How to build a carbon model: the basics

Maria Manidaki, senior engineer, Mott MacDonald explains.

Carbon modelling need not be complex. At its simplest, a carbon model shows the quantity of each material used in a project and multiplies that by that material’s emission factor to calculate a carbon footprint.

Levels of added detail create more complexity but do not alter this fundamental structure: What materials are you modelling, and where did your carbon data come from? To what extent are you modelling transport, construction activities, and emissions indirectly associated with your project? Are your methods consistent and is your data comparable across the entire model?

There are plenty of decisions to make and checks to perform along the way, required to answer these questions.

However, in a nutshell, the process of modelling is as follows.

  1. Establish your system boundaries for both capital and operational carbon. That is, define what will and will not be included in your model. Various industry guidance documents exist to help with this.
  2. Identify the materials and products that the project will use. Suppliers may offer information on the capital and operational carbon content of their products; check that their system boundaries match your own, or insist on having raw data.
  3. Other carbon data is available from government and industry sources. Perform your emissions calculations as required, based on your own knowledge of the quantities required and the building’s likely energy consumption.
  4. Now, turn your attention to the emissions associated with construction and commissioning. It is often difficult to be precise, but consideration of the materials, labour, fuel and other resources required can produce reasonably indicative estimates.
  5. Having built a carbon model of a single asset, don’t let it languish in isolation. Combine it with others to create a programme-scale carbon model. This can be invaluable for enabling identification of carbon ‘hotspots’ across programmes, and for continuous improvement – which is one of the great advantages of any type of model.

For more on crunching carbon, cutting cost talk to Davide Stronati, Mott MacDonald Group sustainability manager.