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Page 4 of 14 Li et al. Carbon Footprints 2024;3:6 https://dx.doi.org/10.20517/cf.2023.54

METHODS
This section initially outlines the calculation methodologies for carbon emissions from automotive air
conditioning. Depending on the defined carbon accounting boundaries, the LCA of automotive air
conditioning can be conducted at two distinct levels: the automotive air conditioning product level and the
automotive air conditioning fleet level. For the product level, E is the life cycle carbon emissions of an
mac
automotive air conditioning product, which require consideration of both direct and indirect carbon
emissions generated throughout its production, transportation, usage, and recycling stages, as illustrated in
Figure 1. For the fleet level, the E is the fleet carbon emissions of all automotive air conditioning products
fleet
at a specific time point, considering the total fleet inventory, distinguishing between vehicles in various
stages - newly sold, in operation, or retired. Therefore, E represents the cumulative carbon emissions of
fleet
all automotive air conditioning products within the fleet inventory at different life cycle stages . The
[16]
distinction between E and E lies in their temporal dimensions. E - reflecting carbon emissions from
fleet
mac
mac
an individual automotive air conditioning product - spans the entire life cycle duration of automotive air
conditioning , while E - representing carbon emissions from the whole automotive air conditioning fleet
[17]
fleet
- is calculated at a specific time point (i.e., a particular year).
Given that carbon emission data for automotive air conditioning products at various lifecycle stages are an
essential component of the fleet carbon emission calculation, the initial step is to calculate the life cycle
carbon emissions for MAC (Equation 1).

E = E + E + E + E + E (1)
EOL
SO
mfg
OT
ref
mac
Where E is emissions during the manufacturing processes of refrigerants and automotive air conditioning
Mfg
components, E is the indirect emissions generated as the automotive air conditioning consumes energy
OT
during vehicle operation while acting as a partial load, E is the indirect emissions produced as the
SO
automotive air conditioning operates and consumes energy, E indicates the indirect emissions generated
EOL
during the disposal and recycling processes of refrigerants and automotive air conditioning systems, E is
ref
the direct equivalent carbon dioxide emissions resulting from refrigerant leakage from the automotive air
[14]
conditioning into the atmosphere. The calculations in this section are based on our previous research .
The emission data for the manufacturing and disposal stages of refrigerants and air conditioning materials
are detailed in Table 2. Performance test data for several refrigerants were obtained from the Jiangsu
Zhongguancun Research Institute of SJTU [18-23] . The urban climate and vehicle travel data required for
carbon emission calculations are primarily sourced from the China Standard Weather Database , the
[24]
Chinese Motor Vehicle AVKT Data Report , and the Road Traffic Analysis Report for Chinese Urban
[25]
Private Cars .
[26]
To visually depict the macroscopic impact of refrigerant replacement on emissions at the fleet level of
automotive air conditioning, it is essential to conduct further calculations for the annual fleet emissions
(Equation 2).

E = Sale × E + Stock × (E + E +E )/t + Scrap × E (2)
EOL
OT
life
y,t
y,t
ref
SO
y,t
Mfg
fleet
where Sale is the quantity of newly sold vehicles in a specific year, Stock is the fleet’s total stock in that
y,t
y,t
year, and Scrap is the number of vehicles scrapped in that year, with “t” representing the fuel type. For the
y,t
sake of convenience in computation, the annual operational emissions and refrigerant leakage emissions of
the fleet are considered averages over the life of automotive air conditioning.