Calculating your carbon footprint

The building blocks of every sustainability journey start with laying a strong foundation. Measuring carbon usage is a critical early step for any organisation transitioning towards net zero, as it provides essential metrics on where the business stands in terms of carbon usage and where it wants to go.

A carbon footprint covers direct and indirect carbon emissions, capturing the amount and type of greenhouse gas (“GHG”) emissions on an annual basis. These emissions can include energy used for heating and lighting, company transport and supply chain operations. An accurate footprint allows a business to assess its own contribution to climate change and inform its tailored sustainability action plan. With corporate environmental performance becoming increasingly under the spotlight, a published report of this kind also meets the expectations of stakeholders.

What to measure

Carbon dioxide (CO2) is the best-known GHG, but others also have a significant impact on the environment: methane, nitrous oxide, sulphur hexafluoride, perfluorocarbons and hydrofluorocarbons are all measured when calculating a carbon footprint. The combination of these gases is expressed as a carbon dioxide equivalent (CO2e). There are three categories of emissions, as determined by the Greenhouse Gas Protocol – this is the world’s most recognisable accounting standard for GHG emissions. These categories are described as scope 1, scope 2 and scope 3.

Scope 1 covers direct activities of the business, such as fuels expended onsite or using company-owned vehicles. Scope 2 includes indirect emissions that a business does not directly control, like purchased electricity. Both these categories are reasonably straightforward to measure. Scope 3 emissions cover indirect emissions that occur fully beyond the control of the business: food, air travel, office furniture and IT equipment are examples. These emissions are the most difficult to quantify and tackle.

To reach net zero, an organisation must reduce these emissions as much as possible, balancing any remaining scope 3 emissions via carbon offsets. The Scottish Government has a target date of 2045 for net zero emissions of all GHG.

Data capture

Capturing data for emissions can be done using a simple spreadsheet. This enables a business to record and update figures regularly.

A 12-month period should be selected to collect activity data using the most recent annual period available, if this is a first report. Consider how the business works in terms of energy use, water consumption, business travel, entertaining, supply chains and waste. When recording, it is important to use correct units such as kWh for gas and electricity, actual fuel consumption for vehicles, and location-based or market-based figures for energy purchased. If there are data that are difficult or impossible to ascertain, the best reasonable estimate should be taken. The Greenhouse Gas Protocol gives detailed guidance on calculating scope 2 and scope 3 emissions.

To calculate GHG emissions associated with a business, the data collected need to be converted using an “emission factor” according to the calculation: Data x Emission Factor = Greenhouse Gas Emissions. Emission conversion factors are determined by the Government and published online with annual updates. From this calculation, a business can produce a report showing its total GHG emissions for the year. As an unexpected upside, many businesses find this data to be very helpful in monitoring and reducing costs.

Handy aids

If the idea of operating a spreadsheet system seems overly onerous in terms of time, there are many handy carbon calculators available. Free and fee-based tools can be found using an online search. For example:

The Legal Sustainability Alliance offers members a free digital tool to keep monthly, quarterly or yearly figures on emissions. Its carbon calculator gives an updated carbon footprint based on core emissions and allows users to set targets for reduction.

Carbon Footprint Ltd has a range of business packages giving access to its carbon calculating software. A free version is available to registered users, with more detailed versions for larger organisations offered for an annual fee.

The Carbon Trust has a free calculator for SMEs, focused on scope 1 and scope 2 emissions, which may be suitable for small operations.

Once a business has a carbon footprint recorded, it can use it to set targets for comparison and improvement over a set period, like five or 10 years. By reducing waste, switching to renewable energy sources, transferring to electric vehicles or car sharing schemes and cutting down on water usage, a business can make considerable improvements to its carbon footprint. Carbon offsetting can then be used to deal with emissions that are difficult to eliminate.