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Abstract Methane is responsible for 20% of the global warming resulting from greenhouse gas emissions. Municipal solid waste (MSW) landfills are the third largest anthropogenic source of methane and are thus important to estimating the global methane budget and evaluating its contribution to global greenhouse gas emissions. Based on the greenhouse gas inventory guidelines from the Intergovernmental Panel on Climate Change (IPCC) and the first-order decay method used to estimate emissions from MSW landfills – and in line with MSW management in various regions – we calculated methane emissions from MSW landfills in various Chinese provinces from 2003 to 2013. During this period, methane emissions from MSW landfills increased from 1141.10 Gg to 1858.98 Gg, representing a mean annual increase of 71.79 Gg. MSW emissions tended to increase more in the northern and western provinces than in the southern and eastern provinces, as methane emissions strongly and positively correlated with population and socioeconomic demographics. MSW decontamination is growing rapidly in China, and landfills predominate in all MSW treatments; moreover, incineration has also dramatically increased in recent years.

Abstract Solar energy has an enormous potential to solve society energy needs in a sustainable way. Notably, photovoltaic systems (PV) permit to obtain electricity based on solar energy. However, some issues must be addressed to establish PV as a reliable source of electrical power, for example, its low energy density. One of the approaches to improve the performance of PV systems is to utilize the solar spectrum in solar cells efficiently. Downconversion (DC) is a process where a high energy photon is converted into two or more photons with lower energy. Trough downconversion is possible to use a wider portion of the solar spectrum raising the efficiency in different kinds of solar cells. The present paper reviews the state of the art of materials and methods used to take advantage of downconversion processes in solar cells. Here we discuss some of the pros and cons of different designs in solar cells as well as the main characteristics of the materials utilized.

Land application of food processing wastes has become an acceptable practice because of the nutrient value of the wastes and potential cost savings in their disposal. Spoiled beets and pulp are among the main by‐products generated by the sugar beet (Beta vulgaris L.) processing industry. Farmers commonly land apply these by‐products at rates >224 Mg ha−1 on a fresh weight basis. However, information on nutrient release in soils treated with these by‐products and their subsequent impacts on crop yield is lacking. Field studies were conducted to determine the effects of sugar beet by‐product application on N release and crop yields over two growing seasons. Treatments in the first year were two rates (224 and 448 Mg ha−1 fresh weight) of pulp and spoiled beets and a nonfertilized control. In the second year after by‐product application, the control treatment was fertilized with N fertilizer and an additional treatment was added as a nonfertilized control in buffer areas. Wheat (Triticum aestivum L.) was grown in the year of by‐product application and sugar beet in the subsequent year. By‐product treatments caused a significant reduction in wheat grain yield compared with the control. This was due to a decline in N availability as a result of immobilization. Based on microplots receiving 15N labeled beets, wheat took up <1% of spoiled beet‐N (approximately 4.7 kg ha−1) during the year of by‐product application. In the second cropping year, sugar beet root yields were significantly higher in the fertilized control and by‐product treatments than the nonfertilized control. The lack of significant difference in sugar beet yield between the fertilized control and by‐product treatments was likely due to the greater availability of N in the second year. Labeled 15N data also showed that the sugar beet crop recovered a 17% of sugar beet‐N, an equivalent of 86 kg N ha−1, during the second cropping year. There was no difference in sugar beet root yield, N uptake, or soil N mineralization during the sugar beet cropping season between the pulp and the spoiled beet treatments at comparable rates of application.

The on-going annual increase in global methane (CH4) emissions can be largely attributed to anthropogenic activities. However, as more than half of these emissions are diffuse and possess a concentration less than 3% (v/v), physical-chemical treatments are inefficient as an abatement technology. In this regard, biotechnologies, such as biofiltration using methane-oxidizing bacteria, or methanotrophs, are a cost-effective and efficient means of combating diffuse CH4 emissions. In this review, a number of abiotic factors including temperature, pH, water content, packing material, empty-bed residence time, inlet gas flow rate, CH4 concentration, as well biotic factors, such as biomass development, are reviewed based on empirical findings on CH4 biofiltration studies that have been performed in the last decades.

The integration of distributed renewable energy (DRE) into grid is experiencing significant growth. Due to its intermittent characteristics, DRE have several impacts on system operation. This integration does not only influence the distribution network, but also it affects the transmission network. This paper analyzes the impact of increased penetration of distributed renewable energy specifically the PV generation on static voltage stability of transmission network and helps to find the maximum allowable capacity of DRE penetration. DRE integration with different weather conditions is studied in this paper. Voltage Collapse Proximity Index (VCPI) is used to evaluate the voltage stability of the system. Simulations are carried out on IEEE-39 bus test system using Power system analysis toolbox (PSAT). It can be concluded that the integration of high level of DRE into the grid affects the voltage stability, and it may lead to voltage collapse. The analysis results can be used to provide guidance for the allowable percentage of DRE integration.

Abstract Chemical looping reforming is a promising option for the conversion of gaseous fuels to high quality syngas suitable for gas-to-liquids (GtL) processes. This work evaluates the potential for syngas, heat, power, and steam generation for diluent production at steam assisted gravity drainage (SAGD) facilities using low cost ilmenite ore pressurized chemical looping reforming (PCLR). Preliminary fixed-bed reactor testing on a naturally occurring Canadian ilmenite ore was performed to determine the optimal operating regime for syngas generation. Based on SEM characterization, EDX elemental mapping, XRD, and Mossbauer spectroscopy measurements it was demonstrated that partial reduction to Fe2.5+ and Fe2+ containing species is required to avoid the production of CO2. Additionally, the reduction to Fe° containing species should be minimized to limit the formation of carbon and metal carbides. These results were used to generate material and energy balances via Aspen HYSYS V9 process simulation software of the entire PCLR process for SAGD applications using a Canada’s Oil Sands Innovation Alliance (COSIA) SAGD facility template. Thorough energy integration of the combined PCLR-SAGD process using Pinch Analysis suggests that steam and diluent requirements can be met, with excess power generation, at lower costs than more traditional syngas generation technologies, while meeting CO2 emissions targets and reducing boiler feed water (BFW) make-up. Having shown that process performance is attractive, a techno-economic assessment to establish the most economical design for the PCLR-SAGD process is now required.

Abstract Natural gas (NG)-diesel dual fuel engines have been criticized for their high emissions of unburned methane. The past research on methane emissions from dual fuel engines has focused on the measurement of methane concentration in exhaust gases. The development of approaches capable of minimizing methane emissions requests the detailed spatial distribution of methane in-cylinder during the combustion and post combustion processes. However, it is difficult to experimentally measure the spatial distribution of methane in-cylinder. This research presents a numerical study on the combustion process of a NG-diesel dual fuel engine using the computational fluids dynamics (CFD) model CONVERGE coupled with a reduced primary reference fuel (PRF) mechanism. The model was validated against the heat release process and the emissions of nitrogen oxide, methane and carbon monoxide measured in a single cylinder dual fuel engine. The validated CFD model was applied to investigate the combustion of methane and n-heptane and the spatial distribution of methane in the dual fuel engine. This is most likely the first attempt to visualize the spatial distribution of methane in dual fuel engines using CFD. The objective of this study is to numerically simulate the methane combustion process, especially the methane present outside the pilot spray, quantify the methane combustion in each combustion stage, and visualize the spatial methane distribution in cylinder. The results showed that the momentum produced by the pilot fuel injection and combustion pushed the combustion products of pilot fuel and methane within the pilot spray plume toward the unburned methane-air mixture. Such a movement enhanced the mixing of the hot combustion products and the relatively cold unburned methane-air mixture during the main combustion process and dominated the combustion of methane presented outside the pilot fuel spray plume. Based on the simulation results at a low load condition (4.05 bar), the main combustion process consumed 43–53% of the methane fumigated into the intake mixture. The post-combustion oxidation process consumed 17–29% of the intake methane, which was 36.2–51.8% methane that survived the main combustion process. In comparison, 27–35% methane emitted the engine without participating the combustion process. The unburned methane at exhaust valve opening was mainly observed at the center of the cylinder. In comparison, the contribution of the crevice and boundary layer around the cylinder liner to methane emissions was relatively small. The slip of methane through the dual fuel engines was due to the fact that the premixed mixture was too lean to support the propagation of the turbulent flame initiated by the pilot fuel and the lack of pilot fuel vapor reaching the center of the combustion chamber because of the geometric limitations of the fuel injection system and the reduced mass of pilot fuel injected into the cylinder. The approaches aiming to enhance the combustion of methane and minimize methane emissions from dual fuel engines should focus on those capable of increasing the volume of pilot fuel vapor formed after injected into the cylinder.

Abstract Nature removes carbon dioxide from the atmosphere through photosynthesis, and by forming carbonate minerals. Following Nature's example, carbon dioxide should not be regarded as a waste, but as a resource from which useful products can be made. Highly concentrated, calcium-rich brines are commonly found associated with subsurface salt deposits. By bringing together the energy and chemical industries, it may be possible to use these brines to lock up carbon dioxide, while at the same time producing calcium carbonate, hydrochloric acid and a variety of other chemical-industrial commodities.

Power system planning, operation, and operational planning methods have evolved over the years to economically supply reliable power to customers. Emerging environmental compliance requirements have dictated needs to develop methods to manage increased uncertainties associated with renewable resources. These new challenges are increasing problems in operational planning, as existing deterministic procedures cannot comprehend these uncertainties to provide suitable indicators in decision making. Uniformity in operational adequacy evaluation methods and quantitative metrics applicable to all power systems is desirable. However, various utilities and independent system operators (ISOs) have their own practices and methodologies to address their unique needs. This paper presents a review of operational planning practices in different ISOs and utilities based on planning-horizon length, granularity, and reliability metrics. The challenges and deficiencies in existing operational planning practices and regulations are identified. Finally, features necessary to maintain the uniformity in operational planning while fulfilling operational adequacy requirements are recommended.