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How to complete a carbon audit for your farm

Date Published: 27/06/2023

Completing a carbon audit involves collection of all relevant data and inputting it into your chosen assessment tool, which calculates the carbon footprint of your farm.

The calculation takes all greenhouse gas emissions into account, giving a total in tonnes of CO2 equivalent, then takes away any carbon which is being sequestered on the farm, to give the overall carbon footprint.

Why measure carbon?   

Identifying the carbon footprint of a farm business is the first step towards quantifying the contribution the farm is making to climate change. A carbon footprint calculation identifies the quantity and source of carbon dioxide, methane and nitrous oxide emitted from the farm (plus carbon sequestered in soils and woodland), highlighting areas where improvements or changes can be made to reduce greenhouse gas emissions.

Reducing carbon emissions in a farming business makes sense on many levels. High carbon emissions tend to be linked to high use of resources, and/or wastage, so reducing emissions also tends to reduce costs. This makes the farm more efficient and improves profitability. As well as the business opportunities that come from reducing emissions, farmers and landowners are in the unique position to be able to sequester carbon in trees, hedgerows and margins and within the soil, which can provide another source of income through schemes such as Countryside Stewardship and the Sustainable Farming Incentive (SFI) in England.

Before acting to reduce emissions, it is necessary to first understand where the emissions are coming from. Are the largest emissions coming from livestock, soils, fuels, or fertilisers? It is vital to get a picture of the farm business – and this is made possible by carbon footprinting.

Choosing a tool  

There are various carbon footprinting tools that have been designed for use by individual farmers (or groups of farmers) interested in understanding what is happening ‘on-farm’.

Currently there are three main options which are available to all UK farmers and growers who are keen to start carbon footprinting - the Farm Carbon Calculator, AgreCalc and the Cool Farm Tool.

Although the simple principle of completing a carbon footprint assessment is the same (emissions minus sequestration equals footprint), there remains some variation between the scope and boundaries that the tools use to calculate the results. Boundaries of a calculation determine what aspect of production is being assessed; for example, whether the emissions associated with one farm enterprise or the whole farm are being calculated, or whether it is assessing operations within the farm gate or taking account of what happens off farm.

Innovation for Agriculture has recently released a pilot carbon decision support tool, which can be used to find out which of the three main carbon calculation tools used in the UK will be of most relevance to your farm business.

It’s also worth considering what the carbon footprint will be used for. If you’re wanting to use the results for marketing purposes, it is a good idea to choose one that has a clear method attached to it, and which sets out what is included and excluded from the calculations.

If the results and the data are to be used as a management tool or to highlight areas to improve in the future, the tool needs to be able to evaluate the impact of changing aspects of farm management. These tools tend to require more data, so that the impact can truly be seen.

The golden rule is, once a tool has been chosen, stick with it for future assessments. There are differences within the methods used in each calculator, which makes comparing results between calculators is meaningless.

Completing a carbon audit

Once the tool has been chosen, the first step is to gather the input data. This includes information on fuel use, livestock numbers, fertiliser inputs, use of materials and waste produced.

The data is then entered into the calculator, which produces a breakdown of greenhouse gas emissions by sector, both in amounts (kilograms or tonnes of CO2e) and percentages of the total footprint by category. Armed with this data, it is then possible to consider how to reduce emissions and increase sequestration.

Next steps 

Once the carbon footprint of the farm has been calculated, deciding what to do is the next key step.

The footprint result will be reflected as a carbon dioxide equivalent but should also show where emissions of nitrous oxide and methane are produced. Key areas to focus on are the management of soils, fertilisers, manures, livestock, cropping, energy and fuel.

Speaking at the Farm of the Future: Net Zero in Practice event in April 2023, farmer and CEO at the Soil Association, Helen Browning OBE, shared how she undertook a full assessment of her farm business by completing a carbon audit and nutrient balance assessments for individual enterprises and the business as a whole.

“I looked at the nutrient balance on the farm, what was going on and what was coming off, by way of N and P especially. We also did a review of our carbon emissions and I wanted to understand what our mitigation options were as part of our ‘getting to net zero’ plan.”

She shared that the results showed they were sequestering 70% of the farm’s emissions, which was down to what the soils were doing, a small area of woodland and some young agroforestry. This leaves over 1,000 tonnes of carbon per year which is being emitted. They are now looking at natural sources for methane inhibition, such as willow and herbal leys, to reduce emissions from livestock, as well as calculating how much more woodland and hedges would be need to offset emissions on the farm.

There are numerous opportunities to reduce both emissions and costs. This leads to improved resilience and profitability, as well as opportunities to improve carbon sequestration and soil health - the ultimate resilient business model! Absorbing more carbon than the farm emits is a goal that all farmers can work towards and understanding the farm’s current carbon position by footprinting is the first key step.

For more information, see the ‘Measuring farm carbon’ section of the Farm of the Future report, which was written by Becky Wilson from Farm Carbon Toolkit. Get started by choosing the right carbon calculation tool for your farm business and conducting your first carbon footprint assessment.