IPCC Volume 4 Chapter 11 · Scope 1
Managed soils, lime and urea
Nitrogen added to soil comes back as nitrous oxide three ways, and IPCC counts all three. Lime and urea spread on fields give up their carbon as CO₂.
On this page you'll learn
- Direct, volatilised and leached N₂O
- Why multiplying by EF1 alone under-reports by a quarter
- Lime and urea, and why urea is two emissions
- Scope
- 1
- Publisher
- IPCC 2006 Vol 4 Ch 11
- Category codes
- managed soils N₂O,
lime_urea_application
Three paths for the same nitrogen
| Path | Equation | Per kg of synthetic N |
|---|---|---|
| Direct | 11.1: N × EF1 | 0.01 |
| Volatilised and re-deposited | 11.9: N × FracGASF × EF4 | 0.10 × 0.01 = 0.001 |
| Leached and run off | 11.10: N × FracLEACH × EF5 | 0.30 × 0.0075 = 0.00225 |
- Direct
- 10.00 kg N₂O-N
- Volatilised
- 1.00 kg N₂O-N
- Leached
- 2.25 kg N₂O-N
- Total N₂O-N × 44/28
- 20.82 kg N₂O
- × 265 (AR5)
- 5,518 kg CO₂e
Multiplying by EF1 alone would give 10 kg N₂O-N: about 25% short of IPCC's Tier 1 total of 13.25.
Direct emissions also cover crop residues, mineralised soil organic matter, flooded rice (its own EF1), drained organic soils by area, and nitrogen from grazing animals, which is where pasture manure from the livestock page is counted.
Lime and urea
| Material | Carbon fraction (EF) |
|---|---|
| Limestone, CaCO₃ | 0.12 |
| Dolomite, CaMg(CO₃)₂ | 0.13 |
| Urea | 0.20 |
Enter tonnes of material
Not tonnes of nitrogen. Urea is bought by its N rating (46%), and entering that here would report 46% of the CO₂ while looking normal.
Urea is two emissions
Its carbon is this CO₂; its nitrogen is an input to the soil N₂O above. Both are real and neither replaces the other.
Quicklime and slaked lime aren't here
They contain no carbonate. The CO₂ was released when they were made, in a kiln, and is counted under industrial processes.
A ceiling, not an estimate
Tier 1 assumes all the carbon reaches the air in the year of application. IPCC's uncertainty is −50% and nothing upward.