Can e-fuels keep combustion engine alive in the future?
Can e-fuels or synthetic fuels based on ‘green hydrogen’ keep the combustion engine alive in the future? In theory, it looks promising, but being twice as expensive as fossil fuels today, it will be hard to find an economical business case.
The petrochemical industry is very much in favor: it is a question of survival in the long run. In Le Libre UGent, professor Sebastian Verhelst goes along to some extent, breaking a lance for banning fossil fuels, but not the internal combustion engine (ICE), as we will need it for long-distance transport.
The basis is ‘green hydrogen’ (H2), created out of water (H2O) by the simple process of electrolysis with surplus electricity of windmills or solar panels. By adding carbon, captured from the air, for instance, (CO2) or fermentation, of organic waste, you can make methane (H4).
From that methane, you can derive methanol (CH3OH), also known as methyl alcohol, a light flammable fuel comparable with ethanol or ‘drinking alcohol’, but far more toxic. But you can go a step further and make synthetic gasoline, diesel, or even kerosine from it. They are called ‘e-fuels’ because electricity was at the origin of them.
They all produce CO2 when used in a combustion engine, but the carbon neutrality is reached by the capturing of the CO2 in the production process first. Why going through all that effort if you can use the ‘green hydrogen’ right away to make electricity again in a fuel cell to propel an electric car with zero emissions, for instance?
BEVs most competitive
Most experts believe fuel-cell cars will remain more expensive than battery-electric vehicles (BEV), and for private vehicles, the latter will be the most competitive option in most cases. For airplanes, ships, and trucks that have to go long distances, batteries aren’t a viable solution, as these batteries would need to be far too voluminous.
For these sectors, e-fuels could be an alternative, Professor Sebastion Verhelst recons in an interview with newspaper La Libre. He warns that today, 70 to 80% of the costs of ‘green hydrogen’ comes from the electrolysis process, not to mention the costs of capturing the CO2.
Needing more electricity than produced
The efficiency of the electrolysis process is considered 70 to 80% today, meaning that you need more electricity to make the hydrogen, than you will generate from it later. A negative balance of 20 to 30%.
There are two main methods used today with alkaline and proton exchange membrane (PEM) electrolyzers. Without going into the technical details, experts believe the latter can be boosted to 86% efficiency by 2030, and even up 94% further down the road.
Ethanol more interesting
Verhelst is convinced the hydrogen will have a place in the mobility of the future but believes it will be more interesting to transform the hydrogen into methanol than use it directly in a vehicle.
One of the disadvantages of hydrogen is its poor density, being a gas that has to be compressed to 700 bar to be used in a car to keep the volume of the tank within reasonable margins. That is less a concern in bigger trucks (at 350 bar) or ships, but it is a problem in aviation, that uses huge quantities of energy for take-off and landing.
10% less energy needed
Using methanol directly in combustion engines has several advantages, according to the professor. Producing methanol requires 10% less energy than synthetic diesel or gasoline.
Burning methanol emits fewer NOx and no fine particulates. “In China, there are taxis, buses, and trucks running on it,” he adds. But even methanol has an energy density that is only half that of gasoline, so you’ll need more to go the same distance.
So, after all, synthetic diesel, gasoline, and kerosine might be a good reason to preserve the combustion engine from extinction, as they can provide a CO2-neutral balance for long-distance transport by trucks, ships, and airplanes.
Twice as expensive
But today, these e-fuels are still twice as expensive as the classic fossil fuels. Nevertheless, the professor estimates they can be a viable solution in ten to twenty years. To the cost of producing the green hydrogen adds the considerable cost of capturing the CO2.
That can be done by catching it at the chimneys of industrial plants, or directly from the open air. Capturing the CO2 from the air, for instance, costs, on average, 600 dollars per ton, says Swiss company Climeworks, claiming to be the only one of three factories in the world specializing in it for the moment.
That price has to come down to 100 dollars per ton to make it interesting to scale up to a production of gigatons, that would be needed to actually bring down the amount of CO2 that affects climate change. But in the long term, that could become a trillion-dollar business, some experts believe.