Since the IPCC put forward the concept of co-benefits in the 1990s, a number of studies have fully confirmed that greenhouse gases (GHGs) emission reduction policies and measures can produce considerable local environmental quality and health benefits. Correspondingly, existing studies have also confirmed that local air pollutants reduction policies and measures also have synergistic benefits for GHGs reduction. Soon after China completed its industrialization, the pressure of local air pollution reached its peak, and at the same time, it faced the tide of international community calling for climate change mitigation, and thus faced the dual pressure of reducing both GHGs and local air pollutants. Therefore, domestic researchers not only paid attention to the one-way co-beneifts evaluation of “from carbon reduction to local pollutants reduction” or “from local air pollutants reduction to carbon reduction”, but also put emphasis on integrated emission reductions. At the beginning of the 21st century, the concept of “co-control” proposed by the US Environmental Protection Agency was introduced into China and warmly embraced. Chinese scholars first defined the connotation of co-control, and believed that co-control was the way to maximize co-benefits. This progress has raised people’s awareness of co-benefits to a new level of “global vision and local action”, and promoted people from passively accepting “co-benefits” to actively seeking “co-control” of both global and local pollutants. It provides an all-round support from epistemology, methodology to practice, for the carbon and local air pollutants co-reduction. On the basis of researches on co-benefits and co-control at home and abroad, Chinese scholars have proposed methods for evaluating co-control effectiveness and planning co-control paths, and verified the scientificity and feasibility of the methods through case studies in multiple industries, cities, and regions. Co-control has become an important national strategy for mitigating climate change and continuously improving the quality of the atmospheric environment. In the process of China’s promotion of the construction of a beautiful China and the realization of its carbon peak goals and carbon neutrality vision, the concept, measures and policies of co-control will play an increasingly important role. In the near future, the co-control objectives will expand from only the atmosphere to the broader eco-environmental system, and the establishment of a co-control governance system will become the key to realize coordination of climate change and ecological environment governance at the macro level.

This study built an evaluation index to quantify the synergistic effect of air pollution control and greenhouse gas emission reduction based on the two-digit four-quadrant map, and established a method to quantify the synergistic effect, sorting out and giving the calculation methods for the emission of major pollutants such as fuel combustion, cement production, and coal-fired power plants, and determining the emission factors and carbon dioxide emission factors of different fuel types and processes. For the evaluation of the “Air Pollution Prevention Action Plan”, the energy structure adjustment and industrial structure adjustment measures were evaluated for the quantified implementation effect of synergy. The results are as follows. The CO₂ emission reduction synergistic effect of all implemented measures to reduce pollutants has a positive synergistic effect, which belongs to pollution emission reduction measures that should be actively encouraged and recommended. The measure to achieve the maximum synergy of CO₂ and SO₂ is to reduce the total coal consumption. In addition, the replacement of coal and oil by electricity, and the replacement of coal by natural gas can also achieve greater SO₂ emission reductions, but their CO₂ emission reductions are relatively small. Eliminating small-scale coal-fired boilers can achieve higher NO₂ and CO₂ emission reduction; eliminating outdated production capacity and dissolving excess capacity also have high synergy effects. The measure of energy consumption reduction has the highest SO₂ and CO₂ synergy evaluation index, followed by fuel substitution measures; the measure of eliminating coal-fired boilers has the highest NO₂ and CO₂ synergy evaluation index, followed by natural gas substitution of coal-fired measures; coal-fired alternative measures has the largest soot and CO₂ synergy evaluation index, followed by energy consumption reduction measures. The implementation of some measures for energy structure adjustment and industrial structure adjustment in the Air Pollution Prevention Action Plan from 2013 to 2017 achieved a reduction in SO₂ emissions of 22.65×10⁶ t, a reduction in NO₂ emissions of 6.56×10⁶ t, and soot emission reduction of 4.69×10⁶ t, while achieving CO₂ emission reduction of 1.46×10⁹ t, having a significant positive synergistic effect.

Transportation sector is one of the key sources of local air pollutants and GHGs emissions in China. Because of rising scale of transportation, the share of emissions from transportation increased compared with those from industrial and residential sources. This research applies an integrated CGE-CIMS model system to quantify the local air pollutants and CO₂ co-control effects of environmental economic policies in China’s transportation sector. Compared with BAU scenario, all environmental economic policy instruments, including environmental tax, carbon tax, fuel oil consumption tax and their policy combinations, will lead to electricity consumption substitution for gasoline, diesel oil and other petroleum products in China’s transportation sector. Even considering the indirect emissions caused by electricity power generation, the comprehensive emission reductions, indicated by Integrated Air Pollutant Co-control Emission Reduction (ICER), are still positive, meaning all environmental economic policies and their policy combinations have co-control effects. This research made policy suggestions for supporting the environmental economic policy implementation in transportation, including focusing on high emission vehicles, applying green transportation subsidies and low carbon electric power development.

Waterless printing technology, as one of the important technologies to replace the source of printing industry, is mainly suitable for publication printing, packaging printing and other plate printing, and has been widely used in the world. Taking a printing enterprise in Beijing as an example, the co-benefit evaluation of Volatile Organic Compounds (VOCs) and CO₂ emission reduction after the introduction of waterless printing technology at the enterprise level was carried out, and the data were obtained through field monitoring and open literature to conduct empirical research. The results are as follows. (1) Compared with the baseline scenario, the implementation of waterless printing technology and the installation of terminal treatment facilities can both reduce VOCs emissions, but the implementation of waterless printing technology has better emission reduction effect, and the emission reduction rate is about 60%. (2) After the implementation of waterless printing technology, the CO₂ emission is significantly reduced, but the installation of terminal treatment facilities will increase the CO₂ emission. (3) The source substitution technology represented by waterless printing can realize the synergistic emission reduction of VOCs and CO₂.

Industrial sectors characterized by high energy consumption are considered as important sources of atmospheric pollutants and greenhouse gases (GHGs). In order to facilitate the integrated management, this paper combined with the practice in the industrial sectors in Chongqing implemented by Ministry of Ecology and Environment, took NOx as a case pollutant to calculate and analyze the synergy effect between NOx removal and GHGs emissions in the industrial sectors. The results are as follows. The effect of NOx reduction by applying end-of pipe technology is negative to control GHGs, that is, the removal of 1 t NOx in the industrial enterprises will directly or indirectly increase CO₂ emissions by 1.811 t. The adoption of SNCR technology and the selection of ammonia and other non-urea denitration agents can help to reduce indirect CO₂ emissions from the process and electricity. In 2017, the reduction of NOx in Chongqing’s industrial enterprises increased CO₂ emissions by 525.7 kt, accounting for 0.3% of Chongqing’s total CO₂ emissions from energy activities. If the power emission factor is reduced by 1% or 5%, the synergetic degree of NOx reduction towards GHGs would be raised by 0.9% or 4.3%, respectively, and the synergistic effect of cement manufacturing is improved the most. It is essential to reduce the negative synergy effect of NOx removal technology by decreasing the use of urea and promoting the development of low carbon power.

It's of great significance to conduct research on the integrated control of air pollutants and greenhouse gases in the transportation sector, which will facilitate the realization of integrated management of energy, environment and climate change. In this study, the co-control of air pollutants and greenhouse gases in the transportation sector was chosen as the starting point to carry out future transport demand forecasts for different sub-sectors in China, such as road transportation, railways, civil aviation, inland shipping, and pipelines. The LEAP model was used to build BAU scenario, pollution reduction scenario, green low-carbon scenario, and enhanced low-carbon scenario on emission reduction technologies and policy choices. The simulation results indicate that energy consumption in the transportation sector will peak in 2037 under the enhanced low-carbon scenario and carbon dioxide emissions will peak in 2035. Under the green low-carbon scenario, carbon dioxide emissions will peak in 2040. Besides, it is essential to reduce air pollutant emissions from road transportation sector by taking effective actions, including eliminating old cars, promoting road-to-rail freight, encouraging road-to-waterway freight, and so on. Moreover, some energy structure optimization measures such as the development of hydrogen fuel and bio-jet fuel technology will further reduce pollutant emissions from the transportation sector. To achieve green and low-carbon development in the transportation sector, energy saving and carbon reduction measures, coordinated emission reduction measures should be respectively implemented for passenger and freight transport, and comprehensive policies are considered as an important guarantee for achieving peak goals in energy consumption and carbon emissions.

An evaluation was conducted on the co-control effect of energy-saving and emission reduction measures in the iron and steel industry. The results could be used to support the co-control planning of local air pollutants and greenhouse gases reductions. The emission factor method was used to calculate the emission reduction of various local air pollutants and greenhouse gases by different measures. Various emission reductions were then converted into Integrated Air Pollutant Co-control Emission Reduction (ICER). Co-control effects coordinate system, co-control cross elasticity, unit pollutant reduction cost and the marginal abatement cost curve were applied to examine the co-control effects for different measures. The results show that, in 2025, the 28 measures in the iron and steel industry can reduce SO₂ emission by 518.0 kt, NOx by 713.5 kt, PM10 by 290.7 kt, and CO₂ by 664 Mt. Except for end-of-pipe decarbonization and pollution reduction measures that do not have co-control effects, the other 25 measures have good co-control effectiveness. The “High-Temperature/High-Pressure Boiler Technologies for Coke (T3)” has the lowest cost, and the “Ultra-Low Emission Retrofitting (T28)” has the highest cost. Most energy-efficiency improvement measures, raw (fuel) material substitution measures can bring benefits (or reduce costs). Structural adjustment and energy-efficiency improvement measures have the greatest potential for emission reduction. In the future, the co-control technology development and co-control planning in the iron and steel industry should be strengthened to realize the optimization of the co-benefits of local air pollutants and greenhouse gases synergetic reductions.

Cement industry is a key sector for co-control of greenhouse gases and local pollutants. In the past, research on the industry’s co-control evaluations either was targeted at individual companies, or applied top-down and bottom-up simulation models in combination with scenario analysis to evaluate the industry’s co-control benefits. There is rarely research on systematic evaluation of the cement industry’s full range of energy-saving and emission reduction measures’ co-control effects. In the paper, a new index of Integrated Air Pollutant Co-control Emission Reduction (ICER) of 24 different measures is calculated. Co-control effects coordinate system, co-control cross elasticity, unit pollutant reduction cost and the marginal abatement cost curve are applied to examine the co-control effects for different measures. The results show that most energy-saving and emission reduction measures can synergistically reduce pollution; the greatest potential for emission reduction is from structural adjustment measures; the unit cost of energy efficiency improvement and energy-saving measures is relatively low, but the potential for emission reduction is limited. The analysis of the co-control performance of the energy-saving and emission reduction measures can provide a reference for the industry to carry out co-control path planning.

Large amounts of methane (CH₄) and nitrous oxide (N₂O) are released during the operation of sewage treatment plants, which are important sources of man-made greenhouse gas emissions. Based on 2005-2015 statistical data and IPCC accounting methods, the CH₄ and N₂O emissions from domestic sewage treatment plants in China from 2005 to 2015 were estimated, characteristics and influencing factors were analyzed. Three emission reduction scenarios (low emission reduction, medium emission reduction and high emission reduction) were set based on the carbon neutral background, and emission trends and temporal and spatial changes from 2020 to 2050 were estimated. The results showed that the greenhouse gas emissions of sewage treatment plants increased steadily from 2005 to 2015. CH₄ increased from 11.35 Mt CO₂e to 15.01 Mt CO₂e, and N₂O increased from 26.51 Mt CO₂e to 27.87 Mt CO₂e, the average annual growth rate was 2.8% and 0.5%, respectively. Under the three emission reduction scenarios, CH₄ and N₂O emissions from 2020 to 2050 show a trend of increase first and then decrease, and CH₄ and N₂O emissions under the low emission reduction scenario will peak in 2036 and 2025, respectively, with 24.31 Mt CO₂e and 28.19 Mt CO₂e; CH₄ peaks in the medium and high emission reduction scenarios will occur in 2027 and 2025, respectively, while the peak N₂O emissions will both occur in 2025. Compared with the low emission reduction scenario, the respective emission reduction rates of CH₄ emissions under the medium and high emission reduction scenarios are about 47% and 94% in 2050. N₂O emissions under the low, medium and high emission reduction scenarios in 2050 will be reduced by 12%, 53% and 95% respectively compared with 2015. There are significantly spatial differences in the emissions of CH₄ and N₂O. East China has the highest emissions and Northwest China has the lowest ones. The overall emission pattern is that the provinces in the southeast are higher than those in the northwest. Among the influencing factors, the level of economic development is closely related to greenhouse gas emissions.