Assessing the ammonia mitigation potential from the Indian agriculture sector for improving air quality in India

As an agrarian country, India heavily depends on fertilizers for food production to meet consumption demands, which contributes to a significant portion of global ammonia emissions. Ammonia is an essential precursor gas to form secondary PM_2.5 by reacting with SO₂ and NO₂ and degrades air quality significantly. Thus, it is imperative to implement mitigation strategies to reduce ammonia emissions from the agricultural sector for air quality improvement. In this study, we have updated the sub-sectoral agriculture activity data for each state of India, using 2022 as the base year. Ammonia emissions from each sub-sectoral activity for each state were estimated in the GAINS model for baseline and future scenarios under the current policy framework. We estimated the mitigation potential for ammonia emissions in agriculture by applying different alternate control scenarios. Under the current baseline scenario, the ammonia emissions (in Kilotons) from urea application are the highest among all the states, followed by other livestock such as sheep and horses, other cattle (Beef), dairy cattle, poultry, nitrogenous fertilizer use and production, and agricultural waste burning. The major contributor states to annual ammonia emissions (in Kt/yr) from urea application are Uttar Pradesh (625 ), followed by Andhra Pradesh (290.67) and Madhya Pradesh (271.32). The major contributor states to NH₃ emissions from livestock sectoral activities (other cattle, dairy cattle, sheep and horses, poultry, etc.) are Uttar Pradesh (827.73) followed by Andhra Pradesh (478.65) and Rajasthan (491.13). The NH₃ emissions (kt/y) from nitrogenous fertilizer production and consumption was highest from Uttar Pradesh (23.28), followed by Gujarat (10.86) and Maharashtra (10.44), while the contribution from agriculture waste burning was estimated largely from Uttar Pradesh (61.10), followed by Andhra Pradesh (32.91) and Tamil Nadu (30.04).  We consider several strategies, such as deep manure placement, low nitrogen feed, scrubber for livestock housing, urea substitution, neem-coated urea, and biochar additives to reduce NH₃ emissions and estimate their mitigation potentials in this work. To date, there are no specific regulations in India targeting agricultural ammonia emissions at the same level as those of other sector pollutants. Therefore, our results will be useful for policymakers for developing state-specific sub-sectoral mitigation strategies to address this critical issue.

Keywords: Ammonia, fertilizer, livestock, emissions, control scenarios