China tackles N2O emissions, leading change

Thanks to a governance approach that combines pollution control with climate action, China has seen the growth rate of anthropogenic emissions of nitrous oxide level off and steadily decline since 2013. N2O is a greenhouse gas far more potent than carbon dioxide.

China's experience shows that economic growth does not necessarily mean higher emissions of this heat-trapping gas.

The remarks were made on Saturday by Han Yinghui, associate professor at the University of Chinese Academy of Sciences' college of resources and environment, at an event on controlling non-carbon dioxide, or non-CO2, greenhouse gas emissions. The event was held at the Chinese pavilion on the sidelines of the 30th session of the Conference of the Parties to the United Nations Framework Convention on Climate Change, or COP30, in Belem, Brazil.

"N2O is decisive for achieving our temperature goals," Han said, highlighting the importance of anthropogenic N2O emissions control.

The Paris Agreement aim is to keep global temperature rise this century below 2 C above pre-industrial levels, with efforts to limit the increase to 1.5 C. Scientists increasingly agree that keeping global warming under 1.5 C is essential to avoid severe and catastrophic impacts.

As the third most significant long-lived greenhouse gas, N2O has a global warming potential nearly 300 times that of CO2 and remains in the atmosphere for more than a century, Han said. Globally, most N2O emissions come from agriculture, but energy, waste, and industrial sources also contribute. While agriculture produces the largest share, industrial sources offer the greatest potential for reduction.

Han noted that while developed countries have historically contributed the most cumulative N2O emissions, recent increases have mainly been from emerging economies in Asia. "This makes N2O governance a complex challenge, involving both historical emissions and current development needs and requiring global cooperation," she said.

China's progress, however, offers a hopeful signal. Han credited "synergistic governance" as the key to China's success.

To reduce nitrogen oxide emissions for cleaner air, China has widely adopted a technology called selective catalytic reduction, or SCR, in coal-fired power plants. The effort has resulted in 70 to 90 percent mitigation in the emissions of coproduced N2O in the sector.

"This represents a unified technical strategy for reducing air pollutants and greenhouse gases, and shows China's successful integration of climate goals into environmental management," Han said.

Her team also studied the link between provincial GDP and N2O emissions in China. "It shows a weak dependence, meaning that higher economic development does not automatically lead to more N2O emissions," she said.

China continues to advance N2O control. In September, authorities introduced an action plan targeting N2O emissions in the industrial sector. Proven technologies are already being applied, such as exhaust gas purification in adipic acid production, which removes more than 95 percent of N2O emissions while recovering the gas as a useful industrial product.

To encourage reductions, China is incorporating N2O data from the nitric acid industry into its national carbon trading system and promoting N2O mitigation projects under the China Certified Emission Reduction program. Under CCER, companies can earn carbon credits by taking actions such as expanding renewable energy and planting forests.

"China's validated industrial technologies are scalable and ready to be shared through cooperation platforms, helping others avoid carbon-intensive development pathways," Han said.

houliqiang@chinadaily.com.cn