Nitrogen (ammonia): Emissions
Fertiliser's surprisingly heavy carbon footprint
Fertiliser's surprisingly heavy carbon footprint What this tab covers The greenhouse-gas footprint of the commodity at a global level, split by lifecycle phase: extraction (or farming), refining and processing, movement, usage, and recycling or end of life. Intensities are per unit of product; the global total combines intensity with world output. Also covers other environmental impacts and the main levers to cut emissions. Emission intensity 10.5 t CO2e per t N range about 5-21 by region · cradle-to-grave, global average 2018; Latin America about double the average Global emissions per year 1,130 Mt CO2e per year 2018 · published total for the synthetic N fertiliser supply chain, about 2.1% of global GHG emissionsPer t of nitrogen (N) supplied as synthetic fertiliser, cradle-to-grave including field emissions. Intensity: Menegat, Ledo and Tirado (2022), Scientific Reports. Global total: Menegat et al. (2022).
Share of footprint by lifecycle phase
Refining / processing 38.8% Movement 2.6% Usage 58.6%Footprint by lifecycle phase
| Phase | Intensity | Share | Main sources of emissions | Notes | Source |
|---|---|---|---|---|---|
| Extraction | included in manufacturing in the source | – | natural gas and coal supply, including methane leaks upstream | Not reported separately by Menegat et al. | Menegat et al. (2022) |
| Refining / processing | about 4.1 t CO2e per t N (438.5 Mt); ammonia alone about 2.4 t CO2 per t NH3 | 38.8% | steam reforming of gas or coal gasification, Haber-Bosch synthesis, nitric acid N2O | Coal-based ammonia emits roughly twice gas-based; China's manufacturing intensity about 5.7 t CO2e per t N against India's about 3.0 (derived) | Menegat et al. (2022); IEA Ammonia Technology Roadmap 2021 |
| Movement | about 0.28 t CO2e per t N (29.8 Mt) | 2.6% | shipping, rail and truck of urea and ammonia | small share | Menegat et al. (2022) |
| Usage | about 6.1 t CO2e per t N (field use) | 58.6% | direct soil N2O (379.9 Mt), leaching N2O (130.1 Mt), urea CO2 release (86.0 Mt), volatilisation N2O (66.3 Mt) | N2O has a 100-year warming potential of 273 (IPCC AR6); urea releases the CO2 captured in making it once applied | Menegat et al. (2022); IPCC AR6 |
| Recycling / end of life | not applicable | – | fixed nitrogen is not recycled; manure and legumes return some N | losses to water are counted in field use | USGS MCS 2026 |
Other environmental impacts
Nitrate leaching pollutes groundwater, and runoff causes coastal dead zones. Ammonia volatilisation forms fine particulate air pollution. Ammonia is toxic and ammonium nitrate is an explosion hazard.
Levers to cut emissions
- Better nutrient management could cut N2O by 0.03-0.7 Gt CO2e a year by 2050 (Menegat et al. 2022)
- Carbon capture on reformers (blue ammonia) and electrolytic hydrogen (green), at 10-100% higher cost (IEA 2021)
- Abate nitric acid N2O with catalysts
- Nitrification inhibitors, coated urea and precision placement
- Replace some synthetic N with manure and legumes
India
India accounted for 14.7% of world fertiliser-N emissions (165.5 Mt CO2e in 2018), mostly from field use; its gas-based urea plants are relatively efficient, but the Talcher coal-gas plant will raise intensity (Menegat et al. 2022; content tile).
Emission figures are indicative global averages from the life-cycle studies named; actual footprints vary widely by site, energy mix and method.