Reading gas bus

While gas trucks are still a rare sight on UK roads, buses operating in towns and cities have been running on natural gas for years.Reading Buses is a good example, so MT went to talk to John Bickerton, head of engineering and innovation at Reading Buses, to see what lessons CV operators can learn from his experience.

“They are the most reliable buses in our fleet,” is Bickerton’s initial comment when asked about his gas vehicles. And he has had experience with most powertrains in his 13 years in the bus industry.

While today’s Euro-6 diesel engines are comparable with gas in terms of emissions of local pollutants NOx and particulates, back in 2013 when Reading started on the gas journey, Euro-5 was starting to move to Euro-6.

“With Euro-5 there were significant NOx benefits from moving to gas,” says Bickerton (pictured below). “A Euro-5 gas engine was cleaner than a diesel engine, especially for NOx, where the Euro-6 standard was already achieved. By 2013 that improvement had been eroded because Euro-6 diesels had improved so much.

“However, it was a very easy way for us to go carbon neutral because we can buy biomethane. And because it's made from food waste and cattle slurry it has none of the food versus fuel arguments you get with biodiesel. Nor do you get any of the fuel quality issues that you get with some biodiesel. I've run vehicles on 100% biodiesel and it didn't go well.”

John Bickerton

While many operators in the CV market believe that bus operators work in an easy highly-subsidised environment, Reading Buses has to regularly bid for its contracts in competitive tenders. But most of its work is commercial and 80% of revenue comes over the cab door.

“We went to gas to provide a clean carbon-neutral bus service as part of the contract bid,” Bickerton says. “That bid included 20 gas vehicles and installation of the gas station. The gas station could fuel more buses so it was fairly simple at that point to take a second batch of 14 vehicles.”

Bickerton is a gas convert and enthusiastically shows us a Scania single-deck bus powered by a 5-cylinder, 9-litre gas engine.

“The nice thing is we understand it,” he says. “It's all familiar and the only new bit is the spark plugs and coil pack. The gas engine is actually a lot simpler - there's no particulate filter or AdBlue system. If it's not there it can't go wrong.

“We took the first 20 vehicles and I was interested in it but to be honest I didn’t think it had legs. This bus is a 13-plate so it’s over five years old with nearly 100,000 miles on the clock and it’s one of the most reliable buses we have on our fleet. So the decision to expand our gas fleet was easy.”

Reading’s buses run on compressed natural gas (CNG), most with gas tanks mounted on the roof. The current generation are at 200 bar but the next vehicles can hold gas at 250 bar to increase capacity.

Amazingly quiet

Climbing aboard the bus while it is ticking over, it is amazingly quiet, even right at the back next to the engine. This is partly because a spark-ignition gas engine runs at a lower compression ratio than a diesel. “It’s 9:1, as it's just a petrol engine that runs on gas,” says Bickerton. “The big benefit is it's simple and drivers love them. These are 260hp while the double-decks are 305hp. They go very well and are as quick as their diesel equivalents.”

The financial case for moving to gas is currently based on the government pledge to maintain fuel duty on gas at a significantly lower level than diesel for at least five years to encourage take up.

“The fuel cost is quite a lot less than diesel but you use more of it because being a petrol engine it is not as efficient,” says Bickerton. “The cost comes out to be about 80% the cost of diesel against today’s prices; more importantly we have an agreed 10-year gas price, which is a game-changer.

“Also we don’t have the maintenance overhead for the AdBlue system and particulate filter and we don’t have to buy AdBlue so that saves probably another 3% or 4% in fuel costs.

“If they remove the duty differential completely it wouldn't help, but then if they increase the duty on diesel that wouldn't help us either. At the moment gas is good, it's clean and it's reliable. Now, to be honest, if it costs the same, I'd still buy gas for the reliability.”

Diesel option

Despite clearly being a big fan of gas, of Reading’s fleet of 170 buses only 72 are gas and it has recently bought 28 double-deck Euro-6 diesels.

“When we bought those, you couldn't buy a gas double-decker at Euro-6,” Bickerton explains. “We were the first buyer of double-deck gas but they didn't make them up until that point. We will still buy diesel for range, for outstations and for resale.”

The latest double-deckers have four gas tanks under the stairs and upstairs there are four more much larger tanks, but they take away a row of seats. While buses have the advantage of being back at base every night for refuelling, they have to carry enough gas to complete a full day’s work.

“We'll see a better solution on the next generation bus because every time we buy them we move them on a little bit,” says Bickerton. “If you forget to put gas in a bus it will run out in the middle of the afternoon on the second day. The same is true with a diesel bus.”

Gas capacity

The gas capacity of the tanks varies from 150kg to 200kg, which with careful planning is enough to do a day’s work on even the longest routes.

Looking ahead, Bickerton is conscious that gas will not be clean enough as the UK drives from low towards zero emissions.

“I can see a point in 20 or 25 years from now where zero emissions is an increasing requirement,” he reflects. “Over that timescale, we'll understand more about the cost of electric vehicles.”

Hydrogen v batteries

Some cities including Aberdeen and London are experimenting with expensive hydrogen fuel cell buses but Bickerton is not a fan.

“I’m not sure every town needs true zero emissions when Euro-6 is so clean,” he says. “Hydrogen's not a fuel, it's a storage system. You've got to get it from somewhere and I can't buy carbon-neutral hydrogen. If I do, I can't burn it, or catalyse it or run it through a fuel cell for the price I can buy gas buses for. The experience in London's shown is they're not that reliable yet either.

“I think our next technology will be electric, but I'm going to let somebody else do all the work to de-risk it first. We were some of the first adopters of hybrid and it really hurt. We were among the first to go for gas and it hasn't hurt.”

So for now, gas is a known, safe and reliable quantity after Bickerton’s bad experience with diesel/electric hybrids, which he says break down twice as often as his gas buses and are ruinously expensive.

“We have 31 hybrids which we bought a year before the first gas buses and if we'd replaced the whole fleet with them, the company would've gone into administration,” he says. “I'm not joking. Those 31 buses have cost me £1m and we only turn over £34m a year.

"Every one of them has had a new battery within its five-year warranty and the batteries are £30,000 apiece. The worst in the fleet have had four batteries in five years.

“After five years, the warranty pretty much runs out. How much is a new warranty? £50,000 a bus, times 31. For less than the cost of the warranty, I can convert them back to diesel. So, half the vehicles we've taken a warranty on and half the vehicles we've converted, acknowledging conversion may also be a risk. After extending the warranty for five more years I have a 10-year-old bus with a hybrid system and no warranty.”


Reading depreciates its vehicles over 15 years but Bickerton likes to sell them at 10 years when they still have good residual values. The hybrids are not looking like a good investment on that basis however.

“They were £250,000 new plus £100,000 for the hybrid system (supported with Green Bus funding) and £50,000 worth of diesel conversion and they might be worth £11,000 after 10 years, which tells you something about the value of the bus,” Bickerton says. “The hybrids do drive beautifully. It's such a shame they don't work as reliably as the rest of the fleet.

“We trialled a single-deck electric bus recently with £150,000 worth of battery pack and the story with the battery life was exactly the same as with the hybrids. How long will the battery last? Seven years. How long is the warranty? Five years. Once bitten, twice shy.

“I have concerns about the ‘Road to zero’ and the cost for operators. The test drive is wonderful, but five years later it's going to drop you with £100,000 bill and you don't know when it's coming. It's a technology risk and therefore a cost. For me, Euro-6 gas answers a lot of those questions as it's cheap to run and it's reliable.”

Working on gas buses

Reading runs its own garage maintaining the entire fleet so is well placed to compare the running costs of gas and diesel engines. We caught up with vehicle technician Mark Wiggins as he serviced a Scania gas engine.

Like Bickerton, Wiggins has been fully converted to gas. “It's cheap, it's reliable, good for the environment and people seem to like them. The drivers like them because they're quick and quiet as well,” he says. “It's an all round good package. There really are not many problems with them.”

Gas comes down from the tanks at 200 or 250 bar to a regulator that feeds low pressure gas to the engine. Working on the high pressure pipework requires a two-day training course but Wiggins says any issues with leaks have been fixed.

“The regulators were prone to leak when they first came in, but Scania has redone all the pipework and fittings,” he says. “The aftersales service side of it is actually pretty good.”

One major advantage of gas is that the engines are very close to the familiar diesels.

“To look at it, it is just like a normal diesel engine,” says Wiggins. “The only big difference is the spark plugs, which are basically the same as a car.”


The spark plugs are buried deep inside the engine and require a long spanner to remove and replace them every year. These spark plugs also cost a lot more than those you would use on your car.

“We are on an annual cycle to change the spark plugs, and they're quite expensive at £520 a set,” says Wiggins.

“It's a Scania-only part number. It may look like the one in my lawnmower, but it has a special heat rating and only Scania have the part number. I'm not going to fit non-standard parts.”

Bickerton adds: “What's annoying is that on the mileage we do, the spark plug change interval under Scania's guidelines is 22 months. We can't quite get to two years, so we just do them every year.”

Replacing the plugs every year improves reliability, as Reading has experienced a couple of spark plug failures in service.

“They sit quite deep in the engine, and the gas engines run really warm,” says Wiggins. “They're normally pretty good, but we've had a couple that have cracked and caused a misfire.”

To keep life simple with a mixed fleet, Bickerton uses the same engine oil in the gas and diesel vehicles. While the buses are routinely inspected every six weeks, the engine oil is drained every six months.

“The same product is approved in everything we've got,” he says. “We harmonised on OWS Ecolight. If you change the oil twice a year, even if the oil will go a bit further, it means if somebody accidentally puts in the wrong product it gives you two goes a year to get rid of any contaminants.”


Buying and using green gas

Reading buys its biogas from the Gas Bus Alliance, which has partnerships with several biomethane providers operating anaerobic digestion (AD) plants around the UK. Through a system of renewable fuel certificates, the biogas is injected into the gas grid and Reading is able to draw conventional gas from the main to fuel its fleet.

“The nice thing commercially is that the cost of operating the AD plant is completely different from the oil industry,” says Bickerton. “Because their costs are broadly known, I have a 10-year fixed price plus RPI on gas. I have nobody who'll give me a 10-year price on diesel, or if somebody would I don't think it would be that attractive. The duty is a risk on top of that, but we all trust our government, don’t we.”

Reading’s gas fuelling station has been relocated above the garage to avoid taking up valuable parking space in the yard and has been upgraded from two to three compressors with much more storage capacity at a cost of £2m.

“We're quite restricted by the gas pressure coming into our site,” says Bickerton. “We take gas out of the domestic gas main at 22 millibar – a 7-bar gas main would be lovely but we don't have that. From that, we compress in three stages up to 250 bar for the storage tanks. It's a fair-sized machine.”

That machine draws 90kW, a sizeable running cost and potential carbon footprint.

“The cost of running this is about 10% of the whole operation but we can buy green electricity the same as we buy green gas,” says Bickerton. “We have solar panels but 90kW is an awful lot of solar and these run between 6.30pm and midnight when it tends to be dark.”

The vast majority of the gas is used in Reading’s own fleet, though it is open to anyone needing CNG.

“We are not a public fuel site but I'll sell gas to anyone who wants it,” says Bickerton. “The restriction is obviously that if the vehicle comes in between 6pm and midnight it'll be in a queue.”