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Agribusiness News June 2024 – Sector Focus: Carbon Calculators

31 May 2024

Carbon calculators update

Carbon calculators help farms to estimate their greenhouse gas (GHG) emissions and highlight ways to reduce them, a hugely important tool towards tackling agricultural emissions and achieving net zero for the whole economy. UK farmers have been encouraged and incentivised to undertake farm carbon audits for a number of years. However, farmers have been feeding back that the calculators on the market can return different results for the same farm, leading to questions about their consistency and trustworthiness.

In January 2024, the UK Department for Environment, Food and Rural Affairs (DEFRA) published a report titled ‘Harmonisation of Carbon Accounting Tools for Agriculture.’ The report shortlisted six calculators which are used most by British farmers.  The report investigated what drives the differences in their results, with the goal of ‘harmonising’ or bringing them in line with each other. The six tools were each tested on 20 farms covering the nine most common types of British farming.

How do they differ?

The report confirmed that the tools can indeed output different emissions estimations for the same farm. These differences are a result of factors including the boundaries on which parts of the farm business are included in calculations, the precision to which calculators use emissions factors (i.e. reference figures used to model farm emissions), how soil carbon sequestration is handled, and the 3rd-party review standards to which they align. Because these differences in methodology are more relevant to some farming types than others, there is greater divergence among some types of farms for example:

  • those with organic and peaty soils
  • where more soya feed is used
  • lowland beef and sheep enterprises

but more consistent results among others e.g. dairy systems.

Which is right for my farm?

If different calculators give different results, which can a farmer trust as a decision-making tool? Whilst differences persist, the report highlights that these calculators are still trustworthy and following their recommendations will help farmers reduce emissions. The climate crisis requires urgent action and farmers should not delay in engaging with these tools. However, it is worth taking the time to make an informed decision. Farmers should ask questions about how suitable a calculator is for their type of farming and the outcomes they are looking to achieve. While reducing emissions is the goal of engaging with these calculators, achieving more efficient use of resources and farm inputs boosts the profitability of farm enterprises. Therefore, farmers should ask their farm advisor if they are aware of, and have considered, the differences between the tools available for carbon audits.

Figure 1: Excerpt from a results table of the Defra report For different farm types, a percentage difference for the calculator which returned the highest and lowest emissions estimate.


Percentages in bold denote farm types where the highest value was over twice as high as the lowest; Italics denote those for which high was less than 50% higher than low.

What happens next?

While farmers will get better results from learning about the inputs, methodologies, and outputs of these calculators; it is the companies behind the calculators who have the responsibility of improving the accuracy of their methods and making sure all tools on the market are robust and trustworthy. The Defra report makes several asks, including for industry and government to define which parts of farm businesses should be included in farm-level assessments and for calculators to increase transparency to drive increased understanding of emissions sources.

Several tools have published articles which address the recommendations made in the report head-on, tracking progress and giving timelines for when they hope to fully comply with the report’s standards. As calculators take action to implement the recommendations, it is reasonable to expect more consistency between results in the future. As before, the most important thing is for farms to choose a calculator which suits their enterprise type and stick with the same one, as this is the only way to establish a robust baseline and monitor change over time.

Brady Stevens,

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