UK: Chiltern Railways has switched to using hydrotreated vegetable oil in its fleet of Class 68 diesel locomotives, as part of a long-term strategy to decarbonise London’s last remaining all-diesel suburban network.
Introduction of the low-carbon fuel was marked by an event at London Marylebone on July 27, attended by MP Nicky Aitken and other stakeholders.
Responding to local concerns about the noise emitted by the Class 68s and the impact of diesel exhaust from the station on the surrounding area, Managing Director Richard Allan told Rail Business UK that the use of HVO in place of diesel would reduce CO2e emissions by between 85% and 90%, depending on the locomotives’ duty cycle. It would also bring a reduction in particulates and NOx, although this has not been quantified.
Chiltern currently deploys five Class 68s, which are owned by Beacon Rail and sub-leased from DRS. They work with push-pull trainsets of MkIII coaches on services between London and the West Midlands, with four locomotives in use each day.
According to Chiltern’s Head of Engineering Commercial Philip Andrews, the small fleet works a limited range of diagrams, which means that they can all be refuelled at Stourbridge Junction, where a dedicated HVO tank has been installed.
The Caterpillar engines were already authorised to use HVO as an alternative fuel, and DRS had been a ‘very receptive partner’ in the engineering change process, which was also supported by Beacon Rail. In aggregate, the Class 68s use around 15 000 litres per week, which is around 4% to 5% of Chiltern’s total fuel consumption.
Parent company Arriva Trains UK has contracted with Green Biofuels Ltd for a supply of HVO manufactured from feedstock deemed unfit for human consumption. Chiltern insiders confirmed that the fuel was slightly more expensive than conventional diesel, noting that diesel prices had fallen in recent weeks. The operator hoped that ‘market-led supply and demand’ would see a fall in HVO prices as the take-up increased.
Andrews confirmed to RBUK that Chiltern is in discussion with rolling stock leasing companies about switching its Class 165 and 168 DMUs to HVO, but there is still some uncertainty about the compatibility of the alternative fuel with older engine types, and any life-cycle cost implications. Chiltern is also taking advice from its engine maintainer, Wabtec subsidiary LH Services.
Fleet replacement prospects
Allan told RBUK that Chiltern would be ‘going to market in the next week or two’ with a Request for Proposals to replace the aging Class 165s by a new fleet of zero- or low-emission trainsets. He pointed out that its fleet was now the third oldest in Britain, with an average age of almost 29 years, according to ORR data. As such, he felt it had ‘a good case’ to be the next operator in England to order new rolling stock.
Reporting that the operator was broadly back to pre-pandemic ridership volumes, with 18·5 million passenger journeys in 2022, Allan said the business had reduced its call for taxpayer support from £100m in 2021 to around £30m, and was ‘closing in’ on covering operating costs from revenue. He hoped that investment in a new and more attractive fleet would encourage ridership growth, justifying the higher costs associated with leasing new trains.
Earlier this month, Chiltern launched its Right Route 2030 strategy, setting out how the operator intends to deliver ‘easier, greener, and better rail services’ through investment in fleet renewal over the next decade. It said replacing the ageing diesel fleet would unlock ‘essential benefits’ for customers and stakeholders, including more capacity and improved air quality, as well as supporting economic growth.
The first step will be to replace the Class 165s, which date from 1990 and are mainly used on shorter-distance suburban services. Insiders suggest that the 65 km London – Aylesbury route could be worked by battery multiple-units recharging at each end, but some partial or discontinuous electrification might be advantageous.
Having made initial market soundings last year, Chiltern has obtained agreement from the Department for Transport to invite proposals from potential suppliers. It expects responses by the end of this year, helping to inform the preparation of a formal business case, and hopes to be able to award a contract within the next 12 months. This could see the new trains in service around 2027-28.
Allan said the next step would be to look at options for replacing the Class 168s, which were the first post-privatisation DMUs with the oldest sets dating to 1998. These are used on longer-distance services to Oxford and the West Midlands, which is beyond the range of a pure battery trainset. The operator would aim to keep its HVO-fuelled push-pull sets in operation during the transition to provide the necessary capacity, he added.
He confirmed that trials with two DMU cars converted to diesel-battery hybrids were not being taken forward.
A Class 168 modified in conjunction with Rolls Royce and Porterbrook has been operating in revenue service, but the project had demonstrated that the benefits were insufficient to compensate for the cost of conversion. The unit is therefore to be ‘deconverted’ to restore compatibility with the rest of the fleet.
A second trial with Angel Trains and Wabtec to modify a Class 165 did not reach the stage of commercial operation, and insiders report that this vehicle is still at Wabtec’s Doncaster plant.
