How to calculate the carbon emissions from your own farm business

Page last updated: Monday, 28 March 2022 - 2:06pm

Please note: This content may be out of date and is currently under review.

Farming systems produce greenhouse gas (GHG) emissions, primarily in the form of methane (mostly caused by animal digestion and respiration) and nitrous oxide (mostly from fertilisers). Trees, plants, grasses and soils take up carbon dioxide from the atmosphere and use it to grow.

A baseline carbon account for your farm will give the total GHG emissions for the farm and the carbon intensity of your products such as wool, meat and grain. This is important so that any decision on how much carbon needs to be captured (sequestration) or emissions reduced (mitigation) is based on actual emissions.

Depending on your goal, you may choose to focus on reducing your farms impact on climate change (total farm emissions expressed as tonnes per hectare of carbon dioxide equivalents: t/ha CO2 e-) or focus on producing a low carbon product (emission intensity expressed as kilograms of carbon dioxide equivalents per kilogram of product: kg CO2 e-/kg product) to meet a market.  Just focussing on reducing the emissions intensity of your products may not decrease your total farm emissions as you may choose to run or grow more product.

Typical emission sources on mixed farms in WA (largest to smallest)

  • Sheep and cattle (ruminants) emissions (methane)
  • Crop nitrogen (nitrous oxide)
  • Flock or herd manure (nitrous oxide)
  • Fertilisers and herbicides
  • Diesel
  • Supplementary feed for livestock
  • Electricity and other services like maintenance and repairs

Farm baseline accounts usually include all emissions on farm, emissions from purchased inputs such as fertiliser and feed and electricity.  These are classified as Scope 1, 2 and 3 emissions:

Scope 1: All emissions on-farm from agricultural activity

Scope 2: Emissions from the production of purchased electricity

Scope 3: All emissions associated with producing inputs such as fertilisers, herbicides, veterinary services etc.

The accuracy of the baseline account is dependent on the quality and detail of the data used so accurate farm records are essential. Because livestock emission are likely to be a large proportion of the farms emissions it is vital that these are as complete as possible.

The data you will need:

  1. Stock numbers on hand (numbers x days on farm per year)
  2. Liveweight at slaughter or disposal x age
  3. Weight of each class of animal
  4. Amount of wool produced per animal per year
  5. Yield of each crop with area and harvested weight
  6. Amount of fertiliser and herbicide applied per crop and pasture
  7. Purchased livestock and purchased animal feed
  8. Diesel use per enterprise
  9. Electricity and other energy sources
  10. Repairs, maintenance costs
  11. Purchased services and travel

These inputs allow an estimation of enteric methane, nitrous oxide from manure, methane from manure, indirect nitrous oxide emissions arising from volatilised ammonia or nitrogen lost via leaching and run-off (direct and indirect nitrous oxide emissions from cropping).

For more information on how the National Clean Energy Regulator estimates emissions from these sources please see National Greenhouse Account Factors.

Calculators available and their features

Producers can choose to have a complete carbon account or Life Cycle Assessment (LCA) for their properties conducted by an accredited consultant (this is important if you are keen to register your product as carbon neutral or want to enter into a Carbon Farming Agreement to sell ACCUs) or use one of a number of carbon calculators available on line which will give a good approximation of emissions and allow you to regularly run scenarios as part of reducing your carbon footprint.

Most of these web-based carbon emissions accounting tools focus on the grain/cropping enterprise or livestock but few exist that cover both enterprises in the same business. Tools that have comprehensive information on sequestration are also limited. Both mitigation and sequestration measurements are important in informing the planning process of any farm business interested in this space.

DPIRD recently commissioned a report on the value of on-farm calculators available for producers.  The full report can be accessed via the sidebar..

The report found:

  • the emissions results varied between calculators.
  • the amount of information and level of detail required varied across all calculators from very simple to highly detailed and was not correlated to the final emissions value.
  • each calculator addressed emissions intensity values, which is the most useful in determining management strategies to offset or reduce carbon emissions, from a simplistic whole of farm value to detailed, by emissions type value.
  • each calculator had strengths and weaknesses, no one calculator demonstrated a complete package.

The two calculators that we recommend at this stage are the Greenhouse Gas Framework and Cool Farm Tool. See below for a brief description and links.

Greenhouse Accounting Framework (GAF)

The Beef and Sheep (BS-GAF), and Grains (G-GAF) Farm Greenhouse Accounting Framework tools were developed and are maintained by the Primary Industries Challenge Centre and the University of Melbourne using MS Excel spreadsheets and are freely available to download.

The tools utilise and are maintained to align with the Australian National Greenhouse Gas Inventory (NGGI) method, to measure the scale and sources of greenhouse gas emissions from farms.

The two excel spreadsheets, one for grain and one for sheep and beef are easy to download on to a computer and easy to use with a simple spreadsheet layout and allows the user to see the underlying emissions factors and calculations.

Data entry into the crop template took approximately 10-15 minutes including the collation of the information. The sheep template took longer at approximately 30 -35 minutes including collating the information.

Information for the sheep calculator was simple and were numbers that most users would have at hand including sheep class numbers, liveweight by class and liveweight gain by class which was broken down into spring, summer, autumn and winter.

Information for the crop calculator was also simple with information that the majority of users will have to hand such as crop area and yield, although the nitrogen component of the fertiliser section would require some thought by the user before entry.

The Cool Farm Tool

The Cool Farm Tool is an online platform that was developed by Unilever, the University of Aberdeen, and the Sustainable Food Lab. It is maintained through the Cool Farm Alliance which includes industry, academia, NGO’s, and consultancies and quantifies on-farm greenhouse gas emissions and soil carbon sequestration.

The Cool Farm Tool platform emissions calculations are based on grower inputted data and site sensitive empirical research from a broad range of published data sets and IPCC methods. The platform is one of the few that includes calculations of soil carbon sequestration based on results of published studies built from over 100 global datasets.