Synthetic fuel can cut emissions without new engines: what's the catch?

What if we told you there was a way to cut emissions from your car and it didn’t involve any changes to the engine? A Swiss chemical engineer is developing a synthetic, “drop‑in” fuel that works with existing vehicle and aircraft parts and infrastructure. 
 
In this episode of The Swiss Connection science podcast, host Jo Fahy and SWI swissinfo.ch journalist Simon Bradley find out how the fuel is made and why it isn’t already available at your local petrol pump.  

Journalist: Simon Bradley
Host: Jo Fahy
Audio editor: Michele Andina
Distribution and Marketing: Xin Zhang

SWI swissinfo.ch is a public service media company based in Bern, Switzerland. 

Transcript

The Promise Of Drop-In Fuel

Jo Fahy 0:00

SwissInfo podcasts.

SPEAKER_01 0:04

Synthetic fuels are not a new invention, but as countries and industries search for alternatives to fossil fuels, interest in these fuels has surged.

SPEAKER_05 0:13

It's a competitive environment, but there is so much fossil fuel to replace that there is a lot of space.

SPEAKER_01 0:18

For the Swiss researcher, it's important that her solution can be implemented as easily as possible.

SPEAKER_05 0:23

We don't need to replace the engine, we don't need to modify the engines. The fuel that we produce from a chemical point of view, it's very similar to fossil gasoline.

SPEAKER_04 0:33

It's more costly to produce synthetic fuels than digging it out of the ground. That's a given.

Jo Fahy 1:04

But not everyone is in a position to buy a brand new electric car. So could climate-friendly fuels offer a different path? Could we keep our existing cars on the road while dramatically reducing their emissions? That's what we're exploring in this episode of the Swiss Connection Science Podcast.

What Synthetic Fuels Really Are

Jo Fahy 1:36

Millions of combustion engines are still powering vehicles, machines, and aircraft around the world, and many will remain in use for years to come. Researchers at EMPA in Dubendorf, Switzerland, are exploring an alternative idea: a synthetic drop-in fuel that works with today's engines and infrastructure, potentially offering a cleaner way forward. So what exactly is this drop-in fuel and how does it work? To find out, I'm joined by my colleague Simon Bradley. Welcome, Simon. Hi Jo. A climate-friendly synthetic fuel for existing combustion engines. It kind of sounds like a solution to all of our problems. Is it really that simple?

SPEAKER_01 2:17

It would be nice if it were that simple, wouldn't it? Synthetic fuels are not a new invention. In fact, they were first developed more than a century ago. But as countries and industries search for alternatives to fossil fuels to meet their climate goals, interest in these fuels has surged. Researchers and major companies around the world are developing synthetic alternatives to conventional petrol, diesel, and jet fuel. They're experimenting with different production methods and technologies, some of which have a smaller carbon footprint than others. Much depends on where the raw materials come from and whether the fuel is produced using renewable energy. Unlike conventional fuels refined from crude oil, synthetic fuels are manufactured through industrial processes. The big advantage is that they can often be used in existing engines and fuel infrastructure. The downside, for now they're generally more expensive to produce than traditional fossil fuels.

EMPA Prototype And Scaling Plans

Jo Fahy 3:12

Okay, well, tell us how they're made.

SPEAKER_01 3:15

So the project I looked into is being developed at EMPA in Dubendorf. It's a top Swiss research institute that specializes in bridging the gap between research and practical industrial applications. Hello, Alessia. Hi, Simon. Nice to meet you. We met researcher Alessia Cesarini at the reception. And she took us inside her lab. We walked through a network of pipes and custom-built modules until we reached a prototype fuel unit she spent two years building.

SPEAKER_05 3:43

We built it ourselves. So from uh What do you call this? This is our prototype. That's how I would have to do that.

SPEAKER_00 3:49

A prototype, right.

SPEAKER_05 3:50

Because it's still it's still based in a lab. The scale is not too big and it can still be run in a lab. It has some components that are absolutely not optimized, so it's not an in in it doesn't use industrial parts. It uses like some smaller mimics of uh industrial parts. The idea was to do the first testing of scalability here before moving to something that resembles modern industry.

SPEAKER_01 4:17

Cesarini's lab prototype only produces small quantities, but down the corridor, a much larger test machine is also in action, able to produce around 10,000 litres of synthetic fuel a year. With support from EMPA, Cesarini's goal is to scale up her technology and to turn it into a business, offering a viable alternative to conventional fossil fuels.

SPEAKER_05 5:09

We don't need to replace the engine, we don't need to modify the engines. The fuel that we produce from a chemical point of view, it's very similar to fossil gasoline. So the components in it match the performance of a fossil fuel. So you don't need to change anything, you don't need to do expensive retrofitting, you can just swap the fuel and your car will run as it should.

Why Drop-In Matters For Emissions

Jo Fahy 5:33

What kind of an impact are we talking about here then? It sounds like it has really big potential.

SPEAKER_01 5:38

Definitely. Transport accounts for nearly half of Switzerland's energy-related CO2 emissions. A Swiss study estimates that around 2 million combustion-driven vehicles will remain on the country's roads by 2040. And globally, 55% of cars will still run on combustion engines by that time. But also for sectors such as aviation, long-term decarbonisation will depend heavily on the adoption of renewable fuels. I spoke to Natalie Cassas, the head of EMPA's Energy, Mobility and Environment Department, about the importance of these new synthetic fuels being developed.

Carbon Cycle And Best Locations

SPEAKER_04 6:13

Climate-friendly gasoline or fuels in general are important because we want to close the carbon cycle. If you think about gasoline in general, it's stored underground. We take it out of the ground, we burn it, and the CO2 goes back into the air. If we talk about synthetic or climate-friendly gasoline or fuels, we take CO2, for example, out of the air or from the biosphere, we make a fuel, we burn it and bring the CO2 back into the air. So the concentration of CO2 in the atmosphere is not increasing. It's not decreasing because we take it out of the air and it goes back into the air, but it's not increasing.

SPEAKER_01 6:54

And why is this topic important for Switzerland?

SPEAKER_04 6:57

I think we have the commitment of being net zero by 2050. This means we need to investigate all possible solutions. What I think will not happen that we will produce a lot of uh synthetic fuels in Switzerland because it's an in energy-intense process and we need renewable energy. And we need to do this renewable fuels in a place where there is abundant uh renewable energy. For example, in the sun belt of the Earth. So that would be in uh Northern Africa or Exactly, Northern Africa, the Arabic countries, Brazil could be an option. So there are many options around, um, and we need to have good collaboration with them. But what what Switzerland is very strong at is innovation and also companies who can sell this innovation to the world or bring it to the world.

SPEAKER_01 7:52

Synthetic fuel research is expanding rapidly, especially in China, the US, and Europe. The International E-Fuels Observatory 2025 lists more than 120 large-scale projects in 28 countries, but it remains early stage and highly concentrated, with a clear shift from conceptual work to industrial pilot projects. Switzerland would like to become an advanced research hub combining CO2, green hydrogen, and innovative chemistry to produce low-carbon fuels. Cesarini's work targets a unique niche by focusing initially on drop-in gasoline using energy-efficient catalysts, while many of her peers are exploring aviation fuels or working on sun to liquid solar processes.

SPEAKER_05 8:38

It's a competitive environment, but it's also there is so much to do, there is so much fossil fuel to replace that there is a lot of space. We focused mostly on producing the right composition because the idea was always that if it's there, it should be very easy to implement. Any modification required throws you into an endless loop of uh regulation, testing, and also some like pushback from companies, from individuals that they don't want to change what they already have.

SPEAKER_01 9:13

There are other research projects in Switzerland, in particular in synthetic fuels. Um, what makes your work so unique compared to the other climate-friendly fuels being researched

How EMPA Builds Synthetic Gasoline

SPEAKER_01 9:24

here?

SPEAKER_05 9:24

It's a different type of process. So you can make fuels from different directions, different source materials and different reaction processes. So you can, for example, go from very long molecules like oils and break them down into shorter ones. And this usually leads you to having more like diesel fraction or kerosene, or you can go the other way around, you can build it up. So, what we do is we do exactly that. We start from very small molecules, so like small Lego building blocks, and we combine them together into longer hydrocarbons. And this transformation is done then by the catalyst. And the catalysts that we are using are different than others, there are many processes around, but what we have specialized is that in this type of catalyst material that can combine these building blocks in the right way to get a fuel that can be used as it is.

SPEAKER_01 10:19

At the heart of Cesarini's innovation is a chemical process called oligomerization, which converts ethylene or propylene molecules into a liquid fuel closely resembling conventional gasoline. The cycle starts with carbon dioxide being removed from the biosphere or atmosphere and transformed into alcohols like methanol or ethanol. Water is then removed from these liquids via an existing method known as dehydration, converting them into ethylene and propylene. These gases are then sent to a reactor where a catalyst breaks the molecules apart and recombines them into longer hydrocarbons, creating a synthetic fuel that can be used directly in cars, planes, or other machinery. The catalyst is a key element to make the process efficient and keep energy consumption low.

SPEAKER_02 11:08

You've found a catalyst that seems to work, right? What can you tell us about that?

SPEAKER_05 11:13

Not much, because it's uh it's the source of our process. So what I can tell you is that the advantage is that it's very selective for making the gasoline. So it can really arrange very well these molecules into the 200 plus different type of molecules that we need to have in our liquids. Gasoline is a very broad mixture of more than 200 molecules that combine together give this property of the octane rating. You need to be able to control the length. This is where the catalyst comes in. The transformation in principle is simple. So you have this type of molecules, you break them apart and you glue them together in a different way so that you get the right liquids that you want. We don't need to use very high process temperature. We work at mild conditions, and this of course then saves uh cost and uh allows us to work with common electricity.

Jo Fahy 12:12

Well,

Costs, Scale, And Market Barriers

Jo Fahy 12:13

so far so good. But what about the costs of this gasoline? Is it going to be commercially viable?

SPEAKER_01 12:18

The cost is obviously a key issue. I asked Cesarine how it compares with standard gasoline.

SPEAKER_05 12:23

We made some calculations because this was the base of whether we can actually then scale it and bring it to the market. Based on a larger chemical plant, of course, we need to always take the scale into consideration. This is one of the main problems of uh technologies.

SPEAKER_00 12:39

How big will you have to be?

SPEAKER_05 12:42

Let's say uh few million liters, like 20, 40 million liters, uh, you will need to have that bare minimum to be cost competitive.

SPEAKER_01 12:52

Will consumers be willing to pay for this fuel? I asked Natalie Cassus about this.

SPEAKER_04 12:57

Yes. So people want to do something good for the climate. However, if they need to pay more for the gasoline, which they will, obviously, it's more costly to produce synthetic fuels than take digging it out of the ground. That's a given. They I would say in Switzerland are even open to pay a little premium. However, they're not willing to pay, let's say, two to the double or three times more.

SPEAKER_01 13:21

For it to be rolled out uh in in petrol stations, where are we now with the project? How many years away are we from that?

SPEAKER_04 13:28

The bottlenecks right now are the upscaling. So getting the money to to test it at a rather bigger scale. And if you talk to industry, they say, Yeah, we need the customers. And the customers say we need the governmental or or or the legal framework in order to have a proper accounting. So it's it's it's quite tricky and it's very hard to predict how long it takes.

SPEAKER_01 13:54

How close are we to seeing your uh climate-friendly fuel in a sort of standard avia gas station in Switzerland?

SPEAKER_04 14:03

This can be pretty soon at a very small scale, right? And that's also if you look at the legislation for aviation fuels, they start with one percent of a synthetic fuel, then they have to increase it to five percent to ten percent by a certain year. So having a small amount in uh mixed to the normal fuels can be done pretty soon.

SPEAKER_01 14:27

Independent tests have shown that EMPA's synthetic fuel already reaches a research octane number of 95, a key benchmark for standard unleaded gasoline, and initial estimates suggest it could be cost competitive with fossil gasoline once produced at industrial scale. Despite the many hurdles they face producing their synthetic fuel, the EMPA team is confident demand and investors will materialize. Here's Natalie Cassis again.

SPEAKER_04 15:04

However, now the world is changing and I think the whole landscape is becoming more difficult. So it's still a huge challenge. I hope we manage.

SPEAKER_01 15:15

So what costs and scales are we talking about exactly? To give us an idea, the two researchers took us into the larger test production facility on the Emperor campus.

SPEAKER_04 15:29

Often, if you are working in the lab, you have a small reactor and small tubes and nice measurements, and you can heat it very easily and properly. If you go big, suddenly heating becomes a problem. Or the connection between the different reactors. And it's all about improving energy consumption. So that's one of the big challenges the technology has. And in order to do so, you need to connect many things, right? You need to connect hot with cold in order to let heat flow. So these connections need to be tested, and they can only be tested at a certain scale. And here it starts with the money, right? To build something like this, you need million, two million, three million. But that's a small unit. If you want to go big and scale up, you need much bigger. So you if you do deep tech, you very quickly get into the let's say 10, 50, 100 million range in order to have a plant of a proper size. And 100 million is still a very small size. Yeah.

Pilots And Policy For Switzerland

SPEAKER_01 16:40

The first pilot application for their sustainable fuel is the forestry sector. It's easy to access and only requires small quantities, allowing controlled usage and making market testing easier.

SPEAKER_05 16:51

After we've done the forestry pilot phase, we will go into more like the real road applications. So for that, we will need a larger volume to be produced every year because you need to supply a certain amount, secure amount.

SPEAKER_00 17:04

What sort of volumes are you?

SPEAKER_05 17:06

Uh what we could uh do uh initially with the demonstrator that the we have here at EMPA would be to produce approximately one million one, two million liters. This is the scale we're talking about. And then we can start doing pilot with single car customers. We discuss with petrol stations. Our target in the end will be to have the fuel in the petrol stations themselves.

SPEAKER_00 17:27

What's your most ideal ideal time frame, would you say?

SPEAKER_05 17:31

A few years, so not too not too long. We're not talking about okay, we will have it ready in 2040. This will be too far away.

SPEAKER_02 17:39

What's the size of the budget for the project?

SPEAKER_05 17:42

We are talking about millions. It's not something cheap is hardware, so you need to build the infrastructure and you have to do it in the smartest way possible. The advantage is that we don't need a very specialized reactor system, but we can use systems that already exist in the industry, and we can uh put run our reaction with these systems, which then lowers the cost.

SPEAKER_01 18:04

It's still too early to tell what impact this fuel could have on Switzerland's emissions, and its success will depend in part on political decisions. I asked Natalie Cassas about that. With what's going on at the moment in the Gulf and the blockades, um have you noted any changes of attitudes towards your work at the moment?

SPEAKER_04 18:22

Not yet. So I think people are waiting, and there they are two aspects of it, right? People realize, hey, we are very dependent. But if we come back to what I told you before, it's we need a lot of energy to produce these fuels. So I think it's not very likely that we produce a lot of fuels here in Europe because we don't have renewable energy in abundance. Maybe in Spain, maybe southern Italy, but here in Switzerland we are fighting to get enough renewable energy for the electrical application. It's not a local problem, it's a global problem. And if we can, as Switzerland, help the world to decarbonize their fuel, their industry, that's a very strong asset we have and we can provide to the world.

Jo Fahy 19:17

Thanks a lot, Simon. I really didn't know that fuel could be made in the lab. But if I understood this right, it will only be green if it uses CO2 from the atmosphere.

SPEAKER_01 19:26

Exactly. And as I said earlier, the energy used to produce it has to be renewable. How to capture CO2 from the atmosphere is a story on its own, which we've not really talked about on this episode. There are various technologies being developed in Switzerland and abroad, so yes, making green synthetic fuels also depends on how well we'll manage to get CO2 out of the air.

Jo Fahy 19:49

Okay, well it's good that you're mentioning this, Simon, and if you're listening to this episode, you can find several articles on our website about this topic. For instance, about the Swiss carbon removal firm Climewax, and we also had a podcast episode here on the Swiss Connection about the Swiss startup Neustark, which is filtering CO2 from sewage plants and permanently storing it in recycled concrete. So thanks again, Simon.

SPEAKER_01 20:13

You're welcome. Thanks, Joe.

Subscribe And What’s Next

Jo Fahy 20:17

Coming up in the next episode of the Swiss Connection Science Podcast, we're looking into diagnosing diseases. Specifically, when does diagnosing a disease do more harm than good? And how does new tech such as AI help us with this? Hit subscribe now in your podcast feed and make sure you don't miss out. If you're looking for more science stories, you can go to our website, cisinfo.ch, and you can help others to find our podcast by leaving us a five-star review, or just share our podcast with a friend.