Investigation into the use of bio-ddiesel fuels on Britain's railwaysRail Safety & Standards Board
Investigation into the use of sulphur-free diesel fuel on UK railways
Conclusions:
"Sulphur-free diesel (SFD) testing has shown a potential power reduction on sulphur-free diesel of up to 2 to 2.7% at full load."
"Testing showed a potential fuel consumption increase at this reduced power setting of up to 2%"
"the lower energy content of sulphur-free diesel still indicates that overall fuel usage will increase. Assuming a nominal 2% increase, this equates to some £3.06m and £1.29m cost increase per annum for the passenger and freight fleets respectively. "
Rail Safety & Standards Board
Investigation into the use of bio-ddiesel fuels on Britain's railways
Conclusions:
"biodegradability is a key benefit to the use of biodiesel. However, its improved degradability does make it more susceptible to water absorption...leading in turn to potential increased microbial contamination and corrosion, particularly with fuel injection equipment, and possible filter plugging. This is a particular issue for fuel storage."
"HIGHER CLOUD POINT AND POUR POINT. The consequence of this situation is that, whilst the effect on engine starting and operation in temperate climates may largely be unnoticed, operability in low temperature climates with high biodiesel blends may require further fuel additives."
"Negative operational aspects of biodiesel include: -
• Reduced energy content (by approximately 8-10%).
• Increased fuel consumption.
• Increased nitrogen oxide, and possible tailpipe CO2, emissions.
• Poor low temperature starting and operation.
• Poor oxidation stability and water absorption characteristics.
• Incompatibility with certain elastomers and natural rubbers.
• More rapid lubricating oil degradation.
• Degradation during long-term storage."
UK Department for Transport (DfT)
Fuel Quality Directive Gas Oil Requirements
Conclusions:
"Sulphur free gas oil containing biodiesel will also be more prone to bacterial contamination than current gas oil. Bacterial growth can also potentially result in blockage of fuel filters and increased corrosion. Prolonged use of contaminated fuel could result in damage to engines. Bacterial growth can be prevented by eliminating water from fuel storage tanks and conducting monthly checks that tanks remain free of water. Where a bacterial growth outbreak has occurred, this can be addressed either by emptying and cleaning the tanks, or by seeking specialist help to tackle the outbreak with biocide additives and filtering."
"Because of these changes in fuel quality, increased care will be needed in the storage of sulphur free gas oil where this contains biodiesel. The oxidation stability of this fuel will be poorer than that of current gas oil. Over time oxidation can precipitate solids with potential to block filters in fuel distribution systems or in off-road equipment fuel systems."
Caterpillar
"A range of potential problems with biodiesel use is identified. These include lower energy content, elastomer compatibility ("still being monitored"), microbial growth and oil change intervals."
Cummins
"Biodiesel has a natural affinity to water, and water accelerates microbial growth." "Care must also be taken when storing biodiesel in bulk storage tanks. All storage and handling systems must be properly cleaned and maintained. Steps must be taken to minimize moisture and microbial growth in storage tanks." "Biodiesel fuel is an excellent medium for microbial growth. Microbes cause fuel system corrosion and premature filter plugging."
MTU
"Bacterial attack and sludge formation may occur in the fuel under unfavorable conditions. In such cases, the fuel must be treated with biocides in accordance with the manufacturer's specifications. Overconcentration must always be avoided."
"Diesel fuels in winter operation - At low outdoor temperatures, the diesel fuel's fluidity can be inadequate on account of paraffin precipitation. In order to prevent operational problems (e.g. clogged filters) during the winter months, diesel fuel with suitable cold-flow characteristics should be used.
Flow improvers - Flow improvers cannot prevent paraffin precipitation but they do influence the size of the crystals and allow the diesel fuel to pass through the filter. The effectiveness of the flow improvers is not guaranteed for every fuel. Certainty is only assured after laboratory analyses of the filtering capability. Required quantities and mixing procedures must be carried out according to the manufacturer's instructions."