Editing IPCC:AR6/WGIII/Chapter-10 (section)

=== Harmonisation method ===

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First, the datapoints were separated into categories based on the approximate classification (e.g., heavy-duty vs medium-duty trucks), powertrain (i.e., internal combustion engines (ICEV), hybrid electric vehicles (HEV), battery electric vehicles (BEV), fuel cell vehicles (FCV)), and fuel combination. For each category of vehicle/powertrain/fuel, a simplified LCA that harmonises values from across the reviewed studies was constructed, using the following basic equation:

[[File:0b1ba35db35b3694c2691a7794fa8b06 IPCC_AR6_WGIII_Appendix_10_1_Equation.png]]
Where:

• Lifecycle GHG intensity represents the normalised lifecycle GHG emissions associated with each transportation mode, measured in gCO 2 -eq per passenger-kilometre (pkm)or gCO 2 -eq per tonne-kilometre (tkm).

'''•''' FC is the fuel consumption of the vehicle in megajoules (MJ) or kilowatt hours (kWh) per km.

'''•''' P represents the payload (measured in tonnes of cargo) or number of passengers, at a specified utilisation capacity (e.g., 50% payload or 80% occupancy).

'''•''' EF is an emissions factor representing the lifecycle GHG intensity of the fuel used, measured in gCO 2 -eq MJ –1 or gCO 2 -eq kWh –1 . A single representative EF value is selected for each fuel type. When a given fuel type can be generated in different ways with substantially different upstream emissions factors (e.g., hydrogen from methane steam reforming vs hydrogen from water electrolysis), these are treated as two different fuel categories. The fuel emissions factors that were used are presented in Table 10.8.

'''•''' VC are the vehicle cycle emissions of the vehicle, measured in gCO 2 -eq per vehicle. This may include vehicle manufacturing, maintenance and end of life, or just manufacturing.

• LVKT is the lifetime vehicle kilometres travelled.

Note: for plug-in hybrid electric vehicles (PHEV), the value of FC/P*EF is a weighted sum of this aggregate term for each of battery and diesel/gasoline operation.

Fuel emissions factors used are presented in Table 10.8. Note that the fuel emissions factors were compiled from several studies that used different global warming potential (GWP) values in their underlying assumptions, and therefore the numbers reported here may be slightly different if the 100-year global warming potential (GWP100) from the AR6 had been used. This difference would be small given the small contribution from non-CO 2 gases to the total lifecycle emissions. For example, methane (CH 4 ) emissions exist in the lifecycle of natural gas supply chains or natural gas-dependent supply chains such as hydrogen from steam methane reforming (SMR). Recent data from the US suggests emissions of approximately 0.2–0.3 gCH 4 per MJ natural gas ( [[#Littlefield--2017|Littlefield et al. 2017]] , 2019), which would range by no more than 1–2 gCO 2 -eq per MJ natural gas (&lt;3% of natural gas lifecycle emissions) when converting from a GWP100 of 25 (AR4) or 36 (AR5) to the current (AR6) GWP100 of 29.8.

For LDVs, the entire distribution of estimated lifecycle emissions is presented for each vehicle/powertrain/fuel category (as a boxplot) in Figure 10.4. For trucks, rail and buses, only the low and high estimates are presented (as solid bars) in Figures 10.6 and 10.8, since the number of datapoints were not sufficient to present as a distribution. Table 10.9 presents the low and high estimates of fuel efficiency for each category. The references used are reported in the main text.

For transit and freight, the lifecycle harmonisation exercise allows two aggregate parameters to vary from the low to high among submitted values within each category: FC/P and VC/P. Aggregate parameters are used to capture internal correlations (e.g., fuel consumption and payload; both depend heavily on vehicle size) and are presented in Tables 10.10 to 10.14. The references used are reported in the main text.

'''Table 10.8 | Fuel emissions factors used to estimate lifecycle greenhouse gas (GHG) emissions of passenger and freight transport pathways.'''

{| class="wikitable"
|-
| '''Fuel'''

| '''Emissions factor'''

| '''Units'''

| '''Source'''

|-
| Gasoline

| 92

| gCO 2 -eq MJ –1

| Submissions to IPCC data call (median)

|-
| Diesel

| 92

| gCO 2 -eq MJ –1

| Submissions to IPCC data call (median)

|-
| Diesel, high

| 110

| gCO 2 -eq MJ –1

| Diesel from oil sands: average of in-situ pathways ( [[#Guo--2020|Guo et al. 2020]] )

|-
| Biofuels, IAM EMF33

| 25

| gCO 2 -eq MJ –1

| From Chapter 7

|-
| Biofuels, partial models CLC

| 36

| gCO 2 -eq MJ –1

| From Chapter 7

|-
| Biofuels, partial models NG

| 141

| gCO 2 -eq MJ –1

| From Chapter 7

|-
| Compressed natural gas

| 71

| gCO 2 -eq MJ –1

| Submissions to IPCC data call (median)

|-
| Liquefied natural gas

| 76

| gCO 2 -eq MJ –1

| Submissions to IPCC data call (median)

|-
| Liquefied petroleum gas

| 78

| gCO 2 -eq MJ –1

| Submissions to IPCC data call (median)

|-
| DAC FT-Diesel, wind electricity

| 12

| gCO 2 -eq MJ –1

| From electrolytic hydrogen produced using low-carbon electricity ( [[#Liu--2020a|Liu et al. 2020a]] )

|-
| DAC FT-Diesel, natural gas electricity

| 370

| gCO 2 -eq MJ –1

| From electrolytic hydrogen produced using natural gas electricity; extrapolated from [[#Liu--2020a|Liu et al. (2020a)]]

|-
| Ammonia, low carbon renewable

| 3.2

| gCO 2 -eq MJ –1

| From electrolytic hydrogen produced using low-carbon electricity via Haber-Bosch ( [[#Gray--2021|Gray et al. 2021]] )

|-
| Ammonia, natural gas SMR

| 110

| gCO 2 -eq MJ –1

| From H 2 derived from natural gas steam methane reforming; via Haber-Bosch ( [[#Frattini--2016|Frattini et al. 2016]] )

|-
| Hydrogen, low carbon renewable

| 10

| gCO 2 -eq MJ –1

| From electrolysis with low-carbon electricity ( [[#Valente--2021|Valente et al. 2021]] )

|-
| Hydrogen, natural gas SMR

| 95

| gCO 2 -eq MJ –1

| From steam-methane reforming of fossil fuels

|-
| Wind electricity

| 9.3

| gCO 2 -eq kWh –1

| Submissions to IPCC data call (median)

|-
| Natural gas electricity

| 537

| gCO 2 -eq kWh –1

| Submissions to IPCC data call (median)

|-
| Coal electricity

| 965

| gCO 2 -eq kWh –1

| Submissions to IPCC data call (median)

|}

'''Table 10.9 | Range of fuel efficiencies for light-duty vehicles by fuel and powertrain category, per vehicle kilometre.'''

{| class="wikitable"
|-
| rowspan="2"| '''Fuel'''

| rowspan="2"| '''Powertrain'''

| colspan="2"| '''Fuel efficiency'''

'''(MJ per vehicle-km)'''

| colspan="2"| '''Electric efficiency'''

'''(kWh per vehicle-km)'''

|-
| '''Low'''

| '''High'''

| '''Low'''

| '''High'''

|-
| Compression ignition

| ICEV

| 1.34

| 2.6

|
|-
| Spark ignition

| ICEV

| 1.37

| 2.88

|
|-
| Spark ignition

| HEV

| 1.22

| 2.05

|
|-
| Compression ignition

| HEV

| 1.15

| 1.51

|
|-
| Electricity

| BEV

|
| 0.12

| 0.242

|-
| Hydrogen

| FCV

| 1.14

| 1.39

|
|}

'''Table 10.10 | Range of fuel efficiencies for buses by fuel and powertrain category, at 80% occupancy.'''

{| class="wikitable"
|-
| rowspan="2"| '''Fuel'''

| rowspan="2"| '''Powertrain'''

| colspan="2"| '''Fuel efficiency'''

'''(MJ per passenger-km)'''

| colspan="2"| '''Electric efficiency'''

'''(kWh per passenger-km)'''

|-
| '''Low'''

| '''High'''

| '''Low'''

| High

|-
| Diesel

| ICEV

| 0.16

| 0.52

|
|-
| CNG

| ICEV

| 0.25

| 0.61

|
|-
| LNG

| ICEV

| 0.27

| 0.37

|
|-
| Biodiesel

| ICEV

| 0.16

| 0.52

|
|-
| DAC FT-Diesel

| ICEV

| 0.16

| 0.52

|
|-
| Diesel

| HEV

| 0.11

| 0.37

|
|-
| Electricity

| BEV

|
| 0.01

| 0.04

|-
| Hydrogen

| FCV

| 0.11

| 0.31

|
|}

'''Table 10.11 | Range of fuel efficiencies for passenger rail by fuel and powertrain category, at 80% occupancy.'''

{| class="wikitable"
|-
| rowspan="2"| '''Fuel'''

| rowspan="2"| '''Powertrain'''

| colspan="2"| '''Fuel efficiency'''

'''(MJ per passenger-km)'''

| colspan="2"| '''Electric efficiency'''

'''(kWh per passenger-km)'''

|-
| '''Low'''

| '''High'''

| '''Low'''

| High

|-
| Diesel

| ICEV

| 0.36

| 0.40

|
|-
| Biofuels

| ICEV

| 0.36

| 0.40

|
|-
| DAC FT-Diesel

| ICEV

| 0.36

| 0.40

|
|-
| Diesel

| HEV

| 0.33

| 0.33

|
|-
| Electricity

| BEV

|
| 0.03

| 0.03

|-
| Hydrogen a

| FCV

| 0.18

| 0.18

|
|}

a Occupancy corresponds to average European occupancy rates ( [[#IEA--2019e|IEA 2019e]] ).

'''Table 10.12 | Range of fuel efficiencies for heavy-duty truck by fuel and powertrain category, at 100% payload.'''

{| class="wikitable"
|-
| rowspan="2"| '''Fuel'''

| rowspan="2"| '''Powertrain'''

| colspan="2"| '''Fuel efficiency'''

'''(MJ per tonne-km)'''

| colspan="2"| '''Electric efficiency'''

'''(kWh per tonne-km)'''

|-
| '''Low'''

| '''High'''

| '''Low'''

| '''High'''

|-
| Diesel

| ICEV

| 0.38

| 0.93

|
|-
| CNG

| ICEV

| 0.48

| 1.45

|
|-
| LNG

| ICEV

| 0.43

| 1.00

|
|-
| Biofuels

| ICEV

| 0.38

| 0.93

|
|-
| Ammonia a

| ICEV

| 0.38

| 0.93

|
|-
| DAC FT-Diesel

| ICEV

| 0.38

| 0.93

|
|-
| Diesel

| HEV

| 0.34

| 0.59

|
|-
| LNG

| HEV

| 0.46

| 0.51

|
|-
| Electricity

| BEV

|
| 0.03

| 0.09

|-
| Hydrogen

| FCV

| 0.25

| 0.43

|
|-
| Ammonia b

| FCV

| 0.25

| 0.43

|
|}

a Ammonia ICEV trucks are assumed to have the same fuel economy as diesel ICEVs due to lack of data.

b Ammonia FCV trucks are assumed to have the same fuel economy as hydrogen FCVs due to lack of data.

'''Table 10.13 | Range of fuel efficiencies for medium-duty truck by fuel and powertrain category, at 100% payload.'''

{| class="wikitable"
|-
| rowspan="2"| '''Fuel'''

| rowspan="2"| '''Powertrain'''

| colspan="2"| '''Fuel efficiency'''

'''(MJ per tonne-km)'''

| colspan="2"| '''Electric efficiency'''

'''(kWh per tonne-km)'''

|-
| '''Low'''

| '''High'''

| '''Low'''

| '''High'''

|-
| Diesel

| ICEV

| 0.85

| 2.30

|
|-
| CNG

| ICEV

| 1.08

| 2.54

|
|-
| LNG

| ICEV

| 1.05

| 1.41

|
|-
| Biofuels

| ICEV

| 0.85

| 2.30

|
|-
| Ammonia a

| ICEV

| 0.85

| 2.30

|
|-
| DAC FT-Diesel

| ICEV

| 0.85

| 2.30

|
|-
| Diesel

| HEV

| 0.81

| 1.54

|
|-
| Electricity

| BEV

|
| 0.12

| 0.22

|-
| Hydrogen

| FCV

| 0.65

| 0.99

|
|-
| Ammonia b

| FCV

| 0.65

| 0.99

|
|}

a Ammonia ICEV trucks are assumed to have the same fuel economy as diesel ICEVs due to lack of data.

b Ammonia FCV trucks are assumed to have the same fuel economy as Hydrogen FCVs due to lack of data.

'''Table 10.14 | Range of fuel efficiencies for freight rail by fuel and powertrain category, at an average payload.'''

{| class="wikitable"
|-
| rowspan="2"| '''Fuel'''

| rowspan="2"| '''Powertrain'''

| colspan="2"| '''Fuel efficiency'''

'''(M per /tonne-km)'''

| colspan="2"| '''Electric efficiency'''

'''(kWh per tonne-km)'''

|-
| '''Low'''

| '''High'''

| '''Low'''

| '''High'''

|-
| Diesel

| ICEV

| 0.11

| 0.78

|
|-
| Biodiesel

| ICEV

| 0.11

| 0.78

|
|-
| DAC FT-Diesel

| ICEV

| 0.11

| 0.78

|
|-
| Electricity

| BEV

|
| 0.01

| 0.12

|-
| Hydrogen

| FCV

| 0.10

| 0.10

|
|}

<div id="Appendix 10.2: Data and Assumptions for Lifecycle Cost Analysis" class="h1-container"></div>

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