Environmental impacts of modal shift to rail in Tangshan

China’s State Council seeks to reduce air pollution via several strategies, including shifting bulk freight transport from on-road heavy-duty vehicles, which are a major source of urban air pollution, to railroads and waterway. Accordingly, and because of the especially severe air pollution in the Beijing-Tianjin-Hebei region, the key industrial city of Tangshan will shift transport of all iron ore imports from the Tangshan port from truck to rail.

This study evaluates the environmental and energy performance of this strategy by comparing the fuel life-cycle emissions and energy use of various truck and rail technologies. Rail transport is generally more efficient for bulk transport, and we find the modal shift would eliminate 30,000 truck trips daily. However, as illustrated in the figure below, doing so with the current train fleet would reduce local emissions of nitrogen oxides (NO_x) but increase tank-to-wheel (TTW) emissions of particulate matter (PM). Additionally, when the upstream emissions are included, they are higher than those in the current truck fleet for PM and carbon dioxide (CO₂) on a well-to-wheel (WTW) basis.

Results also show that tighter emission controls on the railway system are required to match the environmental benefits that would be achieved by using China VI trucks. But with advanced emission control technologies, either for upstream emissions from electricity production or on rail engines powered by diesel, modal shift to rail in the electric train fleet with a cleaner grid and advanced diesel fleet scenarios would avoid a majority of the emissions associated with the transport of iron ore imports. This would also help meet the targets for an ultralow-emission steel production industry.

中国国务院目前正在寻求通过各种战略措施减少空气污染，这其中就包括将城市空气主要污染源之一的大宗货运从道路重型车运输转换至以铁路和水路运输为主。由于京津冀地区的空气污染问题严峻，在“公转铁”战略背景下，京津冀重点工业城市唐山将把集港铁矿石全部由卡车运输转为铁路运输。

此次研究通过对多种卡车和铁路技术的燃油全生命周期排放和能耗进行对比，对“公转铁”战略的环境和能耗性能进行了评估。整体而言，铁路运输在大宗货运方面具有很明显的能效优势，实施“公转铁”转换约可减少3万次卡车日常运输车次。然而，如下图所示，直接利用现有铁路系统进行“公转铁”转换能够减少唐山本地的氮氧化物（NOX）排放，但“油箱到车轮”（TTW）阶段的颗粒物（PM）排放却是有所增加的。另外，如果进一步考虑上游排放，当前铁路系统运输铁矿石的“油井到车轮”（WTW）阶段颗粒物（PM）和二氧化碳（CO2）排放会比目前卡车运输更高。

研究结果表明，要想获得与全部更换国VI运输卡车相仿的环境收益，需要加严对铁路系统的排放控制，如果能够从上游对电力生产加以排放控制，在下游对尚未电气化的柴油铁路机车应用先进的排放控制技术，则在“电气化铁路机车+清洁电网”和“先进柴油铁路机车”情景下，“公转铁”战略将能够大幅削减运输铁矿石所产生的污染物排放，也将有助于实现钢铁行业超低排放的目标。

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