Toward an Integrated Nitrogen Budget for India: Multi-Sectoral Flows, Circularity, and Environmental Losses

Area of Science:

• Environmental Science
• Biogeochemistry
• Industrial Ecology

Background:

• Nitrogen (N) pollution is a significant environmental challenge.
• India's nitrogen budget and its environmental impacts are not well understood.
• Previous studies have not offered a comprehensive, multisectoral view of India's N economy.

Purpose of the Study:

• To conduct the first comprehensive, multisectoral assessment of India's nitrogen budget.
• To quantify nitrogen inputs, flows, circularity, and losses across ten economic sectors.
• To estimate sectoral nitrogen use efficiency (NUE) and identify key intervention points for mitigation.

Main Methods:

• Development of a scalable Environmentally Extended Input-Output (EEIO) framework.
• Tracing 198 nitrogen flows to estimate conversion potential to reactive nitrogen (Nr) losses.
• Estimation of sectoral nitrogen use efficiency (NUE) for India in 2020.

Main Results:

• Total N input in India is ~50 Tg-N yr-1, dominated by Haber-Bosch fixation, imports, biological N fixation, and fossil fuel combustion.
• Cropland and industry receive ~90% of N inputs; industry has higher NUE (62%) than cropland (56%).
• 37% of N inputs are emitted as reactive nitrogen (Nr), with significant atmospheric (NH3, NOx, N2O) and hydrosphere (runoff, leaching) losses.

Conclusions:

• India's nitrogen economy exhibits significant inefficiencies and substantial environmental Nr load.
• Dietary shifts towards animal protein and processed foods amplify Nr emissions.
• Targeted interventions are crucial for reducing N inefficiencies and mitigating environmental pollution in India.