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 warranty claims.
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 organic feedstock.
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 street.
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 subject.”
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 biofuels present.
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 system.
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 volume.
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.
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 suspect fuel.
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 [diesel particulate filter] regeneration. Ricardo has also undertaken substantial research into the use of B30 in heavy duty engines, looking at effects of unregulated emissions.
“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.”