Virtual Water Embodied in Interregional Energy Trade in China: A City-Level Analysis.

Large volumes of water are used in energy production for both primary (e.g., fuel extraction) and secondary energy (e.g., electricity). In countries such as China, with a large internal trade in fuels and long-distance transmission grids, this can result in considerable water inequalities. Previous research focused on the water impacts of energy production at the national and provincial levels, which is too coarse to identify the spatial differences and make specific case studies. Here, we take the next step toward a spatially explicit economically integrated water-use for energy assessment by combining a bottom-up assessment approach with a city-level multiregional input-output model. Specifically, we examine the water consumption of energy production in China, distinguishing between water for primary and secondary energy at the level of coal mines, oil and gas fields, and power plants for the first time. Of the total energy-related freshwater consumption of 4.9 Gm3 in 2017, primary energy accounted for 19% (940 Mm3) and secondary energy accounted for 81% (3955 Mm3). Coal was the largest water consumer for both primary and secondary energy (540 and 3880 Mm3, respectively), with both oil (361, and 0.5 Mm3, respectively) and gas (7 and 69 Mm3, respectively) also consuming large amounts. Intercity virtual water, that is, water embodied in energy trade across cities, reached 54% (2.6 Gm3) of energy-related freshwater consumption. Across China, 32% of cities see a bilateral trade in secondary- and primary-energy-related virtual water (e.g., Daqing city exports virtual water embodied in primary fuel to other cities that is then used to produce electricity in those cities, part of which is used back in Daqing via transmission). For these 32% of cities, 73% export more virtual water than import and 27% import more virtual water than export. This study reveals significant differences in city-level virtual water patterns (e.g., scale and direction) between primary and secondary energy to provide information for cities about their virtual water inflow and outflow and the potential collaboration partners for water management.

Transition towards dual control of CO2 emissions and intensity through supply chain management in China.

To mitigate global climate change and achieve CO2 emissions reduction goals, China proposed to shift to dual control of total CO2 emissions (CE) and CO2 emissions intensity (CEI) as early as possible. Accurately assessing provincial sectoral CE and CEI and developing reasonable regulatory strategies is a prerequisite for achieving the goal of dual control. However, there is a lack of comprehensive analysis from different perspectives of the supply chain. Therefore, this paper evaluates the CE and CEI in provincial sectors of China in 2017 from production-based and consumption-based perspectives according to multi-regional input-output (MRIO) model. Then, we analyze the supply chain of transmission sector by betweenness-based method as a supplementary perspective. The results show that: (1) The CE and CEI from different perspectives are different and can complement each other. (2) Production and distribution of electric power and heat power in Inner Mongolia (P5D24), construction in Jiangsu (P10D27), distribution of electric power and heat power in Beijing (P1D24) are the critical sectors for dual control of CE and CEI from production, consumption, betweenness-based perspectives, respectively. (3) Construction in Jiangsu (P10D27) and Shanxi (P4D27) have the highest embodied CE and CEI in China respectively. Energy and raw material sectors from upstream supply chain contribute large CE to construction sectors. This research suggests that paying attention to critical sectors from different perspectives of the supply chain and taking different measures to decrease CO2 emissions. Taking both CE and CEI into consideration and allocating CO2 emissions reduction pressures reasonably among provincial sectors. At the same time, taking care of relevant upstream sectors of the supply chain to help a single sector achieve CO2 emissions reduction goals and promote China's transition to dual control of CE and CEI.

Double-edged sword of technological progress to climate change depends on positioning in global value chains.

Technological progress (TP) is a double-edged sword to global climate change. This study for the first time reveals rebound and mitigation effects of efficiency-related TP in global value chains (GVCs) on greenhouse gas (GHG) emissions. The integrated effects of TP depend on the positioning of sectors in GVCs. The cost-saving TP in upstream sectors would stimulate downstream demand. This produces stronger rebound effects than mitigation potentials and leads to global GHG emission increments (e.g. TP in the gas sector of China and petroleum and coal products sector of South Korea). In contrast, sectors located in the trailing end of GVCs have greater potentials for GHG emission mitigation through TP, mainly due to the reduction of upstream inputs. (e.g. the construction sector of China and dwelling sector of the United States). Global GHG emissions and production outputs can be either a trade-off or a win-win relationship on account of TP than rebound effects, because TP in different sectors could possibly increase or decrease the emission intensity of GVCs. This study could recognize the most productive spots for GHG emission mitigation through efficiency-related TP. It provides a new perspective for international cooperation to promote global GHG emission mitigation.

Tracing global N2O emission mitigation strategies through trade networks.

Nitrous oxide (N2O) is the third most potent greenhouse gas (GHG) and the most important ozone depleting substance. But how global N2O emissions are connected through the interwoven trade network remains unclear. This paper attempts to specifically trace anthropogenic N2O emissions via global trade networks using a multi-regional input-output model and a complex network model. Nearly one quarter of global N2O emissions can be linked to products traded internationally in 2014. The top 20 economies contribute to about 70% of the total embodied N2O emission flows. In terms of the trade embodied emissions classified by sources, cropland-, livestock-, chemistry-, and other industries-related embodied N2O emissions account for 41.9%, 31.2%, 19.9%, and 7.0%, respectively. Clustering structure of the global N2O flow network is revealed by the regional integration of 5 trading communities. Hub economies such as mainland China and the USA are collectors and distributors, and some emerging countries, such as Mexico, Brazil, India, and Russia, also exhibit dominance in different kinds of networks. This study selects the cattle sector to further verify that low production-side emission intensities and trade cooperation can lead to N2O emission reduction. In view of the impact of trade networks on global N2O emissions, achieving N2O emission reduction calls for vigorous international cooperation.

Mapping spatial supply chain paths for embodied water flows driven by food demand in China.

Identifying critical spatial supply chain paths for embodied water flows driven by food demand can guide the development of more spatially explicit food-related policies for water savings. Previous studies have quantified water uses caused by food demand, but overlook intermediate transfer paths within and among regions. That is, spatial supply chain paths describing step-by-step transfer stages between water uses and final food demand have not been well characterized. Based on the multi-regional input-output model and structural path analysis, this study exhaustively identifies critical spatial supply chain paths for provincial water withdrawals driven by final food demand in China. Results show that the final demand of food products from critical sectors (e.g., agricultural products processing, rice, and swine) and regions (e.g., Xinjiang, Heilongjiang, and Guangdong) drives large amounts of water withdrawals. Critical supply chain paths indicate that agricultural products processing, food manufacturing, and catering should pay special attention to increasing the use efficiency of rice, poultry, cotton, water, and gas products, which can effectively reduce national water withdrawals. The interregional paths further provide evidence for interregional cooperation to save food-related water resources, such as the transfer of capital and technologies from agricultural products processing in Shandong to cotton production in Xinjiang and rice production in Heilongjiang. These critical supply chain paths provide spatially explicit and targeted hotspots for demand-side policies. They can also serve for the evaluation of measures in each stage of the supply chain paths.

Understanding the industrial NOx and SO2 pollutant emissions in China from sector linkage perspective.

Since the most stringent-ever clean air policy was implemented in 2013 in China, main industrial air pollutant emissions have notably decreased. However, there are few studies on air pollutant emissions of industrial sectors driven by supply chain before and after implementing this policy. This paper attempts to provide a new perspective from industrial linkage to understand the emission of air pollutants. Based on Input-Output model framework, we revealed the linkages of SO2 and NOx emissions between sectors from 2012 to 2017 and the driving forces behind emission changes. Moreover, we simulated the possible impact of the key sector linkages on air pollutant emissions. Results show that the most noteworthy change during this period is that the metal melting sector has replaced the power sector, as the largest pollutant output emission sector associated with other sectors, especially the transport equipment sector. The main reason of this phenomena is that the emission intensity reduction rate of metal smelting sector (e.g., only 17% for NOx) is far less than other sectors. In the future, the development of the equipment manufacturing may put pressure on the metal smelting sector to reduce emissions. For example, when the transport equipment sector increases total output by 20% ~ 40%, the metal smelting sector will be driven to emit 0.04Mt ~0.08Mt of NOx. This paper provides a basis to quantitatively analyze the industrial sector linkages and identify the key sectors from 2012-2017, and helps decision makers better understand the impact of sector linkage on pollutant emissions.

Spatially Explicit Global Hotspots Driving China's Mercury Related Health Impacts.

Over 100 nations signed the Minamata Convention on Mercury to control the adverse effects of mercury (Hg) emissions on human beings. A spatially explicit analysis is needed to identify the specific sources and distribution of Hg-related health impacts. This study maps China's Hg-related health impacts and global supply chain drivers (i.e., global final consumers and primary suppliers) at a high spatial resolution. Here we show significant spatial heterogeneity in hotspots of China's Hg-related health impacts. Approximately 1% of the land area holds only 40% of the Chinese population but nearly 70% of the fatal heart attack deaths in China. Moreover, approximately 3% of the land area holds nearly 60% of the population but 70% of the intelligence quotient (IQ) decrements. The distribution of hotspots of China's Hg-related health impacts and global supply chain drivers are influenced by various factors including population, economy, transportation, resources, and dietary intake habits. These spatially explicit hotspots can support more effective policies in various stages of the global supply chains and more effective international cooperation to reduce Hg-related health impacts. This can facilitate the successful implementation of the Minamata Convention on Mercury.

Quantifying Direct and Indirect Spatial Food-Energy-Water (FEW) Nexus in China.

Food, energy, and water resources, which are interconnected with one another, are essential to human beings and sustainable development goals. Existing studies have quantified direct interconnections of food, energy, and water (FEW) systems in China but overlooked their indirect and spatial interconnections through production systems of other products. Quantifying both the direct and indirect spatial interconnections of food, energy, and water systems is the basis of holistic FEW resource management. The spatial interconnections of the FEW systems within China's economic supply chains at the provincial level were quantified from both demand-driven and supply-push perspectives in this study. Results show that food and energy subsystems have tighter coupling relations than the other relationships in the FEW nexus from the demand perspective, and food and water subsystems have tighter coupling relations from the supply perspective. Findings of this study highlight the necessity of demand-side and supply-side measures by identifying critical final consumers and primary suppliers. For example, primary inputs of energy extraction sectors in Inner Mongolia, Shanxi, and Heilongjiang are crucial for national water withdrawals. Sustainable management of FEW resources in China can be better achieved through strengthening the interdepartmental and interregional cooperation from both the demand and supply sides.

Saving less in China facilitates global CO2 mitigation.

Transforming China's economic growth pattern from investment-driven to consumption-driven can significantly change global CO2 emissions. This study is the first to analyse the impacts of changes in China's saving rates on global CO2 emissions both theoretically and empirically. Here, we show that the increase in the saving rates of Chinese regions has led to increments of global industrial CO2 emissions by 189 million tonnes (Mt) during 2007-2012. A 15-percentage-point decrease in the saving rate of China can lower global CO2 emissions by 186 Mt, or 0.7% of global industrial CO2 emissions. Greener consumption in China can lead to a further 14% reduction in global industrial CO2 emissions. In particular, decreasing the saving rate of Shandong has the most massive potential for global CO2 reductions, while that of Inner Mongolia has adverse effects. Removing economic frictions to allow the production system to fit China's increased consumption can facilitate global CO2 mitigation.

Network resilience of phosphorus cycling in China has shifted by natural flows, fertilizer use and dietary transitions between 1600 and 2012.

The resilience of the phosphorus (P) cycling network is critical to ecosystem functioning and human activities. Although P cycling pathways have been previously mapped, a knowledge gap remains in evaluating the P network's ability to withstand shocks or disturbances. Applying principles of mass balance and ecological network analysis, we examine the network resilience of P cycling in China from 1600 to 2012. The results show that changes in network resilience have shifted from being driven by natural P flows for food production to being driven by industrial P flows for chemical fertilizer production. Urbanization has intensified the one-way journey of P, further deteriorating network resilience. Over 2000-2012, the network resilience of P cycling has decreased by 11% owing to dietary changes towards more animal-based foods. A trade-off between network resilience improvement and increasing food trade is also observed. These findings can support policy decisions for enhanced P cycling network resilience in China.