“If it weren’t for unwanted side effects—such as dependencies on more or less despotic states or gradual global warming—it would be a miracle fuel:
Liquid fuel derived from petroleum boasts an energy density of around ten kilowatt-hours per liter—a figure unmatched by other energy sources.
The best mass-produced batteries from Chinese manufacturers achieve only about one-twelfth of this value at the cell level.
For new cell chemistries, researchers anticipate that it will eventually be possible to reach one kilowatt-hour per liter. It is hardly surprising, then, that liquid fuels dominate the market wherever mobility is the primary goal of energy conversion. The rule of thumb here is: the larger and heavier the cargo, the harder it is to do without them.
More than any other sector, the transport industry in Germany currently relies on fossil fuels; the share of renewable energy recently stood at barely more than seven percent.
The status quo is not set in stone, so it is worth asking what avenues exist to reduce this dependency. There is no single answer that applies to everyone and everything; the solution depends on what is being moved—and where.
Cars
The Power of Mass
The fact that electric cars—including plug-in hybrids—have managed to capture around a third of the new car market has done little to alter fuel sales figures. On the contrary: according to the Working Group on Energy Balances (*Arbeitsgemeinschaft Energiebilanzen*), sales of gasoline in Germany actually rose by one percent last year to around 18 billion liters, while diesel sales grew by two percent—though private cars account for only a small fraction of the 33 billion liters refueled. The reason lies in the very slow turnover of the vehicle fleet: at the turn of the year, there were 29 million gasoline-powered cars and 13 million diesel cars on German roads, compared to just two million electric cars. Since the average age of vehicles registered in Germany is steadily rising—it now stands at eleven years; even with an immediate ban on new internal combustion engine cars, it would take quite a long time for gasoline and diesel to cease playing a role. However, what actually flows from the pump into the tank in this country is by no means derived solely from crude oil. Fuels may only be placed on the market if they comply with various regulations—regulations that mandate, among other things, specific minimum quantities of non-fossil components. In practice, this results in two grades of gasoline: E5 and E10 (where "E" stands for ethanol and the number indicates the percentage). Ethanol is an alcohol derived primarily from food production residues. Some car manufacturers are advocating for E20. In Germany, the bio-content in diesel is at least seven percent. The diesel substitute HVO 100 consists entirely of organic waste, though it is currently available at just over 400 filling stations.
Trucks
The Burden of the Load
It was not long ago that we heard an executive from a commercial vehicle manufacturer declare that a battery-electric truck in the 40-tonne class would never become a reality. Since then, Daimler and MAN have brought heavy trucks to market that run exclusively on battery power. Under optimal conditions, a range of around 500 kilometers is achievable in long-haul transport. However, batteries with capacities exceeding 600 kilowatt-hours and weights of over four tonnes come at a high price. While this cost is partially offset—for instance, by toll exemptions—the decisive factor for the fleet operator is ultimately the cost per tonne-kilometer. If electricity becomes cheaper and diesel more expensive, the market could tip in favor of electric—provided a crucial condition is met. If the daily driving distance cannot be covered by overnight charging, super-fast charging stations—so-called "megachargers"—are required. Currently, these exist at only a few pilot locations. The question remains as to when the power supply infrastructure in this country will be sufficiently expanded to handle all the trucks currently clogging up rest areas will need to be powered. So, for the time being, does that leave only diesel? Just as with passenger cars, diesel doesn't have to be derived entirely from fossil crude oil; all modern engines are compatible with HVO 100—hydrotreated vegetable oil made from food production residues. Since large haulage companies generally install refueling stations at their own depots anyway, the currently limited availability on the road isn't an issue; if necessary, standard diesel can simply be used. Using hydrogen in a fuel cell remains a theoretical option for now—though one that Daimler, Toyota, and Volvo continue to pursue. For a rather small niche, Iveco offers tractor units that run on biogas.
Aviation
Price is Paramount
In the third dimension, energy for aircraft of a certain size, fuel density—measured by heating value per kilogram—is more critical than it is for ground vehicles, making liquid fuel indispensable.
While kerosene outperforms gasoline in this regard, it is not superior to diesel; however, keeping diesel in a liquid state at typical cruising altitudes of ten kilometers—where outside temperatures hover around minus 50 degrees Celsius—would be technically too complex.
The fuel approved for general aviation, known as Jet A-1, only freezes at minus 47 degrees; heated fuel lines are used to ensure it never actually reaches that point.
It is possible to produce a substitute with identical chemical and physical properties without using crude oil; all that is required is carbon, hydrogen, and a substantial amount of energy. In industry terminology, the result is known as Sustainable Aviation Fuel (SAF). SAF is already available in small quantities, with the carbon almost always derived from plant-based residues.
In the future, carbon could also be captured from industrial exhaust gases or even ambient air—a product known as e-kerosene.
While the fundamental viability of these processes has been proven, they face a challenge: as long as crude oil is distilled in refineries, a kerosene fraction is automatically produced alongside gasoline and diesel. Consequently, the fuel is inexpensive—a crucial factor for an industry where customers are constantly hunting for the cheapest ticket.
However, if the current oil crisis persists, it could actually accelerate the development of sustainable aviation fuels. Conversely, taking to the skies using pure hydrogen is unlikely to happen in the medium term. The prototype originally scheduled by Airbus for 2035 will not arrive until 2040 at the earliest. Even for long-suffering frequent flyers, that is a significant delay.
Construction & Agricultural Machinery
Accumulating Work
From an engineer’s perspective, there is little difference between a power shovel and an agricultural tractor; both are work machines. Their manufacturers rarely develop and build their own engines; instead, they usually source the powertrains from specialized companies. These suppliers naturally aim to cover as many vehicle types as possible with a single base engine.
Consequently, these engines are almost exclusively diesel-powered today. One distinctive feature is that most of these units have an extremely robust "digestive system," allowing them to cope with very poor-quality fuel in export markets.
Domestically, this capability can be leveraged to fuel agricultural machinery directly with vegetable oils. Such fuels differ from biodiesel and HVO in that the oil is obtained through mechanical pressing, eliminating the need for an energy-intensive refining process. In Germany, rapeseed is the primary source. According to the Bavarian Competence Center for Renewable Raw Materials, high-quality animal feed can also be produced from the remaining press cake.
For construction machinery, on the other hand, hybrid technology offers a way to reduce diesel consumption—which arises primarily from the work being performed rather than from driving. The equipment typically executes repetitive movements that require braking after only a short distance. If a generator is used for braking, it can—much like in an electric car—generate electricity and store it in a battery. Smaller machines, such as micro-excavators with a digging depth of less than two meters, are already available as purely battery-powered tools.
However, in operations that run around the clock beyond the reach of existing power grids—such as harvesting—liquid fuels will likely remain the standard for the foreseeable future.
Ships
Freedom of Cargo
100,000 hp. - that is the minimum power output an engine needs to propel a 400-meter-long container ship across the world's oceans.
At sea, ships still typically derive their energy from heavy fuel oil—a crude mixture left over after higher-quality products, ranging from gasoline to light heating oil, have been separated out at the refinery.
Consequently, the exhaust emissions are highly polluting, releasing soot, nitrogen oxides, and sulfur dioxide into the air.
On the upside, the fuel is cheap; prior to the current oil crisis, it cost less than 50 cents per liter.
Curiously, it is the largely globalized commercial shipping industry that has been a driving force behind alternatives to crude-oil-based fuels. Unlike other sectors, shipping is governed by a supranational regulatory body: the International Maritime Organization (IMO), an agency of the United Nations. For two decades, the IMO has been establishing not only emission control areas—starting with the Baltic Sea—but also climate protection targets. Although a final agreement remains pending due to opposition from the current US administration, shipowners, shipyards, and engine manufacturers have already laid the groundwork.
The first freighters—such as those operated by Maersk—are using methanol, a chemical industry staple that burns cleanly and efficiently and can be produced synthetically.
As a completely carbon-free fuel ammonia is also an option for the shipping industry.
The German engine manufacturer Everllence—a spin-off from MAN—is delivering its first engines this year; its initial customers include a Chinese logistics group. The shipping sector demonstrates that technical alternatives are emerging even where electrification hits physical limits. That does not mean, however, that electricity and water are incompatible: an increasing number of electric ferries are operating on short-haul routes around the world.” [1]
1. Weg vom Öl?: Sagt sich leicht. Und ist eine harte Nuss für Ingenieure. Aber zu knacken. Frankfurter Allgemeine Zeitung; Frankfurt. 22 Apr 2026: B2. Von Johannes Winterhagen
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