China is attempting a shift from coal to natural gas in an effort to address the country’s severe air pollution. A new study shows that although such a switch generally has benefits for air quality, carbon mitigation, and water stress, some options may in fact increase carbon emissions and water consumption.
A team of researchers from the International Institute for Applied Systems Analysis (IIASA), Princeton, and the University of Maryland investigated the environmental impacts of transitioning from coal to natural gas in China, exploring implications on air quality, carbon mitigation, and water stress by 2020.
The findings, published in Nature Sustainability, warn that the use of coal-based synthetic natural gas (SNG) would increase carbon emissions and water demand, especially in regions of China that already experience high per capita carbon emissions and water scarcity.
The researchers found that a switch from coal to other natural gas types does produce air, carbon, and water co-benefits when methane leakage, a powerful greenhouse gas, is well controlled. There are however trade-offs when it comes to the degree of improvements for air quality and water scarcity, depending in which sector the natural gas is used to substitute for coal, and where that substitution takes place.
The study is among the first to analyse the interactions between air quality, carbon emissions, and water use in both energy production and consumption, and highlights the need for an integrated, strategic approach when reshaping energy systems. While the study focuses on China, its general conclusions are widely applicable.
Assessments on local, regional, and global levels
“Assessing air quality, carbon emissions, and water scarcity impacts across local, regional, and global levels is crucial to capturing potential co-benefits while avoiding unintended consequences,” says study first author Yue Qin, who started working on the research as a participant in the 2016 Young Scientists Summer Program (YSSP) at IIASA before returning to Princeton University as a doctoral candidate. She is currently a postdoctoral scholar at the University of California, Irvine.
The researchers set out to analyse the relationship between the energy industry and its effects on air quality, carbon, and water. These environmental issues are frequently addressed individually, but the energy sector affects each area in distinct ways and energy policies can bring either co-benefits or dis-benefits. The team was specifically interested in the broader environmental implications of moving from coal to natural gas, which has global implications for sustainable development.
Increased carbon emissions and water consumption
To understand the environmental impacts of such a switch, the researchers combined an energy production/use lifecycle analysis, which charts a product’s life from start to finish, with an integrated environmental impact assessment. They found that although replacing coal with natural gas generally has benefits for air quality, carbon mitigation, and water stress, coal-based synthetic natural gas increases carbon emissions and water consumption, particularly in China’s northwestern provinces, which already suffer from high per capita carbon emissions and severe water scarcity.
“Importantly, as the regions with high air pollution do not overlap with regions with high water stress, and substitution in different sectors bring different levels of air quality and water impacts, there are trade-offs in the magnitude of air quality and water improvements,” explains Qin. “Our findings show why it is critical to understand the underlying air-carbon-water synergies and trade-offs so that China and other developing countries, can properly design clean energy transition pathways according to their local environmental priorities”.
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