Is the combustion engine ready for its comeback?

Battery-electric trucks dominate the zero-emissions conversation, But, as CHARLEEN CLARKE reports, new work on hydrogen, methane and ammonia suggests the internal combustion engine may still have a future in freight.

For years, the transport industry has been told that the future is electric. In many applications, that is almost certainly true. Battery-electric vehicles (BEVs) are already proving their worth in urban delivery, depot-based operations and predictable short-haul routes.

Long-distance trucking, however, is more complicated. Heavy trucks need range, payload, short refuelling times and reliable energy infrastructure. In many countries (including South Africa) the power grid, charging network and operational realities of freight transport make a single-technology solution unlikely.

This is where gaseous fuels enter the picture. According to a recent paper from global premium solutions and components provider, Phinia*, hydrogen, natural gas and ammonia could all play important roles in future transport systems. Crucially, they may also give the internal combustion engine (ICE) a second life in a lower-carbon world.

Not just diesel vs batteries

The paper argues that future mobility will not be a simple contest between diesel vehicles and BEVs. Instead, the energy system is likely to become more fragmented, with different fuels serving different applications.

Hydrogen is receiving significant attention as a zero-carbon fuel, whether used in fuel cells or ICEs. Methane, including compressed natural gas (CNG) and biomethane, is already widely available in some markets and can reduce CO₂ emissions compared with diesel. Ammonia, while less familiar in road transport, is carbon-free at the point of use and easier to store than hydrogen.

For freight operators, the significance lies in flexibility – different regions will have different energy sources, infrastructure and cost pressures. A technology pathway that allows trucks to use alternative gaseous fuels could therefore be highly valuable.

Why gaseous fuels matter

The paper’s authors point out that renewable electricity alone may not solve every transport challenge. Solar and wind energy are growing rapidly, but they do not always produce power when demand is highest. Fuels can store energy, move it across long distances and provide resilience where electricity infrastructure is constrained.

This matters in transport. A truck is not a passenger car – downtime is expensive, routes are long and operators cannot afford to wait hours for energy replenishment. For heavy-duty and long-haul applications, gaseous fuels could offer faster refuelling and greater operational flexibility.

Hydrogen is attractive because it produces no CO₂ at the tailpipe when used in an ICE. Methane can offer lower emissions than conventional fossil fuels, particularly when produced from renewable sources. Ammonia is more challenging from an ignition and combustion perspective, but it brings its own advantages in storage and distribution.

The combustion engine evolves

The key point in Phinia’s paper is that the ICE is not standing still. Future engines running on gaseous fuels will need advanced injection, ignition and control systems. This is where the engineering becomes important: hydrogen, methane and ammonia behave very differently in the combustion chamber. They have different flame speeds, ignition requirements, storage pressures and energy densities. A conventional diesel or petrol fuel system cannot simply be reused without major adaptation.

Phinia has therefore been developing gaseous fuel injection and ignition systems for more than a decade. First-generation systems for port fuel injection and low-pressure direct injection are now available, while second-generation systems are being developed to simplify fuel systems and improve performance. In practical terms, this means engines can be adapted to run on alternative gaseous fuels while maintaining the performance, durability and controllability required in commercial transport.

Hydrogen for heavy trucks

One of the most relevant developments for FOCUS readers is Phinia’s work on a 13-litre commercial vehicle engine platform. The company converted a heavy-duty diesel engine to run on hydrogen, while retaining much of the base engine architecture. A port fuel injection system was used, and the diesel injector was replaced with a centrally mounted spark plug and ignition system.

The result is particularly interesting. Phinia reports that the hydrogen engine showed strong alignment with the diesel torque curve in key operating ranges, with further optimisation underway. The company also reports a broad efficiency zone above 40% brake thermal efficiency at cruise speed and load, together with very low NOx generation at low to medium loads.

For long-haul transport, that is important – it suggests that hydrogen combustion could potentially deliver familiar truck-like performance while dramatically reducing tailpipe CO₂ emissions.