From paddy to pollution – Part I

In one of the previous blogs, we talked about Delhi’s air quality concerns, its seasonal trend, the source of pollution and critical pollutants. Now that we have identified the problem, in this two part series, we first dig deeper to find the root of the problem and then address it from an economic lens.

India has typically been an agrarian nation, with the North Indian state of Punjab being the “Granary of India”. While the state only accounts for 1.5% of India in terms of land area, 22% of rice and 39% of wheat for the central pool comes from the state of Punjab. Other than wheat (45%) and rice (36%), some of the other crops grown in this region include cotton (6.5%), maize (1.7%), sugarcane (0.9%) and pulses (0.25%), however their numbers have sharply reduced in comparison to rice and wheat (Figure 1). While today, Punjab is a rice-wheat mono-culture, this wasn’t always the case. Since rice and wheat both are nutrient intensive long-duration crops, it would be impossible for the farmer to grow both in one agricultural year. Hence, a Punjab farmer in the 50s-60s typically grew wheat with the other crop being maize, millet, cotton or pulse. Due to this agricultural history, the state of Punjab came to being known as the “Wheat bowl of India” or “India’s breadbasket”.  However, to make India food secure, the Green Revolution in the 1960s brought industrialization to the Indian agricultural sector and introduced short-period high-yield variety seeds for grains. This opened up the possibilities for the farmer to grow both rice and wheat in the same agricultural year. To further ensure food security, Govt. of India incentivized certain grains such as rice and wheat in the form of lucrative support prices, while the state Govt. of Punjab fully subsidized electricity for the agriculture. While these incentives pushed India to become agriculturally self-reliant, it came at the cost of some major ecological and environmental consequences.

Figure 1. Share of crops grown in Punjab (1960-2010)

The traditional farming practices of Punjab though wheat dominated were fairly diverse. However, the past few decades have transformed Punjab’s agriculture to rice-wheat mono-culture, with rice sown in summer months and wheat sown in winter months. Both of these crops are water intensive. A kilo of wheat consumes around 1000 liters of water, while the same amount of rice requires 4500 liters of water. And although the state of Punjab has one of the finest irrigation systems in India with 98.8% of crop land under irrigation, it falls under semi-arid region. The free power supply provided by the state Govt. of Punjab allowed for unabated extraction of groundwater to grow rice and wheat. This unchecked extraction lead to over-consumption of groundwater and what economists call – Tragedy of the Commons. Today, nearly 3/4th of Punjab has groundwater at “over-exploited level”, while the remaining 1/4th is under a “critical level”.

To mitigate rapid fall in groundwater level, the state government introduced the Subsoil Water Preservation Act in 2009. This act prohibited farmers from transplanting paddy before a notified date, thus shifting paddy from the summer (May – August) to the monsoon period (July – October), while any violators were liable to penalty. While the policy did succeed in bringing down the rate of drop in groundwater level, it shifted rice harvest extremely close to sowing period for wheat. With little time in hand and with no economic value of the paddy residue, the farmer simply burns any paddy waste (around mid-late October) causing huge spike in pollutant levels in the air. October, the month of paddy harvest also marks the onset of winter. And while some wheat residue is also burnt around May, the meteorological conditions in the winter with slow winds and temperature inversions further exacerbates the situation as pollutants settle over the North India leading to sever air quality issues for months. Figure 2 below plots Air Quality Index (AQI) variation over New Delhi for the past three years with a clear spike starting late September/early October.

Figure 2. AQI variation over New-Delhi (2017-19)

Lack of air quality has become one of the major concerns not only for Punjab but for the entire Indo-Gangetic Plane (Figure 3). Open field burning of crop residue emits carbon monoxide (CO), oxides of nitrogen and sulphur (N2O, NO2, SO2), methane (CH4) and particulate matter (PM10, PM2.5), all of which negatively affect human health. Burning a tonne of paddy residue produces 3 kg of particulate matter, 60 kg of carbon monoxide, and 1460 kg of CO2 along with other pollutants mentioned above. Some studies estimate 80-90% of the paddy residue in the state being subjected to open field burning, causing significant deterioration in air quality of the surrounding region. This, along with all the other  biomass burnt during the months of winter alone results in 120-140 µg/m3 spike in particulate matter concentration. The average particulate matter levels thus reach 375 µg/m3 during this period in New Delhi, against national standard of 60 µg/m3 and WHO standard of 20 µg/m3.

Figure 3. PM10 and PM2.5 concentration on October 28, 2019

This high concentration of particulate matter in the air has serious consequences to human health leading to premature deaths. Particularly susceptible are the young, the elderly, pregnant women, and patients with chronic lung and heart diseases. In addition, particulate matter also affects visibility and can also lead to eye, throat and skin related problems. These effects are evidenced by the increase in number of hospital visits during this period. The practice of open field burning also affects nutrient composition of soil, as the minerals present in the soil are lost in the process. Thus, the pursuit of agricultural progress and food security, the falling groundwater level and the efforts to mitigate it, and consequently the practice of burning paddy residue results in poor air quality. This poses significant cost to India that needs to be addressed. In the next blog, we will try to address this issue through the economic lens.

Some of the key references for this work include:
– Gupta, N., 2019. Paddy Residue Burning in Punjab: Understanding Farmers’ Perspectives and Rural Air Pollution.
– Kumar, P., Kumar, S., Joshi, L., 2015. Socioeconomic and Environmental Implications of Agricultural Residue Burning: A Case Study of Punjab, India.
– Sharma, M., Dikshit, O., 2016. Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi.
– Tripathi, A., Mishra, A.K., Verma, G., 2016. Impact of preservation of subsoil water act on groundwater depletion: the case of Punjab, India. Environmental management 58(1), 48-59.

Leave a Reply