Straight vegetable oil - Misplaced Pages

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Definition

Straight Vegetable Oil (SVO) is a fuel for diesel engines that can be either pure new vegetable oil or Waste vegetable oil that has been cleaned, although this is normally referred to as WVO. The most noticeable difference between an engine running on diesel and SVO is that latter is quieter, but (with rapeseed based SVO) only produces 96% of the equivalent power of diesel.

The original diesel engine was designed to run on peanut oil, so SVO burns well in some diesel engines. However, due to its relatively high viscosity, using SVO with unmodified engines can lead to poor atomisation of the fuel, incomplete combustion, coking in the injectors, ring carbonisation, and accumulation of fuel in the lubricating oil.

Application/Usability

Most diesel car engines are suitable for the use of SVO with modifications. One common solution is to add an additional fuel tank, one for SVO and a separate tank of diesel (petrodiesel or biodiesel) and an electric valve to switch between them. The viscosity of the SVO is reduced by preheating it using heat from the engine; the engine is started on diesel, switched over to SVO as soon as it is warmed up and switched back to diesel shortly before being switched off to ensure it has no SVO in it when it is started from cold again. In colder climates it is often necessary to heat the SVO’s fuel lines and tank as it can become very viscous. Another common solution (the one-tank system) is to add electric pre-heating of the fuel and if necessary upgrade the injection pumps and glow-plugs to allow SVO fuel use with one tank.

With unmodified engines the unfavourable effects can be reduced by blending, or “cutting”, the SVO with diesel fuel. For normal use, without either blending or a second tank and associated modifications in a petrodiesel engine, vegetable oil has to be transesterified to biodiesel.

Many cars powered by indirect injection engines supplied by inline injection pumps, or mechanical Bosch injection pumps are capable to run on pure SVO in all but winter temperatures. Turbo diesels tend to run better due to the increased pressure in the injectors. Pre-CDI Mercedes and cars featuring the PSA XUD engine tend to perform well too, especially as the latter is normally equipped with a coolant heated fuel filter.

According to uncited sources,you can also bypass all modifications on any diesel-engine by adding 5% unleaded fuel to the SVO. It will keep your engine clean and there won't be any starting problems in cold weather. However, this information has not been cross-checked and its value is unclear. See discussion page for more information.

Properties

The main form of SVO used in the UK is rapeseed oil which has a freezing point of -10°C, however the use of sunflower oil which freezes at -17°C is currently being investigated as a means of improving cold weather starting. Unfortunately oils with lower gelling points tend to be less saturated (leading to a higher iodine number) and polymerize more easily in the presence of atmospheric oxygen.

Cetane number is highest with coconut oil, palm stearine, palm kernel, palm oil, palm oleine, lard and tallow. Coconut oil, palm oil, palm stearine, talow and lard have the lowest iodine numbers.

Examples

Some Pacific island nations are using coconut oil as fuel to reduce their expenses and their dependence on imported fuels while helping stabilize the coconut oil market. Coconut oil is only usable where temperatures do not drop below 17 degrees Celsius (62 degrees Fahrenheit), unless two-tank SVO kits or other tank-heating accessories, etc. are used. Fortunately, the same techniques developed to use, for example, Canola and other oils in cold climates can be implemented to make coconut oil useable in temperatures lower than 17 degrees Celsius.

Taxation of Fuel

Taxation on SVO as a road fuel varies from country to country, and it is possible the revenue departments in many countries are even unaware of its use, or feel it sufficiently insignificant to legislate. Germany offers 0% taxation, resulting in their leading on most developments of the fuel use. There seems to be no clear taxation system in the USA, however given the low rate of fuel taxation, it is unlikely to face anything unfavourable, although charges could vary from state to state. Ireland currently adds exise duty at 48 cents per litre and then adds 21% VAT to this total when SVO is used as a road fuel. Despite its use being common in France, it would appear there has been no legislation to cover this. In the UK drivers using SVO have been prosecuted for failure to pay duty to Customs and Excise. With this department renamed Her Majesty's Revenue and Customs the rate of taxation was originally set at 27.1p per litre, but recently, without a change in the law, HMRC decided to reclassify it as 47.1p per litre. The change seems to contradict the UK Governments commitments to the Kyoto Protocol and to many EU directives. Attempts are also being made to make the increase retrospective, with one organisation being hit with a 16 000ukp back tax bill. The change in taxation effectively makes use of SVO in the UK unviable by all but environmentalists, as the combined price of SVO and taxation for its use, considerably exceeds the price of mineral diesel.

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