Rice residue burning trajectories in Eastern India: Current realities, scenarios of change, and implications for air quality

Abstract

In 2019, the Government of India launched the National Clean Air Program (NCAP) to address the pervasive problem of poor air quality and the burdens it creates for public health, particularly in the 122 non-attainment cities that exceed national air quality standards. In much of Northern India, achieving and sustaining air quality improvements requires coordinated efforts to prevent agricultural burning of crop residues. Historically, rice residue burning has been most prevalent in Northwestern IGP (Indo-Gangetic Plain) but the practice is rapidly expanding into the populous Eastern IGP states, including Bihar, with uncertain consequences for regional air quality. This research has three objectives: (1) characterize historical rice residue burning trends since 2002 over space and time in Bihar State, (2) project future burning trajectories to 2050 under ‘business as usual’ and alternative scenarios of change, and (3) simulate air quality outcomes under each scenario to estimate public health burdens. Historical trends were modelled and extended to mid-century burning projections, which were coupled with the Community Earth System Model (CESM v2.1.0) to characterize air quality impacts under each scenario. These analyses suggest that contemporary Bihar State burning levels contribute a small daily average proportion (8.1%) of the fine particle pollution load (i.e. PM2.5, particles < = 2.5 μm) during the burning months, but up to as much as 62% on the worst of winter days in Bihar’s capital region. With a projected 142% ‘business as usual’ increase in burning prevalence anticipated for 2050, Bihar’s capital region may experience the equivalent of 30 PM2.5 additional exceedance days, according to the WHO standard, due to rice residue burning alone in the October to December period. If historical burning trends intensify and Bihar resembles the Northwest States of Punjab and Haryana by 2050, 46 days would exceed the WHO standard for PM2.5 in Bihar’s capital region.