Greenhouse gases
I gas a effetto serra (greenhouse gases, GHG) descrivono i gas responsabili del cosiddetto effetto serra, ovvero i gas che compongono la carbon footprint.
Possono essere rilasciati in atmosfera sia naturalmente sia per cause antropiche.
Secondo il Protocollo di Kyoto, i gas a effetto serra comprendono il biossido di carbonio o anidride carbonica (CO₂), considerato il gas serra di riferimento, il metano (CH₄), il protossido di azoto (N₂O) e altri gas meno conosciuti come H-FKW/HFC, FKW/PFC, esafluoruro di zolfo (SF₆) e trifluoruro di azoto (NF₃). Altri gas a effetto serra, come il monossido di carbonio (CO), gli ossidi di azoto (NOx) o gli idrocarburi volatili, escluso il metano (il cosiddetto NMVOC), sono considerati gas a effetto serra indiretti e sono disciplinati dal protocollo di Montreal.
As mentioned earlier, carbon dioxide (CO₂) is the most common greenhouse gas and is considered the reference for other GHG. The global warming potential (GWP) of the various GHGs, is in fact expressed precisely in carbon dioxide equivalent units (CO₂ eq): this makes it easy to compare the impact between different gases. The GWP over a 100-year time horizon (reference period as defined by the Intergovernmental Panel On Climate Change - IPCC) is given below:
Carbon dioxide CO₂ 1
Tetrafluoropropene C3H2F4 4
Methane CH₄ 28
Nitrous oxide N₂O 265
TetrafluoroethaneC2H2F41,300
Chlorofluorocarbons (CFCs) e.g. CClF313.900
Fluorocarbons (PFCs, HFCs) e.g. CHF3 12,400
Nitrogen trifluoride NF₃ 16,100
Sulphur hexafluoride SF₆ 23,500
These values should be understood as follows: if one ton of SF₆ were released into the atmosphere, the greenhouse effect of this ton would be as large as 23,500 tons of carbon dioxide in the atmosphere. Consequently, it quickly becomes clear why it is so important not to focus only on carbon dioxide (CO₂), but to reduce the concentration and production of all GHGs.
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