CH4 CO2 N2O

Global Warming Potential (GWP) – LCA Measure Details

Global warming potential is a reference measure. The methodology and science behind the GWP calculation can be considered one of the most accepted LCIA categories. GWP will be expressed on an equivalency basis relative to CO₂ – in kg or tonnes CO₂ equivalent.

Carbon dioxide is the common reference standard for global warming or greenhouse gas effects. All other greenhouse gases are referred to as having a "CO₂ equivalence effect" which is simply a multiple of the greenhouse potential (heat trapping capability) of carbon dioxide. This effect has a time horizon due to the atmospheric reactivity or stability of the various contributing gases over time.

As yet, no consensus has been reached among policy makers about the most appropriate time horizon for greenhouse gas calculations. The International Panel on Climate Change100-year time horizon figures have been used here as a basis for the equivalence index:

CO₂ Equivalent kg = CO₂ kg + (CH₄ kg x 28) + (N₂O kg x 265)

A recent IPCC report, "CLIMATE CHANGE 2013 The Physical Science Basis" provided an updated list of GWP equivalence factors, that have not as yet been updated (June 2014) in TRACI, but the Impact Estimator includes updated values for nine of the most common GWP contirbutors (Methane, Nitrous Oxide (N₂O), CFC-11, CFC-12, HCFC-22, HCFC-141b, HCFC-142b, HFC-134a and Sulphur Hexaflouride). When the EPA publishes an updated list of TRACI characterization factors, the Impact Estimator will be updated with all the new factors.

While greenhouse gas emissions are largely a function of energy combustion, some products also emit greenhouse gases during the processing of raw materials. Process emissions often go unaccounted for due to the complexity associated with modelling manufacturing process stages. One example where process CO₂ emissions are significant is in the production of cement (calcination of limestone). Because the Impact Estimator uses data developed by a detailed life cycle modelling approach, all relevant process emissions of greenhouse gases are included in the resultant global warming potential index.

 

Please note that the GWP total includes biogenic carbon, if users wish to have GWP without biogenic carbon, they can subtract GWP biogenic from GWP total.

 

Global Warming Potential Biogenic (GWP-Biogenic) – LCA Measure Details

Biogenic carbon is an expression for the carbon dioxide (CO2) flows between the atmosphere and bio-based products. Living plants absorb CO2 from the atmosphere, store it as carbon in their mass, and the carbon is eventually released upon combustion or decomposition of the material. The biogenic carbon dioxide emissions are included in the GWP total results and additionally called out separately in this measure, per ISO 21930:2017.

 

Global Warming Potential Calcination (GWP-Calcination) – LCA Measure Details

Calcination is a chemical process in cement production that causes carbon dioxide emissions. Calcium carbonate (limestone) is heated to create lime, with carbon dioxide as a by-product. The carbon dioxide emissions for concrete due to calcination are included in the GWP results and additionally called out separately, per ISO 21930:2017.