Carbon footprinting for growers

Carbon footprinting for growers

Tackling climate change is one of the top priorities for governments across the globe. The Welsh Government has signalled its determination to address the issue through a Climate Emergency Declaration made in April 2019. In addition, Natural Resources Wales has published the results of its Climate Positive Project as part of a wider programme of work to address climate change.

Food and agriculture industries make a significant contribution to Greenhouse Gas emissions, accounting for about 20% of global emissions according to the FAO . However, they also have enormous potential to sequester carbon, for example through increasing soil organic matter and re-forestation, and are therefore also part of the solution.

The first step to managing anything is to be able to measure it. The last 20 years has seen a rapid rise in the availability of carbon calculators. This guide explains how they work and gives details of two systems that are particularly suitable and appropriate for horticultural producers.

Foot-printing land-based businesses

Calculating the footprints for farms is more complicated than for other types of business because:

  • Agricultural and, especially, horticultural businesses are complex systems
  • In most industries, the main greenhouse gas emitted is carbon dioxide (CO2). In agriculture and horticulture methane (CH4) and nitrous oxide (N2O) are much more important. Only about 8% of total agricultural emissions are of CO2*.
  • As discussed above, they can sequester as well as emit carbon

*Different gasses have different global warming potential. In order to take account of this, CO2, equivalents (CO2 e) are used. 1Kg of CH4 has the same effect as 25Kg of CO2 (although it has a much shorter life in the atmosphere) and therefore has 25 CO2 e. N2O has 298 CO2 e

Why calculate carbon footprints?

  • To help growers measure, monitor and reduce their environmental footprints and subsequently improve the efficiency and performance of their businesses
  • As a marketing tool to help environmentally conscious consumers choose the products that they buy
  • To inform strategy and policy development and to demonstrate the delivery of ‘Public Goods’. The latter will become increasingly important as it will be the basis on which government support payments are made to growers

How carbon calculators work

The principle on which all calculators work is very simple. There are two components

  • A database with standard figures for emissions (or sequestration rates) associated with each individual item or process
  • Farm specific data (e.g. size measured in hectares, tillage practices, quantity of fertiliser/ manure applied)

The calculator multiplies these two components together to give total emissions associated with each parameter. It then adds them all together to provide an estimate of the net emissions associated with that particular farm or enterprise, as shown below

  Item Details Units CO2e (t) TOTAL CO2e (t)
EMISSIONS Fuel Red diesel (l) 500 0.0034 1.70
Cash Crops Potatoes (t) 8 0.0312 0.25
Field veg (t) 20 0.0094 0.19
Fertility Building crops Vetch (ha) 0.25 0.666 0.17
Red clover (ha) 0.25 1.004 0.25
Inputs Rock phosphate (t) 1 1.1 1.10
N Fertiliser (t) 0.6 2.81 1.69
Pesticides 0.08 0.03 0.0024
Total Emissions       5.34


Soil Organic matter 0.2% increase over 5 years (ha) 2 3.19 6.38
Hedgerows (m) 600 0.0007 0.42
Field margins 600 0.0002 0.12
Total Sequestration       6.92
NET EMISSIONS         -1.58

Derived from Farm Carbon Toolkit based on a hypothetical farm

Scope of carbon calculators

The ‘scope’ defines what is included in the standard database figures.

  • Scope 1 refers to direct emissions from sources that are owned or controlled by the farm. This includes emissions from diesel used by tractors, propane used to heat propagation tunnels and direct emissions from soils
  • Scope 2 also includes emissions associated with the generation of purchased electricity consumed on the farm
  • Scope 3 refers to indirect emissions associated with the production, processing and distribution of inputs into the farming system. These include the carbon ‘embedded’ in the production of seed, fertilisers and pesticides

These definitions have been developed by the World Business Council for Sustainable Development (WBCSD) and are internationally accepted.

Calculating emissions of products

The example above calculates the net emissions of a production system, but there is growing interest in foot printing individual products, rather than farms. This process accounts for all the environmental impacts associated with a product from raw material acquisition through to production, use and disposal. This approach is referred to as ‘Life Cycle Assessment’ and was first applied to crops through the pioneering work of Professor Gareth Edwards – Jones at Bangor University.


The standard database is the foundation on which the calculators is built and any weaknesses in the dataset will be reflected in the final results. Ideally the standard emission figures are independently verified, but in some cases the data is simply not available or are subject to differing views within the scientific community. This is of particularly true of Scope 3 data and carbon sequestration rates.

International standards

Prior to 2008, there was no standard approach to calculating carbon footprints. As a result, it was often difficult to interpret results and almost impossible to compare the outputs of one calculator to another. To address this issue, PAS (Publicly Agreed Specification) 2050 was introduced as an agreed methodology to measure the ‘Life cycle’ GHG emissions. The details are available here, but for the purposes of this guide it is sufficient to know that these standards exist and that all the main calculators currently in use, including the two highlighted below, adhere to them.

Choosing the right calculator

There are a number of the key issues to consider when choosing a calculator:

  • Ease of use. This includes factors such as; how easy it is to enter data; how the system takes you through each step of the calculation process; the ease of navigation between different screens or spreadsheets; and the overall ‘feel’ of the programme (e.g. fonts, colours, amount of information on each screen etc).
  • Simplicity vs accuracy. As a general rule, systems should be as simple as possible. However, there is a certain level of complexity below which the results are unlikely to be representative or useful. Over and above this, there are trade-offs between simplicity, accuracy and the time required to complete an assessment.
  • Scopes and datasets. Make sure that the scope of footprint is appropriate for the purpose for which the calculator is intended.
  • Interpreting the results. The results should be easy to understand give sufficient detail to identify practical, farm specific steps to reduce the footprint of the business.

Some key calculators

There are many calculators available, but this guide will focus on just two: The Farm Carbon Calculator and the Cool Farm Tool. These have been chosen for their relevance to horticulture, their ease of use, and the appropriate balance they strike between being relatively quick to use and generating useful information of reasonable accuracy.

Their key characteristics are summarised below.

  Farm Carbon Calculator Cool Farm Tool
Carbon emissions ü ü
Carbon sequestration ü
Water ü
Biodiversity ü
Food waste ü
Range of horticultural crops Narrow Wider
Ease of use (Data entry) Easy Easy
Clarity of reporting and interpretation Good Good
Data entry time 30 mins 30 mins
PAS 2050 Compliant ü ü
Focus on organic/ agroecology Strong Medium
Cost Free Free

Farm Carbon Calculator


The Farm Carbon Calculator was developed by producers, one of whom is a market gardener, and this reflected in its relevance to growers. It strikes a balance between being reasonably accurate on one hand and not being too onerous on the other. It is designed to provide enough information to enable growers to identify the actions needed to decrease emissions and increase sequestration. It has a strong focus on agroecological and organic farming systems, reflected by a wider range of options for fertility building crops and green manures compared to most other systems. It also enables a much more detailed assessment of the sequestration potential of the farm compared to most to other calculators.


The scope of the Calculator is scopes 1, 2 and 3 and therefore covers direct and indirect emissions. The Farm Carbon Calculator is PAS 2050 compliant.

Gathering and entering data

Gathering the farm data to input into the system is the most time-consuming stage, but once it has been completed for the first time, it will be easier for subsequent calculations. A spreadsheet to assist you is available here.

Data entry is simple, clear and intuitive, and takes approximately 30 mins.


The system automatically generates reports and presents them as tables of graphs at several different levels including:

  • Net carbon emissions for the whole farm
  • The contribution of each category makes to carbon emission/ sequestration in absolute terms and relative to one another
  • The contribution of different components within each category (for ‘fuels’ are broken down into ‘red diesel’, ‘propane’ and ‘gas’).

Detailed results for a hypothetical farm can be found here, and an overview is given below.

Cool Farm Tool


The Cool Farm Tool has been developed by the Cool Farm Alliance which includes key producers, processors and retailers of food. It has a broader remit than the Farm Carbon Calculator also covering:

  • Water
  • Biodiversity
  • Food waste

There is less focus on biological fertility building crops and green manures and it does not attempt to assess the carbon sequestration potential of the farm. It does, however, have standard data for a broader range of crops, which for horticulture includes: apples; potatoes; tomatoes; raspberries, blueberries and strawberries.


The scope of the Calculator is 1, 2 and 3 and therefore covers direct and indirect emissions and is compliant with PAS 2050

Gathering input data

The following information, covering the last previous 12 months, will be required:

  • Summary of farm including enterprises and cropping areas
  • Crop residues volumes and management
  • Basic soil data (classification, pH, Organic Matter)
  • Inputs including organic and inorganic fertility inputs and pesticides
  • Fuel & energy consumption
  • Food loss and waste
  • Haulage (to market)

Like the Farm Carbon Tool, data inputting is simple, clear and intuitive and likely to take approximately 30 mins.


The system automatically generates reports and presents them as tables of graphs at several different levels including:

  • Net carbon emissions for the whole farm
  • The contribution of each category to carbon emission in absolute terms and relieve to one another
  • The contribution of different components of each category

Results for GHG emissions the hypothetical farm, are given below with details as follows:

  • 2 ha of mixed field vegetables
  • Average yield 20t/ ha
  • Fertility based on 170 Kg N/ Ha, supplemented with manures
  • Judicious use of pesticides and fungicides
  • Biodiversity features include:
    • More than 7 species of crops
    • 400 m of hedgerow
    • 100 track verge
    • 1 of uncultivated areas (e.g. field corners and wet patches)


Emissions – Cool Farm Tool


Biodiversity – Cool Farm Tool


  • A guide to PAS 2050 (2011) Carbon Trust, Defra, British Standards Institute

Welsh Government makes climate emergency declaration (April 2019)