Can China Peak Its Non-CO2 GHG Emissions before 2030 by Implementing Its Nationally Determined Contribution?

Opportunities beyond net-zero CO2 for cost-effective greenhouse gas mitigation in China

Achieving net-zero CO2 emissions is the current main focus of China's carbon neutrality goal. However, non-CO2 greenhouse gases (GHGs) are more powerful climate forcers, making their emission reduction an opportunity to rapidly mitigate future warming. Here, we evaluate non-CO2 mitigation potentials, costs and climate benefits in the context of China's carbon neutrality goals. The assessment is conducted by coupling the integrated assessment model GCAM with a climate emulator. The findings indicate that mitigation technologies can largely reduce fluorinated gas emissions from industrial sectors, but long-term non-CO2 reductions of energy sector activities rely heavily on fuel switching. Furthermore, the cumulative costs of deploying non-CO2 mitigation technologies are projected to be less than 10 % of the total costs of achieving carbon neutrality from 2020 to 2060. If non-CO2 mitigation measures are included in the overall mitigation portfolio, the benefits of avoided warming would by far outweigh the total mitigation cost increase. Our results thus highlight that incorporating a wider suite of GHGs into climate change mitigation strategies can enhance the cost-effectiveness of mitigation efforts.

Recent advances in abatement of methane and sulfur hexafluoride non-CO2 greenhouse gases under dual-carbon target

With the clarification of the CO2 abatement targets and pathways, the management and control of non-CO2 greenhouse gases (GHGs) have been widely emphasized. As the potent GHGs restricted by the Kyoto Protocol, methane (CH4) and sulfur hexafluoride (SF6) emissions contribute to a significant and increasing share of the total global GHG emissions, resulting in a continuous impact on the environment. Hence, the abatement of CH4 and SF6, the potent GHGs, is a matter of urgency. This paper focuses on recent advances in abatement of lean CH4 and SF6 waste gas. Firstly, a systematic review of abatement technologies for lean CH4 is presented, and two methods, namely, pressure swing adsorption and catalytic combustion, are emphasized. Additionally, the current status of four mainstream methods such as adsorption separation, thermal (catalytic) degradation, photocatalytic degradation, and non-thermal plasma degradation, as well as emerging technologies for SF6 abatement are summarized, and the inherent shortcomings and industrialization potentials of each technology are analyzed from multiple perspectives. This review demonstrates that, under dual-carbon target, existing abatement technologies are inadequate to meet the complex and diverse demands of the power and coal industries. There are many drawbacks for lean CH4 abatement technologies such as high investment in utilization devices, low processing capacity, high operating cost and requirement of high CH4 concentration. Degradation technologies for SF6 waste gas also suffer from low energy efficiency, high investment in catalytic degradation devices, and secondary pollution of degradation products. Based on this, two large-scale processing schemes with high feasibility are proposed. Finally, the current research hotspots, challenges, and future directions are put forward. This review aims to contribute some new perspectives to the abatement efforts of non-CO2 GHGs, so that the dual-carbon target can be realized as soon as possible.

Methane emission and influencing factors of China's oil and natural gas sector in 2020-2060: A source level analysis

The Chinese oil and gas industry requires targeted policies to reduce methane emissions. To achieve this goal, it is necessary to predict future methane emission trends and analyze the factors that influence them. However, changing economic development patterns, insufficient analysis of various factors influencing emissions, and inadequate resolution of methane emission inventories have made these goals difficult to achieve. Accordingly, this study aims to expand the methane emission estimation method to compile source-level emission inventories for future emissions, analyze the factors influencing them, and form a mechanistic understanding of the methane emissions from the local oil and gas industry. The research results indicate that methane emissions deriving from this industry will increase rapidly before 2030, after which they will decline slowly in all scenarios. The production and utilization processes in the natural gas supply chain, i.e., compressors and liquid unloading, include the main sources of methane emissions. Emissions are affected significantly by total production and consumption. Change in the overall supply and demand of natural gas affects change in methane emissions more significantly than adopting new technologies and strengthening facility maintenance, i.e., the overall supply and demand of natural gas are the dominant factors in controlling methane emissions. This study suggests that controlling the total demand for oil and gas should be at the core of the methane emission control policy for the local oil and gas industry. Moreover, equipment maintenance and emission reduction technologies should be used more effectively to reduce total emissions.

Characteristics and reduction assessment of GHG emissions from crop residue open burning in China under the targets of carbon peak and carbon neutrality

Driven by the goal of carbon peak and carbon neutrality, greenhouse gas (GHG) emissions from the crop residue open burning (CROB) in China cannot be ignored. In this study, we have established a high-resolution (0.05° × 0.05°) GHG emissions inventory (including CO2, CH4, and N2O) of CROB from 2012 to 2021 in China based on the VIIRS data and official statistics. To improve the results accuracy, we compared the two commonly used bases for grid allocation, fire counts (FC) and fire radiative power (FRP), in the construction of high-resolution inventory. In 2012, GHG emissions are overestimated by 599 t CO2e per grid on average in 24,577 grids, and underestimated by 1096 t CO2e per grid on average in 13,546 grids based on FC compared to FRP. Then, we characterized the spatial and temporal distribution of GHG emissions from CROB by using the FRP-based method. From 2012 to 2021, total GHG emissions from CROB in China have decreased by 31.2 %, of which the East and South-Central China contributed 22.51 and 9.12 Tg CO2e of GHG reductions, while the Northeast China contributed 10.73 Tg CO2e of GHG growth, respectively. In addition, GHG emissions from CROB on the time scale are mainly concentrated in April, June, and October, with variations between years and regions influenced by the policy, climate, and farmers' perceptions. Finally, we assessed the GHG emission reductions from CROB under different scenarios in the future. By 2060, GHG emissions would be significantly reduced by 57.3 %-77.9 % compared to 2021 under effective control measures. We believe the results will be of great significance for GHG policy formulation and emission reduction potential assessment.

Mitigation of Fully Fluorinated Greenhouse Gas Emissions in China and Implications for Climate Change Mitigation

Fully fluorinated greenhouse gases (FFGHGs), including sulfur hexafluoride (SF6), nitrogen trifluoride (NF3), and perfluorocarbons (PFCs), have drawn attention because they have long atmospheric lifetimes (up to thousands of years) and high global warming potential. Targeting SF6, NF3, and four PFCs (CF4, C2F6, C3F8, and c-C4F8), this study projects future FFGHG emission patterns in China, explores their mitigation potential, and evaluates the effects of FFGHG emission reduction on the achievement of the country's carbon neutrality goal and climate change. FFGHG emissions are expected to increase consistently, ranging from 506 to 1356 Mt CO2-eq yr-1 in 2060 under the business-as-usual (BAU) scenario. If mitigation strategies are sufficiently employed, FFGHG emissions under three mitigation scenarios: Technologically Feasible 2030, Technologically Feasible 2050, and Technologically Feasible 2060, will eventually decrease to approximately 49-78, 70-110, and 98-164 Mt CO2-eq yr-1 in 2060, respectively, compared to the BAU scenario. Extensive implementation of FFGHG emission mitigation technologies will curb temperature rise by 0.008-0.013 °C under the slowest mitigation scenario, compared to 0.013-0.026 °C under the BAU scenario. Well-coordinated policies and reforms on FFGHG emission mitigation are recommended to prevent potential adverse effects on the climate to a certain extent.

Recent progress of catalytic methane combustion over transition metal oxide catalysts

Methane (CH4) is one of the cleanest fossil fuel resources and is playing an increasingly indispensable role in our way to carbon neutrality, by providing less carbon-intensive heat and electricity worldwide. On the other hand, the atmospheric concentration of CH4 has raced past 1,900 ppb in 2021, almost triple its pre-industrial levels. As a greenhouse gas at least 86 times as potent as carbon dioxide (CO2) over 20 years, CH4 is becoming a major threat to the global goal of deviating Earth temperature from the +2°C scenario. Consequently, all CH4-powered facilities must be strictly coupled with remediation plans for unburned CH4 in the exhaust to avoid further exacerbating the environmental stress, among which catalytic CH4 combustion (CMC) is one of the most effective strategies to solve this issue. Most current CMC catalysts are noble-metal-based owing to their outstanding C–H bond activation capability, while their high cost and poor thermal stability have driven the search for alternative options, among which transition metal oxide (TMO) catalysts have attracted extensive attention due to their Earth abundance, high thermal stability, variable oxidation states, rich acidic and basic sites, etc. To date, many TMO catalysts have shown comparable catalytic performance with that of noble metals, while their fundamental reaction mechanisms are explored to a much less extent and remain to be controversial, which hinders the further optimization of the TMO catalytic systems. Therefore, in this review, we provide a systematic compilation of the recent research advances in TMO-based CMC reactions, together with their detailed reaction mechanisms. We start with introducing the scientific fundamentals of the CMC reaction itself as well as the unique and desirable features of TMOs applied in CMC, followed by a detailed introduction of four different kinetic reaction models proposed for the reactions. Next, we categorize the TMOs of interests into single and hybrid systems, summarizing their specific morphology characterization, catalytic performance, kinetic properties, with special emphasis on the reaction mechanisms and interfacial properties. Finally, we conclude the review with a summary and outlook on the TMOs for practical CMC applications. In addition, we also further prospect the enormous potentials of TMOs in producing value-added chemicals beyond combustion, such as direct partial oxidation to methanol.

Carbon dioxide emission characteristics and peak trend analysis of countries along the Belt and Road

Under the pressure of global carbon neutrality, it is necessary to study the characteristics of carbon emissions and the trend of "carbon peaking" in countries along the "Belt and Road." Because most of these countries have not yet reached their peak carbon emissions, they still have great potential for growth, and peak carbon emissions are a prerequisite for carbon neutrality. This paper divides the countries along the Belt and Road into 9 country groups according to the level of economic development and industrial structure. Based on the carbon emission panel data of countries along the "Belt and Road" from 1970 to 2018 and environmental Kuznets curve (EKC) theory, a panel model was established for each country group for research. This paper analyzes the characteristics of carbon emissions and the trend of "carbon peaking" in these countries and analyzes the economic growth and carbon emissions in combination with the Tapio decoupling model. The decoupling relationship changes on the time scale as a supplement. The results show that in the study area, some countries have completely passed the "carbon peak." The reasons for this are as follows: first, the carbon peak is achieved through industrial upgrading; second, the "carbon peak" is caused by the drastic changes in Eastern Europe and the disintegration of the Soviet Union and deindustrialization; and third, the carbon peak is caused by poverty and population growth. Most of the remaining countries have not yet achieved the carbon peak. Among them, some countries represented by the Middle East are highly coupled with their economic development and carbon emissions. Middle-income and high-industrial-dependence countries are in the transitional period in terms of the carbon peak. Low-income and medium- and high-industrial-dependence countries are currently still in the stage of barbaric development. From the research on the decoupling situation, the relationship between the economic growth of countries along the "Belt and Road" and their carbon emissions has been improving in recent decades, and it is expected that a more ideal state of decoupling will be achieved in the future.

Carbon footprint, yield and economic performance assessment of different mulching strategies in a semi-arid spring maize system

Crop productivity maximization while minimizing carbon emissions is of critical importance for achieving sustainable agriculture. Socio-economic and ecological benefits should be taken together under the circumstance of stagnant farming profitability and climatic variability. The effectiveness of various mulching strategies in rain-fed semiarid areas has been confirmed, but scarce the comprehensive evaluations of the conventional and new mulching strategies in terms of yield, economic benefit, and carbon footprint based on life cycle assessment (LCA) have been conducted. Hence, a two-year field experiment was conducted on maize (Zea mays L.) crop to explore the effects of four mulching strategies (PM: plastic-film mulching, SM: maize straw mulching, BM: biodegradable-film mulching, and NM: no mulching) on the yield, net return, greenhouse gas (GHG) emissions, and carbon footprint (CF). The results revealed that PM and BM significantly increased maize yield by 11.3-13.3% and 9.4-10.6%. PM marginally raised the net return by 2.0-2.4% whereas BM slightly reduced it by 4.6-8.8% relative to NM. Unexpectedly, the yield and net return were the lowest under SM, and intensified N₂O emissions, GWP_direct, and yield-scaled GWP_direct were observed. When the GHGs using LCA concept and SOC sequestration rate were considered, the lowest net GWP (1804.1-1836.4 kg CO₂-eq ha^-1) and CF (148.9-119.9kg CO₂-eq t^-1) were observed in the SM treatment due to the boost of soil organic carbon (SOC) sequestration. Conversely, PM and BM significantly increased the net GWP and CF compared to NM. When the tradeoffs between the high production, high net return and low net GWP were assessed by an integrated evaluation framework, the NM was recommended as an efficient low-carbon agricultural practice in the rain-fed semiarid areas.

Policy-enabled stabilization of nitrous oxide emissions from livestock production in China over 1978-2017

Mitigating livestock-related nitrous oxide (N₂O) emissions is key for China to meet its 2060 carbon neutrality target. Here we present a comprehensive analysis of the magnitude, spatiotemporal variation and drivers of Chinese livestock N₂O emissions from 1978 to 2017. We developed scenarios to explore emissions mitigation potential and associated marginal abatement costs and social benefits. The average growth rate of China's livestock N₂O emissions increased by 4.6% per year through 2006, falling sharply over 2007-2015 and gradually declining in 2017 due to a slowdown in population and meat-consumption growth rates. We estimate the technical mitigation potential of livestock N₂O emissions in 2030 to be 7-21% (or 23.1-70.9 Gg N₂O), with implementation costs of US$5.5 billion to US$6.0 billion. Priority regions for intervention were identified in the North China Plain, Northeast Plain and Lianghu Plain. Among mitigation opportunities, anaerobic digestion offers the greatest social benefit, while low crude protein feed is the most cost-effective option.

Carbon emissions index decomposition and carbon emissions prediction in Xinjiang from the perspective of population-related factors, based on the combination of STIRPAT model and neural network

In the present study, the STIRPAT model was adopted to examine the impacts of several factors on dioxide emissions using the time series data from 2000 to 2019 in Xinjiang. The said factors included population aging, urbanization, household size, per capita GDP, number of vehicles, per capita mutton consumption, education level, and household direct energy consumption structure. Findings were made that the positive effects of urbanization, per capita GDP, per capita mutton consumption and education on carbon emissions were obvious; the number of vehicles had the biggest positive impact on carbon dioxide emissions; and household size and household direct energy consumption structure had a significantly negative impact on carbon emissions. Based on the aforementioned findings, the GA-BP neural network was introduced to predict the carbon emission trend of Xinjiang in 2020-2050. The results reveal that the peak time of the low-carbon scenario was the earliest, between 2029 and 2033. The peak time of the middle scenario was later than low-carbon scenario, between 2032 and 2037, while the peak time of the high-carbon scenario was the latest and was unlikely to reach the peak before 2050.

Towards carbon neutrality: A study on China's long-term low-carbon transition pathways and strategies

As the world's biggest carbon dioxide (CO₂) emitter and the largest developing country, China faces daunting challenges to peak its emissions before 2030 and achieve carbon neutrality within 40 years. This study fully considered the carbon-neutrality goal and the temperature rise constraints required by the Paris Agreement, by developing six long-term development scenarios, and conducting a quantitative evaluation on the carbon emissions pathways, energy transformation, technology, policy and investment demand for each scenario. This study combined both bottom-up and top-down methodologies, including simulations and analyses of energy consumption of end-use and power sectors (bottom-up), as well as scenario analysis, investment demand and technology evaluation at the macro level (top-down). This study demonstrates that achieving carbon neutrality before 2060 translates to significant efforts and overwhelming challenges for China. To comply with the target, a high rate of an average annual reduction of CO₂ emissions by 9.3% from 2030 to 2050 is a necessity, which requires a huge investment demand. For example, in the 1.5 °C scenario, an investment in energy infrastructure alone equivalent to 2.6% of that year's GDP will be necessary. The technological pathway towards carbon neutrality will rely highly on both conventional emission reduction technologies and breakthrough technologies. China needs to balance a long-term development strategy of lower greenhouse gas emissions that meets both the Paris Agreement and the long-term goals for domestic economic and social development, with a phased implementation for both its five-year and long-term plans.

Decoupling without outsourcing? How China's consumption-based CO2 emissions have plateaued

The shift of China’s economy since 2013, dubbed the “new normal”, has caused its production and consumption emissions to plateau, with the country seeming to embody the tantalizing promise of decoupling its economic growth from carbon emissions. By using multi-region input-output analysis, we find that China’s relative decoupling in the new normal is technology driven, evidenced by the narrowing gap between its technology-adjusted and non-adjusted consumption emissions. By applying structural decomposition analysis, we further explore the driving forces behind the slowdown in China’s imported emissions growth, finding that it is attributable to restructuring of import patterns resulting from changes in the structures of domestic demand. These changes could have been caused by China moving along the global value chain and rebalancing its industrial linkages toward trade in carbon-efficient goods to avoid transferring emissions-intensive production to other regions, indicating a shift to less emissions-intensive trade rather than pure outsourcing.

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China’s consumption-based CO₂ emissions have plateaued during the “new normal” period

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Technology-adjusted consumption emissions show relative decoupling is technology driven

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The slowdown in import emissions growth is related to restructuring of import patterns

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Improvements in trade patterns have occurred, rather than pure outsourcing of emissions

China's CH4 emissions from coal mining: A review of current bottom-up inventories

As the world's largest CH₄ emitter, China's CH₄ emissions contribute to climate change more than the amount emitted by many developed countries combined. The rapid growth of China's coal demand has important implications for CH₄ emissions from coal mining or coal mine methane (CMM) emissions. This paper aims to present an overview of bottom-up estimation of China's CMM emissions, including the trend in the last four decades and the limitations of current understanding on CH₄ emissions. Although characterized by significant differences in inventory compilation, statistically, the total CMM emissions rose from 4.64 to 16.41 Tg with a peak of 21.48 Tg from 1980 to 2016. Large discrepancies of inventory results existed in previous studies, which were affected by the coverage of emission sources, emission factors and activity-level data. The disagreements can be largely attributable to the emission factors of underground mining, which contain substantial variances in both spatial and temporal dimensions. To develop more reliable CMM inventories and make targeted mitigation measures, more attention should be paid to the transparency of the estimated results, coal statistics, on-site CMM emission factors, and the emissions from abandoned coal mines. As the leading CH₄ emission source in China, the estimations of CMM emissions urgently need to overcome existing and emerging challenges for compiling a consistent and accurate inventory.