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This paper examines the long-term effects and related short-term movements of energy security (ENS), economic policy uncertainty (EPU), and government ecological expenditure (GEE) on China's carbon dioxide (CO 2) emissions by applying the quantile autoregressive distributed lag approach. The empirical findings demonstrate that ENS and EPU have prominent negative and positive impacts, respectively, on CO 2 emissions in the long term for the majority of quantiles, while their short-term influences are less obvious. In addition, the effect of GEE is short-term and concentrated in high quantiles. The following are the article's main contributions. This study builds special energy security indicators based on the actual situation in China, providing a basis for better understanding the interaction mechanism between ENS and CO 2. Considering that China is the largest oil importer and greenhouse gas emitter, this study explores for the first time the linkages between ENS and CO 2. Both short- and long-term impacts are observed, and long-run effects are dominant in the linkages among variables, suggesting that the level of CO 2 emissions is mainly driven by long-term shocks. In addition, to clarify the nexus between ENS and CO 2 , time- and quantile-varying analyses are used, which take into account not only varied CO 2 emission levels but also distinct time periods for events. The findings emphasize the importance of market participants to form a better understanding of how ENS, EPU, and GEE affect CO 2 under different emission levels. Some detailed policies, including optimizing the energy consumption structure, making prudent economic policy adjustments, and strengthening ecological protection expenditures, are provided to curb pollution. • Energy security and carbon neutralization are main targets for China. • Energy security negatively affects carbon dioxide in the long-term. • Time-varying and quantile-varying features are captured for Energy security. • The quantile autoregressive distributed lag model is utilized in this paper. [ABSTRACT FROM AUTHOR]

One promising solution for developing low-emission power technologies is using gaseous fuel combustion in pure oxygen when the exhaust gas mixture is composed of H 2 O and CO 2 , and where CO 2 is separated after steam condensation. The paper presents the results of computational analyses providing to the Spray-Ejector Condenser (SEC) development, which is one of the crucial components of the negative CO 2 gas power plant (nCO 2 PP) cycle development. The proposed design of the ejector-condenser to ensure the high effectivity of vapor condensation and CO 2 compression with preparation to separation, ready for application in gas power cycle, is a novelty of this research. Different computational techniques leading to the development and better understating of ejector operation were applied. The main operating conditions in the characteristic connected with the developed nCO2pp cycle points were investigated to evaluate the impact of the operating conditions on SEC performances. The amount of motive water needed for the cooling purpose is susceptible to the inlet water pressure and temperature and strongly affects the generated pressure of the suction stream. The preliminary results confirm that the SEC's basic design and geometrical dimensions can be applied in the negative CO 2 power plant cycle. Results from CFD modeling give the possibility to investigate the turbulent flow of water/steam/CO 2 mixture together with the condensation process occurring at this same time. It is found that the average droplet diameter and motive water supplying method significantly effects the condensation intensity. The further direction of the presented computational research activities and results is to test various designs of Spray-Ejector Condensers that will enable the evaluation of the direct contact condensation process and develop the final geometrical design. • Spray-Ejector Condenser application in negative CO 2 gas power plant is presented • Performances of Ejector Condenser were calculated using developed model to provide guidelines for a detailed design process • The basic design of the Spray-Ejector Condenser in two variants was developed • CFD model for Direct Contact Condensation was developed, and the impact of water droplet size was studied [ABSTRACT FROM AUTHOR]

Abstract: This paper employs a simulation model of the European power sector to analyze the abatement response to a CO2 price through fuel switching, one of principal means of reducing greenhouse gas emissions in any economy. Abatement is shown to depend not only on the price of allowances, but also and more importantly on the load level of the system and the ratio between natural gas and coal prices. The interplay of these different determinants vitiates any simple relation between a CO2 price and abatement and requires the development of more than two-dimensional graphics to illustrate these complex relationships. In the terms of the literature on the use of marginal abatement cost curves (MACCs), we find that these MACCs are not robust as usually defined and we suggest that the more complex topography developed in this paper may be more helpful in visualizing this abatement response to a CO2 price. [Copyright &y& Elsevier]

Crop residue-based bioenergy (CRB) is a green replacement for fossil fuels and an effective way of utilizing crop residues. Understanding CRB's GHG reduction effects is critical for predicting its contributions to carbon neutrality. However, many studies have focused on single products or regional assessments, and results remain uncertain and lacking in systematic examination of the diversity in products, feedstock types and their supply. Therefore, this paper systematically investigates the GHG reduction efficiency, driving factors and abatement costs of principal CRB products using a database of 225 cases composed of 71 carbon trading projects and 154 projects analyzed in scientific publications. The results show that bio-power and/or heat (bio-P&H) is highly efficient (689 kg CO 2 e/t dry CR) and economical (269 $/t CO 2 e) in reducing GHG emissions, but liquid biofuels is not encouraged because of its inefficient performance. Plant size and feedstock collection radius significantly affected GHG reductions of bio-P&H and liquid biofuel. Recommended plant sizes and feedstock types for CRB production were identified from environmental and economic perspectives. Overall, these results clarify the patterns and driving factors of GHG reduction efficiency and abatement costs of various CRB products, providing a framework for optimizing CRB development to combat climate change. [Display omitted] • AsSessing GHG reduction patterns of various crop residue-based bioenergy products. • Comprehensive assessment of the environmental and economic performance. • Identifying the impacts of key factors influencing GHG reduction efficiency. • A meta-analysis based on both scientific publications and project datasets. • Bio-power & Heat shows good GHG reduction efficiency with lower abatement cost. [ABSTRACT FROM AUTHOR]

This paper examines convergence clubs for per capita CO 2 emissions among 28 European countries in two main activity sectors (Industry and Manufacturing) between 1970 and 2018, with a focus on the energy sector. The method used is the Phillips-Sul log t -test using two ordering criteria to run the algorithm for the panel countries. The first one is using the last observation and the second one uses the sample average. The results of analyses of data strongly support the existence of convergence clubs, indicating that five groups of European countries are converging to distinct steady states for the aggregate CO 2 emissions. We also find evidence of convergence clubs for industry sectors while manufacturing sector shows clubs convergence only when we use the first criterion while in the second case, we find only a single steady state. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The rapid growth in coal and oil consumption has led to increasing emissions of greenhouse gases as well as air pollutants in China. In response to this, the Chinese government has begun to formulate policies to retard the increasing use of energy consumption and to improve air quality. This paper attempts to quantify the co-benefits of reducing carbon dioxide emissions and improving air quality from policies that are originally formulated to improve energy efficiency and to abate emissions of air pollutants from energy use. The present authors have developed an integrated approach, combining an energy projection model, an emission estimation model, an air quality simulation model, and a health benefit evaluation model, to assess the co-benefits of two different sets of energy policies of China. The modeling results show that significant benefits, including 1469 million tonnes of reduced emissions of CO2, 12–32% decline in air pollutant concentrations, and more than 100 billion US$ of health benefit, can be achieved around the year 2030 if aggressive energy policies are implemented. The analyses suggest that such energy policies could do a lot of benefit to the environment. Moreover, better industry structure and energy structure is essential for higher air quality. [Copyright &y& Elsevier]

Abstract: Growing concerns over greenhouse gas emissions have driven extensive research into new power generation cycles that enable carbon dioxide capture and sequestration. In this regard, oxy-fuel combustion is a promising new technology in which fuels are burned in an environment of oxygen and recycled combustion gases. In this paper, an oxy-fuel combustion power cycle that utilizes a pressurized coal combustor is analyzed. We show that this approach recovers more thermal energy from the flue gases because the elevated flue gas pressure raises the dew point and the available latent enthalpy in the flue gases. The high-pressure water-condensing flue gas thermal energy recovery system reduces steam bleeding which is typically used in conventional steam cycles and enables the cycle to achieve higher efficiency. The pressurized combustion process provides the purification and compression unit with a concentrated carbon dioxide stream. For the purpose of our analysis, a flue gas purification and compression process including de-SO x , de-NO x , and low temperature flash unit is examined. We compare a case in which the combustor operates at 1.1bars with a base case in which the combustor operates at 10bars. Results show nearly 3% point increase in the net efficiency for the latter case. [Copyright &y& Elsevier]

Carbon dioxide in the atmosphere is a major greenhouse gas. Increasing atmospheric concentrations are believed to be responsible for a gradual warming of the Earth. Strategies to reduce anthropogenic CO2 emissions to the atmosphere by sequestration underground or in the deep ocean are being investigated. An international collaboration to conduct a field experiment on CO2 ocean sequestration was initiated in December 1997. The primary objective of this project is to obtain data that can be applied to assess environmental impacts of direct injection of CO2 into the deep ocean. The collaboration is being implemented by a research team comprising engineers and scientists from five nations: Japan, the US, Norway, Canada, and Australia. This paper focuses on studies being conducted as part of the field experiment to investigate the influence of decreased seawater pH from CO2 dissolution on bacterial production in the ocean. A preliminary analysis of the variation in bacterial production under different values of pH and temperature, conducted in July 1999, indicated that there was no measurable effect on the microbial population in the first 24 h of the experiment. However, there was a rapid decline in bacterial production with decreases in pH over a 96 h incubation period. In addition, the impact of reduced pH was more pronounced when the bacteria were grown at warmer temperatures, i.e. with a more rapid potential production rate. Subsequent laboratory experiments were conducted in June 2000 using pressure chambers to determine the effect of depressurization on bacterial production. For this effort, seawater samples were collected from a 600 m deep pipeline off the Kona coast of the island of Hawaii. Water was placed in a pressure chamber and allowed to stabilize for 48 h at the ambient pressure and temperature of 600 m depth at the sampling location. After 48 h, the water was depressurized and acidified with CO2 to pH values of 6.95 and 5.6. The acidified water and an un-amended sample were incubated at 5, 10 and 15 °C for 96 h and sampled every 24 h. Similar impacts to those observed previously on the bacterial production were noted. The overall result was that longer incubation times and warmer temperatures reduced bacterial production in samples exposed to the lower pH. This observation is beneficial to develop an understanding of the long term effects of CO2 releases on basic elemental cycles that support aquatic food chains. Future work needs to investigate long term variation in the bacterial community, the impact on nutrient recycling, and the population growth efficiency. [Copyright &y& Elsevier]

If deep reductions in anthropogenic greenhouse gas emissions are to be achieved, the introduction of CO2 capture and storage in geological reservoirs is likely to be necessary. The technology would be deployed alongside other mitigation measures such as renewables, energy efficiency and fuel switching. Currently, research programmes on the geological storage of CO2 are underway in the United States, the European Union, Australia and Japan.The aim of this paper is to present an overview of the research work that is currently underway and provide an analysis of the current state of knowledge on geological storage of CO2. The analysis will be broken down to address the key geological storage options: deep coal seams, depleted hydrocarbon reservoirs and deep saline aquifers. In each case, areas of uncertainty will be highlighted as well as areas where it is considered that further work will be needed so that the technology can be accepted by Governments and the general public as a mitigation option suitable for wide-scale application throughout the world. [Copyright &y& Elsevier]