Tracking Carbon Flows in China's Iron and Steel Industry

CO2 emissions associated with China's real estate development: 2000-2020

Transitioning real estate development toward low-carbon operations is a critical strategy for China to achieve its carbon peaking and neutrality targets. Accurately calculating CO2 emissions from real estate development is essential for effective implementation of low-carbon strategies. However, research that specifically addresses CO2 emissions from real estate development is lacking. To fill this knowledge gap, this study examined CO2 emissions from China's real estate development between 2000 and 2020, presenting a comprehensive analysis of the production and consumption aspects of emissions, and inter-provincial transfers of emissions driven by the sector. Our findings reveal a significant increase in embodied CO2 emissions from China's real estate development, escalating from 145.5 Mt in 2000 to 477.3 Mt in 2020. The proportion of emissions attributable to real estate development among China's total CO2 emissions ranged from 5 % to 6 % between 2000 and 2020, underscoring the sector's non-negligible impact on the country's overall CO2 emissions. Our analysis demonstrated that building material production, especially steel and cement, contributed significantly to the sector's emissions, underscoring the need for decarbonization and the adoption of green building materials. Additionally, a marginal increase in CO2 emissions per constructed area requires enhanced sustainable construction practices. Furthermore, our study revealed that the ongoing rise in inter-provincial CO2 emissions transfer due to real estate development intensifies carbon inequality across provinces. These findings are instrumental for policymakers and stakeholders to develop targeted interventions to mitigate CO2 emissions and promote sustainable growth in China's real estate sector.

Uneven renewable energy supply constrains the decarbonization effects of excessively deployed hydrogen-based DRI technology

Hydrogen-based direct reduced iron (H2-DRI) is crucial for decarbonizing the steel sector but is limited by the availability of renewable energy. Here, we propose H2-DRI deployment schemes in China's steel sector at moderate and aggressive scales, incorporating three renewable energy sources with a resolution of 1 km × 1 km across 570 steel units. Results indicate that 52.6-55.8% of China's current steel units lack sufficient renewable energy supply for H2-DRI deployment due to uneven distribution of these energy sources. Renewable energy can fulfill 97-100% of hydrogen demand at the moderate scale, whereas the aggressive scale requires supplemented fossil fuels accounting for one-third to one-half. H2-DRI can decarbonize steel production to 0.15-0.91 t CO2 t-1 steel at the moderate scale, but the emissions would raise by up to over sixfold at the aggressive scale. Furthermore, H2-DRI fueled by solar and wind energy exhibits poorer economic and water usage performance at the aggressive scale. We highlight the necessity of avoiding excessive H2-DRI deployment and recommend prioritizing its implementation in steel units located in regions with abundant solar and wind sources nearby.

Coordinating Interprovincial Scrap Supply for Technology Transition to Minimize Carbon Emissions of China's Iron and Steel Industry

Provincial inherent heterogeneity in resource endowment, steel demand, and managerial guidance poses not only challenges but also chances to the decarbonization of China's iron and steel industry (ISI). Previous studies have primarily concentrated on the technological dimension at the national level or plant level but have neglected potential regional synergies. This study proposed a framework encompassing macroeconomic models and multi-objective algorithms to optimize interprovincial allocation of scrap resources for coordinating the steelmaking process transition, aiming to minimize total carbon emissions from ISI. Results indicate that optimizing scrap allocation can reduce carbon emissions by 173.97-215.66 million tons, achieving a 99% reduction by 2060 compared to 2020 levels. Under the coordination strategy, 19 out of 28 provinces can achieve carbon neutrality and realize more than 90% pollutant reduction in the ISI. Notably, provinces such as Hebei, Inner Mongolia, Shanxi, Heilongjiang, and Liaoning still need to import more scrap resources and implement innovative low-carbon technologies. Finally, we propose interprovincial coordinated transition strategies, including regional integration management, national data platform, and preferential economic instrument. This work guides national and provincial administrations to formulate differentiated low-carbon transition targets and collaborative actions in ISI, which can be also applied to other substantially heterogeneous industries to achieve carbon neutrality.

Quantitative sustainability assessment for in-situ electrical resistance heating coupled with steam enhanced extraction: An effective approach for the development of green remediation technologies

There is a lack of quantitative methodology for the sustainability assessment based on field data in the process of innovative technology development for groundwater remediation. This study developed a quantitative assessment framework, a model based on the life cycle assessment integrated with best management practices (LCA-BMPs), to evaluate the environmental, economic, and social sustainability of in-situ electrical resistance heating coupled with steam enhanced extraction (ERH-SEE), an innovative technology being demonstrated in the field. The results indicated that ERH-SEE offered better environmental sustainability performance compared to ERH only, with a reduction in carbon emissions by 52.6 %. ERH-SEE also significantly reduces human toxicity, resource consumption, and ecosystem impacts under the same remediation scenarios. The further assessment indicated that if taking the renewable energy share in energy structure in different countries into consideration, higher shares of renewable energy used in energy supplies can substantially reduce the environmental footprint of the studied scenarios. The economic sustainability assessment results showed that ERH-SEE was more sustainable than ERH only, as it reduces direct economic costs by 35.7 % and provides higher levels of worker employment. Regarding the social sustainability, ERH-SEE involved more complex operational procedures and presented more health risk exposure scenarios compared to ERH only, resulting in slightly more pronounced worker safety issues. Based on the final normalized results, the overall sustainability results of ERH-SEE and ERH only were 78.4 and 61.5, respectively, demonstrating that the sustainability performance of ERH-SEE was better than ERH only. It can be concluded that the application of ERH-SEE in groundwater remediation where significant heterogeneities occur in subsurface can increase the sustainability in developing countries, due to the lower percentage in renewable electricity in the energy supply. This study provided new insights into the technology development for the remediation of soil and groundwater contamination.

Tracking Carbon and Ammonia Emission Flows of China's Nitrogen Fertilizer System: Implications for Domestic and International Trade

China is the world's largest producer, consumer, and exporter of synthetic nitrogen (N) fertilizer. To assess the impact of domestic demand and international exports, we quantified the life-cycle CO2eq and ammonia (NH3) emissions by tracking carbon (C) and nitrogen (N) flows from coal/gas mining through ammonia production to N fertilizer production, application, and export. In 2020, China's N fertilizer system emitted 496.04 Tg of CO2eq and 3.74 Tg of NH3, with ammonia production and N fertilizer application processes contributing 36 and 85% of the life-cycle CO2eq and NH3 emissions, respectively. As the largest importers of N fertilizer, India, Myanmar, South Korea, Malaysia, and the Philippines collectively shifted 112.41 Tg of CO2eq. For every ton of N fertilizer produced and used in China, 16 t of CO2eq and 0.18 t of NH3 were emitted, compared to 9.7 t of CO2eq and 0.13 t of NH3 in Europe. By adopting currently available technologies, improving N fertilizer utilization efficiency and employing nitrification inhibitors could synergistically reduce CO2eq emissions by 20% and NH3 emissions by 75%, while energy transformation efforts would primarily reduce CO2eq emissions by 59%. The production of ammonia using green electricity or green hydrogen could significantly enhance the decarbonization of China's N fertilizer system.

Quantifying China's iron and steel industry's CO2 emissions and environmental health burdens: A pathway to sustainable transformation

Assessing the iron and steel industry's (ISI) impact on climate change and environmental health is vital, particularly in China, where this sector significantly influences air quality and CO2 emissions. There is a lack of comprehensive analyses that consider the environmental and health burdens of manufacturing processes for ISI enterprises. Here, we present an integrated emission inventory that encompasses air pollutants and CO2 emissions from 811 ISI enterprises and five key manufacturing processes in 2020. Our analysis shows that sintering is the primary source of air pollution in the ISI. It contributes 71% of SO2, 73% of NO x , and 54% of PM2.5 emissions. On the other hand, 81% of total CO2 emissions come from blast furnaces. Significantly, the contributions of ISI have resulted in an increase of 3.6 μg m-3 in national population-weighted PM2.5 concentration, causing approximately 59,035 premature deaths in 2020. Emissions from Hebei, Jiangsu, Shandong, Shanxi, and Inner Mongolia provinces contributed to 48% of PM2.5-related deaths in China. Moreover, the transportation of air pollutants across provincial borders highlights a concerning trend of environmental health inequality. Based on the research findings, it is crucial for ISI manufacturers to prioritize the removal of outdated production capacities and adopt energy-efficient and advanced techniques, along with ultra-low emission technologies. This is particularly important for those manufacturers with substantial environmental footprints. These transformative actions are essential in mitigating the environmental and health impacts in the affected regions.

Air quality and health benefits for different heating decarbonization pathways in China

The urgent need for decarbonization in China's heating system, comprised of approximately one hundred thousand boilers, is imperative to meet climate and clean air objectives. To formulate national and regional strategies, we developed an integrated model framework that combines a facility-level emission inventory, the Community Multiscale Air Quality (CMAQ) model, and the Global Exposure Mortality Model (GEMM). We then explore the air quality and health benefits of alternative heating decarbonization pathways, including the retirement of coal-fired industrial boilers (CFIBs) for replacement with grid-bound heat supply systems, coal-to-gas conversion, and coal-to-biomass conversion. The gas replacement pathway shows the greatest potential for reducing PM2.5 concentration by 2.8 (2.3-3.4) μg/m3 by 2060, avoiding 23,100 (19,600-26,500) premature deaths. In comparison, the biomass replacement pathway offers slightly lower environmental and health benefits, but is likely to reduce costs by approximately two-thirds. Provincially, optimal pathways vary - Xinjiang, Sichuan, and Chongqing favor coal-to-gas conversion, while Shandong, Henan, Hebei, Inner Mongolia, and Shanxi show promise in CFIBs retirement. Henan leads in environmental and health benefits. Liaoning, Heilongjiang, and Jilin, rich in biomass resources, present opportunities for coal-to-biomass conversion.