The Burning Issue: Why it’s so urgent to stop burning agricultural residues in the Indo-Gangetic Plain and Himalayan Foothills of South Asia

South Asia has the highest population-weighted pollution concentration in the world (HEI-Report, 2020), and the Indo-Gangetic Plain (IGP) and Himalayan Foothills (HF) of South Asia is the region’s pollution hotspot.

The impacts of these emissions are manifold.

The health impacts of toxic air are so stark that they alone provide the imperative for action.

Globally, every year, over eight million people die as a result of diseases caused by breathing polluted air (including respiratory and cardiovascular illnesses IHME, 2024), making it the leading environmental threat to human health (World Bank, 2020).

In South Asia, air pollution is currently the second-leading risk factor for adverse health outcomes and the third-leading risk factor for premature deaths. It accounts for 11% of premature deaths and results in 40 million disability-adjusted life years, with the majority of the disease burden attributed to particulate matter (PM) (S. A Jabbar et al, 2022).

It’s also been proven to cause cognitive impairments, including in children’s brain development and educational attainment. This means that breathing pollution of the severity we routinely see in this region when young can cause changes to cognition and examination achievements that ricochet down a child’s entire life course.

Pollution in South Asia also disrupts everyday life and livelihoods. It causes schools and public spaces to close, the grounding of vehicular and air transport, and construction work to stop. The hit to the region’s Gross Domestic Product (GDP) is also significant.

Less well-publicised perhaps, in this region at least, is the link between air pollution and temperature rise.

It has just been confirmed that 2024 was the first time that temperatures worldwide passed 1.5ºC above preindustrial times.

We know the Hindu Kush Himalayan region is warming at double the global average, with frightening implications for regional water, food, and energy security due to the losses such warming causes to the region’s vitally important frozen water stores.

Air pollution accelerates these losses in two ways.

First, a significant percentage of air pollution in this region is composed of greenhouse gases (GHGs). These regional pollutants – carbon dioxide (CO₂), non-methane volatile organic compounds (NMVOCs), carbon monoxide (CO), black carbon (BC), nitrous oxide (N₂O) and methane (CH₄) – contribute to long-term warming, accelerating cryosphere losses and intensifying extreme precipitation and other weather events, including heatwaves, and droughts.

Secondly, regional pollutants add to the already-accelerating melting of glaciers in the short term too, with sooty deposits, called ‘black carbon’, from combustion being carried long distances and settling on top of glaciers. These deposits darken snow and ice – transforming white surfaces so the cryosphere absorbs, instead of reflects, heat from the sun’s rays.

It has also been proven, in a cruel irony, that air pollution can actually impede the transition away from fossil fuels – limiting the effectiveness of solar panels by blocking sunlight and dirtying solar panels that should be able to power the urgent shift away from planet-warming combustion.

While a variety of combustion sources contribute to South Asia’s now world-renowned toxic air, smoke from burning agricultural residues is one of the biggest sources, particularly during the pre-monsoon (March, April, May) and post-monsoon (October, November) seasons. With everything we now know about the impacts of continued incineration, taking action to curtail this practice should now be a top priority for policymakers, environmentalists, stakeholders, and agricultural bodies. So, how did the burning of agricultural residues become so prevalent, and what can we do to reduce it?

Smog – the byproduct of a leap forward in farming in the Indo-Gangetic Plain-Himalayan Foothills (IGP-HF)

The IGP-HF comprises 13.5 million hectares, which span Bangladesh, India, Nepal, and Pakistan.

The rich water resources of the Indus and the Ganges rivers make these regions among some of the most intensely farmed areas on the Sub-continent, and the four largest contributors to emissions from agricultural waste, Bangladesh, India, Nepal, and Pakistan, are hugely dependent on farming. The farming sector contributes 24% to Pakistan’s GDP, is the largest source of livelihood in India, and engages 66% of the population in Nepal and nearly half of the population in Bangladesh.

Until the middle of the 20th century, in this region, farmers used agricultural residues as animal feed, fodder, fuel, roof thatch, and mulch for packaging and composting or fertiliser for the soil, with just a small amount burnt in fields.

Burning agricultural residues on the scale now seen is an unintended byproduct of the 1960s Green Revolution, which saw the introduction of faster-cropping cereal varieties and mechanised farm tools.

These new crops and technologies, while boosting productivity and yields, resulted in shorter cropping windows and faster harvesting cycles, meaning that the burning of agricultural residues became an expedient way to clear the ground after harvests, especially in October and November, to make way for a second planting.

A number of sources continue to label the burning of agricultural residues as ‘agricultural waste burning’, though even this nomenclature contributes to continuation of the harmful practice. As noted by the World Bank (Cassou, 2018), “Burning, for example, can be held in place by the notion that crop residues are a form of waste, rather than a resource, and the customary belief that burning is the least costly way of removing a cumbersome waste stream. The idea that crop residues are a waste stream can also minimise the feeling of loss associated with burning.”

As well as the opportunity to fit two or more crops into one calendar year, the practice also continues to be fuelled by:

1. a misconception that burning residues increases soil fertility by replenishing soil nutrients when this is scientifically proven to be untrue (SAARC, 2019)
2. a belief that alternative ways to dispose of crop residue, such as making biochar, are expensive or unavailable (SANDEE_Policy_Brief). In fact, these approaches have the potential to generate income
3. a lack of resources or logistical facilities to transport residues for processing (for bioenergy production or animal feed)
4. a lack of awareness of the full environmental, climate, and health impacts of burning agricultural residue.

The chemical composition of smoke from burning agricultural residues

Burning agricultural residues can feel like a quick fix. However, such combustion unleashes a combination of substances – including planet-heating GHGs, suspended particles (aerosols), most of which are known or suspected carcinogens, and toxic compounds and heavy metals that deplete the ozone layer and can form secondary GHGs (Mehta & Badegaonkar, 2023; Lin et al., 2022; Bhuvaneshwari et al., 2019).

In the wider South Asian context – which also covers Afghanistan, Bhutan, Maldives, and Sri Lanka in addition to the countries of the IGP-HF – the gas pollutants produced through burning are:

• by far the largest, at 70%, CO₂ –a GHG, contributes to temperature rise and extreme weather events
• 11% NMVOCs – harmful to human health, which can also produce secondary GHGs like surface ozone (O₃)
• 7% CO – linked to health impacts like headaches, dizziness, confusion, and linked to formation of O₃
• 2.1% N₂O – a GHG, ozone depletion can lead to increased UV exposure, contributing to skin cancer and cataracts
• 0.66% CH₄ – a very potent GHG, contributes to the formation of O₃ and harmful to human health.

The region’s emissions from crop residue burning also release PM – suspended particles, also known as aerosols, that are particularly linked to adverse health effects. In South Asia, the burning of agricultural residues releases:

• 70% PM, measuring 2.5 micrograms in diameter (PM_2.5) – the most dangerous for respiratory diseases. PM_2.5 exacerbates conditions such as asthma and chronic obstructive pulmonary disease (COPD), also contributing to haze and reducing visibility.
• 40% BC – a short-term climate forcer, BC deposits on snow and ice, reducing surface reflectivity and accelerating melting

Agricultural residue burning by country

Bangladesh: Agricultural residue burning is responsible for 39% of Bangladesh’s total emissions (WRI CAIT, Mehta & Badegaonkar, 2023). Open burning of rice straw is not currently widely practised in Bangladesh, as crops continue to be mostly harvested manually, with residual straw tending to be ploughed back into the ground. Recently, however, with the rise in the use of combine harvesters and reapers, more farmers are burning residues. Farmers in Bangladesh choose to burn long types of straw, such as the residue of Aman rice, in the low-lying areas of the country. In 2020–21, 73.36 million tonnes of agricultural residue were produced, out of which 0.22 million tonnes were burnt.

Figure 1: Open burning of agricultural residues is still a major challenge throughout the IGP-HF despite strict regulations and grave concerns about air pollution. Photos: Chimi Seldon/Anil Maharjan, ICIMOD

India: India is the second-largest crop producer in the world (FAO), producing around 500 million metric tonnes (MT) of agricultural residues annually, of which 100  MT are burnt. According to the Economy Survey of India, 2020, the total amount of agricultural residue generation in India rose from 80  MT in 1950–1951 to 520 MT in 2017–2018 (Lan et al., 2022). Since the early 2000s, there has been a rise in the burning of agricultural residues, which has led to PM_2.5 levels that are 15–45 times higher than the safety standards set by the World Health Organization (WHO). Between 2003 and 2019, burning agricultural residues caused 44,000 to 98,000 premature deaths annually owing to PM exposure in Punjab, Haryana, and Uttar Pradesh (Lan et al., 2022). Recent data shows that the Air Quality Index (AQI) over Delhi ranges between unhealthy and hazardous levels, which severely impacts people’s health, transportation, well-being livelihoods, etc.

Nepal: 52% of Nepal’s total GHG emissions in 2013 came from agriculture (both burning of agricultural residues and enteric fermentation from livestock Mehta & Badegaonkar, 2023). Burning of agricultural residues continues to rise in Nepal, increasing from 2,280 gigagrams (Gg) in 2003–04 to 2,908 Gg in 2016–17, which represents a 25% rise. Over 90% of residue burning in Nepal takes place in the Terai region, the southern part of the country and its main rice-growing area. According to Das et al (2023), as with Bangladesh, one reason for the rise in agricultural stubble burning is the adoption of modern agricultural equipment like combine harvesters.

Pakistan: 20% of Pakistan’s emissions come from the agriculture sector. Between 2000 and 2014, the aggregate amount of crop residues from four crops (rice, wheat, sugarcane, and maize) was 757,000 Gg, of which, approximately 228,000 Gg was incinerated in the field (Azhar et al., 2019;Raza, M. H., 2022). Air pollution causes more than 22,000 premature adult deaths (Iqbal, M.P., 2024) in the country each year. In the  last two weeks of October 2024  , the country has withstood acute air quality spikes, with AQI in Lahore hitting unhealthy to hazardous level. On November 15, Lahore recorded AQI of nearly 1,600 making it the most polluted city in the world. Government measures to avoid hospitalisations include shutting schools, airports, and highways, with a significant impact on GDP.

The way ahead

South Asia consists of approximately 57 percent of arable or agricultural land, and around 60 percent of the population is involved in farming (FAO).

Burning rice stubble continues to be a common practice for millions of farmers in the region, especially across the IGP-HF.

Given the large population sizes involved, transforming emissions from the burning of agricultural residues in the IGP-HF region will require a huge collective effort.

A wide array of stakeholders – from researchers, policymakers, businesses, and beyond – are already working hard to advance this work: from prototyping, scaling, incentivising, and marketing solutions to creating the right regulatory environment to support change and generating the evidence base to inform decision-making.

This work could not be more urgent, and with burning of agricultural residues such a significant contributor to total emissions in the region, tackling the practice is a key route for countries to meet their commitments under the 2015 Paris Agreement and other agreements, as well as meet citizens’ expectations for improved living and health standards.

ICIMOD continues to stand by to support policymakers and other stakeholders in its regional member countries in clearing the air.

A footnote on our analysis of agriculture residue burning

We used the information from the CAMS Global Fire Assimilation System (GFAS) to make an estimate of the number of pollutants that were released into the atmosphere by fires over the IGP-HF during the month of October 2024. This was done so that we could better comprehend the effects of burning. The fire radiative power (FRP), the dry matter burned, and emissions from biomass burning are all components of the GFAS data output for a wide variety of chemical, GHGs, and aerosol species that are available at a horizontal resolution of 0.1 degrees beginning in 2003 and continuing onward. With the help of the Emissions Database for Global Atmospheric Research (EDGAR) version 8.1 datasets, we determined the emissions from burning of agricultural residues of CH₄, NH₃, NO_x, PM_2.5, and NMVOC for 2022 for the countries of Bangladesh, India, Nepal, and Pakistan. All countries except Bangladesh show the highest emissions of PM_2.5 followed by NMVOC, but in Bangladesh, NMVOC emission is more than PM_2.5.

Table 1: Edgar v8.1 Emissions of pollutants from burning of agricultural residues in 2022

Furthermore, we made use of the real-time fire detection data and information that was provided by the Geo-KOMPSAT-2A (GK2A), which is a geostationary (GEO) satellite managed by South Korea. This satellite is capable of providing high-resolution pictures with a variety of spectral bands, such as visible, near infrared, and thermal infrared. These bands are helpful for monitoring atmospheric phenomena, land surfaces, and fires. The Advanced Meteorological Imager (AMI) instrument onboard GK2A provides continuous observation of fire events in real-time and detection of fire hotspots at intervals of 10 minutes during the daytime. In addition, it provides a combined product that can recognise smoke, cloud cover, and flames that are medium to large in size. On the other hand, its spatial resolution, which is less than 4km across the Hindu Kush Himalaya (HKH), makes it difficult for it to identify smaller fires in the area.

In comparison, we also take into account the satellites that are in low earth orbit (LEO), which are known as the Visible Infrared Imaging Radiometer Suite (VIIRS) and the Moderate Resolution Imaging Spectroradiometer (MODIS). These satellites are responsible for providing global fire detection products. MODIS, which is carried by NASA’s Terra and Aqua satellites, and VIIRS, which is carried by the Suomi NPP and NOAA-20 satellites, both collect data in spectral ranges that are comparable to one another. These ranges include thermal infrared bands, which are sensitive to the heat that is released by fires. To detect small-scale fires that GK2A is unable to detect, MODIS and VIIRS combined data products that have a spatial resolution of 1 km and 375 metres are used, respectively.

Figure 2.1 illustrates the spread of fires that occurred throughout the IGP-HF region from 1–25 October 2024. This particular time was selected since a large-scale emission from fires and burning was taking place in various regions at the time. For instance, the Indian Agricultural Research Institute reported that the state of Madhya Pradesh, in central India, had the largest number of stubble-burning cases, totalling 536, between the dates 19–25 October 2024. Punjab had 410 cases, and Haryana had 192 cases.

Figure 2.2 presents the RGB (red, green, and blue) true-colour imagery captured by GK2A-AMI, which depicts haze and smoke over the IGP-HF – features that are strongly associated with ongoing fires. This imagery offers a clear visualisation of the atmospheric effects caused by fire activity, illustrating how toxic gases/pollutants from fires contribute to reduced air quality and visibility over the affected areas.

Figure 3 demonstrates that regions that are classified as fire hotspots are responsible for emissions and contribute to an increase in the background concentration of pollutants. Within the scope of this analysis, we focus on the emissions of NH₃, CH₄, BC, and PM_2.5 that are produced by fires. However, there are additional pollutants that are released during fires that influence the air, ecology, and health.

Acknowledgment

This impact analysis was conducted using the GK2A-AMI and MODIS/VIIRS satellite data accessed through SERVIR-HKH. Additionally, data was used from the freely accessible emission inventories, including the Emissions Database for Global Atmospheric Research (EDGAR), Copernicus Atmosphere Monitoring Service (CAMS), Global Fire Assimilation System (GFAS), and ICIMOD AQ Monitoring System.  

The author would like to thank Arun B. Shrestha, Bertrand Bessagnet, and Bhupesh Adhikary for their review and guidance, which helped to do this analysis. The author would also like to thank the ICIMOD communication team, mainly Annie Dare, Gillian Summers, and Chimi Seldon, for editing.

References

Abdul Jabbar, S., Tul Qadar, L., Ghafoor, S., Rasheed, L., Sarfraz, Z., Sarfraz, A., Sarfraz, M., Felix, M., Cherrez-Ojeda, I. (2022). Air quality, pollution and sustainability trends in South Asia: a population-based study. Int J Environ Res Public Health. 2022 Jun 20;19(12):7534. doi: 10.3390/ijerph19127534.

Azhar, R., Zeeshan, M., & Fatima, K. (2019). Crop residue open field burning in Pakistan; multi-year high spatial resolution emission inventory for 2000–2014. Atmospheric Environment, 208, 20-33.  https://www.sciencedirect.com/science/article/abs/pii/ S1352 23 1019 30202X

Bhuvaneshwari, S., Hettiarachchi, H., & Meegoda, J. N. (2019). Crop residue burning in India: Policy challenges and potential solutions. International Journal of Environmental Research and Public Health, 16(5), 832. https://pmc.ncbi.nlm.nih.gov/articles/PMC6427124/

Cassou, E (2018). Field Burning (English). Agricultural Pollution. Washington, D.C., World Bank Group. http://documents.worldbank.org/curated/en/989351521207797690/Field-Burning

Das, B., Puppala, S. P., Maharjan, B., Bhujel, K. B., Mathema, A., Neupane, D., & Byanju, R. M. (2023). Crop residue burning and forest fire emissions in Nepal. In Vegetation fires and pollution in Asia (pp. 71–84). Cham: Springer International Publishing. https://link.springer.com/chapter/10.1007/978-3-031-29916-2_5

Iqbal, M.P., 2024. Air Pollution: Challenges to Human Health in Pakistan. Journal of the College of Physicians and Surgeons--Pakistan: JCPSP, 34(5), pp.507-508.

Lan, R., Eastham, S. D., Liu, T., Norford, L. K., & Barrett, S. R. (2022). Air quality impacts of crop residue burning in India and mitigation alternatives. Nature Communications, 13(1), 6537. https://www.nature.com/articles/s41467-022-34093-z

Lin, M., & Begho, T. (2022). Crop residue burning in South Asia: A review of the scale, effect, and solutions with a focus on reducing reactive nitrogen losses. Journal of Environmental Management, 314, 115104. https://www.sciencedirect.com/science/article/pii/S0301479722006776

Liu, T., Mickley, L. J., Singh, S., Jain, M., DeFries, R. S., & Marlier, M. E. (2020). Crop residue burning practices across north India inferred from household survey data: Bridging gaps in satellite observations. Atmospheric Environment: X, 8, 100091. https://www.sciencedirect.com/science/article/pii/S2590162120300319

Mehta, C. R., & Badegaonkar, U. R. (2023). Sustainable management of crop residues in Bangladesh, India, Nepal and Pakistan: Challenges and solutions. United Nations Economic and Social Commission for Asia and the Pacific (UNESCAP). https://www.unescap.org/kp/2023/sustainable-management-crop-residues-bangladesh-india-nepal-and-pakistan-challenges-and#

Raza, M. H., Abid, M., Faisal, M., Yan, T., Akhtar, S., & Adnan, K. M. (2022). Environmental and health impacts of crop residue burning: Scope of sustainable crop residue management practices. International Journal of Environmental Research and Public Health, 19(8), 4753. https://www.mdpi.com/1660-4601/19/8/4753

https://www.saarcenergy.org/wp-content/uploads/2022/01/09-12-2021-Possible-Uses-of-Crop-Residue-for-Energy-Generation-Instead-of-Open-Burning-Final.pdf