Synthetic Gas Would Cut Air Pollution but Worsen Climate Damage in China

Chris Emery for the Office of Engineering Communications ・ Princeton Environmental Institute

Severe air pollution has plagued China’s industrial regions in recent decades, a situation that has received worldwide attention thanks to photos of Beijing and other smog-blanketed Chinese cities. 

More than just an eyesore, China’s smog has created a public health crisis that has led the Chinese government to declare a war on air pollution. In addition, as part of the Paris climate agreements, China has committed to peaking its CO2 emissions by 2030 or sooner. A new study led by researchers at Princeton University analyzes a conflict between these goals in China’s plans to use synthetic natural gas, a fuel derived from coal that is relatively free of conventional air pollutants but the production of which increases emissions of carbon dioxide, relative to direct coal combustion.

Using synthetic natural gas (SNG) instead of coal could improve air quality and public health by reducing illness and premature mortalities due to air pollution. But it would also markedly increase CO2 emissions because creating synthetic natural gas from coal produces more CO2 than burning the coal directly as fuel. The Princeton-led study recommends a way for China to maximize improvements in air quality while minimizing the additional CO2 emitted from the production and use of SNG.

The study, published April 24 in the Proceedings of the National Academy of Sciences, examined the impact of switching from coal to synthetic natural gas in three broad areas: electricity production, industry and residential use. The researchers found that switching to synthetic natural gas in industry and electricity production would have little impact on smog-related deaths and cause a major increase in CO2 emissions. However, switching from coal to synthetic natural gas for residential uses, such as heating and cooking, would substantially reduce deaths due to air pollution and cause less of an increase in CO2 emissions. In residences, many Chinese families burn coal in small stoves that are inherently inefficient and have uncontrolled emissions of air pollutants. By contrast, power plants and industrial operations burn coal much more efficiently and employ pollution-control devices that reduce emissions of health-damaging air pollutants. Thus, switching to SNG for electricity production and other industry results in a much smaller health benefit.