Carbon calculators – arable farming and net zero

Environment and climate
NFU Deputy President Tom Bradshaw pictured on his arable farm in Essex

NFU Deputy President Tom Bradshaw tested three of the most commonly used carbon calculators on his arable farm. Here's what he discovered.

Types of carbon calculator

Carbon sequestration is a huge part of any assessment and is what puts agriculture in the unique place of being both a source and sink of carbon emissions.

Tom tested the three most commonly used calculators, Agrecalc, the Cool Farm Tool and the Farm Carbon Calculator.

He said: “It was really important to have a look at some of the calculators available. The variability in results shows just how important it is that we are able to create an accurate baseline. This will be fundamental before we are able to access future opportunities around carbon sequestration.”

Each asks for slightly different data requirements, or asks the questions in different ways.

It's not always clear what emissions factors each of these calculators use for their assessment. Therefore the reasons behind the differences in results are unclear. 

Data sources used

  • BPS records – for hedges, precise cropping, fallow, environmental, forestry areas.
  • Soil bulk density and soil organic matter measurements.
  • Fertiliser and spray records. It helps if you have these as precise as possible, although calculators may aggregate the applications into amounts of passes through the crop.
  • Waste and water records. Recycling of spray cans counts in your favour. Make sure you have your fresh water use, if available.
  • Energy and fuel use. Diesel for tractors, drying and heating are all accounted for at some point.
  • Yield data and infrastructure inventory. Some tools ask for machinery and kit while others ask about new buildings and the respective materials.


The exercise was relatively straightforward due to having all relevant data to hand in preparation.

However, it is crucial that farm records are up to date and accurate in order for the calculators to be as effective as possible.

This being said, some assumptions or best guesses have to be made for some of the questions, due to the way they are asked.

It was helpful when reference figures were provided. 

Differences between tools

Agrecalc: 225.45tCo2e.

  • No sequestration and no machinery accounted for.

Cool Farm Tool: 249.56tCo2e.

  • Calculates on a crop by crop basis. No machinery is accounted for. 

Farm Carbon Calculator: 456.01tCo2e (before sequestration), -1669.43tCo2e (with sequestration).

  • Machinery accounted for but entire machinery across contracted area, so would only be a percentage of machinery emissions.
  • Sequestration counts for an enormous reduction, we are unsure how accurate this large sequestration value is.

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