article first appeared in Ricardo Quarterly Review. It is used here with
Biofuels are widely perceived as an environmental
asset capable of cleaning up vehicle emissions overnight. But in reality first
generation biofuels may cause as many problems as they solve.
Of all the methods for reducing CO2 emissions
available to the automotive industry, the use of biofuels is proving to be one
of the most challenging. Biofuels are being widely touted as an easy way of
cutting emissions of greenhouse gases – irrespective of whether those fuels are
the product of a sophisticated manufacturing process or derived from recycled
cooking oil in a back-street lock-up.
But nothing could be further than the truth:
biofuels vary enormously in their environmental impact and in the other concerns
they raise. In fact, there is growing unease in the automotive industry that the
unregulated use of biofuels could lead to widespread engine failures and
Lack of regulation may also mean that while
biofuels help to reduce CO2, some may actually cause other types of harmful
emissions which until now have remained unregulated. Perhaps the biggest problem
is that while gasoline and diesel are two distinct fuels manufactured to
exacting, recognised standards on a global basis, the term ‘Biofuel’ does not
represent one fuel or even two.
In fact it refers to any fuel manufactured from an
Biofuels can take the form of ethanol-based fuel
blended with gasoline, or oils either blended with, or used as a substitute for,
diesel. European gasoline and diesel may contain up to five per cent ethanol or
biodiesel (the latter officially defined as baseline EN590 diesel and rapeseed
methyl ester/RME blend) respectively without the base fuel standard being
affected and are quite safe to use in standard engines without ill effect.
Much more than that, however, and the situation
becomes more complicated.
Standards – or lack of standards
Each family of biofuels can be manufactured using
different techniques, yet despite active work in this area there are no real
standards in place for biofuel and no specifications governing their formulation
other than for constituent parts.
While ethanol is a fairly standard substance
whatever the feedstock or manufacturing process used to make it, the chemical
makeup of biodiesel can potentially be extremely varied, having been derived
using anything from animal carcases to rape seed. In the real world this could
mean one point of sale may be offering a biodiesel fuel with completely
different properties, formulation, additives and contaminants to another across
The situation was summed up by Angela Johnson,
principal engineer, technology and systems department, at Ricardo when she
declared simply, “all biofuels are not equal.” Indeed, they are anything but
equal, and the implications for engine, fuel systems and aftertreatment
manufacturers are potentially serious.
Johnson is part of a Ricardo team charged with
staying one step ahead of the biofuels phenomenon, providing information,
analysis and advice to many vehicle and component manufacturers in the
automotive sector whose products are becoming affected by the new fuels.
“Part of my role has been to look at biofuels from
a strategic point of view,” she explained, citing a long list of areas of
concern: “The markets, the well-to-wheel implications [see Assessing the Alternatives], the variability among
fuels (in particular fuel quality), the processes involved, issues faced by
vehicle makers, security and sustainability of raw material supply for
production, the blending of fuels and its variation across the supplier base,
fuel distribution and the impact on consumers (too much choice is confusing) and
the vehicle parc. There’s a huge degree of variability across the whole
In road fuel terms, the large scale adoption of
biofuels would represent a huge cultural upheaval in the industry. “The question
is,” Johnson continues, “how can we practically use this? Is it a short term
measure or a sustainable long term solution?”
There are two sides to the challenge which
The first is their true value in reducing
emissions on a well-to-wheel basis. The second relates to the mechanical
implications of using biofuel either blended with conventional fuel or, in
particular, when it is in concentrated or pure form.
Biofuels can be powerful solvents, flushing
deposits from fuel systems to potentially block or damage injection systems.
Alcohol-based biofuels are often hygroscopic, absorbing moisture which can in
turn cause corrosion; they can also attack seals in the engine and fuel
Put simply, there are huge incompatibilities
between current engine technologies and biofuels when those fuels are used in
high enough concentrations.
Ethanol is not so much of a problem and is much
the same molecule whether cracked from hydrocarbons or fermented from sugar
cane. As a result, there are few issues with bioethanol fuel as far as
specification is concerned, and standard engines can run on gasoline containing
up to five per cent ethanol without a problem. Beyond that, flexfuel vehicles
are needed: these are vehicles whose engines have modified components to resist
chemical attack from the fuel and can adapt to the different combustion
characteristics resulting from a higher ethanol content.
Apart from technical considerations, there are
other factors that may affect the consumer too. Because the existing European
gasoline standard EN228 includes fuel blended with up to five per cent ethanol,
the fact that that fuel contains ethanol at the point of sale is not necessarily
publicised to the customer. Yet ethanol contains less energy than gasoline by
Research is actively being pursued in this area.
In the US, Ricardo is working with Bosch and the University of Michigan on
Department of Energy sponsored research to develop an optimised flex-fuel
vehicle capable of running on any blend of ethanol up to and including E85.
Key nations are setting biofuel targets
EU – Binding commitment to 10 per cent
market share of biofuels in transportation by 2020
USA – Renewable Fuel Standards stipulate
25.7 billion litres biofuel by 2010, 227 billion by 2030
China – Objective set for biofuel to meet
15 per cent of transportation energy by 2020
India – Considering a 10 per cent target by
Brazil – All gasoline contains 24-27 per
cent ethanol; 2013 target of 2.5 billion litres biodiesel
Australia – 2010: 1 per cent biofuel; 2020:
5.75 per cent biofuel
Biodiesel: the main worry
Biodiesel is a different matter and is where most
of the concern lies. Again, the European EN590 standard for conventional diesel
allows it to be blended with up to five per cent biodiesel. But unlike ethanol
used in gasoline, globally the term ‘biodiesel’ can be applied to a wide range
of substances and the difficulties arise with blends above five per cent – or
even the use of 100 per cent (B100) biodiesel.
Commonly used feedstocks are rape seed from Europe
and palm oil from Indonesia and Malaysia, while the USA relies heavily on soya.
Different types of oil each have a different chemistry, explains Jon Andersson,
manager, chemistry department, at Ricardo. “If not properly eliminated in the
production process, each will contain a different set of contaminants that may
affect engine performance and durability. The fuels can also degrade over a
period of time or through exposure to heat and light.”
A typical problem scenario is the traveller who
drives hard and fast to the airport, arriving with a hot engine and warm fuel.
Worse still, the tank may be left almost empty, the remaining dregs left exposed
to air in the tank and possibly hot sunshine in the summer. “When the blend was
mixed it was one thing,” explains Andersson, “but two weeks later it may have
become something completely different.”
Points of sale may suffer similar problems. For
the large supermarket selling large quantities of fuel quickly, fuel quality
could remain fairly consistent. But at smaller sites, fuel may degrade in
underground tanks over a longer period. This potential for fuels to change
character makes them almost impossible for manufacturers to deal with.
Combustion properties vary too, so accurate engine calibration becomes a moving
target. Fuel systems can be affected by corrosion and deposits, with serious
consequences for manufacturer warranties.
Instances of drivers using crudely recycled
vegetable oil, harvested from restaurants, in modern diesel engines have
produced some alarming results. Unburned fuel mixing with the engine’s
lubricating oil is already a problem in conventional cars but the use of
unmodified vegetable oil fuels (non transesterified) without fuel-enhancing
additives can react with the lubricating oil to form polymers with very
different lubricating properties. There have been similar occurrences in fuel
systems, raising the spectre of increasing numbers of warranty claims from
disgruntled customers who may have unwittingly damaged their otherwise perfect
engines by using incompatible fuel. Some component suppliers are already coming
to Ricardo seeking clarification on whether specific failures were caused by
Too much variability
Even with well-produced fuels, pinning down
calibration standards is proving very difficult.
“In the diesel arena,” says Johnson, “ultimately,
it may be possible to make synthetic diesel (a second generation fuel which can
be better quality than the standard diesel we have today) on a large-scale
production basis. What we don’t like at the moment are the fuel variability and
quality issues associated with first-generation biodiesels.
“Nobody has enough money to develop and validate
their engines to be capable of coping with all the types and blends that are out
there. There’s a risk of spending a lot of money developing engines to run on
fuels that may only be around for a decade or so until more stable, second
generation fuels come on stream.”
Currently, some heavy duty engine manufacturers
will warrant their engines for use with B100 but with specific conditions
regarding fuel standard, service intervals and driving conditions.
Emissions can vary wildly too. A variety of fuels
was tested on Ricardo’s heavy-duty Euro VI diesel development project recently
conducted with AECC.
“We looked at running B30 (30 per cent
biodiesel),” said Andersson. “There were apparent reductions in HC and CO in
response to reductions in engine power. Particle number emissions increased and
effects on NOx emissions were uncertain, though PM levels and the effectiveness
of the emissions control system was unchanged.”
High percentages of biodiesel have a dramatic
effect on the way the fuel is combusted. Andersson digs deeper into the detail
of what can happen inside the engine: “Biodiesel is more dense, with a heavier
hydrocarbon component, a proportion of which can survive combustion. We’ve seen
different effects with different engines, but these components can hang around
in the combustion and provide a degree of quenching – which reduces NOx.
“But they can also end up deposited on the
combustion chamber walls, creating higher levels of particulate matter. There
are a number of different effects and it depends on the individual design and
how well the injection system is coping. That is why it is so difficult to
contemplate a single generic engine design to cope with all biofuels.”
Ricardo: research for UK government
In 2001 Ricardo undertook some research for the UK
Department of Transport into burning vegetable oil. It has also tested a wide
range of blends – including B10, B20 and B30 – for various vehicle makers,
investigating jet deposits, general durability and the effect on DPF
regeneration. Ricardo has also undertaken substantial
research into the use of B30 in heavy duty engines, looking at effects of
“All of these tests have tended to be ‘bolt-ons’,
to test programmes running on conventional fuel,” Andersson continues, “but a
major issue is the inconsistency and uncertainty with biofuel quality and
longevity for engine type approval because the pass-off tests for emissions
regulations are based on conventional fuel.” The auto industry is currently
requesting that type approval be permitted on either current reference fuels or
B5 and E5. If granted, this will not become law for at least a year.
“We are trying to open the window of understanding
on the implications of running these fuels in modern engines – what we really
lack is information on the durability impact of these fuels. We have to nail
down what the properties of the fuels are and how they degrade in order to
understand how we can create a matrix that is realistic.”
Tying down standards is proving difficult. The oil
industry does not have the engineering expertise and legislators don’t view
biofuels from the same perspective as either the oil or automotive industries.
With over 25 years experience in biofuel research, this puts Ricardo in a key
position in terms of knowledge – and all of its courses and seminars on the
subject have been oversubscribed. Its biofuel specialists also spend a great
deal of time working with EU legislators and talking to trade groups. “Our first
approach,” Andersson continues, “is to help the standards regulators.”
Second-generation biofuels will be the answer
Most of the problems will be addressed by the
introduction of so-called second generation biofuels. Most of the biofuel
produced today is first generation, produced in the case of ethanol by
fermenting crops, or from a wide range of different types of organic oils when
it comes to biodiesel. Second-generation fuels will be produced using
Fischer-Tropsch gas-to-liquids (GTL) technology.
This involves specialised heat treatment of
biomass to generate a ‘dirty’ producer gas. After cleaning, the producer gas is
converted to a synthesis gas of carbon monoxide and hydrogen. This is then
processed to form liquid fuel. It is not a new process and was developed in the
1920s, but it produces accurately formulated ‘designer’ fuel to tight standards.
“In this way it is possible to build fuels from
very small molecules,” Andersson continues, “producing a high quality substitute
for either gasoline or diesel.”
The likely source material or feedstock will be
biomass. This can comprise a wide range of waste material including wood chips
as well as varied organic waste. Relatively few companies are using the process
commercially today and there is some way to go, perhaps 10 years or so, before
commercially-produced designer fuel is available in larger quantities. When it
does, the true well-to-wheels and emissions benefits of biofuels can be realised
properly, without any damaging side-effects to engines and their components.
In one sense, that time can’t come soon enough –
but the intervening period can be put to good use. “It’s sufficiently far away,”
concludes Andersson,”for both the automotive and oil industries to specify
exactly what they want.”
Key challenges for energy suppliers and
Significant issues can occur in the blending of
ethanol and gasoline; suppliers may need to use Refinery Base Oxygenate
Blendstock (RBOB) rather than standard gasoline.
Fuels containing bio-content (especially ethanol)
cannot be transported through multi-product pipelines. Biofuel use requires
extensive cleaning programmes at filling stations to remove all water in
gasoline tanks prior to using ethanol blended fuel. Ethanol is hygroscopic
(draws in water), which can lead to corrosion issues in vehicle fuel
There is a general lack of fuel standards covering
biofuels – currently no standards exist for E10, E85 or B10, B30 or other
Considerable cost will be incurred installing
dedicated pumps. Many forecourts do not have enough space to permit additional
pumps for E85 and other incremental fuels: too much choice could be confusing
for the consumer, heightening the risk of using the wrong fuel.