LIKE their counterparts elsewhere, Britain’s rail freight operators are keen to point out the obvious environmental benefits of moving goods by rail, but they have a problem. At present, around 90% of their trains are hauled by diesel locomotives burning fossil fuel, and although rail with its 700 diesel vehicles in total is responsible for only 1.5% of total transport emissions in Britain, the government wants diesel-only traction to be phased out by 2040 in order to meet the national target of achieving net-zero emissions by 2050.

Only 10% of British freight trains are hauled by electric locomotives, and Britain has traditionally been slower than its European counterparts to embrace electric freight operation. The hopes of maintaining a rolling national electrification programme that would have enabled freight operations on key routes such as the Midland Main Line to be decarbonised appear to have been dashed by the high cost of the infrastructure work required, while across Europe rising energy prices are pushing up the cost of electric operation, in some cases even forcing rail freight operators with their tight margins to return to diesel.

Even before the Russian invasion of Ukraine led to a dramatic rise in energy prices, Freightliner announced that it was temporarily replacing electric traction with diesel due to a 210% increase in wholesale energy prices in Britain between September and October 2021. Ironically, Freightliner has Britain’s largest fleet of electric freight locomotives, and had only recently acquired 13 class 90 electric locomotives in order to help further decarbonise its operations.

Like Britain’s other major rail freight operators such as DB Cargo UK or GB Railfreight, the mainstay of the Freightliner fleet is the rugged and reliable class 66 diesel locomotive, the EMD Co-Co design that first arrived in Britain in 1998. Over 450 class 66 locomotives are now in service with a total of five freight operators in Britain, hauling over 80% of freight on the national network.

Concepts for repowering the class 66 with engines that combust two fuels simultaneously, enabling diesel to be partly replaced by renewable fuels with net zero carbon emissions, have been developed by G-volution and SBL-Rail.

Renewable fuels

G-volution has been working on dual-fuel engines since 2008, and on the class 66 concepts since 2019. As the company’s research director, Mr Shimon Shapiro, explains, they involve replacing the class 66’s EMD 12-710 engine with a new dual-fuel engine developed by G-volution that meets European Union (EU) Stage V emissions standards. The new engine would burn a mixture of diesel and biomethane, diesel and biopropane, or diesel and hydrogen, and further modelling has been conducted of introducing ammonia into the dual-fuel mix. Shapiro points out that no diesel-only after 2040 refers to fossil diesel fuel, and not the compression-ignition internal combustion engine named after Rudolf Diesel.

Biomethane is manufactured by anaerobic digestion of organic material, such as food, farm or sewage waste, and G-volution says there are currently 670 plants in Britian producing this fuel which is a renewable replacement for natural gas.

Biopropane can be produced in a number of ways, including from biomass, and is a renewable replacement for liquefied petroleum gas (LPG). The diesel component of dual fuel could be replaced by renewable biodiesel. Burning biodiesel alone would also lower CO₂ emissions, as it is also net zero, but this would do little to lower emissions other than CO₂. G-volution points out that dual fuelling also lowers particulate emissions, and if a diesel particulate filter (DPF) is fitted, the engine spends less time working against increased back pressure as the DPF fills, improving engine efficiency and lowering fuel consumption.

The simulations found that installing a new dual-fuel engine running on diesel and biomethane would produce a 51% reduction in CO₂ emissions.

G-volution has also developed a dual-fuel evolution of the class 66’s 12-710 engine, part of the 710 range first introduced by EMD in 1985. But as Shapiro says, “modern engines offer higher efficiency, the opportunity to use advanced combustion control strategies and compliance with the latest emission standards.” The dual-fuel concepts would see the class 66’s original fuel tank replaced with a smaller diesel tank and cylinders to contain biomethane, biopropane or hydrogen installed in the space freed up beneath the underframe. G-volution says a range of fuel tank solutions has been developed for each fuel, including using smaller cylinders or fewer, larger cylinders.

To assess the performance of the dual-fuel concepts, G-volution simulated operation on actual routes using data from on-train monitoring recorders (OTMR) installed on class 66 locomotives, supplied by freight operators. This OTMR data was used in combination with dual-fuel engine models based on G-volution research. The simulations found that installing a new dual-fuel engine running on diesel and biomethane would produce a 51% reduction in CO₂ emissions, and cut operating costs by 29%. Using diesel and biopropane would cut emissions by 42% and operating costs by 21%, while running the class 66 on diesel and hydrogen would reduce emissions by 49% but produce only a 7% saving in operating costs.

Fuel consumption

For the dual-fuel evolution of the EMD 12-710 engine, diesel and biomethane would produce an 81% reduction in diesel fuel consumption, and a 39% saving in operating costs. With diesel and biopropane, diesel fuel consumption is cut by 71% and operating costs by 26%. A 79% reduction in diesel fuel consumption is delivered by diesel and hydrogen, but using this dual fuel would actually increase operating costs by 28%. This is because, in G-volution’s calculations based on 2020 prices, green hydrogen produced by electrolysis using renewable power was six times the cost of diesel, while hydrogen produced using natural gas was 1.3 times the cost of diesel.

To offer operating cost savings over diesel, green hydrogen needs to become cheaper, a situation that has unfortunately in some ways become less likely since 2020. Shapiro points out that the minimum cost of renewable energy in Britain per hour is pegged to the price of natural gas, which has increased dramatically since the invasion of Ukraine. If renewable generators were able only to charge their full costs of production, then green hydrogen could become more viable, he suggests.

In contrast, diesel is at a price disadvantage when compared with biomethane and biopropane, as they are disconnected from increases in the cost of crude oil and their prices are expected to fall as production volumes continue to ramp up. Based on 2020 prices and on an energy equivalent basis, biomethane was 0.47 times the cost and biopropane 0.58 times the cost of diesel fuel refined from crude oil.

In general, G-volution says that for the class 66, the new four-stroke dual-fuel engine offers a 10% improvement in fuel consumption compared with the original two-stroke EMD 12-710 engine. While the dual-fuel evolution of the EMD engine offers higher diesel replacement rates, it is still a two-stroke engine design that is less efficient than a new four-stroke dual-fuel engine and does not meet the latest Stage V emission standards.

The class 66 also operates in mainland Europe, and Shapiro says G-volution is currently at work on three similar dual-fuel projects outside Britain. In its home market, it has also developed a dual-fuel concept for the class 37 locomotive powered by an English Electric 12CSVT engine and which first entered service in 1960, as well as twin-engine concepts using smaller dual-fuel engines for the class 66 and the class 59. For the moment, its single-engine dual-fuel concepts for the class 66 have yet to progress to prototype stage, but a dual-fuel evolution using diesel and biopropane has been developed for the class 73/9 and these locomotives are now in the final stages of gaining approval to operate on Network Rail infrastructure.

At present, there is no strong external incentive for freight operators in Britain to embrace the new technology, such as strict emissions reduction targets, government grants to reduce emissions, a scrappage scheme for older locomotives or even reduced track access charges for rolling stock with lower emissions. This contrasts with the United States, for example, where Shapiro points to the requirement to reduce emissions when undertaking the well-established practice of rebuilding freight locomotives, when engines are often replaced or upgraded using packages supplied by the OEMs.

In Britain, Shapiro sees the major incentive as being the savings that dual fuel promises to deliver for freight operators. “The costs speak for themselves,” he says.

Replacing the reliable but less fuel-efficient EMD engine with smaller, more powerful and more fuel-efficient designs would also free up space within the locomotive to install exhaust-treatment equipment. Given the long service life of freight locomotives, compared with truck fleets that are typically renewed every five years, this offers an opportunity for freight operators to reduce costs while further strengthening their green credentials.