# How do I calculate the carbon footprint of growing wheat per tonne?

Canonical: https://senseible.earth/answers/wheat-farming-emissions-per-tonne

Add nitrogen fertiliser N2O with IPCC Tier 1 defaults, urea CO2, tractor and harvester diesel at 2.68 kg CO2 per litre and irrigation electricity at 0.710 kg per kWh, then divide by tonnes harvested per acre. Fertiliser N2O is often the largest field source.

## Field sources

- N2O from urea and DAP nitrogen.
- CO2 released from urea.
- Diesel for tillage, sowing, spraying and harvesting.
- Irrigation pumping.

## Data from the farm

Fertiliser bags or invoices, diesel bought or hire hours, pump hours or the electricity bill, and the harvested weight from the mandi slip.

## What is left out

Fertiliser manufacture, pesticides and seed are upstream inputs. Add them from supplier figures when you have them, and say which are missing.

## Worked example: one acre of wheat (illustrative inputs)

- Direct N2O: 55 kg N x 0.01 = 0.550 kg N2O-N x 44/28 x 273 = 236.0 kg CO2e
- Indirect N2O: 55 x (0.10 x 0.01 + 0.30 x 0.0075) = 0.179 kg N2O-N x 44/28 x 273 = 76.7 kg CO2e
- Urea CO2: 100 kg x 0.733 = 73.3 kg CO2
- Diesel: 20 litres x 2.68 = 53.60 kg CO2
- Irrigation electricity: 300 kWh x 0.710 = 213 kg CO2
- Per acre: 652.5 kg CO2e
- At 1.80 t an acre: 652.5 / 1.80 = 362.5 kg CO2e per tonne

IPCC 2006 Tier 1 defaults (EF1 0.01; 10 percent volatilised, 30 percent leached for irrigated land); AR6 GWP 273 for N2O. Fertiliser rates, litres, units and yield are illustrative, and fertiliser manufacture is not included.

## What Senseible does here

Senseible reads diesel, electricity and fertiliser invoices into dated, fingerprinted records that support a farm or crop figure. Field emissions such as N2O and methane are calculated with IPCC defaults in your method note and labelled as estimates, not measured values.

- [Fertiliser N2O emissions](https://senseible.earth/answers/fertiliser-n2o-emissions-calculation)
- [Tractor diesel emissions per acre](https://senseible.earth/answers/tractor-diesel-emissions-per-acre)
- [Flour mill carbon per tonne](https://senseible.earth/answers/flour-mill-carbon-footprint-per-tonne)

Sources: [2006 IPCC Guidelines, Volume 4 AFOLU, Chapters 10 and 11](https://www.ipcc-nggip.iges.or.jp/public/2006gl/), [IPCC AR6 WG1, Chapter 7, Table 7.15 (GWP100)](https://www.ipcc.ch/report/ar6/wg1/), [CEA CO2 Baseline Database, version 21.0](https://cea.nic.in/cdm-co2-baseline-database/?lang=en)

Last reviewed 2026-10-21.