能源替代政策能否改善空气质量——兼论能源定价机制的影响

Does energy substitution improve air quality: analysis from energy pricing mechanism

中国城市严重的空气污染与企业及家庭对燃煤的依赖密切相关。因此,以天然气等清洁能源替代燃煤被视为治理空气污染的重要手段。在能源替代政策的推进下,"煤改气"工程正在众多大城市如火如荼地进行。在此背景下,本文针对清洁能源替代问题进行经济学讨论,并对城市"煤改气"政策施行效果进行实证检验。本文首先利用包括西气东输等天然气长输管道项目作为外生冲击,考察了城市天然气供应对空气污染的影响。利用城市面板数据回归的结果发现,长输管道的联通对城市空气污染有显著地遏制作用,而这种作用在煤炭城市更为明显。在稳健性检验部分,利用城市液化石油气代替天然气进行安慰剂检验,发现天然气长输管道对于液化石油气的供给并没有显著促进作用,后者也未影响天然气替代煤炭对城市空气污染的减排效应。其次,在考察城市特征对天然气长输管道联通影响的基础上,考察途经城市是否存在选择效应,结果发现空气污染、煤炭消费等变量对管道联通均无显著影响,表明城市天然气管道联通并不存在明显的选择效应。在机制分析部分,进一步分析城市天然气管道长度、供应量与使用人口对空气污染的影响,发现天然气主要通过替代城市民用燃煤来遏制空气污染,对工业燃煤造成的污染则减排作用不明显。最后,从价格角度讨论了天然气难以通过替代工业燃煤遏制空气污染的可能原因,并分析了"煤改气"政策在现阶段的局限性。

Serious air pollution in China’s urban areas is closely related to firm’s and household’s coal consumption. Therefore,the replacement fire coal with natural gas and other types of clean energy is deemed to be the crucial means to control air pollution.Promoted by the energy substitution policy,the ‘coal to gas’ engineering is taking place like a raging fire in numerous big cities.Under this background,this paper carries out economic discussion about the issue of energy substitution policy and conducts empirical tests on the effect of the execution of the ‘coal to gas’ policy. The paper firstly uses the west-east natural gas long-distance pipeline project as exogenous shocks to investigate the effect of natural gas consumption on urban air pollution. Estimating with urban panel data,we find that city’s pipeline connection significantly reduces air pollution and it is more prominent in coal cities. As for the robustness test on the research result,this paper firstly carries out a placebo test through the substitution of the liquefied petroleum gas for natural gas. According to the test results,natural gas long-distance pipeline can’t significantly promote the supply of the liquefied petroleum gas. In addition,the latter doesn’t influence the reduction effect of the substitution of natural gas for fire coal on the city air pollution. Secondly,this paper also inspects the influence of the urban characteristics on the connection of natural gas long-distance pipeline to study whether the cities on the way of transportation can exert selection effect. The results show that the air pollution,coal consumption and other variables don’t have significant influence on the connection of the pipeline. Consequently,the connection of the natural gas pipeline won’t exert a significant selection effect. As for the mechanism analysis,this paper further analyzes the effect of city’s natural gas pipe lengthen,gas supply,and accessed population. By virtue of the data on the per capital industrial and civilian coal consumption as well as the data on various industrial and civilian air pollutants,we find that natural gas mainly substitutes urban civil coal consumption rather than industrial coal consumption to improve air quality. Finally,we discuss this difference from the aspect of natural gas pricing and analyze the limitation of ‘coal to gas’ policy at current stage.