A recent video at Engineering Explained (one of my favorite YouTube channels) took on the topic of synthetic fuels. If done correctly, they’re carbon neutral, and they’d allow for almost as much energy density as today’s gasoline or diesel. With all of those advantages, some have been saying they’re a great alternative to electric vehicles. Jason goes through the entire situation, and even does the math for us on this.
The result? Synthetic fuels just aren’t going to replace EVs.
Why Synthetic Fuels Tempt People
In the upper-left part of his whiteboard presentation, he goes into what synthetic fuels are, and why people think they’re a good idea. In theory, they would be made from carbon that was taken out of the atmosphere, so the carbon in the vehicle’s exhaust isn’t adding to the problem of climate change. Also, there’s no real risk of running out of the stuff. With oil being a finite resource, that’s an advantage, too.
It sure would be a lot easier to keep gas stations and cars like they are for most people now, but change what fuel is getting dropped off in the tankers. The cost of added infrastructure, changing out cars, changing supply chains, and changing how the dealer ground game is played (far less service department billable hours) are all avoidable with synthetic fuels.
Also, the pain of road trips powered by DC fast charge stations (anywhere from 10-60 minutes per stop, depending on the EV) could be avoided. Most people don’t do this very often, but it’s still a factor that makes people want to keep ICE.
The Problem: Complexity & Cost
In the lower-left part of the presentation, he gives an overview of what the process for making synthetic fuels looks like compared to EVs and hydrogen fuel cell vehicles (FCEVs). This is where we can see how problematic the process really is.
To start out, there’s zero advantage to making synthetic fuels if you’re not using renewable energy to create the hydrogen and then combine the hydrogen with carbon to create fuels. The whole benefit of synthetic fuels is that they’re carbon neutral, and introducing carbon in the production phases ruins that. That’s why he sticks with renewables for the comparisons here.
With an EV, you take the renewable electricity, transmit it along wires to the car, charge the car’s battery, and then power the electric motor to turn wheels. That’s a fairly simple process.
With a fuel cell vehicle, you add extra steps. The electricity is used to catalyze hydrogen (ideally), which is pumped, stored in tanks, taken on tanker trucks, stored again at the fueling station, pumped into a car’s tank, used by the fuel cells, put in a battery, which then turns the wheels. That’s a bunch of extra steps, and energy is lost at each step of that journey. This makes hydrogen a crappy option for most cases.
Synthetic fuels are even more complex. You start with hydrogen (that’s already several steps into the process). Then, hydrogen is combined with captured carbon, transported, pumped, and then burnt in an internal combustion engine with 50% efficiency maximum. This is not only more complex in the supply chain, but very wasteful at the end of the process.
At the end of the processes, the clear efficiency winner is the EV, with between 40 and 70% of the original energy going to the wheels of the car to move it (the rest is lost in heat, transmission, etc). That sounds bad, but hydrogen fuel cells are 33% efficient at best, and 23% at worst. Synthetic fuels only get from 6-18% of the original renewable energy to the wheels when all is said and done.
It’s pretty clear what technology makes the best use of renewable energy, and which is the worst.
Cost is even worse. The cost of fuel is anywhere from 2-10x worse in a vehicle using synthetic fuels compared to an EV. Over the course of a year, the cost of running synthetic can even be as bad as the whole purchase price of an EV!
And, that’s assuming they ever get the cost of synthetic fuels to $10/gallon (before tax and other expenses are built in). In reality, synthetic fuels are as bad as $38/gallon today, meaning the price of fuel is astronomical by ICE standards and universe-scale by EV standards. It just doesn’t make sense at any of these prices, and there are hard limits to lowering them in the future.
Where Synthetic Fuels Might Make Sense (For Now)
If you’re buying fuel for an application that requires a lot of energy density, and the price doesn’t matter as much, synthetic fuels might be a good match. For a car, the big and heavy battery packs needed to make up for the low energy density of lithium-ion batteries isn’t that big of a deal. The added weight has disadvantages, of course, but they aren’t complete deal breakers that keep you from making it down the road.
For aviation and trans-oceanic shipping, it might make sense to use synthetic fuels. The extra size and weight of the enormous battery packs that would be needed leave no room for cargo on ships and would probably keep longer-range planes from even getting off the ground. Keep in mind, though, that this is only what the situation is today in 2021. As battery technology improves, synthetic fuels might not make sense for any application.
It’s worth noting that hydrogen might make sense for some energy storage applications, but only when long-terms storage is needed. However, alternatives like pumped storage may be better for trans-seasonal applications.
Limitations To This Comparison
Keep in mind that the video only ran a comparison between a full battery EV and a vehicle that uses synthetic fuels for all trips (short, long, city, highway — everything). The fact that the EV wins that competition is clear. The complexity and cost of synthetic fuel production is just too high to justify using them for cars and most trucks.
If we reduce gas burned by 90% or more, it isn’t that big of a deal when the remaining applications are still using fossil fuels. The overall environmental mix (90% of transportation uses batteries charged by renewables) might even be better than synthetic fuels because there’s far less waste on the 90% renewable side than there would be producing synthetic fuels.
There’s room to argue about that stuff, but not room to argue over synthetic fuels straight up burnt in an ICE.