Type of fixation | N2 fixed (106 metric tons per year) |
Non-biological | |
Industrial | about 50 |
Combustion | about 20 |
Lightning | about 10 |
Subtotal of non-biological | about 80 |
Biological | |
Agricultural land | about 90 |
Forest and non-agricultural land | about 50 |
Sea | about 35 |
Subtotal of biological | about 175 |
Total | about 255 |