According to new research led by researchers at Stanford University in the US, coal-fired power plants are quietly depleting India’s rice and wheat output, destroying up to 10% of the yield in several states.
The emissions from coal power plants include carbon dioxide, nitrogen oxides, sulphur oxides, fly ash, soot, suspended particulate matter, and other trace gases. These pollutants have been linked to smog, acid rain, eutrophication and various other environmental burdens.
An elusive link
In the new study, PhD student Kirat Singh and his colleagues turned the spotlight on the less explored consequences of nitrogen dioxide (NO2) on crop productivity.
The nitrogen oxides in general are an established side effect of India’s coal dependence. They are phytotoxic, meaning they stress plants, and have been known to hinder cellular function and interfere with crucial enzymatic activities. The oxides also contribute to the formation of ozone, which in turn exacerbates crop damage and produces particulate matter that limits the amount of sunlight available for photosynthesis.
“We know that coal-fired power plants contribute significantly to air pollution,” Singh said. “And we also know from past studies that various pollutants, including NO2, can negatively impact crop growth. But there hadn’t been a study linking the two in a systematic way at the power-plant level, particularly in India.”
Tracking plant health
To compensate for the lack of ground monitoring stations in agricultural areas, the researchers used data from satellite images to glean high-resolution insights into NO2 concentration across India. Since multiple power plants contribute to NO2 pollution across different distances, the researchers summed up all coal-attributable NO2 emissions reaching each location instead of isolating individual sources. This approach gave them a comprehensive picture of the amount of pollution to which agricultural regions were exposed.
Then, to estimate how NO2 from coal-fired power plants affected crop yield, the researchers turned to a satellite-derived vegetation index. They used a physical signal called near-infrared reflectance of vegetation (NIRv) as a proxy for plant health. NIRv measures greenness. Healthy crops are richer in chlorophyll, which can’t be detected by visible light but is sensitive to near-infrared light. So a higher percentage of near-infrared light is reflected by leaves in healthy plants.
Using pre-established coefficients, the researchers could link NO2 levels, measured by the TROPOMI satellite, to changes in NIRv. They used India-specific coefficients of 0.0006 for monsoon rice and 0.0007 for winter wheat. For every 1 mol/m2 increase in NO2, for example, the corresponding drop in NIRv was 0.0006 and 0.0007, respectively.
Prior research has already shown a linear relationship between NIRv and crop yield, allowing the researchers to directly estimate how much yield was lost due to pollution. They set a baseline NIRv of 0.007, representing zero crop growth, and calculated the percentage decrease in yield based on pollution-driven declines in greenness. This method helped them quantify the agricultural damage wrought by NO2 without requiring physical field measurements.
Blowin’ in the wind
They also analysed wind patterns to differentiate between pollution from coal plants from that from other industrial and environmental sources. This step helped the team unravel major differences in the effects of coal pollution across States.
For example, Chhattisgarh, a major hub for coal-fired power, had the highest share of NO2 pollution from coal plants: about 19% of NO2 detected in the monsoon season and 12.5% in winter came from coal plants.
Surprisingly, Uttar Pradesh had high overall NO2 levels but only a small portion of that came from coal power, while Tamil Nadu had relatively low NO2 pollution but the bulk of it came from coal power.
Coal’s contribution to air pollution thus varied by region. Not all power plants have the same impact: those located near fertile farmland with a high emissions exposure caused the most agricultural damage, Singh said.
An overlooked loss
Crop damage intensity — measured as monetised loss per gigawatt-hour (GWh) of electricity generated — for wheat and rice touched up to $17,370/GWh (Rs 15 lakh on February 6, 2025) and $13,420/GWh (Rs 11.7 lakh) respectively.
About 20% of coal-fired electricity generation during the monsoon season accounted for half of all coal NO2-related rice losses while 12% of total winter season generation was linked to 50% of wheat losses.
This suggested that targeting a relatively small subset of highly polluting power stations could still have significant benefits for agricultural productivity. To wit, as per the study, the yield of 5.7% of cropland in West Bengal near coal-fired power stations could increase 5-10% while the gains of 1.66% could exceed 10%. Similarly in Madhya Pradesh, the yield in 5.9% of cropland could increase 5-10% yield gains and another 11.9% could gain by more than 10%.
To compare, the annual yield growth for kharif rice and rabi wheat has averaged just 1.7% and 1.5% respectively between 2011 to 2020.
According to the study, India’s rice production could gain $420 million a year and wheat $400 million a year, roughly Rs 7,000 crore in total.
Expected yield gains from eliminating coal-attributable nitrogen dioxide concentrations in major rice- and wheat-producing states. Large tracts of cropland in all key states are expected to see yield improvements of 1% from eliminating coal-related NO2. Data from 2019 growing seasons.
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India and coal
As the 2025-2026 Economic Survey as well as energy experts have noted, coal power plays a crucial role in India’s growth at the moment. The 2025-2026 Union Budget has allocated 255% more for the Ministry of Coal over revised estimates of FY 2024-2025.
India’s demand for food is soaring as well. In 2024, the Global Hunger Index ranked India 105th out of 127 countries on food security. Rice and wheat are staple crops in India and in many parts of the world to which these grains are exported.
Singh said he hopes to inform policy reforms that will allow the coal and agricultural sectors to meet in the middle. “When you’re crafting policy around controlling pollution from the power sector, considering crop impacts alongside health and greenhouse gas emissions can help policymakers prioritise where that pollution control equipment should be installed,” he said.
“If you want to optimise the money that is being invested in installing all of this pollution-control equipment, you want to focus on power plants where it would bring the most benefit. Policymakers might find information in our research that could be helpful in terms of figuring out which power stations to prioritise,” he added.
Singh grew up in New Delhi and said its poor air quality motivated him to study the consequences of air pollution on human as well as crop health. In future, Singh is planning to further study how coal power plants affect agriculture at large in India, including the effects of other pollutants on crop productivity.
Ashmita Gupta is a science writer.
Published – February 27, 2025 05:30 am IST