What is embodied carbon and how do you calculate it?

Darren Evans
March 19, 2021

The embodied carbon of a material or product is the emission of carbon dioxide and other greenhouse gases associated with the production processes for that material or product. A thorough calculation of embodied carbon looks at all stages of a product’s life cycle - ranging from raw material extraction to disposal.

Embodied carbon can be calculated for anything that is manufactured, but the term is particularly prevalent within construction. The demand for raw materials to construct new buildings, combined with the built environment’s contribution to overall carbon emissions, means there is particular focus on the life cycle of construction products.

Using life cycle analysis to calculate embodied carbon

All production processes emit greenhouse gases. Methane, nitrous oxide, ozone and even water vapour all contribute to the greenhouse effect in the earth’s atmosphere, as well as carbon dioxide. The contribution made by other greenhouse gases is measured as a ‘CO2 equivalent’, which is why we talk about ‘carbon emissions’ and ‘embodied carbon’ generally.

It is not only the manufacture of a product that needs to be considered when thinking about embodied carbon. There are production processes associated with the maintenance and repair whilst in use. And once the building in which it is installed has reached the end of its useful life, there are further processes associated with removal and disposal.

Life cycle analysis is the method used to capture and account for all these different processes, and the carbon emissions associated with them, as accurately as possible.

Following a standardised procedure set out in BS EN 15978:2011 ‘Sustainability of construction works. Assessment of environmental performance of buildings. Calculation method’, it is possible to establish the embodied carbon of individual construction products and a building as a whole.

What are the different stages of life cycle analysis for construction products? 

There are four different stages of construction identified for the purposes of life cycle analysis. The first two - ‘product stage’ and ‘construction process stage’ - cover everything up to the practical completion of the building. There are five modules across those two stages.

  • A1 - Raw material extraction and supply
  • A2 - Transport to manufacturing plant
  • A3 - Manufacturing and fabrication
  • A4 - Transport to project site
  • A5 - Construction and installation process

The ‘use stage’ features seven modules. B1 to B5 cover use, maintenance, repair, replacement and refurbishment. B6 is operational energy use and B7 is operational water use associated with the product across the life of the building.

Modules C1 to C4 cover the ‘end of life stage’. Destruction and demolition; transport to disposal facility; waste processing for reuse, recovery or recycling; and disposal are all addressed.

The scope of the modules across these four stages demonstrates the importance of taking an holistic view of construction materials. To use a very basic example, a ‘sustainable’ material that has to be transported around the world is likely to have more embodied carbon than a material that might be perceived as ‘less sustainable’, but which does not have to be transported as far.

It also demonstrates the importance of thinking about more than just how a material helps a building to perform. One insulation material, for example, might help a building to use slightly less energy over its lifetime than another insulation material. But if the embodied carbon of the first material is significantly higher than that of the second then any saving in the building’s operational carbon is essentially inconsequential.

Reduce the embodied carbon of buildings

Life cycle analysis includes a final module D, called ‘benefits and loads beyond the system boundary’. It deals with potential for reuse, recovery or recycling. Where a product can be reused, recovered or recycled, it reduces the total amount of carbon calculated for the product in the rest of its life cycle.

When looking to calculate the embodied carbon of a building, it’s important to establish the scope of the assessment from the outset. This is where terms like ‘cradle to gate’ and ‘cradle to grave’ come in.

Not all products have the same life cycle analysis carried out for them, so when embodied carbon is being considered it’s important that products offer the relevant information to properly assess the impact of their use.

‘Cradle to gate’ covers only modules A1 to A3 (the ‘product stage’). ‘Cradle to grave’, meanwhile, spans all four stages, from module A1 right through to module C4.

In looking to reduce the environmental impact of products and grow the circular economy, it is increasingly common to hear the phrase ‘cradle to cradle’. If a product can be taken from a building that is no longer needed and reused, there are no carbon emissions to be accounted for across modules A1 to A3, which is a significant saving.

At Darren Evans, we can help you to calculate the embodied carbon of your project. Working with your project brief, we can assess your material specifications and help you to understand the life cycle analyses available. By involving us from an early stage, it’s possible to review the proposed design holistically and make recommendations with the aim of reducing the total embodied carbon.

Using our in-depth knowledge of building regulations, standards and current technology, we aim to create buildings and spaces that are more sustainable and energy efficient. We can help you to define embodied carbon targets and then meet them, without excessive costs. To find out more, contact us.

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