Cradle-to-Grave Lifecycle Analysis: Batteries' New Foes Are Supposedly E-Fuels

The Argonne National Laboratory last year updated a 2016 cradle-to-grave lifecycle analysis on the U.S. light-duty vehicle-fuel pathways, namely sedans, and SUVs. While batteries are clearly the best performers in slashing GHG emissions, e-fuels show interesting estimates and seem to give a big chance to ICE cars in the future.
In theory, e-fuels promise to keep alive the ICE 6 photos
Photo: Image by Rochak Shukla on Freepik
Fuel production pathways considered in the studyGHG emissions for midsize sedansGHG emissions for small SUVsBosch is investing much in e-fuelsAudi is among the first carmakers to bet on e-fuels
More than 280 million light-duty mid-size sedans, sport utility vehicles, and light trucks are roaming the U.S. roads today. The vast majority of them are internal combustion engine vehicles. In 2030, half of the new passenger cars are expected to be electric or hydrogen-powered. While it seems a lot, they will only account for roughly 20% of the entire passenger car fleet, including old cars.

2035 is most likely the year when the phase-out of new ICE cars will be enforced in the U.S., while in 2050 the goal is to replace every ICE car with zero-emissions vehicles. It means policymakers must create a proper framework for rapid decarbonization and efficiently direct grants to R&D of new technologies.

Why is this study so important

Argonne’s researchers used an upgraded GREET model – which is the acronym for the Greenhouse gases, Regulated Emissions, and Energy use in Transportation. This model was put in place by Argonne National Laboratory some years ago and it fully evaluates the emissions of fuel and vehicle lifecycle from well to wheel.

The GREET model is now the official methodology for the Inflation Reduction Act 2022 to calculate the GHG emissions lifecycle for all types of fuels and technologies when determining the level of tax credit to be applied. In other words, it’s a tool that everybody relies on for future scenarios and forecasts.

Still, this study takes a “pathway” rather than a “scenario” approach. Hence it examines technically feasible routes believed to be nationally scalable in the future, relying on different federal agencies’ forecasts.

For instance, the study considers the infrastructure available for battery electric vehicles (BEVs) and fuel-cell electric vehicles (FCEVs) projected by the U.S. Department of Transportation in 2030-2040, while the 2035 U.S. grid generation mix is projected by EIA.

In addition, the study also evaluates the potential of e-fuels – the synthetic liquid fuels produced using renewable low-carbon electricity and CO2 sources. They are crucial for the transition to zero-emissions transportation because the ICE cars will still account for a large part of the national vehicles fleet by close to half of this century.

What fuels pathways are being considered

The table below showcases three main directions:

- fuels for internal combustion engine vehicles (ICEVs), which are also found in hybrids (HEVs) and plug-in hybrids (PHEVs)
- hydrogen for fuel cell vehicles (FCEVs)
- electricity for battery-equipped vehicles, mainly 100% electric (BEV), but also plug-in hybrids (PHEVs)

Fuel production pathways considered in the study
Photo: Argonne National Laboratory
As it turns out, there are a number of future technology cases for ICE fuels deemed feasible for replacing fossil fuels’ current technology cases. It’s important to note that none of them have yet proved economically feasible for now, as they rely mainly on government grants for R&D and pilot projects. The e-fuels are promising in theory, but there is a catch.

Argonne’s researchers worked closely with experts from the U.S. DRIVE group. This is “a non-binding and voluntary government-industry partnership”, and among its members there are several oil companies like BP America, Chevron Corporation, Exxon Mobil Corporation, or Shell, but also the USCAR, representing Stellantis, Ford Motor Company, and General Motors.

One cannot ignore that Big Oil and Big Auto are interested in using and benefiting from their core businesses – refining, storing, and transporting the fuels used by internal combustion engines. This is allegedly necessary for transitioning to a zero-emissions transport system, but you should take it with a grain of salt.

On the other hand, Argonne’s researchers revealed that “the most consequential change in the input assumptions between the 2016 study and this current update is in battery costs for BEVs.” This is because they saw dramatic reductions in the past 5 to 10 years, and their performances also improved at a higher pace than predicted.

So, what’s this study all about?

It provides a comprehensive analysis of the different technologies’ costs closely related to the benefits of GHG emissions reduction. The 200-page study estimates costs of driving that directly impact public acceptance of each technology. And there’s also a cost of avoiding GHG emissions, which is an important guide for policymakers.

The fuel taxes or technology subsidies are not taken into account and that way the comparison is clearer. Of course, there are also a lot of factors that weren’t taken into account – for instance, while soybean is an excellent low-emission feedstock for green diesel, its large-scale usage could be challenged by potential damage to soil or negative influence on food prices.

Basically, the question this study is trying to answer as accurately as possible is what technology cases can provide the best ratio between high gains in emissions reductions and reasonable costs for end users. There are two types of passenger cars considered for calculations: mid-size sedans and small SUVs.

The methodology is pretty simple: based on Argonne’s vehicle database and using their Autonomie simulation tool, researchers created a reference mid-size sedan and a reference small SUV. The reference cars are modeled for each technology pathway, and this gives a solid base of comparison.

Of course, in real life differences due to technical particularities will be inherent, in building cars, as well as in creating the fuels. But this study is the best tool, for now, to better understand the pros and cons of each pathway. Now things get a little complicated.

Who is the best contender for GHG emissions reductions

For modeling purposes, Argonne’s researchers considered a full 15-year vehicle lifetime and an average use case scenario for both the reference mid-sized sedan and light SUV. In the graph below we see the combined effects of potential vehicle efficiency gains and using low-carbon fuels on reducing emissions, for each of the fuels considered in the first table.

While it seems complicated, actually it’s very easy to understand it once you know the basics. The black lines represent the average level of emissions in CO2e/mi (CO2-equivalent per mile) using current technology, while the red lines are for using future technology resulting in higher powertrain efficiency gains.

The gray arrow is related to the future low-carbon fuels pathway and it shows the best-case scenario for further reducing emissions. The blue line is the burden of vehicle production – how much emissions are attributable to vehicle production over its entire lifetime, considering the vehicle is operated on a 0 g CO2e/mi basis.

GHG emissions for midsize sedans
Photo: Argonne National Laboratory
Firstly, take a look at the blue line. As you can see, the differences between distinct types of technologies are minimal. There’s no surprise that ICEVs get the best results, with roughly ~30 g CO2e/mi, while all the other technologies relying on batteries are slightly higher, but nevertheless under the 50 g CO2e/mi bar.

What this graph is saying is battery manufacturing-related emissions represent the highest percentage of total emissions in the case of BEVs. But that’s only because BEVs have the lowest total emissions values, over the entire lifetime of the car. Ignoring this fact is simply not being able to see the wood for the trees.

The black lines are self-explanatory, as gasoline, diesel, and CNG ICEVs are all above 300 g CO2e/mi. Only the E85 biofuel fares much better, with 229 g CO2e/mi, which is lower than the hybrid solution and almost on par with plug-in hybrid and fuel-cell solutions. The 200-mile and 300-mile range BEVs are under the 200 g CO2e/mi bar, with 166 g CO2e/mi and 182 g CO2/mi respectively, while the 400-mile long-range BEV is credited with 209 g CO2e/mi, because of a larger battery.

Now, using the same fuel pathways, but considering future vehicles gain for each technological solution, the red lines show there is a good chance of slashing emissions by an average of ~60 g CO2e/mi. The highest gains are for ICEVs, with more than 50 g CO2e/mi reduction (the gasoline could reduce emissions by 95 g CO2e/mi).

Still, BEVs remain by far the most efficient with less than 150 g CO2e/mi. It’s important to note the 120 g CO2e/mi value for BEV200, which is two-thirds of the emissions for biofuel E85 or plug-in hybrid. None of the conventional fuels are as good as batteries in terms of emissions savings up to this point.

Now it’s time to take a look at future low-carbon fuels’ big promises. The gray arrows indicate the potential they have to severely slash emissions. The calculations consider the best vehicle efficiency and the best-advanced fuels. This means the values are the best-case scenario, but with a low probability because of many unknown factors at this point.

E-fuels have the potential to slash emissions for ICEs to values between 87 and 52 g CO2e/mi. That is a reduction of more than 80% in the best-case scenario, where e-fuels are sourced from renewables. HEVs and PHEVs fare a little better, and their best-case scenario is also due to renewables, especially electricity coming from wind and solar.

It's interesting to note that e-fuels bring emission reduction to almost the same level as the best-case scenario for battery electric vehicles, where the electricity is sourced mainly from solar and wind. This looks like a strong argument for the proponents of internal combustion engines.

Meanwhile, hydrogen-powered cars have a rough time, because the gains in reducing emissions are the least impressive. The best-case scenario – low-temperature electrolysis using energy from wind and solar – is expected to slash emissions to more than 60 g CO2e/mi.

This is just a little better than another too little efficient solution: sourcing electricity from natural gas and carbon capture technologies. Also, the pyrolysis of renewable feedstock, like forestry, is not convincing with an estimated just under 100 g CO2e/mi for ICEs.

The biggest disappointment is using soybean for renewable diesel – a level of around 120 g CO2e/mi is almost on par with the red line for BEVs (future more efficient battery technology combined with nowadays electricity, sourced mainly from fossil fuels).

GHG emissions for small SUVs
Photo: Argonne National Laboratory
Similar situations for light SUVs, but the values are higher because the cars are heavier. And this means an average of 10 g CO2e/mi more than mid-sized sedans. This raises a lot of questions about the trend that carmakers seem to favor lately, and maybe it’s time for policymakers to tax SUVs for being less efficient and more polluting.

But are e-fuels really an option?

The e-fuels technology is in its infancy and it’s even more challenging than hydrogen technology. Of course, the same can be said about batteries, so we should be lenient with e-fuels. But don’t forget the clock is ticking and climate change is just getting worse every year.

An internal combustion engine’s efficiency can’t really be improved to a significant degree in real life because of internal friction and heat losses. There’s also the issue of proper maintenance and usage or the increasing emissions due to wear of the engine’s components. The e-fuels sound great, but ICEs are more complex, and they still need a lot of gas treatment devices.

Another key factor is that e-fuels presumably release back into the atmosphere the CO2 used to create them (and this 1-to-ratio is still to be proved on a scaled project). So, it’s not really a solution for reducing emissions in the transport sector, but more about keeping it at the same level.

Still, e-fuels are the best bet for reducing emissions from ICE cars that are now in use and will still be manufactured until the phase-out of gas-powered vehicles will be enforced, most likely in 2035-2040. So a more realistic approach for the reference cars in this study is using advanced fuels combined with a slight improvement of the current vehicle efficiency.

This is to say that e-fuels gains for slashing emissions of ICEVs, HEVs, and PHEVs are not so close to the 50 g CO2e/mi mark, but more likely around and even above 100 g CO2e/mi. And this is IF (a big IF) e-fuels are going to be feasible on a large scale and in a reasonable timeframe.

This study took that as a premise too easily, in my opinion. Excuse my reluctance, but it’s kind of strange for me that this study implies we should use a lot of renewable energy for producing e-fuels that will be used in less efficient ICEs, instead of using this green energy to power more BEVs, that are accountable for much fewer emissions even today.

The debate is going to be a fierce one as hydrogen technology is also at risk because of the conclusions of this study. I really hope it’s just my pessimistic point of view, but I also really, really hope we’re not going to end up in a lose-lose situation. It’s up to you to take a side now.
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About the author: Oraan Marc
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After graduating college with an automotive degree, Oraan went for a journalism career. 15 years went by and another switch turned him from a petrolhead into an electrohead, so watch his profile for insight into green tech, EVs of all kinds and alternative propulsion systems.
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