While general awareness of worsening air quality in the Hindu Kush Himalaya (HKH) has risen in recent years, this attention has not translated into improved emission mitigation efforts from sources such as agricultural residue burning (or open burning). However, some recent work from ICIMOD is attempting to inspire improved efforts to reduce this harmful practice.
Open burning is common in the HKH and a convenient way for farmers to eliminate large quantities of crop residue. This practice also serves to prepare fields for the next crop cycle – wheat in spring and rice in summer. We find crop residue burning used widely across northern India (Bihar, Haryana, Punjab, Uttar Pradesh, and West Bengal) and southern Nepal (Janakpur, Kapilvastu, and Lumbini). The predominant cropping system in this region is rice–wheat rotation.
The prevalence of open burning is partly due to the mechanization of agricultural harvesting. Combine-harvesters typically leave copious amounts of organic debris in the fields and straw stalks that are 10 inches or longer. This straw doesn’t have much value except for feeding cattle and meeting occasional cooking and heating needs. So the easier method is to burn the residue. But in the process, the burning releases an unhealthy combination of pollutants, including fine particles, and gases such as methane, ammonia, nitrous oxide, carbon monoxide, and sulfur dioxide.
Manisha Mehra, a PhD fellow in ICIMOD’s Atmosphere Initiative, has been collecting data on open burning in the Lumbini district of Nepal. According to Arnico Panday, the Atmosphere Initiative Coordinator, Mehra’s study will be the first-ever attempt to measure the composition of smoke particulate matter emitted during post-harvest burning of crop residue.
To collect her data, Mehra is using aerosol filter samplers that will be sent to labs for chemical analysis. This data is complemented by surveys about land holdings in the area, the amount of wheat produced, and farmer estimates of how much residue they use for other household purposes. With this information, Mehra will be able to estimate the quantity of carbonaceous species produced as the result of open burning. Some carbonaceous aerosols are known to have cancer-causing properties.
Mehra’s data will be used to develop a regional emission inventory on crop burning in the near future. In this way, says Dr Siva Praveen Puppala, an ICIMOD scientist co-supervising Mehra, researchers will be able to characterize the chemical composition of open burning emissions, and assess its impact on the air quality in Lumbini.
The emission data collection in Lumbini will continue into 2018. Mehra says the same methods will be used to analyze more wheat residue, and mustard residue, as well.