Context:

• Nitrogen particles make up the largest fraction of PM2.5, the class of pollutants closely linked to cardiovascular and respiratory illness, says the first-ever quantitative assessment of nitrogen pollution in India. The Indian Nitrogen Assessment assesses the sources, impacts, trends and future scenarios of reactive nitrogen in the Indian environment.

Other facts & findings:

• While the burning of crop residue is said to be a key contributor to winter smog in many parts of North India, it contributes over 240 million kg of nitrogen oxides (NOx: a generic term for the nitrogen oxides that are most relevant for air pollution, namely nitric oxide and nitrogen dioxide) and about 7 million kg of nitrous oxide (N2O) per year.
• Though agriculture remains the largest contributor to nitrogen emissions, the non-agricultural emissions of nitrogen oxides and nitrous oxide are growing rapidly, with sewage and fossil-fuel burning — for power, transport and industry — leading the trend.
• Indian NOx emissions grew at 52% from 1991 to 2001 and 69% from 2001 to 2011.
• Annual NOx emissions from coal, diesel and other fuel combustion sources are growing at 6.5% a year currently, the report says.
• As fertilizer, nitrogen is one of the main inputs for agriculture, but inefficiencies along the food chain mean about 80% of nitrogen is wasted, contributing to air and water pollution plus greenhouse gas emissions, thereby causing threats for human health, ecosystems and livelihoods.

Agricultural soils

• Contributed to over 70% of N2O emissions from India in 2010, followed by waste water (12%) and residential and commercial activities (6%).
• Since 2002, N2O has replaced methane as the second largest Greenhouse Gas (GHG) from Indian agriculture.

Chemical fertilizers:

• Chemical fertilizers (over 82% of it is urea) account for over 77% of all agricultural N2O emissions in India, while manure, compost and so on make up the rest. Most of the fertilizers consumed (over 70%) go into the production of cereals, especially rice and wheat, which accounts for the bulk of N2O emissions from India.

Cattle emissions

• Cattle account for 80% of the ammonia production, though their annual growth rate is 1%, due to a stable population.
• India is globally the biggest source of ammonia emission, nearly double that of NOx emissions.
• But at the current rate of growth, NOx emissions will exceed ammonia emissions and touch 8.8 tonnes by 2055, the report says.
• The poultry industry, on the other hand, with an annual growth rate of 6%, recorded an excretion of reactive nitrogen compounds of 0.415 tonnes in 2016.
• That is anticipated to increase to 1.089 tonnes by 2030.
• The authors suggest that nutrient recovery/recycling from waste water for agriculture could cut down N2O emissions from sewage and waste water by up to 40%.

Source:TH