Research

We proposed a solution based on double deep Q-network (DDQN) trains each truck in the fleet to make real-time decisions based on various factors such as in-situ grade (ore or waste), road traffic, estimated queueing, and maintenance requirements. Our results demonstrate that the proposed DDQN solution not only improves productivity and reduces fuel-related GHG emissions, but also significantly improves fleet performance in handling operational disruptions (production loss reduced by over 50%) without human intervention, including unexpected changes in fleet size and shovel grade. Comparative analysis revealed that upgrading the fleet with the proposed DDQN solution to reduce GHG emissions only equates, on average, 47% and 21% of fleet electrification and carbon capture and storage costs, respectively, and can be rapidly adopted in the near term. These advantages position the smart fleet dispatching system as a cost-effective approach to enhance productivity and reduce direct GHG emissions in mining operations for short-term targets.

In typical mining operations, more than half of the direct greenhouse gas (GHG) emissions come from haulage fuel consumption. Smarter truck fleet dispatching is a feasible and manageable solution to reduce direct emissions with existing equipment. Conventional scheduling-based and human-led dispatching solutions often cause lower efficiency that wastes resources and elevates emissions. In this study, a simulated environment is developed to enable testing smarter real-time dispatching systems, Q-learning as a model-free reinforcement learning algorithm is used to improve fleet productivity, decrease waiting time and, consequently, reduce GHG emissions. The proposed algorithm trains the fleet to make better decisions based on payload, traffic, queueing, and maintenance conditions. Results show that this solution can reduce GHG emissions from haulage fuel consumption by over 30% while achieving the same production levels as compared to fixed scheduling. The proposed solution also shows advantages in handling operational randomness and balancing fleet size, productivity, and emissions.

This study uses a plant-level dataset, pair-wise energy flow, and customized index decomposition analysis to investigate the driving forces behind Beijing's rapid electrification and carbon mitigation effects. Our assessment approaches can reveal the role of electrification in driving city-level emissions and identify a reasonable timeline to accelerate electrification for cities. We find that electrification-related factors are responsible for 21.8% of carbon emission changes in Beijing between 1995 and 2019. Particularly, the average emission intensity of Beijing's local power generation has dropped from 860 tCO2e/GWh in 2000 to 370 tCO2e/GWh in 2018, which is far below the critical level at which the high penetration of electricity in transportation and housing should be prioritized for decarbonization. Our results confirm that Beijing is in the best position to accelerate electrification to meet its carbon neutrality goals; however, this will increasingly rely on regionally collaborative decarbonization efforts with surrounding regions.

The waste liquid crystal display (LCD) panels are both harmful and reusable because of the variety of ingredients contained, for example, the liquid crystal, panel glass, and precious heavy metal. This study assumed one treatment technique which consists of crushing, a hydrothermal process, and acid leaching to realize harmless treatment and resource recycling of waste LCD panels based on the previous experimental results in our lab. The environmental impacts of this treatment technique were evaluated by using two methods of life cycle assessment of ReCiPe 2008 and Eco-indicator 99 (EI’99). ReCiPe assessment results show that the adverse environmental impacts from the treatment process are dominated by the input of electricity which is followed by the use of hydrogen peroxide and kerosene. EI’99 analysis reveals that, compared with incineration, the proposed treatment technique of waste LCD panels sharply cut down the negative environmental impacts by 91.5–97.3% under different scenarios.

In rapidly developing countries, considerable quantities of construction materials have been mobilized with the fast expansion of urban areas. The rural to urban land use transition, especially the upgrade and redevelopment of original rural areas, is a noted driver of material flows. In this study, a dynamic material flow and stock model that integrates the historical rural–urban land transition was developed to explore the quantity of material stocks and demolition waste from residential buildings in Shanghai—the largest megacity in China from 1950 to 2100. Our results show that the material stocks from residential buildings in Shanghai increased 41-fold from 1950 to 2010, about 957 MMT (million metric tons), and is estimated to be saturated around 2040. Material stocks have experienced asynchronized growth in rural areas, central urban areas, and rural–urban land transition zones (RULT zones) in Shanghai. The key findings on the trend of construction and demolition (C&D) waste generation and the significant contribution of RULT zones can be used as a reference for the strategic planning of treatment facilities. 

China’s 2050 high renewable energy penetration (HREP) scenario is a roadmap for deep decarbonization. This promising strategy, deploying wind and solar energy, will also reshape other infrastructure sectors. With decarbonization, not only can capital be diverted away from fossil fuel infrastructure towards green power generation, but considerable savings in future transport infrastructure sectors could be achieved as fossil fuels no longer need to be transported. Here, we conduct a material flow analysis (MFA) with a focus on the central role of transportation to examine the interlinkages of coal and steel flows in China’s infrastructure sectors between 1985, 2015, and 2050. We define the coal and steel nexus to be a systems perspective that captures the interdependence and the critical linkages between these two resources. Our results show the coal and steel nexus in China strengthened in the past three decades but could face transitional changes to 2050. The peak time of both coal and steel demand for China is expected to come before 2030. However, investment in cleaner energy and steelmaking technologies will help China mainly rely on secondary steel resources to maintain domestic demand in 2050, further reducing the demand for coal and iron ores.

Material flow analysis is one of the developed tools to analyze regional resource utilization and efficiency, but still, no holistic analysis has been done for African sub-regions. Africa and its sub-regions are experiencing a gradual but transitional development, leading to the steady growth of resource use. This study dived into African nations’ material flow accounts and conducted a statistical evaluation of material use, resource efficiency and driving forces in different sub-regions of Africa between 1980 and 2017 to investigate resource use patterns in Africa. Our results reveal significant disparities of material use and distinguishable driving forces at the sub-regional level of Africa.

Municipal water and wastewater services have complicated sources of greenhouse gas (GHG) emissions. There is also high uncertainty around GHG inventories from wastewater and sludge treatment. Understanding the complete picture of GHG emissions associated with the water, sanitation, and hygiene sector remains a challenging but fundamental requirement for policymakers and practitioners wanting to respond to the grand challenges in water, energy, and climate change.

In this study, we provide a systematic review on GHG emission characterizations of China's urban water infrastructure with the aim of shedding light on global implications for sustainable development. Further research directions may include GHG inventory development for urban water systems at the plant level, quantifications of GHG emissions from sewer systems, emission reduction measures via water reclamation, renewable energy recovery, energy efficiency improvement, cost–benefit analyses, and characterizations of Scope 3 emissions.

Clean water and sanitation is also an essential function of cities, but the impacts from China's future urbanization on unheeded water infrastructure were sparsely estimated, especially from a perspective of urban metabolism. This study examines the complex response in the water sector to Chinese urban policies taking resource efficiency into account GHG emissions. A hypothetical grid-city model was developed to connect technical parameters in urban water infrastructure systems to the socio-economic changes, such as population growth, housing blocks, and water end-use. The results show that the pipeline construction dominates material use and locks in significant GHG emissions in the water sector. The most efficient urbanization scenario can reduce 60% of GHG emissions from the water infrastructure, compared to the case of urban sprawl with residency restriction in large cities. A loosen migration regulation and compact urban planning in the medium- and large-sized cities are recommended, along with advanced water technologies to promote sustainable urban water management in China. 

Drinking water supply and wastewater treatment require significant energy inputs, and considerable greenhouse gas (GHG) emissions. Developing countries such as China are investing significantly in the construction of additional water infrastructure at the cost of increased GHG emissions. To understand the complexities of the inclusive impacts of GHG emissions from urban water systems, this study aims to examine both direct and indirect GHG emissions for water utilities in China's cities. Based on the proposed framework, Scope 3 emissions (indirect emissions other than electricity and heat purchase) for the operation of water utilities were estimated to be 8 Mt CO2-eq, which is significant to the total emission inventory; this corrected the bottom-up estimation in which 90% of Scope 3 emissions were not captured. The main hidden emission sources were upstream emissions of electricity and heat generation (21%), management of water conservancy (9%), manufacture of metal products (15%) and plastics (6%), and other chemical inputs (4%). 

Inter-regional spillover of air pollution can be regarded as a mixture of economic externalities and long-distance transport. To comprehensively reveal this problem, a new consumption-based sulfur dioxide (SO2) emission inventory in 2010 for 30 provincial regions of China was compiled by introducing a source-receptor relationship (SRR) model to integrate the spillover impacts of physical transport from the emitter (producer) region to the receptor region and virtual transfer from the driver (consumer) region to the emitter region. As a mega-city, Beijing induced significant SO2 emissions for power requirement, food consumption, miscellaneous services, and her vibrant research activities through the sectors of the power industry, coal mining, chemical manufacturing, food-related industries, petroleum processing and coking, but 86% of those emissions were outsourced by Beijing. This study demonstrates an analytic framework of strategic planning for joint prevention and control of air pollution regionally to help reduce pollution transfer, control the emitters, and reasonably compensate the damage-receptors.

Elevated ground-level ozone (O3), reflecting atmospheric oxidative capacity, are of increasing concern. High levels of total oxidants (Ox= O3 + NO2) have been persistently observed as a feature of Beijing's air pollution. Beijing is a well-known megacity requiring the enforcement of stringent air quality controls as rapid economic growth continues. To evaluate the effect of air quality controls in recent years, ground-based online measurements at an urban site were conducted in summer and the variations in O3 with simultaneous changes in NOx and volatile organic compounds (VOCs) between 2005 and 2011 were analyzed. Both NOx and total VOCs in Beijing decreased over the study period. However, VOCs reactivity, in terms of OH loss rate, showed an indistinct statistical trend due to unsteady variations from naturally emitted isoprene. Meanwhile, daytime average O3 increased rapidly at an annual rate of 2.6 ppbv yr−1, around 5% yr−1 between 2005 and 2011. Considering the influence of NO titration effect and elevated regional ozone background in the North China Plain, the main reason for such an increase in oxidants was subject to "local" photochemistry. Beijing needs deeper cooperation with adjacent provinces to control ozone pollution together. A faster reduction of VOCs, especially reactive VOCs, in urban areas, should coordinate with China's national NOx emission control programs.