Carbon calculators - arable farming and net zero

Published 12 February 2020

Crops Climate change and renewables Environment Net zero
Tom Bradshaw

NFU combinable crops adviser Chloe Lockhart and NFU agriculture policy graduate Charlie Parkin headed to Essex to look at the carbon footprints of NFU combinable crops board chairman Tom Bradshaw’s arable farm. Here are their results:

Which calculators did we use?

We tried the three most commonly used calculators, those being AgRE Calc, Cool Farm Tool and Farm Carbon Calculator.

Each asked for slightly different data requirements from the business, or asked the questions in different ways. It's not always clear what emissions factors each of these calculators use for their assessment and therefore the reasons behind the differences in results are unclear. 

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

What did we need?

  • 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 etc. counts in your favour and make sure you have 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 ask for machinery and kit while others ask for new buildings and the respective materials.

How did it go?

The exercise went well and 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. 

Results and main differences

AgRE Calc: 225.45tCo2e

  • No sequestration and no machinery 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 % of machinery emissions. Sequestration counts for an enormous reduction, we are unsure how accurate this large sequestration value is.

Cool Farm Tool: 249.56tCo2e

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

Tom Bradshaw, NFU combinable crops board chairman, 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 which will be fundamental before we are able to access future opportunities around carbon sequestration.”

You may also want to read NFU livestock board chairman Richard Findlay's analysis of carbon calculators here. 

Find the full NFU carbon calculator review here 

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