The Volvo Total Lifecycle Carbon Study and the Missing XC-40 PHEV
Volvo's excellent study on total vehicle lifecycle carbon footprint brought to my attention the fact that XC-40 Rehcharge (BEV) starts its lifecycle with a 70% larger carbon footprint than its ICE equivalent XC-40 and slowly recuperates that carbon disadvantage over time at a rate dependent on the renewables mix of the electricity used to charge it.
The higher manufacturing carbon footprint of the XC-40 Recharge is primarily due to greater use of aluminum (30% added carbon footprint) and the battery (40% added carbon footprint) vs the equivalent ICE.
In all cases studied, the XC-40 recharge has a lower total lifecycle carbon footprint, but the difference is determined by the renewables mix of the electricity used to charge it and the total lifecycle miles.
Adding the XC-40 Plug-in Hybrid
Notably absent from the Volvo study is the Plug-in Hybrid (PHEV) version of the XC-40. The PHEV is interesting because it has a much smaller battery (10.7 KwH) compared with the BEV 79, which means it starts at less disadvantage for the carbon associated with battery manufacturing. Under the right conditions, could the XC-40 Plug-in Hybrid have a lower total lifecycle carbon footprint than the BEV XC-40 Recharge?
The following calculator parameterizes the inputs from the Volvo study and allows you to see which vehicle has the lowest total carbon input under what conditions.
Hope you enjoy!
Mileage at end-of-life for all vehicle types
The percentage of renewable electricity used to charge the PHEV and BEV.
Varies by state and presence of a home renewable installation (e.g. rooftop solar).
Size in KwH of the BEV battery
Size in KwH of the PHEV battery
Percent of all miles that are driven in pure EV for PHEV
Percent gain in miles traveled per gallon of fuel used for PHEV over ICE when using fuel. Averages are sourced from EPA estimates of fuel economy for vehicles available in both ICE and PHEV models.
Total Lifecycle Metric Tons CO2
Assumptions and Caveats
One key assumption is that a PHEV has a materials carbon footprint less than or equal to a BEV. The authors of the Volvo study cite the extensive use of aluminum in BEV batteries and powertrains as being a major source of added carbon footprint.
Curb weight is a reasonable proxy for the carbon footprint associated with materials. Looking at vehicles available from major manufacturers in both ICE and PHEV configurations or ICE and BEV configurations, on average a PHEV weighs 14% more than its ICE equivalent, and a BEV weighs 21% more than its ICE equivalent. Thus it is reasonable to assume that a PHEV is no worse (and may be up to 5% better) than a BEV from a materials standpoint.
What about added manufacturing complexity and engineering complexity of the dual powertrains used in PHEVs? The Volvo study suggests that such complexity may be negligble. Both ICE and BEV versions of the XC-40 have 1.4 metric tons of carbon associated with Volvo manufacturing—the second smallest category of carbon footprint (behind EOL carbon). It is difficult to imagine that the PHEV XC-40 has a meaningfully different carbon footprint associated with manufacturing.