High Global Warming Potential Research Articles

A comparative life cycle assessment of dental restorative materials.

Different types of direct-placement dental materials are used for the restoration of structure, function and aesthetics of teeth. The aim of this research investigation is to determine, through a comparative cradle-to-gate life cycle assessment, the environmental impacts of three direct-placement dental restorative materials (DRMs) and their associated packaging. Three direct-placement dental materials; dental amalgam, resin-based composite (RBC) and glass polyalkenoate cements (GIC) are assessed using primary data from a manufacturer (SDI Limited, Australia). The functional unit consisted of 'one dental restoration' of each restorative system under investigation: 1.14g of dental amalgam; 0.25g of RBC (plus the adhesive = 0.10g); and 0.54g of GIC. The system boundary per restoration included the raw materials and their associated packaging materials for each DRM together with the processing steps for both the materials and packaging. The environmental impacts were assessed using an Egalitarian approach under the ReCiPe method using Umberto software and the Ecoinvent database. Nine different impact categories were used to compare the environmental performance of these materials. Dental amalgam had the highest impact across most of the categories, but RBC had the highest Global Warming Potential. The highest sources of the environmental impacts for each restorative material were: Amalgam, derived from material use; RBC, derived from energy use in processing material and packaging material; GIC, derived from material and energy use for packaging. Less intensive energy sources or more sustainable packaging materials can potentially reduce the impacts associated with RBC and GIC thus making them suitable alternatives to dental amalgam.

Introduction to Domestic and International Sulfur Hexafluoride (SF6) Greenhouse Gas Emission Reduction Technologies for Power Grid Enterprises

Since its introduction in 1930, sulfur hexafluoride (SF6) has rapidly become the primary insulation material for high-voltage electrical equipment such as transmission lines, switches, transformers, circuit breakers, and reactors, owing to its exceptional electrical properties. However, the flip side of its excellent performance is its extremely high global warming potential (GWP), which is over 23,000 times that of carbon dioxide (CO2). Managing SF6 has thus become a key aspect of emission reduction efforts. The primary strategies for reducing SF6 emissions include minimizing gas leakage during the production, operation, and maintenance of electrical equipment, as well as purifying and recycling emitted SF6 gas. Various purification and monitoring methods have been developed for routine operations and have already been implemented by power grid companies globally. In addition to ongoing daily monitoring, research is also underway concerning the transformation, degradation, and substitution of SF6 gases. Degradation and transformation methods primarily focus on high-temperature degradation, photocatalysis, and arc degradation. In the context of substitution, the idea is to use conventional gases or various organic compounds to form SF6 mixtures or alternative gases, with the aim of reducing effect of leakage while maintaining performance. Finally, recommendations are made for power grid enterprises to reduce SF6 emissions, emphasizing the importance of source control and the exploration of alternatives. Effective equipment management to prevent gas leakage, comprehensive monitoring and assessment, as well as the proper handling of unusable SF6 devices, are also crucial steps in emission reduction efforts.

Efficient CF4 adsorption on porous carbon derived from polyaniline

BackgroundAs a significant greenhouse gas emitted in large quantities from the electrolytic aluminum and semiconductor industries, tetrafluoromethane (CF4) has an extremely high global warming potential (GWP) and a fairly long atmospheric lifetime. MethodsIn this study, porous carbon was prepared via a thermochemical process involving the carbonization and K2CO3 activation of precursor polyaniline (PANI). The activation temperature (600–800 ℃) and K2CO3/carbonized PANI mass ratio (1–4) had significant influences on the porous structure and CF4 uptake of the PANI-derived porous carbon (PDC). Significant findingsThe prepared PDC-3-800 adsorbent exhibited the largest specific surface area (2268 m2 g−1) and highest pore volume (1.48 cm3 g−1), whereas PDC-2-700 adsorbent demonstrated the highest CF4 uptake of up to 2.16 mmol g−1 at 25 ℃ and 1 bar. Notably, CF4 uptake was predominantly dependent on the presence of narrow micropores with diameters below 0.9 nm at atmospheric pressure. The CF4 adsorption isotherms were well fitted by the dual-site Langmuir (DSL) model. Moreover, the isosteric heat of adsorption and CF4/N2 selectivity of PDCs were investigated. These experimental results demonstrate that PDCs with high CF4 adsorption capacity, excellent CF4/N2 selectivity, and good recyclability, have immense potential for practical CF4 capture applications.

EFFECTS OF VAPORIZATION TEMPERATURE AND SUB COOLING VARIATION ON THE PERFORMANCE OF A VAPOUR COMPRESSION REFRIGERATION CYCLE WORKING WITH R134A, MET ON NEWER SHIPS

R134a is a refrigerant met in several marine refrigeration applications, such as fishing vessels, passenger and cargo ships. In 2014, 26% of the international commercial fleet was using R134a. Although R134a shows a null Ozone Depletion Potential, it has a quite high Global Warming Potential (1300). R134a is a greenhouse gas and, even if it is present on newer ships, the future will be marked by its replacement with substitutes having low GWP. Still, because its GWP is less than 2500, R 134a will continue to be used. Due to the fact that vapour compression refrigeration systems are dominant on board the ships and knowing that these technologies are high energy consumers, analysing their performance in the contemporary energetic context, is imperious required. This paper presents a theoretical analysis of a single stage vapour compression cycle, working with R134a, based on the laws of thermodynamics. The analysis will reveal the influence of the evaporator temperature on the Coefficient of performance and on exergy efficiency, and also the influence of sub cooling on these two efficiency terms, on the refrigerant mass flow rate and compression rate. It was considered a variation of the evaporator temperature in the range (-40÷ -10)oC and of the sub cooling in the range (0÷10)oC. The increase of the evaporator temperature will contribute to a COP increment (50%) and an exergy efficiency decrease (34%). The sub cooling will lead to both COP and exergy efficiency increase (11%). Higher sub cooling degree will provide an increment in the refrigerant mass flow (18%) and a decrease of the compression rate (76%) meaning lower work consumption at the compressor.

Effects of feed formula and farming system on the environmental performance of shrimp production chain from a life cycle perspective

AbstractShrimp is the most popular seafood in the United States; its production plays an important role in the aquaculture industry. However, shrimp farming causes various environment impacts that must be mitigated to ensure the sustainability of shrimp production. This study performed a life cycle assessment (LCA) on two US‐based and one Vietnam‐based shrimp production chains from cradle to US market covering three farming systems and eight shrimp feed formulae. Midpoint environmental impacts including terrestrial acidification, freshwater eutrophication, and global warming were determined. For the intensive production chain (IPC), feed production was identified as the main contributor to the terrestrial acidification potential (TAP) and global warming potential (GWP), and its freshwater eutrophication potential (FEP) was dominated by shrimp farming. Poultry by‐product and fish meals were the feed ingredients contributing high TAP and GWP. However, soybean, wheat, and corn gluten meals produced higher FEP; hence, substituting plant‐based proteins for animal‐based ones in shrimp feeds did not all have positive environmental consequences. Shrimp farming was the hotspot of all the environmental impacts of the semi‐intensive production chain (SPC) and extensive production chain (EPC), except for the TAP of the EPC. Among the three production chains, the IPC had the highest FEP due to the on‐farm discharge of phosphorus‐containing wastewater, and the SPC caused the highest TAP because of the intensive uses of electricity and fertilizers for pond cultivation. Although the EPC was most sustainable in terms of TAP and FEP, open farming in mangrove areas produced the highest GWP owing to land transformation. This LCA study is expected to serve as US shrimp farmers’ decision‐making guidelines to adapt farming practices with lower environmental footprint.

Environmental behaviours and risk perception of domestic consumers: Refrigeration equipment case study

European citizens believe they can play a role in protecting the environment through changes in how they buy, consume, and separate waste, but they also believe they are not doing enough. Household refrigerating appliances, such as refrigerators, freezers, and air conditioning systems (at home or in the car), impact severely global warming due to their high energy consumption and the high global warming potential of the most used refrigeration gases. Despite the unequivocal importance of consumers' actions, their behaviours during equipment purchase, use, maintenance, and disposal at the end-of-life have been largely ignored in policy regulatory strategies. In this work, the gap between consumers’ concerns and their behaviours was addressed by assessing their actions specifically related to the refrigeration gases of their domestic refrigeration equipment (refrigerators and air conditioning systems), at every stage of the equipment life cycle. A questionnaire was conducted with a sample of 648 Portuguese, Spanish and French consumers, aiming at diagnosing the importance and risk attributed to refrigeration gases, and their perception of the actions they can take to reduce this risk. The results revealed that, despite attributing great importance to climate change and considering refrigeration gases a high danger to the environment, most consumers did not consider these gases in their decision when purchasing refrigeration equipment. However, in general, consumers have correct behaviours when there is an equipment malfunction, although they have little information relative to the authorized technicians for installation or maintenance of equipment. The results of this work allowed us to identify the topics that need to be reinforced in future awareness campaigns and to provide some recommendations to promote appropriate consumer behaviour.

Impact of Different Livestock Manures on the Compost Quality and Greenhouse Gas Emissions during Food Waste Composting

Although livestock manure and food waste have emerged to be main issues to cause environmental problems, at the same time, and recycle natural resources, the simultaneous treatment method and impact of two organic wastes are not well understood. In this research, the influence of different types of livestock manures combination on compost maturity, greenhouse gas (GHG) and NH3 emission was evaluated during food waste composting. Apart from a control treatment (only food waste, OF), three co-composting treatments were conducted: (1) food waste + cow manure (FCM); (2) food waste + swine manure (FSM); and (3) food waste + poultry manure (FPM). An 84-day composting experiment was conducted in 62 L composting chamber. During composting process, changes of methane (CH4), nitrous oxide (N2O), ammonia (NH3) emissions and compost pile; temperature, pH, nutrient content, etc., were periodically investigated. The co-composting with livestock manures significantly reduced nitrogen losses by NH3 (11.5 - 44.2%) and N2O (39.1 - 49.7%) emissions. The lowest NH3 emission were observed in FSM treatment. The highest CH4 and N2O production was detected in FCM and OF treatment, respectively. The global warming potential (GWP) value was calculated to evaluate overall GHG impact, then FSM showed the lowest GWP value (7.0 kg CO2 eq. kg-1), which is 109% reduction rate compared to FC (highest GWP, 14.7 kg CO2 eq. kg-1). Nutrients content such as Ca, Mg, and K of final compost product were increased by 33 - 76%, 17 - 76%, 60 - 90% in livestock manure combination treatments. Germination index was increased in FSM and FPM, compared to OF during composting, and then they could accelerate maturation rate. These results suggested that co-composting with food waste and livestock manures is recommendable to improve compost quality, especially, swine manure was an efficient material to reduce GHG and nitrogen loss by NH3 for food waste composting.Total global warming potential (GWP) and ammonia flux of different co-composting treatments during composting process.

A social study of the technicians dealing with refrigerant gases: Diagnosis of the behaviours, knowledge and importance attributed to the F-gases

Compliance with the international agreements and regulations aiming at mitigating emissions of gases with high global warming potential (GWP) requires the involvement of all stakeholders in the value chain of equipment containing refrigeration gases. In particular, the technicians dealing with the installation, maintenance, and dismantling of refrigeration equipment have a relevant role in the prevention of the release of refrigerant gases and their correct management. Besides technical information and training, the awareness of these technicians about the effects of fluorinated gases (F-gases) on global warming is critical for policy, regulations and strategies related to F-gases. This work presents the results of a questionnaire conducted with 586 Portuguese, Spanish, and French technicians to diagnose their behaviours, knowledge, and risk perception face to refrigeration gases and global warming. The results reveal that the repaired equipment mostly contains the pure HFCs R-32 and R-134a, the HFC blends R-410A, R-407C, and R-404A, and the fourth-generation HFCHFO blend R-449A. They also indicate the need to implement more efficient and credible information/awareness campaigns and to improve the training of these professionals in key respects, such as the relation between F-gases and climate change and the importance of their individual responsibility. Several suggestions were provided by the inquired technicians to improve the repair/maintenance process aiming at mitigating the effect of refrigeration gases on climate change, and to improve the awareness of this topic. These suggestions should be taken into consideration to improve legislation and policies.

Tame the super greenhouse gas-CHF3 via F/Cl exchange reaction over partially chlorinated Al-based fluoride catalysts

CHF3 is considered as one kind of super greenhouse gases with extremely high global warming potential which is the byproduct during the manufacture of HCFC-22 (CHClF2). Treatment CHF3 via F/Cl exchange reaction with CHCl3 forming CHCl2F and CHClF2 is a potential resource utilization route rather than high energy-demanding incineration. The results confirmed that the crystal structures of Al-based fluorides were important to the catalytic activity due to it affects the availabilities of the Lewis acid sites. Through the DFT calculation, it found that AlClxFy species acted as the active sites for the CHF3 conversion could decrease the energy barrier for the cleavage of C-F bonds. Furthermore, XPS analysis depicted that lower binding energy of Al-F was more likely to be partially chlorinated to formation AlClxFy species. Correspondingly, θ-AlF3 showed the best catalytic performance for the CHF3 conversion (30%) as well as less coke deposition contributed by the suitable Lewis acidic intensity.

Studies on new Eco-gas mixtures for Extreme Energy Events Project

The Extreme Energy Events (EEE) experiment, a joint project of the Centro Fermi and INFN Italian national research institutes, has a dual purpose: a scientific research program for measurements of the cosmic rays flux at ground level and an intense outreach and educational program with an active contribution of students and teachers in the construction and operation of the detectors in High Schools. The network counts 60 tracking detectors, each made by three Multigap Resistive Plate Chambers (MRPC), operated so far with a gas mixture composed by 98% C2H2F4 and 2% SF6. Given its high Global Warming Potential (GWP), the collaboration, since few years, started a R&D on alternative mixtures environmentally sustainable. Latest results on a C3H2F4 + He eco-friendly mixture are here presented.

Coordinating to promote refrigerant transition and energy efficiency improvement of room air conditioners in China: Mitigation potential and costs

Implementing the Kigali Amendment to the Montreal Protocol has imposed certain restrictions on the production and consumption of hydrofluorocarbons (HFCs). Taking this opportunity to promote the alternatives of high global warming potential (GWP) HFC refrigerants in the room air conditioner (RAC) sector as well as improve the energy efficiency can bring double benefits. With the RAC sector as an example, a demand-emissions-cost model is developed to assess the potential and costs of emission reductions in different regions of China under different scenarios. The model includes three scenarios: a business as usual (BAU) scenario, a Kigali energy efficiency (KAE) scenario with simultaneous energy efficiency improvements following the Kigali amendment, and an accelerated transition energy efficiency (ATE) scenario with accelerated HFCs reduction and energy efficiency improvements. The results show that under the KAE and ATE scenario, the GHG emissions of the RAC sector will peak in 2025 at 389.8–393.9 Mt CO2-eq and 378.8–382.8 Mt CO2-eq in China. The main contribution to this result is the alternative of low GWP refrigerants. From 2021 to 2060, the cumulative direct emission reductions are about 6.4–7.4 Gt CO2-eq and 8.5–9.5 Gt CO2-eq in KAE and ATE, and the cumulative indirect emission reductions for both scenarios are 1.6–1.8 Gt CO2-eq. The cumulative abatement costs are $286–321 billion and $288–322 billion (prices in 2020). Under the ATE scenario, direct emissions from refrigerants in the RAC sector are near zero in 2060, and indirect emissions depend on the power system structure. The RAC sector's average abatement cost varies significantly in diverse climatic environments. Given the variation in average abatement cost, it is critical to tailor mitigation policies to local conditions to ensure maximum benefits.

Elaboration of hydrophobic flax fibers through fluorine plasma treatment

In this study, the goal was to compatibilize flax natural fibers (which are inherently polar) with mostly dispersive polymers, while proposing a way to recover greenhouse gases or refrigerants such as CF4 or C2F5H. Such gases exhibit a high global warming potentials (GWPs) and their recovery at the end of their lifecycle is difficult. Therefore, these two representative problematic gases were used as plasma precursor to graft fluorine atoms onto the flax fiber surface. Chemical investigation (FT-IR, 19F NMR and XPS spectroscopies), demonstrates the covalent grafting of fluorine atoms at the fiber surface, that opens the route of tailoring the surface chemistry of flax fibers. These modifications induced a decrease of the fiber polarity, which allows the treated fibers to become perfectly compatible with mostly dispersive polymer. Moreover, both mechanical properties and fluorine release during fibers combustion were investigated and any negative impact was evidenced. Therefore, thanks to the plasma fluorination, the gap between the surface energies of the fibers and mostly dispersive polymer matrix was reduced improving the wettability of the fibers through an eco-friendly way. This phenomenon promising an improvement in the mechanical performance of eco-composites reinforced with these fluorinated fibers.

Strategies for reducing the use of greenhouse gases from particle detectors operation at the CERN LHC Experiments

A wide range of gas mixtures is used for the operation of the gaseous detectors at the CERN LHC experiments. Some gases, as C2H2F4, CF4, C4F10 and SF6, are greenhouse gases (GHG) with high global warming potential and therefore subject to a phase down policy.The reduction of GHG emissions is of paramount importance for CERN, which has identified four different strategies. The first strategy is based on the optimization of the gas mixture recirculation plants already in use. The second approach is the recuperation of used gas mixtures followed by separation of the GHG for its re-use. Several R&D are ongoing to evaluate this possibility and prepare the design of final systems. A third approach is making use of industrially available solutions for disposal of GHGs. Finally, the search of new eco-friendly gases is object of many R&D programs by the detector communities.The four strategies will be compared by considering investment required, return benefit and technological readiness.

Exploring the Potential of Metal-Organic Frameworks for the Separation of Blends of Fluorinated Gases with High Global Warming Potential.

The research on porous materials for the selective capture of fluorinated gases (F-gases) is key to reduce their emissions. Here, the adsorption of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a) is studied in four metal-organic frameworks (MOFs: Cu-benzene-1,3,5-tricarboxylate, zeolitic imidazolate framework-8, MOF-177, and MIL-53(Al)) and in one zeolite (ZSM-5) with the aim to develop technologies for the efficient capture and separation of high global warming potential blends containing these gases. Single-component sorption equilibria of the pure gases are measured at three temperatures (283.15, 303.15, and 323.15K) by gravimetry and correlated using the Tóth and Virial adsorption models, and selectivities toward R-410A and R-407F are determined by ideal adsorption solution theory. While at lower pressures, R-125 and R-134a are preferentially adsorbed in all materials, at higher pressures there is no selectivity, or it is shifted toward the adsorption R-32. Furthermore, at high pressures, MOF-177 shows the highest adsorption capacity for the three F-gases. The results presented here show that the utilization of MOFs, as tailored made materials, is promising for the development of new approaches for the selective capture of F-gases and for the separation of blends of these gases, which are used in commercial refrigeration.

Biogas improvement as renewable energy through conversion into methanol: A perspective of new catalysts based on nanomaterials and metal organic frameworks

In recent years, the high cost and availability of energy sources have boosted the implementation of strategies to obtain different types of renewable energy. Among them, methane contained in biogas from anaerobic digestion has gained special relevance, since it also permits the management of a big amount of organic waste and the capture and long-term storage of carbon. However, methane from biogas presents some problems as energy source: 1) it is a gas, so its storage is costly and complex, 2) it is not pure, being carbon dioxide the main by-product of anaerobic digestion (30%–50%), 3) it is explosive with oxygen under some conditions and 4) it has a high global warming potential (27–30 times that of carbon dioxide). Consequently, the conversion of biogas to methanol is as an attractive way to overcome these problems. This process implies the conversion of both methane and carbon dioxide into methanol in one oxidation and one reduction reaction, respectively. In this dual system, the use of effective and selective catalysts for both reactions is a critical issue. In this regard, nanomaterials embedded in metal organic frameworks have been recently tested for both reactions, with very satisfactory results when compared to traditional materials. In this review paper, the recent configurations of catalysts including nanoparticles as active catalysts and metal organic frameworks as support materials are reviewed and discussed. The main challenges for the future development of this technology are also highlighted, that is, its cost in environmental and economic terms for its development at commercial scale.

Separation of Azeotropic Refrigerant Mixtures Using Ionic Liquids

Refrigeration and air-conditioning systems are widespread throughout modern society, from the refrigerated cold chain that provides fresh foods and storage of medicines to the air conditioning of homes and buildings. Refrigeration is viewed as one of the most transformative engineering achievements of the 20th century and the demand for cooling will continue to increase as economic conditions improve and the climate continues to warm; however, refrigerants do come with an environmental cost.In 1987, the Montreal Protocol phased out chlorofluorocarbon (CFC) refrigerants because of their high ozone depletion potential (ODP). The replacements, typically mixtures of hydrofluorocarbons (HFCs), are safe for the Earth's ozone layer, but most have high global warming potentials (GWPs). HFCs account for 7.8% of total global greenhouse gas emissions, with 63% of that from “indirect” emissions (i.e., energy for running the system). As a result, 197 countries signed the Kigali agreement in 2016 to phase out high-GWP HFCs, with the goal of reducing emissions by 80% in the next 20 years. Millions of metric tons (mts) of high-GWP refrigerants will need to be reclaimed, but there are no good methods for separating and recycling the individual components, given that many are azeotropic mixtures.Currently, there is no means of separating azeotropic HFC mixtures, and the refrigerants will ultimately have to be incinerated. The commercial HFC mixture R-410A containing 50 wt.% HFC-32 (GWP = 675) and 50 wt.% HFC-125 (GWP = 3500) is a prime example. The HFC-32 can be reused when separated in new low-GWP products such as R-454B (69 wt% HFC-32 and 31 wt% HFO-1234yf) with a 75% lower GWP than R-410A.Ionic liquids are being developed that can separate azeotropic HFC mixtures based on differences in solubility and used as entrainers in extractive distillation. This presentation will provide experimental data on the solubility of HFCs in ionic liquids that have been measured using gravimetric microbalances and modeling using the Peng-Robinson equation of state. ASPEN Plus simulations will show how a pilot process has been designed that can continuously separate azeotropic refrigerant mixtures such as R-410A.

The Impact of Phase Changes of Imidazolium Based Ionic Liquids on the Solubility of Hydrofluorocarbons

Project EARTH (Environmentally Applied Research Toward Hydrofluorocarbons) is focused on developing sustainable processes for selectively separating refrigerant mixtures with high global warming potentials. The initial focus of the project is R-410A which is widely used in both commercial refrigeration systems and residential air conditioning. It is an azeotropic mixture containing 50 wt.% HFC-32 (CH2F2) and 50 wt.% HFC-125 (CHF2CF3). The separation approaches being investigated include membranes, porous media, and the use of ionic liquids as entrainers for extractive distillation.This poster will describe the work being conducted using ionic liquids and will specifically focus on the impact of phase changes of imidazolium based ionic liquids that are solid at room temperature on the solubility of HFC-32 and HFC-125. The poster will include an overview of how we use specialized equipment including a High-Pressure View Cell and Hiden Isochema IGA gravimetric microbalance to build a comprehensive understanding of these solubility differences.

Environment impact and bioenergy analysis on the microwave pyrolysis of WAS from food industry: Comparison of CO2 and N2 atmosphere.

The alarming output of waste activated sludge (WAS) from industries requires proper management routes to minimize its impact on the environment during disposal. Pyrolysis is a feasible way of processing and valorizing WAS into higher-value products of alternate use. Despite extensive research into the potential of WAS through pyrolysis, the technology's long-term viability and environmental impact have yet to be fully revealed. In addition, the environmental effects of utilizing different pyrolysis atmosphere (N2 or CO2) has not been studied before, although benefits of CO2 reactivity during pyrolysis have been discovered. This study evaluates the process's environmental impact, carbon footprint, and bioenergy yield when different pyrolysis atmospheres are used. The global warming potential (GWP) for a functional unit of 1t of dried WAS is 203.81kg CO2 eq. The heat required during pyrolysis contributes the most (63.7%) towards GWP due to high energy usage, followed by the drying process (23.6%). Transportation contributes the most towards toxicity impact (59.3%) through dust, NOx, NH3 and SO2 emissions. The initial moisture content of raw WAS (65%) greatly impacts overall energy consumption and environmental impact. Pyrolysis in an N2 atmosphere will result in a higher overall bioenergy yield (833kWh/tonne) and a lower carbon footprint (-1.09kg CO2/tonne). However, when CO2 was used, the specific energy value within the biochar is higher (22.26MJ/kg) due to enhanced carbonization. The carbon content of gas derived increased due to higher CO yield. From an energy perspective, the current setup will achieve a net positive bioenergy yield of 561kW (CO2) and 833kW (N2), where end products like biochar, bio-oil and gas can be used for power production. Despite the energy-intensive process, microwave pyrolysis has excellent potential to achieve a negative carbon footprint. The biochar used for soil amendment served as a good carbon sink. The utilization of CO2 as carrier gases provides a pathway to utilize anthropogenic CO2, which helps reduce global warming. This work demonstrates microwave pyrolysis as a negative emission, bioenergy-producing approach for WAS disposal and valorization.

Evaluation of Nitrogen Fertilizer Fates and Related Environmental Risks for Main Cereals in China's Croplands from 2004 to 2018.

Assessment of the nitrogen (N) inputs and outputs in croplands would help effectively manage the distribution of N to improve crop growth and environmental sustainability. To better understand the N flow of the main cereal systems in China, soil N balance, N use efficiency (NUE), N losses and the potential environmental impacts of maize, wheat and rice cropping systems were estimated at the regional and national scales from 2004 to 2018. Nationally, the soil N balance (N inputs—N outputs) of maize, wheat, single rice and double rice decreased by 28.8%,13.3%, 30.8% and 34.1% from 2004–2008 to 2014–2018, equivalent to an average of 33.3 to 23.7 kg N ha−1, 82.4 to 71.4 kg N ha−1, 93.6 to 64.8 kg N ha−1 and 51.8 to 34.1 kg N ha−1, respectively. The highest soil N balance were observed in Southeast (SE) region for maize and double rice, North central (NC) region for wheat single rice and Northwest region for wheat, whereas Northeast (NE) region had the lowest N balance for all crops. The NUE increased from 49.8%, 41.2%, 49.7% and 53.7% in 2004–2008 to 54.8%, 45.9%, 55.5% and 56.5% in 2014–2018 for maize, wheat, single rice and double rice, respectively. The fertilizer N losses (i.e., N2O emission, NO emission, N2 emission, NH3 volatilization, N leaching and N runoff) were estimated as 43.7%, 38.3%, 40.2% and 36.6% of the total N inputs for maize, wheat, single rice and double rice, respectively in 2014–2018. Additionally, the highest global warming potential and acidification effects were found in NE and NC regions for maize, NC region for wheat, the middle and lower reaches of Yangtze River for single rice and SE region for double rice, respectively. The highest risk of water contamination by N leaching and surface runoff was observed in NC region for all crops mainly due to high N fertilizer input. Furthermore, the dynamics of N balance for all crops were closely tied with grain yields, except for single rice, the N balance of which was mainly correlated with N fertilizer input. Our results could help researchers and policy makers effectively establish optimized fertilization strategies and adjust the regional allocation of grain cropping areas in response to environmental risks and climate change caused by food crop cultivation in China.

Convective Performance of C5-Flouroketone-Based (C5-FK) and C4-Flouronitrile-Based (C4-FN) Gas Mixtures and SF6

Abstract SF6 is a widely used insulating gas in the electric power industry due to its high dielectric strength. However, SF6 is classified as a greenhouse gas and has a very high global warming potential (GWP). Much research and development efforts have focused on finding alternatives to SF6 which have a lower GWP. An important requirement for an SF6 alternative is that it has similar heat transport properties to SF6, since one aspect of the design of high voltage equipment is the management of the heat dissipated from the flow of current. In the present paper, we compare the convective performances of SF6 and C5-flouroketone (C5-FK) and C4-flouronitrile (C4-FN) based gas mixtures. Mixtures of CO2, O2, and C5-FK/C4-FN have a GWP much smaller than that of SF6, a high dielectric strength, are not classified as toxic, and have good arc interruption properties. The numerical study is based on a semi-coupled computational electromagnetics (CEM) and computational fluid dynamics (CFD) analyses. The results of the numerical study are compared with experiments. There is a good agreement between the simulation results and the experiments. C5-FK and C4-FN based gas mixtures have good convective performance and are well-suited for application in circuit breakers. Thus, from the temperature-rise point of view, C5-FK and C4-FN based gas mixtures represent an alternative to the SF6 insulating gas traditionally used.