Tackling the emissions challenge

Gas power, electric drivelines and diesel upgrades are being deployed by operators as the industry moves to bear down on tailpipe emissions.

Steve Banner reports

Best-known at present for its 53 biogas-powered ADL-bodied Scania double-decks, Nottingham City Transport also runs a large fleet of diesel-powered buses: and it is having their emissions cleaned up.

Baumot is equipping 185 of them with its BNOx system with the aim of cutting their NOx (nitrogen oxide) output by 90 per cent and upgrading them to Euro 6. All the single-decks will be upgraded this year while all the double-decks will have been upgraded by autumn 2019.

The scheme will substantially cut the fleet’s nitrogen dioxide and particulate output. “It will see Nottingham have one of the cleanest fleets in the UK,” says NCT engineering director Gary Mason.

“It is in addition to the recent introduction of two electric buses by Nottinghamshire County Council in Beeston and Stapleford,” says county councillor Phil Rostance, vice-chairman of its communities and place committee.

The electric buses are both 10.8m BYD ADL Enviro200EV single-decks partly funded by the government’s Low Emission Bus Scheme.

BNOx uses AdBlue to control emissions, but does not inject it as a liquid. It creates ammonia gas from it using hydrolysis and a small generator, and injects that instead.

The NCT diesel upgrade is being funded by more than £3million secured from the Department of the Environment, Food and Rural Affairs, courtesy of its Clean Bus Technology Fund. Nottingham City Council won £2.6million while the county council won the balance for the programme.

NCT’s move should be viewed against the background of the steady roll-out of Clean Air Zones in urban areas across the UK – one was originally scheduled for Nottingham – and the strong pressure local authorities are under to sanitise the air people breathe. NCT also plans to replace its remaining Euro 3 and 4 double-decks with more biogas buses.

While retrofitting up to Euro 6 standards is now continuing apace for buses, aided by grant funding, coaches are a different matter.

At the time of writing, no coach retrofit systems have yet been approved under the Clean Vehicle Retrofit Accreditation Scheme, although Eminox reports that its SCRT system has gained a provisional pass follwing trials at Millbrook Proving Ground and is about to be approved for Volvo B9R with 9.4-litre Euro 5 engine applications.

Eminox, like Baumot, is one of the five suppliers approved by Transport for London to retrofit older diesel buses with exhaust after-treatment technology to bring them up to Euro 6. The others are Proventia – the Finnish firm is represented in the UK by Mitcheldean, Gloucestershire-based Excalibre Technologies – HJS and Amminex.

Based in Denmark, the last-named company has forged close links with Eminox, which is now offering its ASDS – Ammonia Storage and Delivery System – in the UK alongside SCRT.

ASDS employs ammonia kept as a solid in a removable and replaceable cartridge and releases it into the exhaust system as a gas. One of its key plus-points is that it works especially well in bitterly-cold weather, says Amminex.

BNOx too performs well when the temperature drops, according to Baumot.

Returning to gas buses, NCT is not the only fleet to have put them into service. Reading Buses is a long-standing adopter – its new Connect Henley-on-Thames services contracted by Henley Town Council run on gas power – and Ipswich Buses has recently finished trialling a biogas Scania.

Liquefied natural gas, compressed natural gas and biogas are not the only gaseous fuels that can be used to propel buses. How about hydrogen?

Ten hydrogen fuel cell buses constructed by Van Hool are in service in Aberdeen and 22 hydrogen buses should be plying the streets of Birmingham next year says the city’s council. The £13.4million project is supported by the Office for Low Emission Vehicles and the hydrogen the buses use will be produced using renewable electricity created by a gasification plant that burns waste wood.

It is worth noting that all London buses entering the Ultra Low Emission Zone proposed for the centre of the capital by April 2019 will have to be electric, hybrid, or run on hydrogen.

Claims are regularly made that certain systems prevent ‘x’ number of tonnes of NOx, particulates or other pollutants from entering the atmosphere.

But how does anybody know? Is it all educated guesswork?

Not according to Amminex.

In Denmark in 2015/16 it upgraded 300 of Copenhagen’s buses with its ASDS package. Since then they have driven over 44 million km and saved over 500 tonnes of NOx, it reports.

Amminex knows this because ASDS has built-in sensors that can measure engine-out NOx levels as well as NOx levels in the exhaust pipe. Data is sent to a server continually so it is possible to see how much NOx has been removed.

Movia, Copenhagen’s public transport agency, is pleased with the progress that has been made.

“Our goal is to reduce NOx emissions from buses by 97 per cent by 2030,” says director of planning, Per Gellert. “It’s an ambitious goal and we’re pleased that the Amminex package has already reached such an important milestone.”

Despite the advent of gas and battery power, one suspects that it will be many years before operators finally scrap their bulk diesel tanks.

With 55 buses and 32 coaches, Holt, Norfolk-based Sanders Coaches recently had its bulk fuel storage facility upgraded by Triscan Group.

It has moved from an underground tank to a 38,000-litre one that sits above ground. Its two pumps have a flow rate of 60 litres a minute, a considerable improvement on the 20 litres a minute that was the norm previously.

The way in which the pumps have been positioned means that two vehicles can be refuelled simultaneously, reducing the risk of a queue of buses and coachesm waiting to be replenished with diesel, spreading out onto the public highway

Switching to an above-ground tank means that any leaks can be spotted immediately and action taken. It also makes it easy for the entire package to be lifted and shifted if the business moves premises.

Although security precautions can of course be taken, unfortunately above-ground tanks are vulnerable to having their contents stolen; and the problem may be escalating.

“It’s more than ‘let’s turn up and steal something’,” warns John Russell, technical director at fuel management specialist Merridale. “It is organised crime on a bigger scale.”

Merridale has seen several companies fall victim to this type of theft recently, with a total fuel loss between them of around a quarter of a million litres.

“Having selected a target storage tank, the thieves will start by drilling an access hole in the side or top,” Russell says. “It will be covered and disguised to avoid detection.

“They will then return at a later date with a suitable vehicle and the equipment required to extract the fuel. Pipe work will be laid through undergrowth and scrubland, often for hundreds of metres, to an out-of-the-way location that is suitable for the operation of pumping equipment and can be accessed by the vehicle,” Russell continues. “The criminals will then pump out several thousand litres at night, then return every two or three nights to repeat the process.

“Tanks at the perimeter of a yard next to trees and bushes are therefore most at risk,” he adds. “Furthermore, our experience shows that security fencing, 24-hour site manning and CCTV do not appear to be barriers to this type of operation.”

The answer, says Russell, is to fit an accurate tank management system that will trigger an immediate warning if there is a sudden and unexplained drop in the tank’s contents. Merridale can combine such a system with its FuelWorks service so that real-time alerts can be sent by both text and email to designated personnel.

If you have an earlier generation of tank gauge or management system, then FuelWorks can still carry out an end-of-day dip and reconciliation. “It has been enhanced to detect any unexplained drop in fuel,” Russell explains. “Should any serious discrepancy be detected, then users set up to receive tank alarm alerts will receive an email warning.

“While this is not as immediate as real-time stock monitoring – it notifies after the event, not while it is happening – it provides older installations with a method of warning site managers that something untoward may be occurring.

“Remember that any large negative adjustment on a stock reconciliation report should always be investigated,” Russell states. “You may simply have entered a delivery incorrectly; but you may be having your fuel stolen.”