DHL Supply Chain’s Consumer division has become the latest – and among the biggest – investor in gas-powered trucks with the replacement of most of the 70-strong fleet based at its multi-user DC at Bawtry near Doncaster, south Yorkshire, with Volvo FM MethaneDiesel dual fuel 6x2 tractor units.

The large scale trial of 63 dual fuel liquid natural gas (LNG) technology is part of DHL’s Go Green initiative to cut CO2 emissions by 30% between 2007 and 2020; it estimates tank to wheel emissions reductions of 12% to 14% depending on how much diesel is substituted by gas.

The move is not entirely altruistic – the cost of converting the trucks and the installation of a BOC gas fuelling station is expected to be paid back within two to three years of the five year vehicle lease term because of the lower price of LNG compared with diesel.

David McDonald, vice president, operations, consumer and life sciences, says: “At 1m sq ft Bawtry is by far the largest site in the consumer and life sciences division. All our customers are interested in our environmental impact and a key driver is customer retention.”

According to Ian MacAulay, DHL innovation manager, fleet engineering services, LNG appears to be the best technology for reducing carbon emissions from the heavy truck fleet.

“We have tried biodiesel, electric and hybrid vehicles and better aerodynamics,” he says. “The Teardrop is an icon within our fleet – we own 1,000 and operate another 400 for customers. But gas is now a core focus for us. A lot of the low hanging fruit – vehicle specs, operational improvement etc – has now been picked. Dual fuel is the best option – there are doubts over the fuel savings from 100% gas spark ignition engines.”

Carbon footprint

DHL Supply Chain operates 7,500 trucks and 10,000 trailers in the UK, and 87% of its CO2 emissions come from the road fleet. Bawtry is among DHL’s top 10 carbon emitting sites, with a carbon footprint estimated at 9,000 tonnes a year, 90% of which comes from its road fleet. The move to dual fuel will cut this annual output by 1,200 tonnes. “That is a significant dent,” says MacAulay.

DHL chose to work with Volvo because the dual fuel conversion is done at the factory in association with Cleaner Air Power and has been developed to maximise diesel substitution, put at 60% to 75% depending on driving patterns. The vehicles have a 100kg LNG tank on the left and a 200l diesel tank on the right – the AdBlue tank has been relocated inboard to make room – giving a range of 650kms on gas/diesel mix and another 150kms on diesel alone. The new trucks are all Euro-5s – Volvo cannot say when it will have a Euro-6 dual fuel vehicle available.

LNG was chosen over compressed natural gas (CNG) because LNG is 2.4 times denser than CNG and so the vehicle tank is smaller. Some operators have struggled to get CNG tanks of adequate size onto a 6x2 unit, leaving them the choice of a smaller range or dropping to a 4x2 unit.

The BOC gas refuelling station has a 29t tank and has been designed to leak no gas to atmosphere – methane is 25 times worse than carbon dioxide in terms of its greenhouse effect, so leaking just 3% negates the environmental benefits of LNG. LNG is delivered by tanker and stored at -160C, with liquid nitrogen used to cool the tank and ensure no gas boils off. BOC LNG business manager Mark Lowe says vapour from hot vehicle tanks can also be captured and reliquefied during refuelling to avoid venting methane to the atmosphere.

The trucks will be double shifted and return to Bawtry at the end of each shift for refuelling, so range should not be a problem, says MacAuley. “We would prefer to use a quality gas refuelling network across the UK but where we have the scale we will go with our own station,” he says. “By the end of the year we will have three gas stations on DHL sites – Bawtry, Scunthorpe and Droitwich.”


Across the UK, DHL now operates over 100 dual fuel trucks and while it has no plans to open up its gas stations to third parties it will be able to refuel its other gas vehicles at Bawtry. The lack of a national refuelling infrastructure is one reason holding back the take off of gas and dual fuel LGVs – few operators have the scale to justify installing in-house fuel stations. This also means the residual value of such vehicles is uncertain – while the dual fuel system can be removed before the vehicles are disposed of, Volvo hopes there will be market for secondhand gas vehicles.

MacAuley shares this aspiration: “Residual values are unknown but a secondhand vehicle with access to a good refuelling network would be attractive.”

LNG is currently delivered to Bawtry in 19t full tanker loads from BOC’s Avonmouth liquefaction plant every five days. This take standard methane from the National Grid so has no biomethane component – which is produced from waste and has up to one third the carbon intensity of diesel. “This is something we are looking to address,” says Lowe.

BOC operates six liquefaction plants around the UK but Lowe says that the most efficient source of LNG for road vehicles is gas which is delivered in liquid form by ship, as this avoids having to expend energy liquefying the gas. The main UK LNG import terminals are currently at Isle of Grain in Kent and Milford Haven in South Wales. While there are no facilities to load LNG road tankers at either port, National Grid is proposing to offer a truck filling service at Isle of Grain within two years.

DHL is about to be joined by Asda in a large scale trial of Volvo dual fuel trucks. Chris Hall, Asda national transport operations manager, has ordered 50 6x2 units with Cleaner Air Power LNG dual fuel conversions.

“Dual fuel is better on cost and the environment,” says Hall. “We are using natural gas which is a step toward biogas. Gas is the only alternative to diesel.”

The vehicles will be based at Asda’s new £70m chilled DC in Bristol, where a BOC LNG refuelling station will be installed. “This is toe in the water,” says Hall. “The technology is reliable and with a payback of three years will not cost us any more.”

Hall says Asda looked at CNG but decided it needed the tank capacity offered by LNG on its 6x2 units.

Another operator - Howard Tenens – is already well down the dual fuel road – though it has opted for CNG or compressed biomethane rather than LNG. It expects to have 88% of its fleet over 18t running on dual fuel by the end of 2013.

Howard Tenens livery

Catherine Crouch, Howard Tenens group CRS director, says the company has been proactively reducing carbon emissions since her arrival in 2008. She estimates that ‘plain’ natural gas yields a 5% to 20% cut in CO2 emissions, while switching to the scarce and more expensive biomethane can cut emissions by 40% to 60%. “Moving from natural gas to 100% biomethane is the only option to achieve a 40% cut in carbon intensity,” she says, “and for us dual fuel is the most appropriate technology.”

Like Asda and DHL, the lack of a national gas refuelling infrastructure meant Howard Tenens has installed its own gas stations, all open to third party operators. Existing CNG stations at its sites on South Ockenden in Essex, Boston in Lincolnshire and Andover in Hampshire are about to be joined by a new facility at Swindon in Wiltshire. Howard Tenens is taking part in three of the Technology Strategy Board’s (TSB) government funded low carbon fuel trials, and the Swindon grid-connected gas station is being partly funded through one of these projects.

Its first fuelling station at Andover is in fact L/CNG – it takes fuel in liquid form at -160C from a road tanker and it is vaporised, compressed and delivered as CNG to the vehicles.

So far 59 vehicles have been converted to dual fuel spread across depots with refuelling infrastructure. Howard Tenens operates a fleet of 150 tractor units, rigids and vans and as the refuelling network improves Crouch says she is aiming for a 100% dual fuel fleet.


Despite some other operators’ concerns about the tank capacity available with CNG, Crouch says the trucks have a range of up to 680kms – which is “as good as or if not better than LNG”.

The first trial started in 2008, running two 6x2 vehicles for six months. “These first trucks had gas tanks on the trailer with an umbilical connection to the engine,” says Crouch. “Over the years we have worked out how to get the maximum containment on the unit.” The latest variations use a Prins Autogas UK conversion suitable for both 4x2 and 6x2 units.

“There are pros and cons of CNG and LNG and this is probably the most difficult decision for any operator,” says Crouch. “We decided on CNG because we felt it was simpler to use, poses less risk of losses to atmosphere and also provides the fuel security we need with on-site grid-connected stations.”

Southampton-based Prins Autogas UK has recently converted 36 4x2 and 6x2 vehicles after an eight month trial on two vehicles. Most are for Swindon with some others going to Andover, Boston and South Ockenden.

“The OEMs’ support for the conversions was extremely important to us,” says Crouch. “Part of the conversion cost is a top-up insurance to protect the warranty– to cover any gas related problems should they arise. We buy Daf and Mercedes-Benz – they have been extremely helpful. We looked at the Volvo but it is LNG so doesn’t meet our current needs. We use dealers for repair and maintenance – their technicians are trained by the conversion supplier to carry out any repair and maintenance work.”

Tank capacity

The original conversions of the 6x2 Mercedes-Benz units retained the standard diesel tanks, though some later versions have upright exhausts, a relocated AdBlue tank and smaller diesel tanks to maximise gas containment. “We wanted a 400 to 450 mile range,” says Crouch. “There are very few routes were the trucks don’t get back to base within that. We also have access to three other CNG fuel stations and will route trucks to go past them. More recently the company has invested in a number of small mid-lift axle 6x2 vehicles which has enabled a simpler conversion while retaining the range required.”

Crouch is now confident that following the TSB/DfT pilot a national natural gas refuelling infrastructure “will come”. “Operators with their own base stations are opening them up to third parties, and motorway network infrastructure is planned, making gas more feasible for most hauliers,” she asserts.

Gasrec Dirft

Specialist gas supplier Gasrec opened the first third party CNG and LNG biomethane refuelling station earlier this year, on the Dirft rail freight terminal in Daventry. “It is the only station currently supplying a biomethane LNG blend, 15% of which is biomethane,” says Crouch.

Crouch believes that after a number of false starts, the transport industry is now ready to adopt gas as a low carbon alternative fuel.

“Historically this industry has not liked change – diesel is easy,” she says. “That however is changing – we are now willing to look at alternatives but we need support from government.”

Apart from the £11m backing for the DfT/TSB trials Crouch is looking for a guarantee that duty on CNG and LNG transport fuel will be held down long enough for truck conversions and refuelling stations to give a pay back. “Support must be long term, with duty held at the right level for a much longer term, not just for three years,” she says. “Plus they need to incentivise biomethane more to help create a competitive market.”

At present the government’s renewable heat incentive encourages biomethane generators to inject it into the national gas grid. Crouch wants to see confirmation that certificates from grid-injected biomethane can be used in mandatory carbon reporting, as this will encourage other transport firms with emissions targets to look at gas for road transport.

Clean fuel

On top of its cost and carbon benefits, Crouch says even standard natural gas taken from the grid is a clean fuel compared with diesel .

“Using natural gas reduces particulate emissions as it is very clean burning,” she says. “This is as important as reducing carbon as particulate matter is a big issue in our towns and cities as it can cause respiratory problems.”

Euro-6 engines are of course very clean in terms of particulates and NOx, but Crouch argues they could possibly be even better running on gas.

“Burning natural gas produces less carbon, NOx and particulate matter,” she states. “It will be interesting to see how OEMs and conversion companies approach dual fuel at Euro-6 and whether an engine running on gas would need less after-treatment – we are sure there will be Euro-6 dual fuel vehicles. It will be three years before Howard Tenens goes to Euro-6 and by then we hope there will be a robust CNG solution.”

Although payback periods for gas conversions are complicated by the relative prices of natural gas and diesel Crouch calculates there will be a financial as well environmental benefit.

“Dual fuel runs on a blend of gas and diesel,” she explains. “The truck starts on diesel and when the driver accelerates the system will start to put gas in. On any particular journey the diesel displacement depends on how the vehicle is driven. While pulling away it is around 20% gas, on the motorway it will be 80%. Our average displacement is 55%.

“The only reason this works economically is because the gas price is lower than diesel. We work on a three year payback on the vehicle and a gas conversion always pays back in three years. We keep our trucks three to five years depending on mileage.”

Crouch has support from the company’s owners – chairman Peter Morris and two of his sons Ben and Dan – for her environmental initiatives. The firm has grown considerably in the 30 years since the management buyout in 1983 and now operates from 14 UK sites. Howard Tenens has an impressive customer portfolio comprising many blue chips and household names.

“We want to do the right thing and we believe natural gas and biomethane are the only viable option for heavy goods road transport,” she says. “Last year we saved 1,000t of carbon emissions. Our customers have environmental ambitions that we want to help them meet.”

This is borne out by a number of testimonials from customers who want to be seen to be green.

“Howard Tenens is at the forefront of low carbon transport and they have trialled dual fuel vehicles for us - we are pleased to be working with a company whose sustainable ethos is a good match for CCE, ” says Wendy Manning, customer logistics director GB, Coca-Cola Enterprises.

“They just get on and do it, and that’s what a partner is there for. But what impresses us the most is that, whereas many logistics providers pay lip service to environmental initiatives, Howard Tenens is investing millions of pounds into making a real difference,” adds Chris Clowes, supply chain manager of Costa Enterprises.

Niche market

While there is a growing number of enthusiastic adopters of gas trucks, most OEMs believe it will remain a niche market for the foreseeable future. At present dual fuel trucks are only available at Euro-5 and no OEM MT spoke to would predict a date for a Euro-6 version. Full gas spark ignition engines are available at Euro-6 but are seen as a specialist niche application for urban operations such as buses and dustcarts where low noise and clean exhaust emissions are key.

Nick Blake, head of product engineering, commercial vehicles, at Mercedes-Benz, says the company currently offers an NGT (Natural Gas Technology) Econic ex-factory and this is available both as a 6x4 and 4x2 rigid or as a 4x2 tractor unit. This uses a 280hp spark ignition engine that enjoys the same warranty as the diesel Econic.

econic ngt

“Dual fuel is available via our technology supplier Hardstaff,” adds Blake. “We are developing the NGT Econic at Euro-6 but as yet we do not have details of the exact specification including the after treatment.”

According to Blake demand is increasing and the TSB trials will undoubtedly help. “We do expect sales to increase over the next five years as operators find that they have to reduce the carbon intensity of their fuel if they are to further reduce carbon emissions, the low hanging fruit having been taken,” he says. “We have not directly been involved in the TSB competition as the method of funding precluded us from direct involvement. However, a large percentage of the vehicles in the trial are Mercedes-Benz.”

Hardstaff is a leading after-market dual fuel convertor, having developed kits for Volvo, Daf and Mercedes-Benz engines; it is currently working on other manufacturers’ vehicles. The Hardstaff OIGI (Oil Ignition Gas Injection) is a dual fuel system developed in conjunction with Loughborough University to substitute natural gas for diesel in light and heavy duty engines.

Hardstaff Haulage was also among the first major haulage companies in the UK and Europe to use natural gas recovered from landfill waste for road transport.

Growth increasing

Renault has gas offers in Europe at 18t and 26t suitable for CNG or LNG , but these are only available in LHD.

“It is clear that the rate of growth in demand is finally increasing,” says a Renault spokeswoman. “As of today, we do not have a UK offer and we cannot claim to be close enough to this market currently to be able to offer an opinion on likely volumes.”

Iveco claims to be among the leaders in the development and production of low carbon CVs, offering more alternative fuel vehicles in the market above 3.5 tonnes than any other manufacturer. It has adopted a two tier strategy to minimise CO2 output: development of alternative fuels and traction systems goes on alongside continual improvement to the conventional diesel engine.

Iveco has specific UK models of the Daily, Eurocargo and Stralis designed to run on compressed biomethane (CBM) or CNG. Specific models of Stralis can also be built to operate on LNG or liquid biomethane (LBM). All are spark ignition and certified to Euro-6.

Despite this wide range, sales in the UK have so far only totalled around 100. “As far as sales are concerned this is still a niche market dependent on infrastructure investment and a clear government strategy,” says Nigel Emms, Iveco director, brand and communications.

Like Iveco and Mercedes-Benz, Scania offers an off the shelf full gas truck with a 9l engine aimed at urban operations, but not a dual fuel version. Martin Hay, Scania’s UK truck sales director, says it has a Euro-6 gas version of its 9.3l engine rated at 280hp and 340hp.

Hay says: “There is a lot of interest from operators, but not surprisingly they are looking for a full package including refuelling infrastructure in a lot of cases, which will delay time to market. We do believe this may be the green fuel of choice going forward for the next few years or so.”


Volvo is currently the only truck maker to offer a dual fuel truck ex-factory with a full manufacturer’s warranty. Its MethaneDiesel FM 13-460 Euro-5 4x2 and 6x2 tractors, converted in conjunction with Cleaner Air Power, have been available for 12 months and a spokesman says 160 have now been sold in the UK – more than in the rest of Europe put together. Volvo does not offer a full gas truck but says demand for its LNG dual fuel truck “is growing”.

While Daf trucks are often used as the basis of dual fuel conversions, the Dutch manufacturer does not offer a factory gas or dual fuel truck.

“Dual fuel trucks are nearly all conversions,” says Tony Pain, until recently Daf Truck’s UK marketing director. “The jury is out but I feel dual fuel is the way forward. Range and lack of refuelling infrastructure are issues but at least dual fuel can always deliver the goods and get home on diesel. But it is an expensive conversion.”

Daf does not give a warranty for converted trucks but Pain says Daf “would not deny a warranty claim on parts not affected”. “We don’t know what gas does to an engine,” he says. “There have been a number of Daf conversions and it seems to work quite well.”

Pain warns that “dual fuel will be very difficult at Euro-6”.

“Euro-6 is complex and the downside of dual fuel is that you need exactly the same after treatment for the diesel fuel,” he says. “Euro-6 will put a hiatus on gas. But there is plenty of work converting Euro-5s for the next two years and by then we might have made Euro-6 work.”

Pain also questions the assumption that biomethane is better used to run trucks than to heat buildings. “It is more efficient to use biogas in buildings because its energy density is lower than diesel,” he argues.

Carbon questions

He also questions the carbon benefits of natural gas, especially in its compressed form.

“Well to wheel, CNG emits the same CO2 as Euro-6,” he asserts. “Biomethane is better because it captures methane that would otherwise escape to atmosphere and avoids using diesel. Well to wheel, LNG offers 10% to 15% cuts in carbon – which is within the possible realms of diesel improvements.”

With the UK running out of oil but discovering shale gas reserves Pain sees one major benefit in switching to gas power however – energy security.

“There is demand for natural gas at Euro-5,” he says. “A number of fleets saw this coming and bought Euro-5 because they can be converted in future.”

Like Mercedes-Benz, Daf is monitoring the progress of its trucks in the TSB trials with interest.

But Pain has been around long enough to know this could be yet another false dawn. “Back in 1997 we said gas was about to take off,” he says. “There was interest in 2007 but then the recession came and operators went into survival mode. Now interest is growing again – I suspect gas won’t catch on but dual fuel might because there are many benefits. In 10 years dual fuel might account for 15% to 20% of trucks on the road.”