The two grains are critical for food security in India, the second most populous country in the world and home to a quarter of all undernourished people globally.
“We wanted to understand the impact of India’s coal electricity emissions on its agriculture because there might be real trade-offs between meeting growing electricity demand with coal generation and maintaining food security,” said Kirat Singh, a PhD student in environment and resources in the Doerr School of Sustainability and lead author of the study in Proceedings of the National Academy of Sciences.
Clean air and food security
Past studies have sought to quantify overlooked costs of burning coal for electricity by estimating the number of deaths linked to resulting pollution. Government agencies and other organizations use these figures – and estimates of the economic value of statistical life – to understand the costs and benefits of various economic development strategies and environmental regulations.
Until now, however, estimates of crop damages specifically tied to coal-fired power stations – which supply more than 70% of electricity in India – have been lacking despite more than a decade of research showing that air pollutants such as ozone, sulfur dioxide, and nitrogen dioxide hurt crop yields.
“Crop productivity is incredibly important to India’s food security and economic prospects,” said senior study author David Lobell, the Benjamin M. Page Professor in the Doerr School of Sustainability’s Earth System Science Department. “We’ve known that improved air quality could help agriculture, but this study is the first to drill down to a specific sector and measure the potential benefits of reducing emissions.”
Crop damage concentrated in key regions and seasons
For the new study, the authors estimated rice and wheat crop losses linked to emissions of nitrogen dioxide, or NO2, from coal power stations. They used a statistical model that combines daily records of wind direction and electricity generation at 144 power stations in India and satellite-measured nitrogen dioxide levels over cropland.
The authors found coal power plants affected NO2 concentrations above cropland up to 100 kilometers, or roughly 62 miles, away. Eliminating coal emissions from all farmland within this range during key growing seasons (January-February and September-October) could boost the value of rice output across India by approximately $420 million per year and of wheat output by $400 million per year, according to the study.
“This study underscores the importance of looking at environmental issues under a systems lens,” said study co-author Inês Azevedo, a professor of energy science and engineering in the Doerr School of Sustainability. “Any policy focused on reducing emissions from coal power plants in India will be ignoring a crucial part of the problem if it does not consider the damages from air pollution to agriculture.”
In some states with high levels of coal-fired electricity generation, such as Chhattisgarh, coal emissions account for as much as 13-19% of the region’s nitrogen dioxide pollution, depending on the season. Elsewhere, like Uttar Pradesh, coal emissions contribute only about 3-5% of NO2 pollution. Other common sources of the gas, which results from burning fossil fuels, include vehicle exhaust and industry.
Broad benefits from emission cuts
The analysis reveals that the value of lost crop output is almost always lower than the mortality damage caused by any given coal power station. But the intensity of crop damage per gigawatt-hour of electricity generated can often be higher. At 58 of the 144 power stations studied, rice damage per gigawatt-hour exceeded mortality damage. Wheat damage per gigawatt-hour exceeded mortality damage at 35 power stations.
“It’s rare to find a single thing – in this case, reducing coal emissions – that would help agriculture so quickly and so much,” said Lobell, who is also the Gloria and Richard Kushel Director of Stanford’s Center on Food Security and the Environment.
The researchers found little overlap among the stations associated with the largest crop losses and those associated with the highest mortality. This means benefits from possible emission reductions in the future could be more significant and widely distributed than previously understood. According to the authors, the results highlight “the importance of considering crop losses alongside health impacts when regulating coal electricity emissions in India.”
“Well-targeted policies to cut emissions could deliver thousands of dollars of increased crop output for each clean gigawatt-hour, in addition to all the climate and human health benefits,” said Singh.
