What do we mean by "operational carbon"?

Great question. We are generally talking about the greenhouse gas (GHG) emissions in carbon dioxide equivalent (CO2e) terms related to the post construction phase of a building’s life up until its demolition. The main ones people immediately think about are the CO2e emissions from burning on-site fossil fuels and the upstream emissions from electricity usage. There are also emissions from water consumption and wastewater production. And if refrigerants are used which have a global warming potential (GWP) greater than zero, then any leakage from those refrigerants results in fugitive emissions considered to be operational carbon.

Let’s do a quick primer on terminology as this is a jargon heavy discipline.

The GHG Protocol establishes 3 distinct categories for GHG emissions. For simplicity I’ll define them thusly:

  • Scope 1 emissions related to a building are those from on-site combustion of fossil fuels and fugitive emissions from refrigerant leaks.
  • Scope 2 emissions are those upstream emissions related to electricity use provided by the utility grid.
  • Scope 3 emissions are virtually everything else like cars of visitors (not company owned), water and wastewater, materials, etc. [The building’s Scope 3 emissions are someone else’s Scope 1 and 2 emissions.]

From this point we also layer on EN 15978-2011’s Whole Life Carbon for its nomenclature.

  • Module A (A1-A5) will cover the materials and construction phase of the building.
  • Module B (B1-B7) includes maintenance and operations during the building’s life.
  • Module C (C1-C4) covers the building’s end-of-life emissions from demolition and disposal.

Operational Carbon is therefore in the B module. And there’s a clear crossover into the C module.

Let’s simplify things into these modules of interest:

  • B1 will include the refrigerant leakage during building operations which will by the earlier definition be a Scope 1 emission.
  • B6 will include all operational emissions from fossil fuel uses on-site, which are Scope 1 emissions and also includes electricity consumption which are Scope 2 emissions.
  • B7 will be the energy-water nexus and is the embedded carbon in water conveyance and treatment to bring the water to the building and the wastewater exported from the site to a treatment facility. These are Scope 3 emissions.
  • C1 is included by some as an operational carbon albeit per 15978 it’s listed as an end-of-life Scope 1 emission. But consider that the end of service life for an AC unit or chiller will occur many times during the course of a normal building’s life.

Here’s a handy diagram from our friends at NBI to show these:

Hopefully this is clear but if not please ask questions or make corrections!


well explained.

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Post script: The Norwegian standard NS 3720:2018 adds a crucially missing module from EN 15978:2011 in the realm of operational carbon emissions. It adds the module B8 to account for transportation-related emissions of the building.