Heating is a rigid need for warm winter in cold regions around the world. However, in recent years, with the improvement of living standard, the resulting problems of excessive energy consumption and severe air pollution have gotten worse. In 2016, in northern China alone, about 400 million tons of standard coal was used for heating, half of which was scattered coal[a]. The massive and insufficient combustion of coal in the heating season has led to a significant increase in pollutants such as PM2.5 and PM10 (Guo et al.,2019;Wei et al., 2020), which not only caused prolonged and large-scale severe haze weather (Tao et al., 2014), but also shortened life expectancy by 3-5 years (Chen et al., 2013; Ebenstein et al., 2017). In this context, it's imminent to transform energy consumption structure and promote clean heating.
The clean renovation in the heating field started early in developed countries. To get rid of the dependence on primary energy and reduce greenhouse gas (GHG) emissions, as early as 1990, European Union (EU) advocated higher building standards to improve the energy efficiency of heating (Cansino et al., 2011), and encouraged Member States to use renewable energy sources for heating and cooling (RES H&C, in Directive 2009/28/EC). After that, Germany and Britain proposed Market Incentive Programme for Renewable Heating (MAP) and Renewable Heating Incentive (RHI) respectively. Existing studies have confirmed that the above actions can reduce GHG emissions (Cilinskis et al., 2017) and probability of illness (Stefko et al., 2021). Christchurch in New Zealand also launched the Clean Heat Project (CHP) in 2003, replacing old solid fuel burners with cleaner heating techniques, which reduced PM10 by 41% on average (Scott & Scarrott, 2011). In China, Beijing started its first attempt in 2001. While launching the “coal-to-electricity” (CtE) and “coal-to-gas” (CtG) projects, it also paid attention to the promotion of clean technologies and the improvement of building energy efficiency. Up to 2010, the central area of Beijing had basically achieved coal-free heating, and PM2.5 had dropped by 11.94% (Liu et al., 2020).
Influenced by the Soviet Union, since the 1950s, with the Qinling Mountains - Huaihe River as the dividing line, China has formed the pattern of “central heating in the north and individual heating in the south”, which has continued to this day. Since 2010, excessive coal combustion and air pollution caused by winter heating in northern regions, have seriously affected the environment and residents’ health, which has aroused the concern of the Chinese government. Drawing lessons from the successful experience at home and abroad, and based on China's actual situation, in 2017, ten ministries and commissions jointly issued the “Winter Clean Heating Plan in Northern China (2017-2021)” (WCHP). It clarified the connotation and implementation approach of "Clean Heating" for the first time: clean heating refers to the low-emission and low-energy-consumption heating mode by using clean energy such as natural gas, electricity and solar energy through high-efficiency energy-using system, which involves three aspects, heat source, heat pipeline network and heat consumer terminals.
Under the guidance of WCHP, in order to promote the process of clean heating, China set up three batches of pilots in 2017, 2018 and 2019 respectively, with a total of 39 cities. Clean Heating Policy (CHP) was only implemented in pilot cities, not in other cities. CHP overcomes the limitations of previous actions. It emphasized the scientific choice of energy according to local conditions rather than specifying a certain source like CtE and CtG. Moreover, CHP is not limited to clean energy, but also includes energy-saving renovation in heating network and terminals. Therefore, CHP can provide reference for other countries that promote clean heating, and has practical significance and research value.
At present, the research on clean heating mainly includes three aspects. The first is to evaluate different clean heating technologies and choose an appropriate approach for a certain region (Zhang et al., 2017; Zhang et al., 2022). The second is to study the role and problems of policy subsidies. Since high cost of clean energy is the main obstacle to the implementation of clean heating (Wang et al., 2019), and free-riding behavior may exist in carbon reduction, subsidy is the main safeguard in practice (Gong et al., 2020). However, there are still some problems. For example, the incentive effect may disappear as subsidy stops (Yu et al., 2021) and differences in subsidy may also lead to heating poverty in less developed areas (Feng et al., 2021). The third is to measure the policy impact on energy, environment and health. Wu et al. (2020), Zhao et al. (2021), found CHP can reduce overall energy consumption and increase the share of clean energy. As a result, air quality can be effectively improved, resulting in a significant decrease in SO2, NOx (Yu et al., 2021; Weng et al., 2022). The reduction of pollutants will decrease the possible harm to human health, in this way CHP can also bring more health and economic benefits, and further increase the total social welfare (Zhang et al., 2019; Lin & Jia, 2020).
Although the existing literature has studied CHP from multiple perspectives, few attentions is paid to its impact on carbon emissions. In 2020, carbon emissions in China were 9.9 billion tons, accounting for 30% of the world[b]. As the global largest energy consumer and carbon emitter, reducing carbon emissions is crucial to China to combat climate change and achieve high-quality development. Whether CHP can exert a positive carbon reduction effect has become a hot topic. With the China Regional Energy System Model (C-RESM), Ma et al. (2021) explored the provincial heating transformation roadmap in northern China and the emission reduction effects under different scenarios. It is found that CHP will reduce carbon emissions by 38% by 2035, and if the limit of “2°C temperature rise” is superimposed on this policy, the reduction ratio can rise to 52%. Using equivalent heating value method, Han et al. (2018) calculated that replacing coal with natural gas for heating can reduce carbon emissions by 31.8 million tons. but compared with other pollutants, the reduction efficiency of CO2 is lower. Lin & Jia (2020) also verified the limited contribution of CHP to carbon reduction through the CGE model. However, the combination with other energy-saving policies, such as improving building energy efficiency, can improve the reduction effect. It can be seen that there are few studies about carbon emissions and has not reached a consensus. Most of them simply equate CHP with the transformation of energy structure, without considering the efficiency improvement of the heating network and terminals. Moreover, models and scenario setting method can’t take spatiotemporal dependence of carbon emissions into account and test the influence channels.
This study solves the above problems and constructs a dynamic spatial DID model to empirically study the carbon reduction effect of CHP and its influence channels. Contributions are as follows. Firstly, different from previous studies using model to predict, this study regards CHP as a quasi-natural experiment, and uses the DID model to quantify the policy impact from an empirical perspective. It is helpful for the government to formulate more reasonable plans based on the actual situation during the pilot period.
Secondly, considering the spatiotemporal characteristics of carbon emissions, this study constructs a dynamic spatial DID model to comprehensively describe the policy effect. It not only alleviates the endogeneity caused by the spatiotemporal dependence which has always been neglected, but also fits the reality more closely and enhances the explanatory power of the model. From the perspective of space and time, this study can provide the evidence for joint control and persistent efforts in carbon reduction.
Thirdly, this study further explores the influence channels. Starting from the three aspects emphasized by the policy, we verify whether the carbon reduction effect is mainly achieved through optimizing the energy structure, improving the thermal efficiency of heat pipeline network and heat consumer terminals. The clarity of influence channels is conducive to the government’s targeted management and improvement of the policy effectiveness. Conclusion and policy implications of this paper are also applicable in other countries, such as ensuring the energy supply, strengthening the construction of heat network and terminals, etc.
[a] Scattered coal is not used for centralized combustion. It has low combustion efficiency and produces huge pollution. The emission of scattered coal can reach 5-10 times that of thermal coal.
[b] Data source: BP statistical review of world energy 2021