So first off my opinion
Synthetic fuels initially sound slightly pointless.
We’ve got renewable electricity.
Great.
So let’s use that electricity to make hydrogen.
Then potentially combine that hydrogen with captured carbon dioxide.
Then process that into a fuel.
Then transport the fuel.
Then burn it to get energy back out.
There are quite a few steps there.
And every time we convert energy from one form into another, we lose some of it.
So why not just use the electricity?
Well…
Sometimes using the electricity directly is difficult.
And that’s where synthetic fuels start becoming much more interesting.
We are really good at using liquid fuels
We’ve spent more than a century building infrastructure around them.
Aircraft.
Ships.
Cars.
Lorries.
Pipelines.
Storage tanks.
Refineries.
Engines.
Fuel stations.
Liquid hydrocarbons contain a lot of energy in a relatively manageable form.
That’s incredibly useful.
A battery can work brilliantly in a car.
Putting enough batteries into a long-haul aircraft is a rather different engineering problem.
Weight matters.
Energy density matters.
Refuelling time matters.
So perhaps there are applications where replacing the fuel isn’t easy.
Which leads to another question.
Could we make a replacement fuel differently?
So what is a synthetic fuel?
There are several routes, but the bit I’m particularly interested in is fuels made using electricity.
You’ll sometimes hear the term e-fuel.
One route starts with hydrogen.
Use electricity to split water using electrolysis.
Now we’ve got hydrogen.
Then potentially combine that hydrogen with captured carbon dioxide through further chemical processing to produce hydrocarbons.
Those hydrocarbons can potentially become fuels such as synthetic methane, methanol or liquid fuels.
So instead of extracting the original hydrocarbon from underground, we’re effectively building one.
That’s quite a thought.
But where does the carbon come from?
This seems rather important.
If we’re going to make a carbon-based fuel, we need carbon.
One option is capturing CO2 from an industrial process.
Another possibility is extracting CO2 directly from the atmosphere.
Then we combine that carbon with hydrogen.
Eventually somebody burns the resulting fuel and the carbon goes back into the atmosphere.
If the carbon originally came from the atmosphere, we’ve potentially created something closer to a carbon cycle rather than continually adding fossil carbon from underground.
At least that’s the idea.
Obviously the details matter enormously.
Particularly where the electricity came from.
The electricity source changes everything
Imagine making synthetic fuel using electricity generated from coal.
That would seem to defeat quite a lot of the point.
So synthetic fuels become particularly interesting when the electricity used to make them is very low carbon.
Potentially even electricity that would otherwise have been curtailed.
That brings me back to the same idea I found interesting with hydrogen.
What do we do when we’ve got renewable electricity available but don’t need that electricity at that particular moment?
Instead of stopping generation, perhaps some of that energy can become a fuel.
Now we’ve moved electricity not just through time, but potentially into an entirely different industry.
The efficiency problem doesn’t disappear
This is still the bit I struggle with.
If I put electricity directly into a battery and then use an electric motor, there aren’t that many conversion stages.
Synthetic fuel has loads of them.
Electricity.
Hydrogen.
Chemical synthesis.
Transport.
Combustion.
Mechanical work.
Every arrow costs us something.
So I don’t currently see synthetic fuels as a particularly convincing argument for keeping combustion engines everywhere.
If direct electrification works well, direct electrification seems difficult to beat.
But that’s not necessarily where synthetic fuels are most interesting.
Aircraft are the obvious example
Aviation needs a lot of energy while keeping weight under control.
Liquid fuel is extremely good at that.
Replacing all of that energy with batteries is difficult, particularly for long-distance aircraft.
So instead of asking:
Can synthetic fuel beat an electric car?
perhaps we should ask:
Can synthetic fuel replace fossil fuel in something that’s extremely difficult to electrify?
That’s a much fairer comparison.
Shipping and some industrial applications might raise similar questions.
And this is a huge data chain
This one could get really interesting.
Where did the electricity come from?
How carbon-intensive was it?
How much electricity entered the electrolyser?
How much hydrogen came out?
Where did the CO2 come from?
How much CO2 was used?
How much synthetic fuel was produced?
How much energy does that fuel contain?
How much energy was used transporting it?
What were the total emissions?
Suddenly proving that a fuel is genuinely low-carbon requires data from the entire production chain.
Not just the final factory.
This feels like a data lineage problem
Which obviously gets my attention.
Imagine two litres of synthetic aviation fuel.
Chemically they might be almost identical.
But environmentally they could be completely different.
One might have been made using surplus wind power and captured atmospheric carbon.
Another might have been made using carbon-intensive electricity.
The fuel itself doesn’t necessarily tell you its history.
The data does.
That means provenance becomes incredibly important.
Where did this energy come from?
Where did this carbon come from?
What happened to it along the way?
That’s basically data lineage applied to molecules.
And I rather like that idea.
So where is my head at?
I’m sceptical of synthetic fuels where they’re being proposed as an alternative to something we can already electrify efficiently.
Making electricity into fuel just so we can burn it and turn it back into useful energy feels like taking the scenic route.
But some sectors genuinely need extremely energy-dense fuels.
Aviation is the obvious example.
That’s where I think this becomes much more interesting.
Maybe synthetic fuels aren’t a replacement for electricity.
Maybe they’re a way of getting low-carbon electricity into places where plugging something into a battery isn’t practical.
And if that’s the case, proving where the electricity and carbon came from becomes almost as important as making the fuel itself.
That’s where my head is at the moment.
Gareth Winterman