) and technologies (internal combustion engine, battery electric, hybrid electric, and plug-in hybrid electric vehicles). We find that in most states, four-wheeler battery-electric vehicles (BEVs) have higher GHG and SO 2 emissions than other conventional or alternative vehicles. Electrification of those vehicle classes under present conditions would not lead to emission reductions. Electrified buses and three-wheelers are the best strategies to reduce GHG emissions in many states, but they are also the worst strategy in terms of SO 2 emissions. Electrified two-wheelers have lower SO 2 emissions than gasoline in one state. The Indian grid would need to decrease its carbon dioxide emissions by 38-52% and SO 2 emissions by 58-97% (depending on the state) for widespread vehicle electrification for sustainability purposes to make sense. If the 2030 goals for India under the Glasgow COP are met, we find that four-wheeler BEVs still have higher GHG emissions in 18 states compared to a conventional gasoline compact four wheeler, and all states will have higher SO 2 emissions for BEVs across all vehicle types compared to their conventional counterparts.

Many researchers, policymakers, and stakeholders view zero-emissions vehicles (ZEVs) as playing an important role in deep decarbonization of the transport sector. Here, we bring attention to one policy that can effectively induce ZEV sales in the long term: a ZEV sales mandate. Although three decades have passed since the first mandate was implemented in California, there is surprisingly little research regarding its policy impacts. From a greenhouse gas (GHG) mitigation perspective, we argue that ZEV mandates should be framed and analyzed as complex policy-with intended impacts on industry, consumers, and institutions over the long term. We present an interdisciplinary framework to address this complexity, summarizing the limited evidence to date on policy effectiveness, efficiency, public acceptability, and transformative potential. We conclude with a critical research agenda to improve understanding of the role of a mandate in an effective policy mix.

Renewable natural gas (RNG) sources are being considered in future energy strategy discussions as potential replacements for fossil natural gas (FNG). While today's supply of RNG resources is insufficient to meet U.S. demands, there is significant interest in its viability to supplement and decarbonize the natural gas supply. However, the studies compare the life cycle global warming potential (GWP) of various RNG production pathways are lacking and focus mostly on a singular pathway. This effort is an attempt to close this gap and provide a comparison between the life cycle GWP of three major RNG pathways and the FNG pathway. The three RNG pathways evaluated are anaerobic digestion (AD), thermal gasification (TG), and power-to-gas (P2G) using various feedstocks. The functional unit is 1 MJ of compressed RNG ready for injection into the natural gas transmission network. The results show that RNG production is not always carbon neutral or negative. Depending on the pathway, the GWP impact of RNG production can range from -229 to 27 g CO 2 e/MJ compressed RNG, with AD of animal manure and AD of municipal solid waste being the least and the most impactful pathways, respectively, compared to the 10.1 g CO 2 e/MJ impact for compressed FNG.

Treatment of domestic wastewater can recover valuable resources, including clean water, energy, and ammonia. Important metrics for these systems are greenhouse gas (GHG) emissions and embodied energy, both of which are location- and technology-dependent. Here, we determine the embodied energy and GHG emissions resulting from a conventional process train, and we compare them to a nonconventional process train. The conventional train assumes freshwater conveyance from a pristine source that requires energy for pumping (US average of 0.29 kWh/m 3 ), aerobic secondary treatment with N removal as N 2 , and Haber-Bosch synthesis of ammonia. Overall, we find that this process train has an embodied energy of 1.02 kWh/m 3 and a GHG emission of 0.77 kg-CO 2 eq/m 3 . We compare these metrics to those of a nonconventional process train that features anaerobic secondary treatment technology followed by further purification of the effluent by reverse osmosis and air stripping for ammonia recovery. This "short-cut" process train reduces embodied energy to 0.88 kWh/m 3 and GHG emissions to 0.42 kg-CO 2 eq/m 3 , while offsetting demand for ammonia from the Haber-Bosch process and decreasing reliance upon water transported over long distances. Finally, to assess the potential impacts of nonconventional nitrogen removal technology, we compared the embodied energy and GHG emissions resulting from partial nitritation/anammox coupled to anaerobic secondary treatment. The resulting process train enabled a lower embodied energy but increased GHG emissions, largely due to emissions of N 2 O, a potent greenhouse gas.

CO 2 -enhanced oil recovery (EOR) can have less GHG emissions compared to conventional oil production methods. The economy of CO 2 -EOR can significantly benefit from the recent rise of carbon prices in carbon markets due to its greenhouse gas (GHG) emission savings. This study conducted a life cycle assessment (LCA) of CO 2 -EOR in major hydrocarbon provinces of the world. Estimated net GHG emissions of CO 2 -EOR were compared with GHG emissions of average produced oil in the given country. When sourcing CO 2 from coal-fired power plants, Kazakhstan and China have net GHG emissions of CO 2 -EOR of 276 and 380 kg CO 2 eq/bbl, respectively, which are lower than the GHG emission factor of average oil produced in each of them. Significantly lower GHG emissions of CO 2 -EOR are observed in other hydrocarbon provinces (Iraq, Saudi Arabia, Kuwait, etc.), where CO 2 could be delivered from Natural Gas Combined Cycle (NGCC) power plants. However, the cost of CO 2 capture is higher at NGCC power plants than at coal-fired power plants. Further, we developed a techno-economic assessment (TEA) model of the CO 2 -EOR and integrated it with LCA to thoroughly consider carbon credits in its economy. The model was built based upon previous investigations and used statistics from a large industrial data set of CO 2 -EOR to produce accurate estimates of the CO 2 -EOR economy. The technical model iteratively estimated the balance of three fluids (crude oil, CO 2 , and water) in the CO 2 -EOR system with a 25 year operational lifespan and obtained actual data for the LCA and TEA models. The model was simulated for the Kazakhstan case with its oil market conditions for a demonstration purpose. TEA results showed that, with the available low-cost CO 2 capture source or high CO 2 cost in carbon trading, CO 2 -EOR can compete with current upstream projects in Kazakhstan by simultaneously increasing oil production and reducing GHG emissions.

Increasing atmospheric carbon dioxide (CO2) is raising seawater CO2 concentrations and thereby acidifying ocean water. But a second environmental problem, eutrophication, is also causing large CO2 inputs into coastal waters. This occurs because anthropogenic inputs of nutrients have fueled massive algal blooms, which deplete bottom waters of oxygen (O2) and release CO2 when the organic matter from these blooms is respired by bacteria. On the basis of a biogeochemical model, these CO2 inputs are predicted to decrease current pH values by 0.25 to 1.1 units, effects that increased with decreasing temperature and salinity. Our model predictions agreed well with pH data from hypoxic zones in the northern Gulf of Mexico and Baltic Sea, two eutrophic coastal systems with large temperature and salinity differences. The modeled and measured decreases in pH are well within the range shown to adversely impact marine fauna. Model calculations show that the acidification from respiratory CO2 inputs interacts in a complex fashion with that from increasing atmospheric CO2 and that these pH effects can be more than additive in seawater at intermediate to higher temperatures. These interactions have important biological implications in a future world with increasing atmospheric CO2, increasing anthropogenic inputs of nutrients, and rising temperatures from CO2-linked global warming. [ABSTRACT FROM AUTHOR]

Methane is the most important non-CO2greenhouse gas (GHG) responsible for global warming with more than 10 % of total GHG emissions. The greenhouse warming potential (GWP) of this gas is much higher than carbon dioxide. Therefore, any reduction in methane emissions is really important in atmosphere reconstruction. Nitrogen is needed to be removed from landfill gas to obtain low grade natural gas as a renewable source of energy from garbage, but the separation is really difficult. Adsorption was considered as a possibility for this separation, and silicalite was studied as the adsorbent. The adsorption behavior of methane and nitrogen with this adsorbent was studied by concentration pulse chromatography and constant volume techniques. Ideal separation factors were obtained from the experimental pure adsorption isotherms by using the temperature independent Toth isotherm model. Mixture adsorption isotherms for the binary system of methane and nitrogen at (40, 70, and 100) °C at 1 bar total pressure were determined experimentally. Corresponding x−ydiagrams and separation factors were obtained from these data. The thermodynamic consistency tests between pure and binary gas adsorption systems were also carried out. The separation factors obtained with silicalite for the separation applications of methane and nitrogen gases in this work are much better than those obtained for other systems in the literature. [ABSTRACT FROM AUTHOR]

The developments of both biodiesel and emulsified diesel are being driven by the need for reducing emissions from diesel engines and saving energy. Artificial chemical additives are also being used in diesel engines for increasing their combustion efficiencies. But the effects associated with the use of emulsified additive/biodiesel/diesel blends in diesel engines have never been assessed. In this research, the premium diesel fuel (PDF) was used as the reference fuel. A soy-biodiesel was selected as the test biodiesel. A biosolution made of 96.5 wt % natural organic enzyme-7F (NOE-7F) and 3.5 wt % water (NOE-7F water) was used as the fuel additive. By adding additional 1 vol % of surfactant into the fuel blend, a nanotechnology was used to form emulsified biosolution/soy-biodiesel/PDF blends for fueling the diesel engine. We found that the emulsified biosolution/soy-biodiesel/PDF blends did not separate after being kept motionless for 30 days. The above stability suggests that the above combinations are suitable for diesel engines as alternative fuels. Particularly, we found that the emulsified biosolution/soy-biodiesel/PDF blends did have the advantage in saving energy and reducing the emissions of both particulate matters (PM) and polycyclic aromatic hydrocarbons (PAHs) from diesel engines as compared with PDF, soy-biodiesel/PDF blends, and emulsified soy-biodiesel/PDF blends. The results obtained from this study will provide useful approaches for reducing the petroleum reliance, pollution, and global warming. However, it should be noted that NOx emissions were not measured in the present study which warrants the need for future investigation. [ABSTRACT FROM AUTHOR]

In contrast to conventional carbon capture systems for power plants and other large point sources, the system described in this paper captures CO2 directly from ambient air. This has the advantages that emissions from diffuse sources and past emissions may be captured. The objective of this research is to determine the feasibility of a NaOH spray-based contactor for use in an air capture system by estimating the cost and energy requirements per unit CO2 captured. A prototype system is constructed and tested to measure CO2 absorption, energy use, and evaporative water loss and compared with theoretical predictions. A numerical model of drop collision and coalescence is used to estimate operating parameters for a full- scale system, and the cost of operating the system per unit CO2 captured is estimated. The analysis indicates that CO2 capture from air for climate change mitigation is technically feasible using off-the-shelf technology. Drop coalescence significantly decreases the CO2 absorption efficiency; however, fan and pump energy requirements are manageable. Water loss is significant (20 mol H2O/mol CO2 at 15 °C and 65% RH) but can be lowered by appropriately designing and operating the system. The cost of CO2 capture using NaOH spray (excluding solution recovery and CO2 sequestration, which may be comparable) in the full-scale system is 96 $/ton-CO2 in the base case, and ranges from 53 to 127 $/ton-CO2 under alternate operating parameters and assumptions regarding capital costs and mass transfer rate. The low end of the cost range is reached by a spray with 50 µm mean drop diameter, which is achievable with commercially available spray nozzles. [ABSTRACT FROM AUTHOR]

To improve their CO2 absorption capacity, alkali-based sorbents prepared by impregnation and wet mixing method of potassium carbonate on supports such as activated carbon and MgO (KACl30, KACP30, KMgl30, and KMgP30), were investigated in a fixed bed reactor (CO2 absorption at 50-100 °C and regeneration at 150-400 °C). Total CO2 capture capacities of KMgl30-500 and KMgP30-500 were 178.6 and 197.6 mg CO2/g sorbent, respectively, in the presence of 11 vol % H2O even at 50 °C. The large amount of CO2 capture capacity of KMgP30-500 and KMgl30-500 could be explained by the fact that MgO itself, as well as K2CO3, could absorb CO2 in the presence of water vapor even at low temperatures. In particular, water vapor plays an important role in the CO2 absorption of MgO and KMgl30-500 even at low temperatures below 60 °C, in marked contrast to MgO and CaO which can absorb CO2 at high temperatures. The CO2 capture capacity of the KMgl30-300 sorbent, however, was less than that of KMgI30-500 due to the formation of Mg(OH)2 which did not absorb CO2. MgO based-sorbents promoted with K2CO3 after CO2 absorption formed new structures such as K2Mg(CO3)2 and K2Mg(CO3)2·4(H2O), unlike KACl30 which showed only the KHCO3 crystal structure. The new Mg-based sorbents promoted with K2CO3 showed excellent characteristics in that it could satisfy a large amount of CO2 absorption at low temperatures, a high CO2 absorption rate, and fast and complete regeneration. [ABSTRACT FROM AUTHOR]

Global warming potentials are estimated for hydrofluoroethers, which are an emerging class of compounds for industrial use. Comparisons are made to the limited data previously available before observations about molecular design are discussed. We quantify how molecular structure can be manipulated to reduce environmental impacts due to global warming. We further highlight the need for additional research on this class of compounds so environmental performance can be assessed for green design. [ABSTRACT FROM AUTHOR]

Smog chamber/FTIR techniques were used to study the atmospheric chemistry of the title compound which we refer to as RfOC2H5. Rate constants of k(Cl + RfOC2H5) = (2.70 ± 0.36) × 10-12, k(OH + RfOC2H5) = (5.93 ± 0.85) × 10-14, and k(Cl + RfOCHO) (1.34 ± 0.20) × 10-14 cm3 molecule-1 s-1 were measured in 700 Torr of N2, or air, diluent at 294 ± 1 K. From the value of k(OH + RfOC2H5) the atmospheric lifetime of RfOC2H5 was estimated to be 1 year. Two competing loss mechanisms for RfOCH(O∙)CH3 radicals were identified in 700 Torr of N2/O2 diluent at 294 ± 1 K; decomposition via C—C bond scission giving a formate (RfOCHO), or reaction with O2 giving an acetate (RfOC(O)-CH3). In 700 Torr of N2/O2 diluent at 294 ± 1 K the rate constant ratio ko2kdiss =(1.26 ± 0.74) × 10-19 cm3 molecule-1. The OH radical initiated atmospheric oxidation of RfOC2H5 gives RfOCHO and RfOC(O)CH3 as major products. RfOC2H5 has a global warming potential of approximately 55 for a 100 year horizon. The results are discussed with respect to the atmospheric chemistry and environmental impact of RfOC2H5. [ABSTRACT FROM AUTHOR]

In contrast to global warming, temperatures in the southeastern United States have exhibited a decreasing trend of up to 1–2 °C over the last century. We investigated the relationship between this cooling trend and the extensive use of organochlorine pesticides—particularly dichloro-diphenyl-trichloroethane (DDT) and toxaphene—in the southeastern U.S. from the mid-1940s through the 1970s. Based on annual use and soil residue estimates, it is shown that enthalpies associated with the endothermic evaporation of pesticides from soil resulted in surface temperature decreases of up to –0.2 °C. This is the first study to show the inverse correlation between surface air temperature and pesticide use. These findings highlight the potential contribution of the extensive use of organochlorine pesticides to changes in the surface air temperature, especially in regions of intensive agriculture and pesticide use. [ABSTRACT FROM AUTHOR]

The article presents information on a survey to assess the misconceptions among students regarding atmospheric environmental chemistry. It is mentioned that students have misconceptions in topics including global warming and ozone depletion. A survey was conducted on science students in the U.S., which found that 56% of the students believed that holes in the stratospheric ozone layer would increase the greenhouse effect. In a survey of Australian students, it was found that 40% of them believed that the ozone hole causes global warming.

The atmospheric histories of two potent greenhouse gases, tetrafluoromethane (CF4) and hexafluoroethane (C2F6), have been reconstructed for the 20th century based on firn air measurements from both hemispheres. The reconstructed atmospheric trends show that the mixing ratios of both CF4 and C2F6 have increased during the 20th century by factors of ∼2 and ∼10, respectively. Initially, the increasing mixing ratios coincided with the rise in primary aluminum production. However, a slower atmospheric growth rate for CF4 appears to be evident during the 1990s, which supports recent aluminum industry reports of reduced CF4 emissions. This work illustrates the changing relationship between CF4 and C2F6 that is likely to be largely the result of both reduced emissions from the aluminum industry and faster growing emissions of C2F6 from the semiconductor industry. Measurements of C2F6 in the older firn air indicate a natural background mixing ratio of <0.3 parts per trillion (ppt), demonstrating that natural sources of this gas are negligible. However, CF4 was deduced to have a preindustrial mixing ratio of 34 ± 1 ppt (∼50% of contemporary levels). This is in good agreement with the previous work of Harnisch et al. (18) and provides independent confirmation of their results. As a result of the large global warming potentials of CF4 and C2F6, these results have important implications for radiative forcing calculations. The radiative forcings of CF4 and C2F6 are shown to have increased over the past 50 years to values in 2001 of 4.1 × 10-3 Wm-2 and 7.5 × 10-4 Wm-2, respectively, relative to preindustrial concentrations. These forcings are small compared to present day forcings due to the major greenhouse gases but, if the current trends continue, they will continue to increase since both gases have essentially infinite lifetimes. There is, therefore, a large incentive to reduce perfluorocarbon emissions such that, through the implementation of the Kyoto Protocol, the atmospheric growth rates may decline in the future. [ABSTRACT FROM AUTHOR]