Rail News


October 27 , 2021

China’s vast high-speed rail is a big emitter but down the line leads to greener freight: study

South China Morning Post 
26 October 2021 (China)

  • When passengers opted out of slower trains in favour of high-speed rail, road freight moved to fill the much greener conventional trains
  • Beijing-Shanghai line led to the highest overall drop in greenhouse gas emissions – more than 3 million tonnes per year on average – according to paper

China’s rapid expansion of high-speed rail has indirectly cut greenhouse gas emissions by creating capacity for freight on conventional trains, according to a new study.

Electricity-powered high-speed rail (HSR) produces more emissions than cars on highways and conventional railway in China where coal power dominates electricity production.

However, the network’s massive growth between 2008 and 2016 has led to an annual reduction in greenhouse gas emissions (GHG) equal to about 11 million tonnes of carbon dioxide – or 1.33 per cent of China’s total transport sector emissions – compared with the pre-high-speed rail era.

When passengers opted out of the slower conventional trains in favour of high-speed rail, road freight moved to fill the much greener conventional trains, causing a drop in emissions, according to the researchers.

China, the world’s biggest energy user and greenhouse gas emitter, has been expanding its high-speed railway network in the past decade to connect major cities, with 38,000km of rail operating by the end of 2020, compared with 19,800km in 2015.

The flow of passenger vehicles on highways dropped 18.5 per cent, while that of goods vehicles fell by about 14.5 per cent following high-speed rail connection, analysis of new passenger and freight traffic data from all highways and national roads in China from 2009 to 2016 showed.

“Since HSRs are not designed for freight transportation, one likely explanation is that the opening of HSRs has helped relieve some of the capacity on conventional rail lines, which serve a mixture of both passenger and freight transportation,” the researchers wrote in an article published in the peer-reviewed journal Nature Climate Change on Monday.

For example, the opening of the Wuhan-Guangzhou HSR line lifted the annual freight capacity of the parallel conventional railway by 87.6 million tonnes, and 84 million tonnes on the Shanghai-Nanjing HSR line, which combined translates to 5 per cent of national freight volume in 2010, according to the study.

Among high-speed railways, the Beijing-Shanghai line led to the highest overall drop in greenhouse gas emissions – more than 3 million tonnes per year on average – the study found.

Carrying the same weight over the same distance, the high-speed railway may emit more than twice as much as cars on highways, more than four times as much as road goods vehicles, or about 70 times as much as the conventional railway, according to the study.

“At first glance, these estimates might appear counterintuitive, but they are less surprising if we consider the structure of electricity production in current China,” the researchers said.

“The GHG-emission level of HSR is highly dependent on the supporting electricity grid system. However, GHG emissions from electricity production are very high in China because of the dominance of coal power,” they said, pointing out that thermal power accounted for around 70-80 per cent of total electricity production in China.

“HSR’s potential in decarbonising the transport sector in China is constrained by the country’s current power-generation structure,” the researchers in mainland China, Hong Kong and Singapore said.

But the situation could change as China shifted towards generating electricity from cleaner sources, they said.

The researchers predicted that if China adopted France’s electricity structure of 70 per cent nuclear power, the overall greenhouse gas emission reduction from the system could almost double to more than 26 million tonnes of carbon dioxide equivalent, or about 3 per cent of China’s transport sector’s emissions.

Similar hypothetical big reductions could also be seen when considering the electricity structures of Canada and Denmark, which are dominated by hydro and wind power respectively, according to the predictions.

Corresponding author Qin Yu, an associate professor in the department of real estate at the National University of Singapore, said the high-speed rail network would continue to be key to China’s economy.

“High-speed rail is more than an important form of transport in China. It also boosts the economy by encouraging investments and attracting talent to different parts of the country. As China expands the network it should take its environmental impacts into account, which our study shows are positive.

“With cleaner electricity conditions, the network can contribute more to, rather than hinder, carbon reduction from the transport sector,” she said, referring to China’s goals of hitting peak carbon emissions by 2030 and carbon neutrality by 2060.


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