Richard Simpson looks at how bus and coach operators can use biofuels to reduce their carbon footprints.
Since the mid 1970s, environmentalists have been telling the rest of us that the world only has about 40 years’ worth of accessible crude oil left, and that we need to find an alternative replacement for this most versatile source of fuels and other materials.
The reality is that it’s now 2016, and oil shows no signs of running out. Indeed, the oil industry’s development of new techniques such as fracking, which enable the extraction of sizeable but hitherto inaccessible oil reserves in North America and elsewhere, has actually prompted an oversupply of crude from other sources.
Put simply, the Saudis, who can pump oil from their wells for $6 a barrel, are looking to force the high-cost producers such as North American frackers out of business by flooding the market with cheap crude (breakeven point for the cheapest fracked oil is about $20 a barrel). This was the reason that retail diesel prices in the UK fell to below £1 a litre at the turn of the year.
The Middle East oil won’t last forever, of course, but the quantity of reserves held by Saudi are a closely-guarded state secret. Meanwhile, the Saudi tactic has paid off, and drilling for shale oil in the USA has come virtually to a standstill for the time being.
While it’s difficult to find agreement as to when the oil might actually run out (or, now, whether it will actually ever run out before we stop using it for a number of reasons), all reputable sources are agreed that there is more than enough left in the ground to meet our needs for the foreseeable future.
‘In European conditions, burning biodiesel sourced from oilseed rape produces 20% more CO2 than fossil diesel, while biodiesel made from sunflower seed is roughly at parity with fossil fuel’
However, environmentalists argue, there is still a case for developing alternatives to oil-based fuel, particularly diesel. The main driver here, of course, is man-made global warming: atmospheric levels of CO2 are rising because of human activities, including primarily the combustion of fossil fuels, and the CO2 in the atmosphere is increasing the temperature at the earth’s surface as the insulating properties of CO2 mean that more of the sun’s heat is trapped by this ‘greenhouse gas.’
Some might argue that this is a good thing – most food plants grow well in greenhouses, and a warm atmosphere rich in the CO2 which plants require for photosynthesis would be a great help in growing food for the world’s increasing population.
All of which is true, to a point. However, temperatures in the polar regions seem to be rising faster than average, and warm winters in the Arctic and Antarctic would lead to ice currently on land melting and finding its way into the sea, with a consequent global rise in sea level. More worrying still, reserves of frozen methane currently captured in permafrost tundra might melt and reach the atmosphere. On release, methane is 26 times more potent as a greenhouse gas than CO2 and it is argued that this could trigger a warming event so intense that the life on earth would become untenable for the majority of humans.
So, attention has turned to reducing CO2 emissions. One way of doing this is to reduce the total amount of fuel burned, which is difficult in a world with an expanding population and an economic system addicted to ‘growth’ – which actually means increased consumption of pretty much everything, including fuels. To the credit of vehicle manufacturers, much effort has been directed towards this, and the latest generation of heavy-duty Euro 6 diesels burn less fuel than their predecessors while offering better performance and emitting less toxic gases.
The other way is to increase the rate at which emissions of CO2 are absorbed by the biosphere. Photosynthesis of CO2 by growing green plants consumes the gas from the atmosphere. For as long as the amount of CO2 released by burning is balanced by the amount absorbed by growing plants, then, overall the amount of CO2 in the atmosphere remains unchanged.
Politics and the environment
That’s the environmental benefit. There’s a geopolitical advantage in switching to biofuels for the West, as well. Countries with oil-producing economies tend to be politically unstable or despotic, and Western Governments are rightly concerned about being over-dependent upon them. Before fracking came to the fore as an oil-extraction technique, an unlikely ‘green-blue’ alliance formed in the USA which saw left-wing internationalists and environmentalists, and farmers and right-wing isolationists unite to promote the benefits of home-grown ‘freedom fuel’ over imported oil.
But there are moral, political and environmental drawbacks as well.
Go back to the start of the industrial revolution, and the UK economy largely ran on biofuels: firewood and charcoal. The result was deforestation on an industrial scale, and it was only the mining of coal that saved what was left of the UK’s forests from the axe.
Today, the race for biofuels is causing similar environmental damage elsewhere, with wild tropical forests being cleared to grow biofuel crops such as soya. A 2008 study of Brazilian rainforest clearance published by The Nature Conservancy of Minneapolis, Minnesota, indicated that clearing 10,000 square metres of forest released 300 tonnes of CO2. It would take 300 years of carbon saving from the soya-based biodiesel grown in its place to make up for the carbon released by the forest clearance. Other crops are even worse. Convert Indonesian rainforest to grow palm oil, and it takes over 400 years to payback the carbon ‘debt’. And these figures take no account of the environmental damage done to hitherto pristine wild habitats. Mark Avery, former Conservation Director of the Royal Society for the Protection of Birds, argues that this “threatens to accelerate the destruction of some of the world’s most precious habitats and wildlife. Without environmental standards, biofuels will be little more than a green con.”
Even growing fuel crops on farmland can have an impact. For instance, Timothy Searchinger of Princeton University, found that when US growers stopped exporting corn (maize) to Brazil for cattle feed and sent it instead to be sent for conversion into ethanol to be blended with diesel and gasoline, the Brazilian agricultural industry responded by clearing forests to grow its own feed. When the carbon release from these clearances was taken into account, it appeared that ethanol was responsible for producing nearly twice as much CO2 as ‘fossil’ gasoline.
In Europe, research by Transport & Environment, which promotes sustainable transport policies, found that the now mandatory inclusion of biofuel into DERV and petrol under EU rules would actually increase greenhouse gas emissions from road transport by 3.5% by 2020.
There are also ethical questions: with an expanding global population how can it be ethical to turn land over from food production to fuel? Some economists argue that it is, in fact ethical to do so. If the West grows its own fuel in place of exporting basic food commodities, then that encourages greater and more profitable food production elsewhere in the world because local small-scale farmers won’t be periodically undercut by the dumping of staples such as rice, wheat and maize on the world market by industrialised farmers at times of glut.
Scania’s Chief Executive Henrik Henrikson enlivened a recent Sustainable Transport Conference which the truck and bus manufacturer hosted in Paris prior to the launch of its new S and R Series trucks by dismissing ethical objections to farming biofuel as ‘rubbish’, pointing out that the EU had more land devoted to golf than biofuel production.
Others take a contrary view. Marc-Oliver Herman, who leads economic justice policy for the Oxfam charity, argues that Europe’s biofuel production exacerbates spikes in world food commodity prices, and has a global knock-on effect, moving food production onto wild land and displacing people living on the margins.
‘A lot of cities now realise that they have a gold mine in terms of waste materials and sewage if they capture the methane that would otherwise be released’
Ethanol vs biodiesel
Engine designers are not so keen on ethanol, which is the easiest fuel to produce from food crops such as maize and soya. It is produced by fermentation, which itself produces CO2. Currently most Euro 6 heavy-duty diesels are certified to run on fuel with an ethanol content of up to 10% (EN10), but no more. Higher concentrations of ethanol attack seals and dissolve plastic to an unacceptable degree, and ethanol also absorbs water, causing further reliability problems.
It’s also of no environmental benefit, at least when the feed crop is grown in temperate regions. Ethanol made from European-grown barley emits 20% more CO2 than fossil diesel, while wheat ethanol offers no improvement. Nevertheless, it is currently the global leader in biofuels, thanks largely to Brazil which alone produces over 25% of global output from its sugarcane crop. There are now almost no vehicles in Brazil running on pure petrol, and it is claimed that thanks to the unique conditions in the country that even when indirect land displacement factors are taken into account, Brazil’s ethanol represents a 61% cut in GHG emissions compared to petrol.
It is doubtful whether similar gains could be made elsewhere, largely because sugar cane, which grows only in tropical and semitropical regions, is one of the most efficient plants for turning sunshine into energy, and plant residues from cane harvesting are used to power the processing of the crop.
But, what about biodiesel, which is produced by extracting oil from plants and purifying it before using it as a fuel?
In European conditions, burning biodiesel sourced from oilseed rape produces 20% more CO2 than fossil diesel, while biodiesel made from sunflower seed is roughly at parity with fossil fuel. Emissions of NOX are generally higher than for fossil diesel too.
Hydrogen-treated vegetable oil looks more promising. Like biodiesel, it comes from biomass feedstocks, but the production process is completely different and the finished product is actually a synthetic diesel which burns cleaner than most fossil diesels, reducing emissions of particulate matter.
The actual benefit in reducing CO2 emissions varies widely according to the feedstock used for production. HVO is being heavily promoted by Mack Trucks in the USA, which cites a whole life cycle analysis from the California Air Resources Board demonstrating widely-varying savings ranging from 15-80%.
Nothing is perfect
The one certainty that emerges from all this uncertainty about the benefits of biofuels is that there is no one optimum solution. For instance, processing the forest products of Scandinavia and North America into paper yields a nasty waste product called black liquor. This can be refined into dimethyl ether (DME): a non-toxic fuel which, although it cannot be subject to high injection pressures, nevertheless is otherwise a possible replacement for conventional diesel.
It’s clean-burning enough to allow for the vehicle to dispense with a PM filter and the associated maintenance, and can provide CO2 reductions of 95% compared to fossil diesel.
Other potential sources of DME include food, plant and animal waste. It can also be refined from natural gas. It is stored in gaseous form, but becomes liquid under light pressure, meaning that it is handled in a similar manner to propane (LPG).
Volvo commenced trials with DME in North American truck fleets last year, but results have yet to be published. Its use is not straightforward. An insider at a fuel-injection company confides that the fuel is known to its development engineers as ‘Dear me!’ because of its inability to handle conventional injection pressures.
Scania is also a keen proponent of sourcing whatever might be an appropriate fuel for the geographic location and duty cycle of the vehicle.
Daniel Milione is the Product Manager for sustainable transport with the Swedish manufacturer.
“Air quality in cities is the most pressing issue of the moment,” he reminded CBW.
“The first step in any city is to go 100% Euro 6, and ensure in-use compliance as well as certification. Then there are three criteria which are used to determine the viability of a biofuel.
“One: does it reduce emissions of fossil carbon?
“Two: is there enough of it?
“Three: is it competitive in terms of cost and is there a viable distribution structure etc?
“When these criteria are applied to currently-available fuels, four emerge as viable.
“First is biodiesel, made from fatty acid methyl ester derived from plants.
“Second is hydrogen-treated vegetable oil (HVO). This can be made from virtually any plant material and also from animal by-products from slaughterhouses: it’s a synthetic diesel.
“Third is ethanol, an alcohol produced by fermenting plant matter.
“And the fourth is gas – methane. This can be ‘natural’ gas, which is a fossil fuel drilled from the earth, or biogas produced from decomposing organic material. From a global warming point of view biogas is far superior, but more production is needed.
“10 years ago, Scania developed a full range of engines capable of running on biodiesel. Biodiesel produces more NOx in combustion than fossil diesel, so a bigger exhaust aftertreatment system is needed. Now all our core engines are biodiesel tolerant, and the difference between them and a biodiesel-specific engine is the larger SCR components in the exhaust system.
“HVO requires no engine modifications at all. It’s a ‘drop-in’ fuel, and you can switch between HVO and fossil diesel as frequently as you like. However, it has 8% less energy in volume terms than fossil diesel, so fuel consumption on a km/litre basis will increase if it is used.
“Ethanol is the most plentiful vehicle biofuel. 70% of global biofuel is ethanol.
“Biogas is an excellent fuel. While supply is a problem, it can be backed-up by natural gas, which is chemically identical.
“There is some confusion among customers as to whether to choose liquefied natural gas (LNG) or compressed natural gas (CNG). The big issue is storage on the vehicle: five litres of CNG contains the same energy as one litre of diesel: this makes it only suitable as a fuel for citybuses or urban distribution trucks. LNG is better in terms of density: 1.6 litres of LNG is equivalent to one litre of diesel – it’s about the same as ethanol. This makes it acceptable for longer-haul operations.
“In terms of noise, gas is 3dBa quieter than the equivalent diesel: this is a 50% reduction in sound level. You can go quieter still if you use a gas engine in conjunction with a hybrid driveline.
“In terms of the negative side, all biofuel vehicles have to have an adapted maintenance requirement. Biodiesel, for instance, requires more frequent oil changes and fuel filter changes. The one exception to this is HVO, which is identical to diesel.
“Operators considering going for biofuels should remember that the CO2 saving must be in terms of ‘well to wheel’ not ‘tank to tailpipe’. In other words, all emissions output during the production and transportation of the fuel must be taken into account, not just the fuel burn in the engine.
“You need supplier-specific data, not global average values. It’s worth noting that natural gas (methane) is not a renewable fuel, but it does still give savings in greenhouse gas emissions of up to 15%, because it has more hydrogen in it than carbon.
“Where methane really is advantageous is when it is in the form of biodiesel and gathered from materials that would otherwise decompose in the atmosphere.
“Methane is 26 times more aggressive a greenhouse gas than CO2 is on its release to atmosphere, and decomposing waste material releases a lot of methane.
“A lot of cities now realise that they have a gold mine in terms of waste materials and sewage if they capture the methane that would otherwise be released.
“The ‘Poo Buses’ which you have running in the United Kingdom are a great way of marketing this advantage.
“One of the other big advantages is that producing biofuel from local resources also creates local employment. This is hugely significant in places like Africa and India.
“I believe markets approach a tipping-point when biofuels form 20% of the market. In Europe, we are currently at 3-4% – the important thing is to get to 20% as quickly as possible. This will ensure viable distribution networks.”
Daniel added that Scania was keen to work with operators and local Governments to advance the case for appropriate biofuels.
“The big challenge is that our customers face a big risk in selecting biofuels, Daniel said. “Unknowns include the pricing and taxation of different biofuels.
“We are forming co-operations between transporters, fuel suppliers and transport buyers to make sure the right choices are made. Where we can do this, we will have success.
“It’s a slow process – we are also promoting better technology and support for operators. We are going ahead to a point where the market will develop on its own, and we will work with companies and cities which are brave enough to do this,” he concluded.
Although not currently a player in the UK bus market, Iveco’s Product Director, Martin Flach, has some interesting insights into future fuels.
“In the early 1700s, the very first steam motor vehicles ran on biofuel – wood!” he pointed out.
“Fossil fuels came along in the 19th century with coal, and petrol arrived at the dawn of the 20th century. Diesel started to take over in the 1930s, and 2008 saw natural gas and biomethane make an appearance.”
He accepts that electricity might be good for some city applications, but range and battery weight are a handicap for anything else.
He is, however, a powerful advocate for gas.
“Natural gas improves both local air quality and CO2 emissions globally,” he argued and pointed out that when the Chinese had an urgent need to improve air quality in the run-up to the Beijing Olympics in 2008, an important part of the solution was to retrofit 5000 CNG engines to the city’s bus fleet.
“But we are now moving from an environmental agenda for gas to an economic case based on total cost of ownership,” he argued, pointing out that while gas was a bulkier fuel, the ability of gas-powered engines to operate without ERG or SCR systems installed and still comfortably meet Euro 6 was a considerable advantage.
“The aftertreatment system on a Euro 6 diesel weighs 250kg, on a Euro 6 gas engine, it’s 45kg,” Martin said. It’s also much easier to package onto a vehicle chassis, which liberates room for more gas tankage. At UK prices, gas is 30-40% cheaper than diesel.”
Flatch’s enthusiasm for spark-ignited, purpose-built gas engines does not extend to so-called dual-fuel aftermarket conversions, which can run on gas or diesel but always use some diesel as an ignition medium.
“Methane slip (where unburned gas enters the atmosphere having passed through the engine and exhaust system) is an issue on these, but it very low on dedicated engines conforming to Euro 6,” he told CBW.
“In a Euro 6 gas engine, every combustion pulse is monitored, and injection is mapped back to individual cylinders. If too much gas escapes one combustion stroke, then that cylinder gets less gas on the next engine revolution.”
Daimler and Cummins’ thoughts
Daimler and Cummins have both embraced the introduction of HVO with enthusiasm. Launching a new line-up of Euro 6 engines at the IAA Show, Cummins Director of on-highway operations for Europe, Ashley Watton, explained that providing the fuel was certified to European standard EN 15940 then HVO and other paraffinic fuels then the manufacturer’s F3.8, B4.5, B6.7 and L9 engines were conformant with Euro 6 when running on it, or any blend of conventional EN 590 fuel and EN 15940.
“Standard fuel filters are retained, and the fuel has the same stability and cold-resistant properties as conventional diesels,” he said. “Tailpipe emissions of PM and NOx are no higher than when using standard diesel.
“HVO diesel and other paraffinic fuels offer a useful low-carbon alternative fuel for transport and have now reached a point of commercial maturity and standardisation at which Cummins is pleased to confirm compatibility with our current Euro 6 engine line-up.
“Our HVO test programme covered a range of vehicle duty cycles, so we are confident that bus and truck operators can undertake a seamless transition to using HVO without impacting their vehicle operations or engine reliability.”
Cummins also reminded operators that its L9N gas engine could be run on biogas, or biogas/natural gas blends, claiming that running on 100% biogas reduced the carbon footprint of the vehicle to that of a battery-powered one.
Daimler pointed out that the EN 15940 standard also covered biomass to liquid, gas to liquid, and coal to liquid synthetic diesels. These were approved for use in all OM 470 and OM 471 engines from the first generation of Euro 6 type onwards and also medium-duty OM 936 and OM 934 engines.
All components and service intervals would remain unchanged if these engines were run on EN 15940 fuel.
So, what does all this mean to the British coach and bus operator?
For those running large fleets of city buses, a biogas initiative is probably worth investigating. The best advice would be to seek partnerships with other companies and organisations, including those which have organic waste material to dispose of, as well as vehicle manufacturers. It would also be worth opening a dialogue with local freight distributors to see if they could be persuaded of the merits of gas vehicles.
Biogas has not always had the best of reputations for quality, but the purification technology is improving all the time. If quality issues persist, then the fuel can be sweetened by the addition either of natural gas or liquid petroleum gas.
A biogas initiative requires considerable investment, not just in specialist vehicles, but also in the supply and fuelling infrastructure. It would be unwise to commit the kind of financial resources required unless binding agreements from local authorities and so on could be reached so the benefit of providing better air quality locally and contributing to the fight against global warming was paid for by those who will benefit most from it rather than those who operate the vehicles doing it.
For others, EN 15940 synthetic diesel looks like a better option. But the standard was only launched in May of this year and the fuel is still not easy to source, although Shell has limited supplies in the UK. Operators can however invest in standard vehicles that have the capability to run on it, which effectively ‘future proofs’ the fleet against any forthcoming legislation regarding CO2 emissions by enabling a mid-life switch at no cost.
Before any commitment is made, operators would do well to heed the advice of Scania’s Daniel Milione and obtain specific details as to the well to wheel carbon footprint and other environmental impacts of the fuel chosen. And if in doubt, stick to diesel.