It seems everything old is new again, including synthetic fuels

In 1923, Germans Franz Fischer and Hans Tropsch created the indirect Fischer-Tropsch process, a series of chemical reactions that gassify the coal first, before converting a mixture of carbon monoxide and hydrogen into liquid hydrocarbons.

Later it was discovered that oil shale could be used, or various forms of biomass. Other options and methods emerged since.

In 1931 the British set up a small facility to make a synthetic liquid fuel from coal.

In 1937 four German coal plants churned out 4.8 million barrels of synthetic fuel, and by early 1944 the Germans had 25 separate plants turning out a combined 124,000 barrels of synthetic fuel per day. The Germans relied on synthetic production in World War II as a source of aviation fuel, diesel and various other petrochemical products like synthetic oil and synthetic rubber.

The Americans initiated the Synthetic Liquid Fuels Act on April 5, 1944, throwing US$30 million at the project over five years. By 1946 a commercial plant using the Bergius process was running in Louisiana, turning out synthetic fuel for only a slightly higher price than crude gasoline. It was shut down in 1953, just a month into Dwight D. Eisenhower's presidency though, based on reports from the National Petroleum Council which for years had concluded "the need for a synfuel liquid fuel industry in this country [USA] is still in the distant future".

E-fuels build upon the same chemistry principles as the first synthetic fuels, except the source of hydrogen is from water (via electrolysis), and carbon comes from carbon dioxide captured from the atmosphere (or it can come from another renewable source). Depending on which indirect method is used, the end result can be a synthetic jet fuel (high-grade kerosene), diesel or petrol. And to be an e-fuel, all the energy put into the process must also be renewable.

Today it's mainly the Germans (and also the Japanese to some degree) who are behind the modern day push to get e-fuels into the global market, including a production facility under construction in Tasmania to produce synthetic petrol and LPG.

An advantage of e-fuels is you can literally make them from, and with, water and air. You'll never amortise the emissions from building, and maintaining, the production facility, but the fuel production processes should be carbon-neutral.

There's also a lot less mining involved compared to electrification, and e-fuels would reduce the climate damage being caused by existing ICE vehicles. However, e-fuels are also being used as a ruse (especially by the Germans) to try and keep producing new ICE vehicles for longer, instead of transitioning to battery electric vehicles (BEVs).

The biggest disadvantage of e-fuels is ICEs will still produce tailpipe emissions so it can't stop them from choking up cities, causing health issues like respiratory problems and premature deaths.

The energy efficiency from wind turbine to the road is also poor. The most efficient way to use electricity to transport lots of people (or stuff) is actually directly with wires to trains and trams, helped by low-friction rails and far superior capacity.

The most efficient use for roads is batteries. Some energy is used sending it through the grid, charging, and then using that charge, but (disregarding the surplus production already on the power grids, which BEVs can help or hinder, depending on the time of day) at least two thirds makes it to the road.

Using green electricity to produce green hydrogen sees more energy lost (used) from wind turbine to road, but it does have its uses (like fast refuelling of trucks, and less weight than batteries which is good for aviation).

E-fuels take that energy loss to a whole new level though, producing hydrogen, then methanol, then petrol, then using it in an ICE. You'll be lucky to get one sixth of the original (electrical) energy to the road.

The cost, for now, is also horrific.