Waste Vegetable Oil As A Diesel Replacement Fuel

Index of Waste Vegetable Oil As A Diesel Replacement Fuel
Introduction
Properties of Triglycerides as Fuels
Oils and their melting point and Iodine Values
In Car installation
Problems Costs Exhaust emissions and Cost efficiency
Saturated oils and possible improvements

Problems Costs Exhaust emissions and Cost efficiency

Use of the oil and preliminary results To date, the vehicle has been driven over 7500 km using canola oil. In the morning, the oil in the tank is cold and quite viscous and a particular start-up routine must be used. In addition, if, at the end of the trip, the vehicle will not be restarted again for several hours, then a shutdown sequence must be followed in order to allow easy restarting.
Glow plugs are used for all starts. When starting cold, the engine is started on diesel and the journey commenced. When the engine temperature has reached ‘ normal’ as shown on the engine temperature gauge, the fuel solenoid is operated, and the journey continues using vegetable oil. For hot or warm starts, the engine is started using the vegetable oil.
Shutdown: In the cooler months, at about 5 km from the end of each journey, the fuel solenoid is released. At the end of the journey, the ignition switch is turned off. If the time delay has not expired, the engine continues to idle, until the end of the delay. During warmer periods, the shutdown delay override switch is used to stop the engine for all stops, except for the last journey of the day.
Comparison of performance and economy Using records of fuel consumption and distance travelled, there has been no noticeable difference in fuel consumption or engine power when operating on diesel, palm or canola oil. The fuel consumption has been found to be approximately 6.9 L/100 km, regardless of what fuel is being used. It is planned that full testing of performance will be carried out in the near future, taking into account different driving conditions and different fuels.

Problems
Cold starting with canola oil: If the engine has been allowed to cool completely (eg overnight) and the shutdown routine not followed, then the engine may be very difficult to restart. It has been found that heating the injectors by, for example, pouring hot water over them or using a hair dryer, will allow the engine to restart with no difficulty.

Costs:
The tank was made using scrap materials and consequently was of negligible cost. It was estimated that if professionally made using new materials, it would have cost approximately $400. Other expenses were: filter - $30, filter elements - $5, heated fuel line - $120, solenoid valve - $95, sundry items - $100. The total cost was $250. Operating costs are $5 per 10,000 km for new filter elements

Exhaust emissions:
At this stage no exhaust emission tests have been done. The level of particulates as gauged by simple visibility checks appears about the same whether running on diesel or canola oil. However, as the oil contains no sulphur, SO2 emissions are not present when running on triglyceride oils. Furthermore, the pungent smell typical of diesel exhaust is not present. Rather the smell is similar to that of a BBQ.
Life-cycle CO2 emissions are substantially reduced. Studies done by Sheehan et al, Beer et al etc indicate that reductions by as much as 80 to 90% compared to fossil diesel fuel can be expected, given the renewable nature of the oil, and that this is a re-use of a spent product. Nitrogen oxides (NOx) emissions would most likely be similar or slightly elevated by ~10% as compared to fossil diesel. In addition to atmospheric nitrogen, most vegetable and animal oils contain small quantities of nitrogen containing proteins, which upon combustion, release various nitrogen oxides. Unburnt hydrocarbon emissions may or may not be increased. Previous research has shown that this is very dependent of the vehicle’ s state of tune, age and the specific properties of the oil.

Cost efficiency:
Using free waste canola oil, fuel costs have been only for the diesel fuel used in the start-up and shutdown periods. Fuel purchase records for 10,000 km show the vehicle has used 240 litres of diesel. Driving this distance on diesel only would normally require approximately 690 litres of fuel. This represents a fuel cost saving of 65%. The conversion has paid for itself with savings in diesel purchases in excess of $400.
Different usage patterns would give obviously give different results. Usage patterns for this vehicle show mainly short trips, with one or two longer (>20 km) journeys per week.
As vehicle use increases, the diesel fuel savings would also be expected to increase. The only requirement for diesel, is that the motor must be allowed to reach operating temperature before operating on triglyceride oils, and that the oil must be diluted or purged from the fuel pump before shutdown.
Due to higher fuel usage larger vehicles would be able to have greater fuel cost savings which would more than offset the increased costs of a remotely located oil tank.
Obviously, if there were to be a greater demand for used and waste cooking oil, the oil may not be available free and the cost of purchasing waste oil must then be taken into account. While this would extend the pay-back period, as long as there was a reasonable difference between the cost of the waste oil and diesel fuel and any extra maintenance costs were not too excessive, it would probably still be economically viable to undertake the modifications and operate on used oil.

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