Incorporating platinum circular economy into China's hydrogen pathways toward carbon neutrality.

Hydrogen is gaining tremendous traction in China as the fuel of the future to support the country's carbon neutrality ambition. Despite that hydrogen as fuel largely hinges on the supply of platinum (Pt), the dynamic interlinkage between Pt supply challenges, hydrogen development pathways, and climate targets in China has yet to be deeply analyzed. Here, we adopt an integrated assessment model to address this important concern and corresponding strategies for China. The results indicate that the booming hydrogen development would drive China's cumulative demand for Pt metal to reach 4,200-5,000 tons. Much of this demand, met through a limited supply pattern, is vulnerable to price volatility and heightened geopolitical risks, which can be mitigated through circular economy strategies. Consequently, a coordinated approach to leverage both global sustainable Pt sourcing and a robust domestic Pt circular economy is imperative for ensuring cost-effective hydrogen production, aligned with a climate-safe future.

Higher total energy costs strain the elderly, especially low-income, across 31 developed countries.

Addressing the total energy cost burden of elderly people is essential for designing equitable and effective energy policies, especially in responding to energy crisis in an aging society. It is due to the double impact of energy price hikes on households-through direct impact on fuel bills and indirect impact on the prices of goods and services consumed. However, while examining the household energy cost burden of the elderly, their indirect energy consumption and associated cost burden remain poorly understood. This study quantifies and compares the direct and indirect energy footprints and associated total energy cost burdens for different age groups across 31 developed countries. It reveals that the elderly have larger per capita energy footprints, resulting from higher levels of both direct and indirect energy consumption compared with the younger age groups. More importantly, the elderly, especially the low-income elderly, have a higher total energy cost burden rate. As the share of elderly in the total population rapidly grows in these countries, the larger per capita energy footprint and associated cost burden rate of elderly people would make these aging countries more vulnerable in times of energy crises. It is therefore crucial to develop policies that aim to reduce energy consumption and costs, improve energy efficiency, and support low-income elderly populations. Such policies are necessary to reduce the vulnerability of these aging countries to the energy crisis.

Promoting Sustainable Development Goals by Optimizing City-Level Solar Photovoltaic Deployment in China.

Solar photovoltaic (PV) installations, which enable carbon neutrality, are expected to surge in the coming decades. This growth will support sustainable development goals (SDGs) via reductions in power-generation-related environmental emissions and water consumption while generating new jobs. However, where and to what extent PVs should be utilized to support SDGs must be thoroughly addressed. Here, we use multiple PV deployment scenarios to compare the benefits of PVs and related SDGs progress in 366 prefectural-level cities in China. We developed an assessment framework that integrates a PV allocation model, an electricity system optimization model, and a benefit assessment approach. We identify vast differences in PV distribution and electricity transmission and elucidate trade-offs and synergies among the SDGs under various PV implementation scenarios. The water conservation-oriented scenario yields substantial carbon reduction, air pollutant mitigation, and water saving cobenefits, leading to the greatest SDGs improvements. Prioritizing employment creation enhances job-relevant SDGs but inhibits environmental resource benefits. SDGs in less developed cities present greater progress across all scenarios. This study highlights the need to consider spatial heterogeneity and the potential trade-offs between different SDGs and regions when designing energy transition strategies.

Country-specific net-zero strategies of the pulp and paper industry.

The pulp and paper industry is an important contributor to global greenhouse gas emissions1,2. Country-specific strategies are essential for the industry to achieve net-zero emissions by 2050, given its vast heterogeneities across countries3,4. Here we develop a comprehensive bottom-up assessment of net greenhouse gas emissions of the domestic paper-related sectors for 30 major countries from 1961 to 2019-about 3.2% of global anthropogenic greenhouse gas emissions from the same period5-and explore mitigation strategies through 2,160 scenarios covering key factors. Our results show substantial differences across countries in terms of historical emissions evolution trends and structure. All countries can achieve net-zero emissions for their pulp and paper industry by 2050, with a single measure for most developed countries and several measures for most developing countries. Except for energy-efficiency improvement and energy-system decarbonization, tropical developing countries with abundant forest resources should give priority to sustainable forest management, whereas other developing countries should pay more attention to enhancing methane capture rate and reducing recycling. These insights are crucial for developing net-zero strategies tailored to each country and achieving net-zero emissions by 2050 for the pulp and paper industry.

Implementation of carbon pricing in an aging world calls for targeted protection schemes.

Understanding the impact of climate fiscal policies on vulnerable groups is a prerequisite for equitable climate mitigation. However, there has been a lack of attention to the impacts of such policies on the elderly, especially the low-income elderly, in existing climate policy literature. Here, we quantify and compare the distributional impacts of carbon pricing on different age-income groups in the United States, the United Kingdom, and Japan and then on different age groups in other 28 developed countries. We find that the elderly are more vulnerable to carbon pricing than younger groups in the same income group. In particular, the low-income elderly and elderly in less wealthy countries face greater challenges because carbon pricing lead to both higher rate of increase in living cost among low-income elderly and greater income inequality within the same age group. In addition, the low-income elderly would benefit less than the younger groups within the same income group in the commonly proposed carbon revenues recycling schemes. The high vulnerability of the low-income elderly to carbon pricing calls for targeted social protection along with climate mitigation polices toward an aging world.

Tracing metal footprints via global renewable power value chains.

The globally booming renewable power industry has stimulated an unprecedented interest in metals as key infrastructure components. Many economies with different endowments and levels of technology participate in various production stages and cultivate value in global renewable power industry production networks, known as global renewable power value chains (RPVCs), complicating the identification of metal supply for the subsequent low-carbon power generation and demand. Here, we use a multi-regional input-output model (MRIO) combined with a value chain decomposition model to trace the metal footprints (MFs) and value-added of major global economies' renewable power sectors. We find that the MFs of the global renewable power demand increased by 97% during 2005-2015. Developed economies occupy the high-end segments of RPVCs while allocating metal-intensive (but low value-added) production activities to developing economies. The fast-growing demand for renewable power in developed economies or developing economies with upper middle income, particularly China, is a major contributor to the embodied metal transfer increment within RPVCs, which is partly offset by the declining metal intensities in developing economies. Therefore, it is urgent to establish a metal-efficient and green supply chain for upstream suppliers as well as downstream renewable power installers for just transition in the power sector across the globe.

China's electric vehicle and climate ambitions jeopardized by surging critical material prices.

The adoption of electric vehicles (EVs) on a large scale is crucial for meeting the desired climate commitments, where affordability plays a vital role. However, the expected surge in prices of lithium, cobalt, nickel, and manganese, four critical materials in EV batteries, could hinder EV uptake. To explore these impacts in the context of China, the world's largest EV market, we expand and enrich an integrated assessment model. We find that under a high material cost surge scenario, EVs would account for 35% (2030) and 51% (2060) of the total number of vehicles in China, significantly lower than 49% (2030) and 67% (2060) share in the base-line, leading to a 28% increase in cumulative carbon emissions (2020-2060) from road transportation. While material recycling and technical battery innovation are effective long-term countermeasures, securing the supply chains of critical materials through international cooperation is highly recommended, given geopolitical and environmental fragilities.

Allocating environmental costs of China's rare earth production to global consumption.

China provides over 80% of global rare earth (RE) that caused serious domestic environmental impacts. However, how much RE-related pollution was transferred to China along global supply chain remains poorly understood. Here we, for the first time, established the RE industry-specific input-output approaches to trace environmental costs transfer through China's RE exports from whole supply chain perspective. We found that foreign consumption contributed over half of the environmental costs from China's RE production, with a gross value increasing from $4.8 billion (65% of total environmental costs) in 2010 to $5.4 billion in 2015 (74% of total environmental costs). Countries in the East Asia (i.e., Japan and South Korea) made the largest contribution (27-37%) to the exports induced environmental costs, followed by North America (i.e., the United States, Mexico, and Canada) with a contribution of 20-27% and the rest East Asia (including countries in Asia-Pacific except China Mainland, by 16-23%). Exports induced environmental costs were mainly from RE raw materials (60%) and high value-added products (22%). Suggestions such as rationalizing RE cost as well as production- and consumption-based measures to mitigate environmental impacts were proposed to enhance RE utilities for global sustainable development.

Using Existing Infrastructure to Realize Low-Cost and Flexible Photovoltaic Power Generation in Areas with High-Power Demand in China.

This study develops a new concept involving using the existing infrastructure for photovoltaic (PV) generation to reduce the costs associated with increased land use and to avoid curtailment due to the mismatch between power supply and demand. We establish a method to estimate the technological potential and economic performance of the PV systems deployed in coal-fired power plants in China. The potential capacity of the examined 1,082 units in China reaches 4 GWe, which is equivalent to 32% of China's newly installed distributed PV capacity in 2019. A total of 87% of PV systems achieve plant-side grid parity compared with desulfurized coal benchmark electricity prices. To the best of our knowledge, this is the first study that investigates the use of rooftops and coal storage sheds in power plants to facilitate low-cost, flexible PV power generation, thus opening a new channel for future PV generation development.

Emission behavior, environmental impact and priority-controlled pollutants assessment of volatile organic compounds (VOCs) during asphalt pavement construction based on laboratory experiment.

Volatile organic compounds (VOCs) release from asphalt pavement construction is a potential emission source. The detailed emission behaviors were simulated in the laboratory, and the corresponding environmental impact was investigated as well. A set of dedicated devices were applied to mirror 3 representative scenarios namely mixture plant, transportation and paving processes with VOCs emission concentrations varied from 4.24 mg/m3 to 104.16 mg/m3. Ozone formation potential (OFP) and secondary organic aerosol (SOA) were built to evaluate the environmental impact, indicating that the reactive ability differed in the specified substances. The alkenes (n ≤ 4) and aldehydes, alkanes (n ≥ 6) and alkylbenzenes with relative lower concentration were the main sources for the OFP and SOA generation, and they contributed to more than 62% OFP and 97% SOA respectively. The top 10 contributors to concentration, OFP and SOA had been identified. For the complex species existed in VOCs emission and the lack of VOCs control standards, this study provided possible access to screen priority-controlled pollutants based on information entropy method, in terms of both environmental and human health impact. In addition, the first-class priority-controlled species had been determined, urgently needing more attention in the future VOCs management during asphalt pavement construction.

Greenhouse gas emissions embodied in the Mongolian economy and their driving forces.

As a member of the Paris Climate Agreement, greenhouse gas (GHG) emission mitigation is a compulsory and urgent task for Mongolia. However, the Mongolian economy dominated by the carbon-intensive industries (such as mining and construction) has been experiencing rapid growth since 2 decades ago, consequently influencing its GHG emissions, while the impact of Mongolia's economic growth on GHG emissions and their socioeconomic driving factors remains poorly understood. Therefore, this study applied a multiregional input-output model to calculate the embodied GHG emissions and a structural decomposition analysis was used to identify the key driving factors of the embodied GHG emissions. Results show that the GHG emissions increased from 8679 Gg CO2e to 17,165 Gg CO2e, with an annual growth rate of 4.65% during 2000-2015. Household consumption and gross fixed capital formation are identified as the key driving factors for the increase in embodied GHG emissions, while technical efficiency is the main factor contributed to the emission decline in Mongolia. China, Russia, and South Korea were the top three regions to outsource their carbon emissions to Mongolia by international trade. Regional collaborative carbon emission mitigation strategies from the system embodiment perspective are suggested.

Disparities in socio-economic drivers behind China's provincial energy-related mercury emission changes.

The legally binding Minamata Convention was ratified by the Chinese government in 2017, implying that mercury emission mitigation policy design has become an urgent task ever since. As each provincial region has different energy structures and technology levels, their mercury emission profiles may have heterogeneity, thus requiring targeted regional control polices. Therefore, this study investigates the provincial energy-related mercury emissions and identifies their underlying socioeconomic factors during 2007-2012, by combining structural decomposition analysis (SDA) with the multi-regional input-output analysis (MRIO). Results show that the rising consumption per capita and decreasing emission factor are the largest contributors to emission growth and decline, respectively. However, their contributions vary significantly across regions. The rising consumption per capita leads to nearly 20 t emission increase in Shandong and Jiangsu, but less than 1 t in Qinghai. The decreasing emission factor's negative effect on mercury emission reduction is extremely important in Jiangsu, Shandong and Guangdong, but not so obvious in most western provinces. Energy efficiency is another critical contributor to mercury reduction in all provinces except Guizhou, as the coal consumption in Guizhou nearly doubled during 2007-2010. Moreover, production structure and consumption structure have opposite effects during 2007-2010 and 2010-2012: they first drive energy-related mercury emissions growing in most provinces, then inhibit the emissions especially in Shandong and Guangdong. These findings point to targeted mercury mitigation strategies (for example: improving energy efficiency in Guizhou and Liaoning, optimizing economic structure in Henan and Sichuan) for each province.