LNG and bio-LNG trucks: where they make sense

An LNG tractor is not an experiment. It is a diesel-architecture truck with cryogenic tanks where the diesel tanks would be, and it drives like the diesel it was derived from. The interesting questions are never about the vehicle. They are about where you can fill it, what is actually in the fuel, and who gets credit for the carbon you did not emit.

Start with why long-haul gas trucks use liquefied methane rather than compressed. Scania puts it plainly: “one unit of liquefied gas energy takes up three times less volume than one unit of compressed gas energy”. CNG is a distribution and municipal fuel. LNG is the only form with the energy density to do a European driving day.

Two engine architectures, and they behave differently

There are two ways to burn methane in a heavy truck, and the choice runs all the way down to your fuel purchasing.

Otto-cycle, spark-ignited. Scania’s gas trucks “use 9-litre or 13-litre Otto-cycle engines which burn methane as fuel”, offered from 280 to 460 hp. One fuel, one filler, one supply contract. The compression ratio is lower than a diesel’s, and so is peak efficiency. The Scania S-series carries this engine as the OC13.

High-pressure direct injection. Volvo’s route keeps compression ignition: “a small amount of ignition fuel is injected with high pressure to enable compression ignition before the gas is added”, which allows a diesel-like compression ratio and, in Volvo’s words, “higher energy efficiency with lower fuel consumption, and increased engine power”. Volvo is explicit that spark-ignited gas engines have “limitations when it comes to the delivery of power and torque”. The Volvo FH gas-powered is quoted at up to 500 hp and 2,800 Nm.

The trade is straightforward. HPDI gives you diesel behaviour on gradients and at weight, and costs you a second fuel: you must buy, carry and account for diesel or HVO as the pilot. Otto-cycle gives you one fuel and a simpler yard, and asks you to accept a softer engine when the hills get long.

Range is not the constraint — refuelling geography is

Scania quotes a driving range of approximately 1,800 kilometres for a semi-trailer tractor on its largest bio-LNG tank package. Volvo quotes up to 1,000 km for the FH gas-powered. Both comfortably cover a European driving day, so range is settled. The question is the map.

The European Commission’s description of what AFIR requires for liquefied methane is that member states “ensure minimum coverage of publicly accessible refuelling points for liquefied methane dedicated to heavy-duty vehicles on the TEN-T core and comprehensive network” — with no spacing attached to it. Compare the hydrogen obligation in the same regulation: stations “with a maximum distance of 200 km in between them along the TEN-T core and the TEN-T comprehensive network and at least one must be available in every urban node”.

For an operator that difference is the entire planning problem. LNG infrastructure is protected by policy but not built to a specified density by it. You plan around the stations that exist on your lanes today, not the ones a target will eventually produce.

Which sets the shape of fleet that LNG suits: fixed corridors, the same lanes every week, known filling points, and ideally a company station at your own yard. Opportunistic general haulage that goes wherever the load goes is the wrong application, and no amount of tank capacity fixes it.

LNG and bio-LNG are two different arguments

Fossil LNG buys a modest tailpipe improvement. Volvo quotes “up to 20% reduction in CO2 (tank-to-wheel)” for switching from diesel to LNG. Methane is itself a potent greenhouse gas, so any slip — unburned methane through the engine, plus losses upstream in production and liquefaction — erodes that gain. It is why the serious environmental case for gas trucks has moved onto bio-LNG rather than the fossil fuel.

Bio-LNG changes the size of the number completely. Volvo quotes “up to 100% reduction of CO2 (well-to-wheel)” for diesel to bio-LNG, and notes that using HVO as the pilot fuel is what gets you to zero. Scania is more conservative and more useful, quoting “50-90%, typically 80% from a well-to-wheel perspective compared to normal diesel”.

That spread — 50 to 90 — is the most important number here. It is wide because the feedstock and the supply chain dominate the result, not the truck. Two bio-LNG contracts sold under the same word can differ enormously. Buy it with certification, feedstock disclosure and a stated well-to-wheel intensity in writing, or you have bought a marketing claim.

Nobody official is counting your bio-LNG

Here is the accounting trap. The EU’s CO2 standards for new heavy-duty vehicles “follow a tank-to-wheel approach, addressing only the tailpipe CO2 emissions of the regulated vehicle groups”. A carbon correction factor, and a registration route for vehicles running exclusively on CO2-neutral fuels, are review items the Commission must assess by 2027 — not current law.

The practical consequence is worth stating flatly: the bio-LNG you buy improves your own reported footprint and your customer’s, but it does nothing for the truck’s certified CO2 figure or for the manufacturer’s compliance against targets of 45% by 2030, 65% by 2035 and 90% by 2040. That asymmetry is why the manufacturers’ engineering money has gone to battery-electric and to diesel efficiency, and why the gas ranges are maintained rather than pushed.

The German toll change reset the business case

Until the end of 2023, natural-gas trucks were exempt from the German road toll. Toll Collect’s own notice is blunt: “CNG/LNG trucks will be subject to toll in the usual way from January 2024”. At the same time, from 1 December 2023, “the toll rate per kilometre will then also depend on how much carbon dioxide (CO2) a vehicle emits”, with the toll extended to vehicles over 3.5 tonnes from July 2024.

For anyone running Germany, that removed a large and entirely reliable per-kilometre subsidy. Every LNG business case written before 2024 needs rebuilding, and the surviving case has to be won on the fuel price spread — which is far more volatile than a toll exemption ever was.

Who it still fits

Fixed-corridor, high-mileage work with secured fuelling, where the refuelling problem disappears by design. Contracts where a shipper has a written CO2 requirement and certified bio-LNG is a commercial deliverable rather than a nice-to-have. Heavy work where a battery truck’s payload penalty is unacceptable and there is no megawatt charging on the corridor. Night and noise-restricted urban delivery, where a gas engine is quieter than the diesel it replaces.

Against the diesel flagships it is priced next to — the Mercedes-Benz Actros L and its peers — the gas tractor is not a cheaper truck. It is a bet on a fuel supply.

What to check before you sign

Confirm which architecture you are buying and whether you can supply the pilot fuel reliably. HVO is not available everywhere diesel is, and an HPDI truck running fossil diesel as its pilot does not reach the headline figure.

Size the tank package to your longest real leg, not the brochure maximum. Tanks are payload and money, and the biggest package exists to win comparison tests.

Understand boil-off. Liquefied methane warms in the tank and vents. A vehicle that stands over a long weekend loses fuel it has already been billed for, so operations with heavy standing time are a poor fit whatever the range figure says.

Settle the bio-LNG supply agreement, the certification and the price mechanism before the truck order, not after. You are exchanging diesel price risk for gas price risk, and the second market has fewer participants.

Price the residual conservatively. The used market for gas tractors is thin and the buyer pool is limited to operators with fuelling access. On a used purchase, ask which engine generation is fitted — Scania states its updated 13-litre biomethane engines are “5% more fuel efficient compared to our former generation”.