Study: Concern Over EVs Emitting More Carbon than Combustion Engine Vehicles Unfounded

A graphic that depicts the lifetime greenhouse gas emissions for each class of vehicle and powertrain. // Courtesy of Woody et al. in Environmental Research Letters, 2022
A graphic that depicts the lifetime greenhouse gas emissions for each class of vehicle and powertrain. // Courtesy of Woody et al. in Environmental Research Letters, 2022

The University of Michigan in Ann Arbor and Ford Motor Co. collaborated on a study to address the question of what the electrification of pickup trucks means for the decarbonization of the transportation industry.

Major automotive manufacturers are ramping up production of electric trucks as a key strategy to reduce the greenhouse gas emissions of their vehicles. This includes Detroit’s Big Three automakers — Ford, General Motors Co., and Stellantis — which all have started investing in and transitioning to electric vehicles in different capacities.

Light-duty vehicles including sedans, SUVs, and pickup trucks, are currently responsible for 58 percent of U.S. transportation sector greenhouse gas emissions. Pickup trucks accounted for 14 percent of light-duty vehicle sales in the U.S. in 2020, and the market share of both pickups and SUVs has grown in recent years.

“This is an important study to inform and encourage climate action. Our research clearly shows substantial greenhouse gas emission reductions that can be achieved from transitioning to electrified powertrains across all vehicle classes,” says Greg Keoleian, study senior author, professor at the U-M School for Environment and Sustainability, and director of the Center for Sustainable Systems.

The study, which was published online March 1 in the journal Environmental Research Letters, also evaluated the savings in greenhouse gas emissions relative to gasoline-powered pickup trucks.

In the study, researchers conducted a cradle-to-grave assessment of the life cycle of pickup trucks and compared the implications of pickup truck electrification to those of sedan and SUV electrification.

With a focus on evaluating greenhouse gas emissions, researchers looked at three different model-year 2020 powertrain option — internal-combustion-engine (ICE) vehicles, hybrid-electric vehicles, and battery-electric vehicles (BEV) — for midsize sedans, midsize SUVs and full-size pickup trucks, accounting for differences in fuel economy, annual mileage, vehicle production, and vehicle lifetime across vehicle classes.

The study found that for sedans, SUVs, and pickup trucks, battery-electric vehicles have approximately 64 percent lower cradle-to-grave life cycle greenhouse gas emissions than ICE vehicles on average across the United States.

“This study can help us to understand the potential impact of electrification from an emissions-reduction perspective, particularly as we introduce new electric vehicles, and how we can continue to accelerate our progress towards carbon neutrality. We’re proud to partner with U-M in this critical work,” says Cynthia Williams, global director of sustainability, homologation, and compliance at Ford.

The study offers several key findings. Researchers, for instance, found that replacing an ICE vehicle with a BEV results in greater total tonnage of greenhouse gas emissions reductions as the vehicle size increases, due to the greater fuel consumption of larger vehicles.

Though the percentage savings is about the same across vehicle classes, on average, replacing an ICE sedan with a BEV sedan saves 45 metric tons of carbon dioxide equivalent; replacing an ICE SUV with a BEV SUV saves 56 metric tons of carbon dioxide equivalent; and replacing an ICE pickup with a BEV pickup saves 74 metric tons carbon dioxide equivalent over the lifetime of the vehicles, says study first author Max Woody, research specialist at U-M’s Center for Sustainable Systems.

The researchers also found that BEVs have larger greenhouse gas emissions in their manufacturing than ICE vehicles due to battery production, but this impact is offset by savings in their operation. For BEVs and ICE vehicles, the break-even time is 1.2 to 1.3 years for sedans, 1.4 to 1.6 years for SUVs, and 1.3 years for pickup trucks, based on the average U.S. grid and vehicle miles traveled.

“This study expands upon previous studies that have focused on comparing battery-electric vehicle sedans to their internal-combustion-engine or hybrid counterparts,” says Keoleian. “We report emissions for vehicle production, use and end-of-life stages on a per-mile basis and over the total vehicle lifetime.

“In addition, we analyzed the regional variation in emissions considering differences in electricity grid mixes and ambient temperatures, and we also explored the effects of the rate of grid decarbonization on emission reduction.”

Vehicle emissions vary across the country, as different temperatures and different drive cycles affect a vehicle’s fuel economy. For electric vehicles, the greenhouse gas emissions intensity of the local electricity grid is also an important factor. The study developed maps to show the lifetime grams of carbon dioxide equivalent per mile for each powertrain and vehicle type by county across the U.S.

Researchers found that public concerns about BEVs having higher emissions than ICE vehicles or hybrids are largely unfounded, as BEVs outperform hybrids in 95 to 96 percent of counties, while they outperform ICE vehicles in 98 to 99 percent of counties, even assuming only modest progress towards grid decarbonization.

Charging strategies can further reduce BEV emissions. The study found that charging during the hours of the day with the lowest grid emissions intensity can reduce emissions by 11 percent on average.

“Deployment of electric vehicles and expansion of renewable energy resources like solar and wind should be done at the same time,” says Woody. “The benefit of each is increased by the development of the other.”

The other authors of the study are Parth Vaishnav of the U-M School for Environment and Sustainability and Center for Sustainable Systems, and Robert De Kleine, Hyung Chul Kim, James Anderson, and Timothy Wallington of Ford’s Research and Innovation Center.

The study was supported by Ford Motor Co. through a Ford-University of Michigan Alliance Project Award.