Fuels for the future

Reducing greenhouse gas emissions is one of the major challenges facing the off-highway sector. With the goal of achieving net-zero emissions in the future, exhibitors at Systems & Components are working on alternative drive concepts and pursuing an open technology approach—one that also prepares established systems for the future. Looking ahead to the innovations being presented from November 9 to 15 at the Hannover exhibition grounds in Germany, one thing is clear: the diesel engine will continue to have its place—but it will no longer be the all-purpose solution for every application.

As varied as the tasks of agricultural and construction machinery may be, most of these vehicles have one thing in common: the diesel engine. It still accounts for over 80 percent of the off-highway market. Its robustness, low operating costs, and the ease and speed of refueling form the basis of its continued appeal. Experts estimate that by 2035, more than three-quarters of vehicles with over 56 kilowatts of power will still be equipped with a diesel engine.

For Petra Kaiser of the DLG (German Agricultural Society), there is no doubt that combustion engines will remain essential for heavy-duty vehicles for a long time to come. However, the Brand Manager of Systems & Components also acknowledges: “The discussions concerning low-emission drive alternatives are not leaving manufacturers of mobile working machines indifferent. Even heavy-duty engines are increasingly coming into focus for engineers, aiming to meet required emission standards across all performance classes while also reducing fuel consumption.”

Exhibitors at Systems & Components are committed to shaping the future of propulsion with an open approach to technology. The concepts presented at Systems & Components are not based on an either-or mindset, but rather on a both-and strategy: the engine platforms are compatible with a wide range of current and future low- and zero-carbon fuels—including natural gas, synthetic fuels, also known as e-fuels, and hydrogen—to ensure a smooth transition to new technologies.

At the same time, existing diesel concepts are being specifically optimized for greater efficiency. “This applies particularly to key components in the area of exhaust aftertreatment, which enable cleaner engines,” confirms Deutz CEO Dr. Sebastian C. Schulte. One approach is to operate the combustion engine in lean-burn mode. This means the engine runs with excess air and, at comparable performance levels, produces lower emissions than a conventional diesel engine.

To ensure that this operating mode does not impair engine dynamics, Liebherr has developed an air booster. It recovers hydraulic energy and uses it to drive a mechanical compressor when needed. If additional power is required at short notice, the system is activated—delivering extra air to the engine enabling it to respond quickly to performance demands.

Heavy-duty sector turns to climate-neutral alternatives

This technology is also of interest for engines powered by alternative fuels—because the hydraulic air booster can help hydrogen engines deliver power more quickly, allowing them to compete with diesel engines. Ammonia engines, which already demonstrate good dynamic performance, could also benefit. Reducing engine speed increases efficiency and lowers fuel consumption.

However, one thing is clear: further developing the diesel engine alone is not enough. The push for climate neutrality and increasingly strict emissions regulations are forcing engine manufacturers to look beyond diesel, which now only meets EU Stage V standards with complex exhaust aftertreatment systems.

Against this backdrop, many operators are working to make their existing fleets of mobile machinery more climate-friendly—using fuels such as HVO (Hydrotreated Vegetable Oil) or ethanol, both produced from waste and residual materials. HVO fuels can reduce CO₂ emissions by up to 90 percent compared to fossil diesel. These solutions are among the most promising short-term options for integration into agricultural and construction machinery.

Ethanol, with its high octane rating, is particularly well-suited for spark-ignition engines in the upper power range. For example, John Deere presented its 9.0 L concept engine at AGRITECHNICA 2023, designed for use with renewable and alcohol-based fuels. Another example is the Liebherr LH60M excavator, which can be fueled with HVO100.

Green Hydrogen Drives Decarbonization Forward

Hydrogen combustion engines remain one of the major trends at Systems & Components. Thanks to their inherent characteristics—such as efficiency, robustness, and low raw emissions—they represent “a promising approach to accelerate the decarbonization of off-road powertrains,” says Mikael Lindner, Head of MAN Engines. Hydrogen engines also complement fuel cells and power-to-liquid processes (for e-fuels), as they require the same storage systems and infrastructure. Another advantage: they can be brought to market relatively quickly and integrated into a wide range of small-series applications with varying load profiles.

“For the start of series production of our hydrogen engine TCG 7.8 H2, we only had to adapt the test bench—the engines run on the same production line,” emphasizes Dr. Petra Mayer, COO of Deutz AG.

The six-cylinder engine delivers 220 kilowatts of power, operates not only CO₂-neutrally but also very quietly, and is based on an existing Deutz engine platform.

A further example of current progress is the MAN H4576, which is derived from the established MAN D3876 diesel engine. Around 80 percent of its components—such as the crankcase, crankshaft, connecting rods, and the cooling and oil circuits including pumps and filters—are shared with the hydrogen version. The nearly identical dimensions simplify integration into existing vehicle platforms. Key modifications were made to the hydrogen supply and combustion components, engine control, and exhaust regulation. Compared to the diesel version, new pistons and cylinder liners are required, as the piston diameter has been increased to 145 mm. This results in a larger displacement of 16.8 liters and a performance output of 368 kilowatts (500 hp), equivalent to that of a 12.4-liter diesel engine.