We study changes in the aggregate carbon intensity (ACI) for electricity at the global and country levels. The ACI is defined as the energy-related CO2 emissions in electricity production divided by ...the electricity produced. It is a performance indicator since a decrease in its value is a desirable outcome from the environmental and climate change viewpoints. From 1990 to 2013, the ACI computed at the global level decreased only marginally. However, fairly substantial decreases were observed in many countries. This apparent anomaly arises from a geographical shift in global electricity production with countries having a high ACI increasingly taking up a larger electricity production share. It is found that globally and in most major electricity producing countries, reduction in their ACI was due mainly to improvements in the thermal efficiency of electricity generation rather than to fuel switching. Estimates of the above-mentioned effects are made using LMDI decomposition analysis. Our study reveals several challenges in reducing global CO2 emissions from the electricity production sector although technically the reduction potential for the sector is known to be great.
•Variations of aggregate carbon intensity (ACI) for electricity of world countries are analysed.•Main drivers of changes in ACI of major electricity producing countries are studied using index decomposition analysis.•Geographical shift in electricity production had a significant impact on global ACI.•Improvements in the thermal efficiency of generation were the main driver of reduction in ACI.
Current methods of chemical vapour deposition (CVD) of graphene on copper are complicated by multiple processing steps and by high temperatures required in both preparing the copper and inducing ...subsequent film growth. Here we demonstrate a plasma-enhanced CVD chemistry that enables the entire process to take place in a single step, at reduced temperatures (<420 °C), and in a matter of minutes. Growth on copper foils is found to nucleate from arrays of well-aligned domains, and the ensuing films possess sub-nanometre smoothness, excellent crystalline quality, low strain, few defects and room-temperature electrical mobility up to (6.0±1.0) × 10(4) cm(2) V(-1) s(-1), better than that of large, single-crystalline graphene derived from thermal CVD growth. These results indicate that elevated temperatures and crystalline substrates are not necessary for synthesizing high-quality graphene.
Aggregate intensity indicators, such as the ratio of a country's energy and emissions to its GDP, are often used by researchers and policymakers to study energy and environmental performance. This ...paper analyzes the relationship between energy (or emissions) and value added (or GDP) from a different viewpoint, namely from the demand rather than the production perspective, using the input–output (I–O) framework. The aggregate embodied intensity (AEI), defined as the ratio of embodied energy (or emissions) to embodied value added, can be defined at the aggregate, final demand category and sectoral levels. The total aggregate intensity can be presented as a weighted sum of the AEIs at the final demand category or sectoral level. Changes of the AEI at different levels can be decomposed to identify the driving forces using multiplicative SDA. A study using the latest 2007 and 2012 datasets of China indicates that (a) its aggregate intensity of CO2 emissions was mainly determined by the AEI in investment and (b) the emission intensity effect generally contributed the most to the AEI ratio changes at different levels. The proposed framework can be applied to other aggregate intensity indicators and extended to multi-country/region analysis.
•We analyze the relationship between energy (or emissions) and value added (or GDP) from demand perspective.•The aggregate embodied intensity (AEI) is defined as the ratio of embodied energy (or emissions) to embodied value added.•The total aggregate intensity is a weighted sum of the AEIs at different levels.•Change of the AEI at different levels can be decomposed to identify the driving forces using multiplicative SDA.
The only comprehensive study comparing structural decomposition analysis (SDA) and index decomposition analysis (IDA) was conducted around 2000. There have since been new developments in both ...techniques in energy and emission studies. These developments have been studied systematically for IDA but similar studies for SDA are lacking. In this paper, we fill the gap by examining the new methodological developments in SDA. A new development is a shift towards using decomposition methods that are ideal. We compare four such SDA methods analytically and empirically through decomposing changes in China's CO
2 emissions. We then provide guidelines on method selection. Finally, we discuss the similarities and differences between SDA and IDA based on the latest available information.
► We review the new methodological developments in SDA in energy and emission studies. ► A shift towards using decomposition methods that are ideal is revealed. ► Four ideal methods are compared analytically and empirically using China's data. ► We provide guidelines on decomposition method selection for SDA. ► We discuss the similarities and differences between SDA and IDA based on the latest available information.
Index decomposition analysis (IDA) and structural decomposition analysis (SDA) are analytical techniques that have been extensively used by researchers to study drivers of changes in energy ...consumption and energy-related emissions for energy and climate policy assessment and development. We compare the two techniques from the methodological and application viewpoints and with specific reference to economy-wide analysis where the overlap between the two is the greatest. Our study brings up to date several previous studies and provides a detailed assessment of the post-2010 developments. In addition, a framework for additive and multiplicative decomposition methods is presented, specific application in policy analysis is discussed with representative examples given, and the selection between the two techniques is described. Despite the differences between the two techniques in terms of origin, there has been some convergence in their application in some specific areas. However, even if the same dataset is used, application of the two techniques will lead to different numerical results due to underlying differences in some core concepts and the meanings of the drivers of change defined. A good understanding of these similarities and differences will help researchers in making sound judgment in their adoption and implementation in policy studies.
•Comparisons of IDA and SDA in decomposition analysis.•Focusing on economy-wide energy consumption and emissions.•Detailed assessment of post-2010 developments of the two decomposition techniques.•Application in policy analysis with representative examples.•Guidelines for selection between the two decomposition techniques.
When students answer an in-class conceptual question individually using clickers, discuss it with their neighbors, and then revote on the same question, the percentage of correct answers typically ...increases. This outcome could result from gains in understanding during discussion, or simply from peer influence of knowledgeable students on their neighbors. To distinguish between these alternatives in an undergraduate genetics course, we followed the above exercise with a second, similar (isomorphic) question on the same concept that students answered individually. Our results indicate that peer discussion enhances understanding, even when none of the students in a discussion group originally knows the correct answer.
Singapore is an island city-state. It lacks conventional energy resources and is alternative energy disadvantaged. In the past decade (2000–2010), its energy-related carbon emissions increased from ...37.8 to 44.4 million tonnes of CO2. This paper analyses the city state's carbon emissions from the demand perspective using the input-output (I-O) method and investigate the drivers of emission changes using structural decomposition analysis (SDA). It is the first comprehensive analysis of Singapore's emissions using the I-O framework. The results obtained show that exports accounted for nearly two-thirds of its total emissions and growth in its emissions in the last decade was largely export-driven. Emissions increased as export-oriented industries and export volume expanded. Fuel switching and energy efficiency, however, helped to lower growth in emissions. Besides exports, household-related emissions accounted for about a quarter of Singapore's total emissions. The emissions related to different household groups remained fairly stable as increases in embodied (indirect) emissions were offset by decreases in direct emissions. The high-income household group registered the largest increase in direct emissions, while the middle-income household group registered the largest increase in embodied emissions. The policy implications of our findings are discussed.
•It is the first comprehensive analysis of Singapore's CO2 emissions using I-O framework.•Singapore's exports accounted for nearly two-thirds of its total emissions.•Singapore's household-related emissions accounted for a quarter of its total emissions.•Growth in Singapore's emissions in 2000–2010 was largely export-driven.
Aggregate energy and emission intensities have respectively been widely used to measure the overall performance of energy consumption and environmental pollution from the production perspective. ...Recently, Su and Ang (2017) propose the aggregate embodied intensity (AEI) indicator, defined as the ratio of embodied energy (or emissions) to embodied value added, to analyze the relationship between energy (or emissions) and value added or GDP from the demand perspective using the input-output (I-O) framework. Besides I-O analysis, structural path analysis (SPA) can be used to split the I-O analysis results into different layers to extract the important paths in terms of energy consumption and the resulting emissions. This paper incorporates the SPA technique with the AEI indicators and structural decomposition analysis (SDA) technique in the context of energy and emission studies. An empirical study using China's 2007 and 2012 datasets is presented to illustrate the AEI at the detailed transmission layers, show their relationships with the AEI indicators at different levels, and further investigate the driving forces to the changes of these AEI indicators. The proposed multi-level AEI framework can also be applied to other indicators and extended to multi-country/region analysis.
•We analyze the relationship between energy (or emissions) and value added (or GDP) from demand perspective.•The AEI at different levels can be decomposed and analyzed by transmission layers using the SPA technique.•The AEI of specific final demand is a weighted sum of AEIs of each transmission layer.•Change of the AEI at different levels can be decomposed to identify the driving forces using multiplicative SDA.
Energy-related CO2 emissions embodied in international trade have been widely studied by researchers using the environmental input–output framework. In the literature two different approaches to deal ...with emissions embodied in a country's imports can be found. One of the approaches is based on the assumption of competitive imports while the other is based on the assumption of non-competitive imports. We show that the implications of the results obtained using different imports assumptions are not the same. The approach using the competitive imports assumption gives estimates larger than those obtained using the non-competitive import assumption. The differences between the two embodiment estimates come from the transition of embodied emissions in China's imports for intermediate consumption to those in China's exports. This explains why relatively high estimates of CO2 emissions embodied in China's exports are reported in several recent studies appearing in Energy Policy.
► We study the issue of imports assumptions in embodied emission studies. ► The implications of the results obtained using two different imports assumptions are not the same. ► The differences between two estimates come from the transition of embodied emissions in imports. ► Special attention should be paid to deal with the competitive imports in embodied emission studies.
•We combine the HEET approach and SWD-EET analysis for regional emission modeling.•A comprehensive study of China’s regional emission embodiments is presented.•How interregional and international ...trade affect China’s regional CO2 are explained.•Developed regions are generally net importers of embodied emissions from trade.•Developing regions are generally net exporters of embodied emissions from trade.
Energy-related CO2 emissions embodied in international trade have been widely studied at the national level in recent years. The embodiment estimates help to explain the “weak carbon leakage” between industrial and developing countries and to reveal the so-called “consumption-based” emissions (or carbon footprint). These findings have implications on national climate policy and international negotiations. For a large country like China, spatial aggregation issues are important in embodied emission studies. Dividing the country into several regions, previous studies propose the hybrid emissions embodied in trade (HEET) approach for regional emission studies and use step-wise distribution of emissions embodied in trade (SWD-EET) analysis to explain indirect absorption patterns. In this paper, we combine the HEET approach and SWD-EET analysis to conduct a comprehensive study of China’s regional emission embodiments. We explain how inter-regional trade and international trade affect China’s regional domestic emissions, and present the resulting regional carbon footprint. Policy implications from the empirical results obtained are discussed.
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