Pathways to More Rapidly Reduce Transportation’s Climate Change Impact

By Dave Foster, John Koszewnik, Wallace Wade, Ward Winer

Current US energy policies are laser-focused on addressing climate change—as they should be. Meanwhile, this summer’s soaring gasoline prices show that US dependence on foreign oil continues to be a significant vulnerability for the economy and national security. Policy options that tackle both issues—reducing climate-warming carbon emissions as well as oil dependence—currently center on encouraging the manufacture and purchase of battery electric vehicles (BEVs). Fully deployed, BEVs could reduce transportation-related emissions to the lowest possible level. But this strategy alone does not recognize some of the limitations of BEVs nor the advantages of other climate-friendly technologies. Expanding current policies beyond their focus on BEVs would engage more of the United States in the transition to lower emissions on a faster timetable.

As engineers who have worked in academia and the automotive industry, we see policy opportunities that could make transportation cleaner and cheaper more quickly. These opportunities can and should be taken during the transition to a fully sustainable zero carbon energy system.   

Government policies directed at lowering carbon emissions balance multiple tradeoffs involving fuels, infrastructure, and vehicles. Sorting through these tradeoffs involves considering not only the carbon emitted by a transportation technology, but also emissions involved in the vehicle’s manufacture and disposal, as well as the production of the fuel or electricity it uses. Such life cycle analyses provide a more accurate picture of the environmental impact of alternative technologies, and can play a crucial role in helping choose transition technologies that minimize total carbon emissions during the nation’s transition to a sustainable future.

Expanding current policies beyond their focus on BEVs would engage more of the United States in the transition to lower emissions on a faster timetable.

The life cycle analysis prepared by the International Council on Clean Transportation (ICCT), an independent nonprofit environmental advocacy group, offers useful insights. Their data compare today’s baseline level of carbon emissions from vehicles solely powered by internal combustion engines and running on gasoline, which constitute 90% of new vehicle sales in the United States, to other combinations of power systems and fuels. BEVs using renewable energy are clearly the most environmentally friendly alternative, even though they are not truly zero emission vehicles when all factors are considered.  

The current approach to addressing climate change focuses primarily on the endgame: taking steps to maximize the number of BEVs on the road as quickly as possible. However, an alternative approach is to focus on more rapidly replacing fossil fuel-burning, nonhybrid vehicles on the road with multiple vehicle and fuel alternatives that reduce emissions. We believe that such policy options are worth exploring as they could reduce carbon dioxide (CO₂) emissions on a faster timetable.

Embracing the power of “second best” technologies

Although BEVs work extremely well for some vehicle owners and applications, they don’t work for everyone. For a homeowner with solar panels on the roof, a 240-volt Level 2 charger in the garage, a backup battery system for sunless days, and a second family vehicle that can be used for vacation trips, BEV ownership is ideal, saving time and money through home recharging. 

But for people who live in apartments, who have only one vehicle, or who live in a cold climate—which can reduce driving range by as much as 40% in the winter—BEVs are not an easy substitution for a gasoline-powered car. The fact that BEVs cost more than gasoline vehicles further raises the barrier to adoption. In fact, a recent study of electric vehicle owners in California found that 97% of them live in single-family homes or townhouses, and 95% of them own a second, gasoline-powered vehicle.

Plug-in hybrids (PHEVs) offer the benefits of electrification to a broader set of consumers while providing a more climate friendly alternative to vehicles that are solely powered by gasoline. As shown in the above chart, PHEVs offer roughly two-thirds of the life cycle CO₂ reduction per mile that a full BEV offers. For those with a daily commute of less than 40 miles, the CO₂ produced during their drive is the same as that of a BEV. PHEVs also enable owners to drive long distances whenever they want to without incurring lengthy delays due to recharging.

For people who live in apartments, who have only one vehicle, or who live in a cold climate—which can reduce driving range by as much as 40% in the winter—BEVs are not an easy substitution for a gasoline-powered car.

In the drive to quickly bring electric transportation to more people, a unique advantage of PHEVs, ironically, is their smaller batteries. According to Toyota, approximately eight PHEV batteries can be produced using the same amount of lithium, cobalt, nickel, and other natural resources as one BEV. This results in fewer CO₂ emissions associated with raw material extraction and battery manufacturing. It also may avoid some of the significant price increases that are likely when demand for battery materials outstrips supply, as demonstrated by the steep increases in lithium prices over the last year.  Plus, it mitigates possible risks of a single country—namely China—controlling nearly three-quarters of the raw materials required to produce lithium-ion batteries.

Government policies have an enormous impact on the acceptance of electric vehicles. Although the incentives included in the Inflation Reduction Act of 2022 will undoubtedly make BEVs and PHEVs more affordable for many households, they are very complex, including vehicle purchase price limits, purchaser income limits, and vehicle qualification requirementsbased on sourcing an increasing percentage of critical battery materials and battery manufacturing within the United States or free trade partners. Given the uncertainty these restrictions may have on total electric vehicle sales, the US Environmental Protection Agency (EPA) should closely monitor the impact of this legislation through the first half of 2023, making recommendations to Congress on any needed changes.  

Create incentives for better performance

While the current policy push towards BEVs and PHEVs is important, not all BEVs are equally environmentally friendly. For example, the Tesla 3 expends half as much energy per mile driven as the Porsche Taycan Turbo S. General Motors’ Hummer EV has a battery over five times the size of the battery for the Nissan Leaf, releasing significantly more CO₂during its manufacture. Even though some BEVs are much better for the environment than others, incentives for all of them are now the same, and consumers have few ways to distinguish among them.  

Today, the EPA requires that dealers place labels on the windows of gasoline and diesel vehicles detailing their fuel efficiency in miles per gallon. Changing the labeling requirements for EVs would enable consumers to make knowledgeable choices about the true environmental impact of the vehicle they are considering and the time that it would really take to charge. Such a change would also create incentives for the auto industry to produce EVs that deliver the environmental impacts and charging times that consumers want.  

To accomplish this, the EPA should mandate a new car window label that ranks the vehicle’s kilowatt-hour/mile and CO₂ emissions against others in its size classification, as well as against the average BEV—just as it does for the fuel economy of gasoline and diesel vehicles. And future federal tax credits should be revised by Congress to reward and encourage more efficient BEV vehicles. 

Window labels could also address currently misleading statements about the time it takes to charge a vehicle. Charging times in press releases and advertising materials are based on the highest power rating that the vehicle can accept and assume availability of a DC fast charger with the same or higher power rating. This can lead to unrealistic customer expectations.   

Changing the labeling requirements for EVs would enable consumers to make knowledgeable choices about the true environmental impact of the vehicle they are considering and the time that it would really take to charge.

For example, in 2020, Cadillac announced that its new battery-electric SUV, the Lyriq, would feature General Motors’ new 800-volt technology, allowing a 90% charge in just 10 minutes. (Automotive manufacturers never share 100% charge time information because the last 10% charge rate is much slower.) Cadillac’s actual marketing materials for the 2023 Lyriq, however, are less impressive, claiming 76 miles of range can be obtained within 10 minutes with “DC fast charging rates.” However, this calculation assumes the charger has a rated power of 190 kilowatts, the highest level the Lyriq can accept. Chargers with this power rating are rare: roughly two-thirds of public DC fast chargers available today in the United States are rated at 50 kilowatts, which decreases the actual range provided within 10 minutes from 76 miles to 20 miles. On such a typical DC fast charger, it would take more than two and a half hours to obtain the Lyriq’s 312-mile range. Even less impressive is the six and a half hours of charging time for the Lyriq on a 240-volt Level 2 charger shown in the EPA’s 2023 Fuel Economy Guide.

To provide consumers with accurate charging time information, the EPA’s window sticker should also include the vehicle’s battery capacity in kilowatt-hours and a comparison of its maximum charging rate (miles/minute) and the average charging rate with a 50 kilowatt charger, at least until such time that higher power chargers become predominant.

The recently enacted Infrastructure Investment and Jobs Act includes $7.5 billion to build out a nationwide network of 500,000 electric vehicle chargers. Although far short of the 2.4 million chargers recommended by the ICCT to support the US vehicle fleet forecast for 2030, it is certainly a step in the right direction. In administering the legislation, the Departments of Energy and Transportation should restrict funding to chargers with a power rating of at least 200 kilowatts, thereby decreasing charging times on today’s public chargers by a factor of four.  

Furthermore, the EPA should also mandate that the actual power level be clearly specified on all public chargers as well as on all websites providing charger locations. 

Prepare for a long transition with supportive policies and multiple fuels

The timelines that lawmakers are presenting for transitioning to BEVs are aggressive, both in the United States and in Europe. In August, the California Air Resources Board signed off on a sweeping plan requiring all new passenger cars and light trucks sold in the state to be electric vehicles or other emissions-free models by 2035. In a similar action, members of the European Parliament in June voted to ban the sale of new petrol and diesel cars by 2035. 

Despite these well-intentioned moves, turnover of the entire vehicle fleet will be slow, and BEVs will continue to share the road with gasoline and diesel vehicles for many decades. The average vehicle driven today is about 12 years old, and new vehicle sales each year represent between 6 and 7% of the total number of vehicles in operation. This means that the aggressive 50% sales mix target proposed by the Biden administration for electric vehicles in 2030 will translate to an incremental shift of only 3 to 4% of the total vehicles in operation each year.   

To reduce transportation-related CO₂ emissions in the interim, we suggest reexamining low-carbon biofuels and synthetic fuels, which can be used in conventional gasoline and diesel vehicles, simultaneously reducing petroleum dependence and CO₂ emissions. Most importantly, these benefits can be realized on the entire fleet of vehicles in operation as soon as these fuels become available, since compatible vehicles and the distribution infrastructure for such fuels already exist. 

Significant gains could come from advancing next-generation “drop-in” biofuels—which don’t require significant infrastructure investments to implement—with better carbon profiles that can entirely replace (or be mixed with) gasoline and diesel. These fuels use a variety of feedstocks, such as leftover cornstalks, genetically modified algae, halophytes (plants that thrive in salt water), and decomposed organic matter, which could create sustainable regional fuel sources as well as jobs. 

Approaches that attempt to tackle two or more societal needs at once could be particularly helpful. For example, Red Rock Biofuels, which uses waste wood products including dead trees, tackles both the growing need for sustainable aviation and diesel fuel and the growing problem of catastrophic wildfires. 

We suggest reexamining low-carbon biofuels and synthetic fuels, which can be used in conventional gasoline and diesel vehicles, simultaneously reducing petroleum dependence and CO₂ emissions.

The United States should continue to invest in the development of cost-competitive sustainable fuels, both bio-based and fully synthetic-based, looking in particular for solutions that reduce emissions, create jobs, and help tackle other economic or environmental problems. 

A final option that should get more attention is hydrogen. A fuel cell vehicle running on hydrogen produces only water as exhaust, and the tank can be refilled in 3 to 5 minutes—comparable to a conventional gasoline vehicle. Most hydrogen available today comes from natural gas. However, there are other, cleaner paths to hydrogen production, with the most encouraging being “green” hydrogen produced from water through electrolysis using renewable energy sources. The US Department of Energy is seeking an 80% reduction in the cost of green hydrogen by 2030, which would make hydrogen a much cheaper vehicle fuel than gasoline.  

Hydrogen fueling is particularly attractive for long-haul heavy-duty trucks and heavy equipment that do not return to a central depot each night, thereby reducing their emissions while avoiding lengthy charging times for electric versions of large trucks. 

Today, California has 53 retail hydrogen refueling stations with another 68 in development. Admittedly, the costs associated with increasing the hydrogen infrastructure are large. But so are the capital costs associated with upgrading the grid to provide sufficient electric power for BEVs and PHEVs. Both infrastructures will be needed to make faster progress on emissions goals.

Hydrogen-fueled internal combustion engines may also prove to be an attractive heavy-duty truck alternative because the engines are less expensive to build, there is an existing manufacturing infrastructure, and they are more tolerant to impurities in the hydrogen supply than are fuel cell engines. 

To encourage hydrogen-fueled vehicles for both fuel cell and internal combustion engine versions, the EPA, as part of their implementation of Renewable Fuel Standards, should mandate that only “green” hydrogen be supplied for transportation use. Secondly, joint government and industry programs should be expanded for the installation of hydrogen fueling infrastructure. 

Perfect should not be the enemy of good

The costs associated with increasing the hydrogen infrastructure are large. But so are the capital costs associated with upgrading the grid to provide sufficient electric power for BEVs and PHEVs.

Multiple vehicle options exist that are better than today’s fossil fuel-powered vehicles. Net zero operating CO₂, as will eventually be provided by fully electric BEVs powered by renewable energy, is certainly part of the long-term endgame. However, even with thoughtful policies, the path to that vision will be slow and haphazard. In the interim, transportation-related CO₂ emissions can be reduced more rapidly by pursuing CO₂ reductions across all vehicles, not just in new BEV vehicles sold to a subset of relatively affluent Americans.

Multiple types of relatively climate-friendly vehicles and accelerated development of sustainable substitute fuels should all be part of the picture. Pursuing all these policies will provide a more rapid reduction in CO₂ emissions in the near-term while ultimate zero emission technologies are being improved and implemented—and ensure that in the transportation sector, perfect does not become the enemy of good.