SVO &WVO diesel fuel
Created | Updated Jan 28, 2002
Diesel engines at the 1900 World Fair were demonstrated running on peanut oil by Rudolf Diesel.
The problem with running diesel engines on vegetable oils (or animal fats) is that their viscosity is far higher at ambient temperatures than mineral diesel oil. The biodiesel methods overcome this by removing the most viscous portion of the oils. However clean, dry Straight Vegetable Oil (SVO) can be used simply by heating the oil to around 60deg C at which temperature its viscosity matches that of normal diesel. This has the advantage of leaving in the chemicals that provide the best lubrication, a desirable element in diesel fuel. The lubricity of SVO exceeds that of both diesel oil and biodiesel.
Some diesel injection pumps are able to cope with the high viscosity of room temperature vegetable oils. There are numerous reports of German drivers of unmodified diesel Mercedes fuelling their cars with salad oil. And motoring happily. For some, however, injection pump failure and coking of injectors have occurred. Coking of engines has been reported in some trials. Whether the viscosity of the SVO was lowered by heating in these trials is unclear.
The environmental benefits of SVO are: low levels of heavy metals and low levels of sulphur giving lower levels of exhaust pollutants (excepting oxides of nitrogen), and carbon neutrality in that the CO2 released by the exhaust is equal to the amount of CO2 taken up by the growing plant to produce the oil.
The last point becomes problematical when the energy inputs and CO2 outputs for fertilizer, transport, processing and packaging are considered.
However for Waste Vegetable Oil (WVO) these inputs occur irrespective of the final use, and so can be ignored when looking at the environmental cost.
The problem with running diesel engines on vegetable oils (or animal fats) is that their viscosity is far higher at ambient temperatures than mineral diesel oil. The biodiesel methods overcome this by removing the most viscous portion of the oils. However clean, dry Straight Vegetable Oil (SVO) can be used simply by heating the oil to around 60deg C at which temperature its viscosity matches that of normal diesel. This has the advantage of leaving in the chemicals that provide the best lubrication, a desirable element in diesel fuel. The lubricity of SVO exceeds that of both diesel oil and biodiesel.
Some diesel injection pumps are able to cope with the high viscosity of room temperature vegetable oils. There are numerous reports of German drivers of unmodified diesel Mercedes fuelling their cars with salad oil. And motoring happily. For some, however, injection pump failure and coking of injectors have occurred. Coking of engines has been reported in some trials. Whether the viscosity of the SVO was lowered by heating in these trials is unclear.
The environmental benefits of SVO are: low levels of heavy metals and low levels of sulphur giving lower levels of exhaust pollutants (excepting oxides of nitrogen), and carbon neutrality in that the CO2 released by the exhaust is equal to the amount of CO2 taken up by the growing plant to produce the oil.
The last point becomes problematical when the energy inputs and CO2 outputs for fertilizer, transport, processing and packaging are considered.
However for Waste Vegetable Oil (WVO) these inputs occur irrespective of the final use, and so can be ignored when looking at the environmental cost.
